Abstract:
The present invention relates to an overload protection device of a press type switch in which the switch main body has slide grooves within the bouncing range of the free end of the conductive strip. The shape of the slide grooves is formed by a plurality of slide rails. A push-pull element is pivotably connected to the inside of the press button. A cross bar is fitted to the bottom of the push-pull element while both ends of the cross bar are disposed in the slide grooves. Accordingly, the push-pull element is able to change path and locating position in the slide grooves. Moreover, the conductive strip can be controlled in on/off-state by means of the force in different directions. Beside, the free end of the conductive strip is kept in an independent state so that the conductive strip is transformed into the off-state in case of overload. Consequently, the safety of the user can be ensured.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an overload protection device of a press type switch, and more particularly to a press type switch in which a push-pull element controlling the switching of a conductive strip slides along a preset path of an 8-shaped slide groove. Accordingly, this switch has not only the function of on/off control, it can also enable the conductive strip to carry out an automatic disconnection in case of overload so that the safety of the user is ensured. 
     2. Description of the Prior Art 
     The types of switches are various. Commercially available switches like see-saw switch, press type switch, spring type switch, microswitch, etc. differ from one another in configuration which are designed to meet the using requirements and habits of the users. Regarding the technical features of the see-saw switch, the inventor of the present invention has disclosed a few previously approved cases so that it won&#39;t be described more hereinafter. The present invention is an improvement of the two-stage press switch. A conventional two-stage press switch, as shown in FIGS. 1 through 4, utilizes a two-stage press element  2  projecting above the housing  1  to move a push rod  21 , thereby controlling the conductive strip  3  in a connection or disconnection state. The press element  2  includes a heart-shaped slide groove  22  at inner side thereof which has several slide rails of different height and a U-piece  23 . The top of the U-piece  23  is pivotably connected to the housing I while the bottom thereof is situated in the slide groove  22 . When the press element  2  is pressed downwards, the top of the slide groove  22  is engaged at bottom end of the U-piece  23 , as shown in FIGS. 1 and 2. At this time, it shows the on-state. In case of overload of the conductive strip  3 , the press element  2  can&#39;t be automatically escaped since it is located by the U-piece  23 . In order to switch to the off-state shown in FIGS. 3 and 4, it should be manually done. Consequently, the conventional press type switch doesn&#39;t have the protection effect in case of overload. 
     SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to provide an overload protection device of a press type switch in which the conductive strip is deformable in the contrary direction for an electric disconnection in case of overload so that the safety in use is attainable. 
     It is another object of the present invention to provide an overload protection device of a press type switch which can be used as a conventional on/off switch at ordinary times. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accomplishment of this and other objects of the invention will become apparent from the following description and its accompanying drawings of which: 
     FIGS. 1 through 4 are schematic drawings of a conventional two-stage press type switch; 
     FIG. 5 is a perspective view of an applicable embodiment of the present invention; 
     FIG. 6 is a perspective exploded view of the partial structure of the applicable embodiment of the present invention; 
     FIG. 7 is a sectional view of the partial structure of the applicable embodiment of the present invention; 
     FIG. 8 is a section of the side view of the applicable embodiment of the present invention in off-state; 
     FIG. 9 is a section of the side view of the applicable embodiment of the present invention in on-state; 
     FIG. 10 is a perspective view of a conductive strip of the applicable embodiment of the present invention, showing a contact piece is downwards; 
     FIG. 11 is a perspective view of the conductive strip of the applicable embodiment of the present invention, showing a contact piece is upwards; 
     FIG. 12 is an enlarged view of part I in FIG. 8, showing the push-pull element is situated at position (A) of the slide groove; 
     FIG. 13 is another enlarged view of part I in FIG. 8, showing the push-pull element slides from position (A) downwards to the lowest position (A′) and is ready to slide upwards; 
     FIG. 14 is a further enlarged view of part I in FIG. 8, showing the push-pull element slides is situated at position (B) and ready to slide downwards to the position (B′) and then upwards to return to position (A); 
     FIG. 15 is a perspective view of part II of the slide groove in FIG. 12; 
     FIG. 16 is a side view of part II of the slide groove in FIG. 12; 
     FIG. 17 is a perspective exploded view of the push-pull element and its relevant elements of another applicable embodiment of the present invention; 
     FIG. 18 is a sectional view of the partial structure of another applicable embodiment of the present invention; 
     FIG. 19 is a schematic drawing of the slide groove of another applicable embodiment of the present invention; and 
     FIG. 20 is a partially enlarged view of part III in FIG.  19 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     First of all, referring to FIGS. 5 through 8, the press type switch in accordance with the present invention includes a main body  4 , at least two conductive plates  43 ,  44  and a push-pull element  6 . 
     The main body  4  is formed as a hollow rectangular case. A press button  41  is installed at the top thereof, and a projection  411  is fitted to each of two sides of the press button  41  and slidable up and down in a longitudinal groove  42  of the main body  4 . At least one resilient element  412  is disposed beneath the press button  41 . 
     A first conductive plate  43  has a conductive boss  431  while a second conductive plate  44  is connected to a conductive strip  5  to whose bottom a conductive nodule  51  opposite to the conductive boss  431  of the first conductive plate  43  is fitted. 
     The push-pull element  6  has a top bar  61  pivotably connected to a projecting ear  413  at inner rim of the press button  41  while the bottom end thereof is able to push and pull the free end of the conductive strip  5 , thereby forming a press type switch. 
     In addition, two slide grooves  7 ,  7 ′ are correspondingly arranged on the inner walls of the rear and front side of the main body  4  within the bouncing range of the free end of the conductive strip, as shown in FIGS.  7  and  7 ′. Each of the slide grooves  7 ,  7 ′ is directed from the highest first locating position (A) downwards in a curved way to the lowest first turning position (A′), thereby forming a first slide rail  71 , and then directed upwards in a curved way to a second locating position B, thereby forming a second slide rail  72 . The second locating position (B) is situated lower than the first locating position (A) and at inner side thereof. And each of the slide grooves  7 ,  7 ′ is directed upwards in a curved way to a second turning position (B′) after intersecting the second slide rail  72 , thereby forming a third slide rail  73 , and then returns from the second turning position (B′) upwards to the first locating position A, thereby forming a fourth slide rail  74  so that the slide groove in 8-shape is formed. Moreover, a stepped drop side  711 ,  721 ,  722 ,  731 ,  732 ,  741  is respectively formed at the connection and the cross positions between every two slide rails. The auxiliary slide groove  7 ′ on inner wall of the front side of the main body  4  is the same in shape to the slide groove  7  on inner wall of the rear side thereof. The auxiliary slide groove  7 ′ is only used to balance the other end of a cross bar  62  so that it doesn&#39;t need the stepped drop sides. 
     Furthermore, the conductive strip  5  has a projecting tongue  52  at front end thereof while the push-pull element  6  has an inverted T-shaped cross bar  62  at bottom thereof. Both ends of the cross bar  62  are respectively installed in the slide grooves  7 ,  7 ′. Besides, a resilient piece  64  is used to exert an inward resilient force on the slide groove at rear side of the main body  4 . One end of the resilient piece  64  is hooked on a protrusion  63  at outer side of the push-pull element  6  while the other end thereof is hooked on the projecting ear  413  of the press button  41  or another objects, as shown in FIG.  7 . 
     Referring to FIGS. 10 and 11, the conductive strip  5  disclosed in U.S. Pat No. 5,760,672 is an alloy plate extended with a contacting plate  53  at center thereof. The aforementioned conductive nodule  51  is mounted on the tail of the contacting plate  53 . By means of the shrinking assembly of the tail of the conductive strip  5  to the second conductive plate  44 , the free end of the conductive strip  5  is wider than the positioning end thereof, thereby forming a dished conductive strip  5  without the help of an additional spring member for pushing or pulling the projecting tongue  52  at free end of the conductive strip  5  at ordinary temperature and having bi-directional switching functions while the conductive strip  5  is transformable (from the shape in FIG. 10 to the shape in FIG. 11) in case of overload. Therefore, an open circuit is attained. The configuration of the conductive strip  5  has been detailed described in prior art so that no further description will be given hereinafter. 
     By means of the above-mentioned technical features, the functions of the present invention are described as follows: 
     Referring to FIGS. 8 and 10, when the front end of the conductive strip  5  is directed downwards and the contacting plate  53  is raised, the conductive nodule  51  at tail portion thereof is separated from the conductive boss  431  of the first conductive plate  43  in an open circuit. At this time, the press button  41  is situated at the highest position by means of an upward resilient force of the resilient element  412 . Meanwhile, the push-pull element  6  rises such that both ends of the bottom cross bar  62  are situated at the first locating position (A) of the slide grooves  7 ,  7 ′. Accordingly, the open circuit is attained. In order to attain a closed circuit, press the press button  41  downwards while the push-pull element  6  is movable downwards therewith. Since both ends of the bottom cross bar  62  of the push-pull element  6 , as shown in FIG. 7, are situated in the slide grooves  7 ,  7 ′ on inner walls of the front and rear side of the main body  4 , the cross bar  62  slides along the first slide rail  71  downwards. When the press button  41  is pressed to the bottom, the cross bar  62  is moved to the first turning position (A′). At this time, the press button  41  is bounced upward by the resilience of the resilient element  412  after releasing the press button  41 , thereby moving the push-pull element  6  upward, as shown in FIG.  13 . When the push-pull element  6  rises, the cross bar  62  between the front and rear slide grooves  7 ,  7 ′ pulls the projecting tongue  52  at front end of the conductive strip  5  upwards so that the conductive strip  5  is transformed upwards, as shown in FIGS. 9 and 10. The tail portion of the contacting plate  53  is directed downwards so that the conductive nodule  51  is in contact with the contacting plate  53  to create the closed circuit. 
     Again referring to FIG. 13, when the push-pull element  6  brings the conductive strip  5  to bounce upwards, the cross bar  62  slides along the second slide rail  72  upwards to the second locating position B, as shown in FIG.  14 . At this time, the push-pull element  6  has changed its position and is situated above the conductive strip  5 . This is very important. In a closed circuit, there are no other blocking objects beneath the conductive strip  5 . In case of overload, the conductive strip  5  is transformable in the opposite direction into a convex shape by means of the shrinking assembly of the alloy plate, thereby creating an open circuit for ensuring the safety of the users. 
     Referring to FIG. 14, in case of no overload, the conductive strip  5  is situated at the position of the close circuit. In order to attain the open circuit, press the press button  41  so that the cross bar  62  at bottom of the push-pull element  6  slides along the third slide rail  73  downwards, thereby pushing the conductive strip  5  downwards. When the push-pull element  6  is pushed to the central position, it bounces to the off-state. Meanwhile, the cross bar  62  slides through the second slide rail  72  to fall into the second turning position B′. By means of the resilient force of the resilient element  412 , the press button  41  rises to bring the push-pull element  6  back to the first locating position A. Therefore, the original open circuit is attained again. 
     That the push-pull element  6  is slidable along the slide rails  71 ,  72 ,  73 ,  74  in the slide groove  7  successively is completed on two pre-conditions. Firstly, a stepped drop side  711 ,  721 ,  722 ,  731 ,  732 ,  741  is respectively formed at the connection and the cross positions between every two slide rails, as shown in FIGS. 12,  15  and  16 . Secondly, the cross bar  41  has always a resilient force in the direction of the rear slide groove  7  by means that the resilient piece  64 , as shown in FIG. 7, is fitted to the outer side of the push-pull element  6 . By means of these two features, the push-pull element  6  is able to slide along the preset path to reach the first locating position (A) and the second locating position B. Moreover, the push-pull element  6  can dodge the conductive strip  5  by means of the 8-shaped design of the curved crossed slide groove  7  so that the conductive strip  5  is freely transformable in case of overload without being blocked by any objects. Thus, the safety of the user can be ensured. In addition to the automatic disconnection function of the non-fuse switch, the present invention can be used as a conventional on/off switch at ordinary times. In other words, when the conductive strip  5  is transformed to the disconnection position in case of overload, the push-pull element  6  can be brought by the press button  41  from the second locating position (B) through the second turning position (B′) back to the first locating position A, as shown in FIG.  14 . The conductive strip  5  can be brought in the closed circuit by means of the action shown in FIG.  12 . 
     In order for the push-pull element  6  can directly return from the second locating position (B) to the first locating position (A) after the conductive strip  5  is transformed in case of overload, the cross bar  62  of the push-pull element  6 , as shown in FIGS. 17 through 20, is extended with a sloping arm  65  beneath while a fifth slide rail  75  is interposed between the first locating position (A) and the second locating position (B). In addition, the joint of the fifth slide rail  75  and the second locating position (B), as shown in FIG. 20, has a higher drop side  751  while the joint of the fifth slide rail  75  and the first locating position (A) has also a drop side  752 . Accordingly, when the conductive strip  5  is transformed in contrary direction in case of overload, the downward displacement of the projecting tongue  52  touches the sloping arm  65  so that the push-pull element  6  displaces itself outwards. Therefore, the push-pull element  6  passes over the drop side  751  to slide from the second locating position (B) to the first locating position A. This design enables the press button  41  after automatic switching in case of overload to return to the original off-state. This embodiment is more progressive than the aforementioned. 
     Many changes and modifications in the above-described embodiments of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.