Switch
FIELD OF THE INVENTION 
     This invention relates to a switch comprising a pair of stationary contacts and a movable contact contacting said stationary contacts. 
     BACKGROUND OF THE INVENTION 
     Heretofore, the type of switch with a vertical section such as that shown in FIG. 1 has been used for lighting the stop lights of motorcycles. This switch has a pair of stationary contacts 2 and 3 in a housing part 1a, the ends of the stationary contacts 2 and 3 protruding backwards as terminals 2a and 3a. Another housing part 1b associated with said housing part 1a contains a slider 4 having a protrusion normally extending outwardly from the housing, as shown in FIG. 1. The slider is urged in the direction to extend its protrusion out of the housing by a spring 5. A movable contact 6 is fixed on the slider 4, and is urged by a leaf spring 7 in the direction to engage the stationary contacts 2 and 3. The action of the switch is, as shown in FIG. 2, that the movable contact 6 always makes contact with the upper surface of a protrusion 3b of one of the stationary contacts 3, and the movable contact 6 either makes contact with the other contact as shown in FIG. 2(A) or separates therefrom as shown in FIG. 2(B) depending on the position of the slider 4. The switch may be considered ON in FIG. 2(A), and OFF in FIG. 2(B). 
     In this type of switch, however, since the movable contact 6 always slides over the protrusion 3b of the stationary contact 3, chattering may occur between the movable contact 6 and the stationary contact 3 during operation. Hence it may be required to provide a chattering compensation circuit within a circuit incorporating this type of switch. Also when such a switch is frequently operated, failure may occur owing to wear of the contacting surface of the stationary contact 3 and the movable contact 6 as shown in FIG. 3. Furthermore, if a large current is supplied to such a switch, the contacting surfaces of the contacts may fuse due to Joule heating. 
     In a conventional switch of the type illustrated in FIG. 4, a notch 4 is made on the side of the slider 4 and a protrusion 6a extends from the side of the movable contact 6. The protrusion 6a may be inserted into the notch 4a to assemble the slider 4 and the movable contact 6. Therefore, the movable contact 6 may come off during assembly due to the force of the leaf spring 7 (FIG. 5), and it is difficult to assemble such a switch. 
     SUMMARY OF THE INVENTION 
     The present invention is, therefore, concerned with solving such problems in conventional switches by providing a reliable switch having a long life with smooth sliding between the movable and stationary contacts, and yet is still free from chattering or wear. 
     The switch of the present invention has a rotary contact in the stationary contact which makes contact with the movable contact, this rotary contact being provided in place of the protrusion 3a in the conventional switch. 
     The objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawings wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical section of a conventional switch; 
     FIGS. 2(A) and 2(B) are diagrams illustrating the operation of the conventional switch; 
     FIG. 3 is a diagram illustrating the conventional switch when worn; 
     FIGS. 4 and 5 are enlarged views of the movable contact components of the conventional switch; 
     FIG. 6 is an exploded perspective view of a switch fabricated according to this invention; 
     FIG. 7(A) is a vertical sectional view of the assembled switch in the &#34;on&#34; position. 
     FIG. 7(B) is a vertical sectional view of the assembled switch in the &#34;off&#34; position. 
     FIGS. 8(A), 8(B) and 8(C) are enlarged views showing the operation of the switch according to this invention; 
     FIG. 9 is a view from the direction IX in FIG. 6; and 
     FIG. 10 is a view from the direction X in FIG. 6. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings, 11a and 11b show housing part made of an insulation material. Four protrusions 11c are provided on the sides of housing part 11a, and four notches 11d are provided on the sides of the other housing part 11b. By fitting these protrusions 11c in the notches 11d, housing part 11a can be fixed to the other housing part 11b. A slot 11e is formed along a side of the housing part 11a, and a stationary contact plate 12 is inserted into the slot 11e. A contacting surface 12a, made by bending over one end of the contact plate 12, is fixed to the upper surface of the base 11f of the housing part 11a, and the terminal 12b protrudes from one end 11g of housing part 11a. The other stationary contact plate 13 is fixed on the front of housing part 11a. One end of the stationary contact plate 13 is bent to form a crank 13a, and by fitting the crank 13a into a groove 11i on the side of housing part 11a, the stationary contact plate 13 is fixed to housing part 11a. The bent end of the stationary contact plate 13 forms the terminal 13b which protrudes from the end 11g of housing part 11a. A support 13c is formed at the other end of the stationary contact plate 13. When the stationary contact plate 13 is fixed to housing part 11a, the support 13c is fitted in the recess 11j in housing part 11a. A pair of support notches 13d are formed on the support 13c, and the ends 14a of a rotary contact 14 are rotatably supported by these notches 13d. The rotary contact 14 is made of the same metal as the stationary contact plates 12 and 13, and is silver-plated on the surface as are the stationary contact plates 12 and 13. 
     A slider 15 made of an insulation material is contained in the housing part 11b. The slider 15 can slide within the housing part 11b in the direction shown by the arrow in FIG. 7. An operating pin 15a is integrally formed on one end of the slider 15, and it protrudes from a hole 11k formed on the housing part 11b. A support pin 15b is integrally formed on the rear end of the slider 15 and is inserted into a spring 16 contained in housing part 11b.  The slider 15 is always urged in the direction in which the operating pin 15a protrudes from housing 11b by the resiliency of the spring 16. 
     A groove 15c is formed on the side of the slider 15 facing housing part 11a, wherein a leaf spring 17 and a movable contact 18 are contained. The leaf spring 17 is bent to be V-shaped and the bend portion 17a contacts the movable contact 18. The movable contact 18 is formed from the same metal as the stationary contact plates 12 and 13 and the rotary contact 14, and is silver-plated on its surface. As shown in FIG. 10, an elongated hole 15f is formed in a side plate 15d. As shown in FIG. 9, the other side plate 15e has a groove 15g and flexible supports 15i located on respective sides of the groove 15g. The flexible supports 15 have claws on their lower ends. When the leaf spring 17 and the movable contact 18 are assembled in the slider 15, first the leaf spring 17 is inserted in the groove 15c, then one arm 18a of the movable contact 18 is inserted into the hole 15f, and the other arm 18b is forced into the groove 15g. The arm 18b is caught by the claws 15h. After the assembly of the leaf spring 17 and the movable contact 18 in the slider 15, the movable contact 18 will not come off due to the resiliency of the leaf spring 17, thus facilitating assembly. 
     The operation of the switch of the above structure will be apparent from the following description: 
     FIGS. 7(A) and 8(A) show the on-condition of the switch. Under this condition, no external force is exerted on the operating pin 15a, and the slider 15 is pushed to the left in the drawing by the spring 16. In this case, the pressure point on the movable contact 18 by the leaf spring 17, i.e., the bend portion 17a of the leaf spring 17, is situated to the left of the tangent point α of the rotary contact 14 and the movable contact 18. The movable contact 18 is, therefore, urged counter clockwise by the leaf spring 17, and makes a sure contact with both the rotary contact 14 and the contacting surface 12a of the stationary contact plate 12. Thus the two stationary contact plates 12 and 13 are made to contact through the rotary contact 14 and the movable contact 18, and the switch is turned on. 
     When the operating pin 15a is pushed to the right of the drawing to move the slider 15 to the right, the movable contact 18 also moves to the right together with the slider 15. Since the movable contact 18 is pressed onto the rotary contact 14 by the leaf spring 17, the rotary contact 14 rolls under the movable contact 18 when the movable contact 18 moves to the right. FIG. 8(B) shows the state during the course of the movement of the slider 15 to the right of the drawing. At this time, the bend portion 17a of the leaf spring 17 is situated just above the rotary contact 14. Therefore, the movable contact 18 becomes horizontal on the rotary contact 14, and the left end of the movable contact 18 separates from the contact surface 12a of the stationary contact plate 12. At this moment, the contact between the two stationary contacts 12 and 13 is broken, and the switch is turned off. 
     FIG. 7(B) and FIG. 8(C) show the state where the operating pin 15a is pressed further to move the slider 15 to the rightmost position in the drawing. In this case, the bend portion 17a of the leaf spring 17 shifts to the right of the tangent point α of the rotary contact 14 and the movable contact 18. Therefore, the movable contact 18 is pressed clockwise by the leaf spring 17, and the right end of the movable contact 18 makes sure contact with the stationary contact plate 13. This is the complete off-condition of the switch. 
     When the pressure on the operating pin 15a is removed, the slider 15 returns to the left-end position by the force of the spring 16, and the switch returns to the on-condition. 
     According to the present invention, since a rotary contact is provided on the stationary contact which always makes contact with the movable contact, so that the movable contact makes contact with the rotary contact through rolling, the action of the movable contact is smooth, and chattering does not occur between the movable contact and the rotary contact. Thus the reliability of the switch is greatly improved. The load on the slider is also reduced because there is no sliding friction between the movable contact and the rotary contact. Furthermore, since the sliding part of the contact does not wear out as happens in conventional switches, the life of the switch is increased.