Abstract:
Two leaf springs of substantially identical width which define first and second movable members are superposed on each other at one end and connected together. A movable contact is attached to the thus connected portion. The first movable member has a slot formed in a middle portion thereof. The width of an end portion of the second movable member is set so that the end portion can be inserted in the slot. A supporting member being inserted in the slot has a portion for swingably supporting an edge portion of the slot and another portion for swingably supporting an end portion of the second movable member opposite to the movable contact. The second movable member is curved so that upon application of a operating force to the first movable member the urging direction of the second movable member changes to cause a snap action to thereby selectively bring the movable contact into contact with one of the two fixed contacts. The width of the second movable member can be increased irrespective of the size of the slot, thus making it possible to provide a large urging force.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a switch device of the type wherein a movable contact portion is connected to and disconnected from a fixed contact portion by the snap action of a movable member of a leaf spring structure. 
     2. Background Information 
     FIGS. 19 through 21 show a conventional switch device used in automobile window regulators. 
     In these drawings, 1 is a movable member of a leaf spring structure with a rectangular shape. Formed therein is a substantially rectangular slot 3 and a curved spring portion 2 extending downward. This movable member 1 has a movable contact 4 provided in its free end portion and a notch-like pivot portion 5 formed in its base end portion. Another notch-like pivot portion 6 is formed in a distal end portion of the spring portion 2. 7 is a switch casing on which a terminal board 10 is provided that has first and second support portions 8 and 9 spaced horizontally from each other. This switch casing 7 further has fixed contacts all and 12 spaced vertically from each other. The movable member 1 is accommodated in the casing 7 such that the pivot portion 5 of the base end portion is fitted in and supported by the first support portion 8 and the pivot portion 6 of the spring portion 2 by the second support portion 9. 
     In the state of FIG. 20, since the free end portion of the movable member 1 is applied with an obliquely-upward urging force from the spring force of the spring portion 2, the movable contact 4 is kept in contact with the fixed contact 11 on the closed side. As shown in FIG. 21, however, when the base end portion of the movable member 1 is depressed downward by a control member 13 so that arm portions 14 of the movable member 1 are moved downward beyond the pivot portion 6 of the spring portion 2, the free end portion of the movable member 1 is applied with an obliquely-downward urging force from the spring portion 2. Consequently, the free end portion of the movable member 1 is quickly moved downward by a downward component of the urging force, so that the movable contact 4 is disconnected from the fixed contact 11 on the normally closed side and brought into contact with the fixed contact 12 on the open side. Upon contact of the movable contact 4 with the fixed contact 12 on the open side, a window regulator motor is energized, so that a window is moved up or down. 
     In the foregoing structure of the prior art, to cause switching such that the movable contact 4 comes to contact with the fixed contact 12 on the open side, a portion of the movable member 1 corresponding to the second support portion 9 must be located below the pivot portion 6 of the spring portion 2 when the movable member 1 is depressed by the control member 13 in order to cause a snap action. Therefore, a slot 3 is needed in the movable member 1 since in the foregoing depressed state the second support portion 9 must penetrate through the movable member 1. With such a configuration, electric current for the motor of the window regulator flows through the arm portion 14 and spring portion 2 of the movable member 1. However, in order to increase the current capacity of the switch device, the width W of the movable member 1 must be increased in order to increase the width of the arm portion 14. Further, to increase the contact pressure of the movable contact 4 with respect to the fixed contacts 11 and 12, the width of the spring portion 2 must be increased, thus increasing the width W of the movable member 1. As a result, there is the problem of the overall size of the switch device becoming large. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a switch device of the snap action type which is large in capacity, small in size and yet is able to provide sufficient contact pressure between a movable contact portion and a fixed contact portion. 
     According to the present invention, to cause snap action, first and second leaf springs are made substantially identical in width and superposed onto each other at one free end. These leaf springs have pivot portions at the base portion that are opposite to the thus superposed portions and are adapted to be fitted to a supporting member. The supporting member is inserted into a slot formed in a middle portion of the first leaf spring. The pivot portion (as edge portion of the slot) of the first leaf spring is pressed against one side of the supporting member. The pivot portion (a base end portion) of the second leaf spring is pressed against the other side of the supporting member. The second leaf spring is resiliently curved, and when an operating forced is applied to the first leaf spring, the urging direction of the second leaf spring is changed to cause snap action. Since the width of the second leaf spring may be increased irrespective of the size of the slot of the first leaf spring, the urging force of the second leaf spring acting on a movable contact with respect to fixed contacts may be increased. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view showing a switch device according to a first embodiment of the present invention; 
     FIG. 2 is a sectional view showing the switch device of FIG. 1 after being switched; 
     FIG. 3 is a plan view of a movable member with a movable contact; 
     FIG. 4 is a development showing the movable member of FIG. 3; 
     FIG. 5 is a perspective view of a supporting member; 
     FIG. 6(A) is a development of a leaf spring; 
     FIG. 6(B) is a perspective view showing the leaf spring of FIG. 6(A); 
     FIG. 7 is a plan view showing a leaf spring according to a second embodiment of the present invention; 
     FIG. 8 is a sectional view showing a switch device according to a third embodiment of the present invention; 
     FIG. 9 is a plan view showing a movable member according to the third embodiment; 
     FIG. 10 is a front view showing the movable member of FIG. 9; 
     FIG. 11 is a sectional view taken along line XI-XI in FIG. 9; 
     FIG. 12 is a development showing the movable member of FIG. 9; 
     FIG. 13 is a plan view showing the process of fabricating a first movable member according to the third embodiment; 
     FIG. 14 is a plan view showing the process of fabricating a second movable member according to the third embodiment; 
     FIG. 15 is a perspective view showing the process of stamping in the third embodiment; 
     FIG. 16 is a perspective view showing a supporting member according to the third embodiment; 
     FIG. 17 is a sectional view showing the process of assembling in the third embodiment; 
     FIG. 18 is an exploded perspective view showing a supporting member and a second movable member according to a fourth embodiment of the present invention; 
     FIG. 19 is a plan view showing a movable member or leaf spring of a conventional switch device; 
     FIG. 20 is a sectional view of the conventional switch device; and 
     FIG. 21 is a sectional view showing the conventional switch device after being switched. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A switch device adapted for use in an automobile window regulator, according to a first embodiment of the present invention will be described below with reference to FIGS. 1 through 6. 
     In FIG. 1, a switch body is formed by attaching a rectangular casing 22, made of an insulating material and having a hollow portion formed on its bottom side, to the upper side of a rectangular base member 21 of insulating material. The base member 21 has a hollow portion 23 formed on its upper side. A fixed contact conductor 24 is provided in the base member 21 by insert molding, which has a terminal member 25 projecting downward therefrom. The fixed contact conductor 24 is exposed to the inside of the hollow portion 23, whose exposed portion has a columnar fixed contact 26 (on the open side) secured thereto. 
     A fixed contact conductor 27 provided in the casing 22 by insert molding has a terminal member 28 projecting downward from the base member 21. A portion of the fixed contact conductor 27 is exposed from the bottom surface of the casing 22 so as to face the fixed contact 26, this exposed portion having a columnar fixed contact 29 (on the closed side) secured thereto. 
     A terminal body 30 formed by bending a conductive plate into a substantial U-shape has a base portion 31 secured in the base member 21 by insert molding. First and second support portions 32 and 33 extend orthogonally from the base portion 31 toward the casing 22. In FIG. 5, the first support portion 32 has a notch-like V-shaped lock portion 32a extending in the traverse direction. The second support portion 33 also has a notch-like V-shaped lock portion 33a extending in the traverse direction. The lock portion 33a of the second support portion 33 is located below the lock portion 32a of the first support portion 32 (i.e. closer to the base portion 31 than the lock portion 32a). The terminal body 30 is connected with a terminal member 34 (see FIG. 1) projecting downward from the base member 21. 
     In FIGS. 3 and 4, a movable contact plate 35 is of a leaf spring structure, which has first and second movable member 36 and 37 connected together by a connecting portion 41. End portions 36a and 37a are adjacent to the connecting portion 41 and have circular holes 38a and 38b  formed respectively therein to which a columnar movable contact 38 is secured. The first movable member 36 has a rectangular slot 39 formed in a laterally central portion thereof. As shown in FIGS. 1 and 2, a middle portion of the second movable member 37 is curved so as to be convex with respect to the base member 21, defining a curved portion 40. 
     As shown in FIG. 4, the movable contact plate 35 having the first and second movable members 36 and 37 connected together by the connecting portion 41 in the form of a single elongate body is fabricated by subjecting a leaf spring board to stamping. 
     With regard to the dimensions, the width W 1  of the first and second movable members 36 and 37 is identical with the width W (FIG. 19) of the movable member 1 in the prior art (W 1  =W). The width of a straight pivot portion 43 at a base end portion is identical with the width of the terminal body 30 (W 2 ). The width W 3  of the slot 39 is slightly larger than the width W 2 . That is, the width W 2  of the pivot portion 43 which is a straight portion of a base end portion of the second movable member 37 is smaller than the width of other portions, particularly, smaller than the width of the curved portion 40. 
     After stamping, the curved portion 40 is formed by bending, and the connecting portion 41 is folded to obtain a superposed state. A straight pivot portion 42 of a base end portion of the first movable member 36 which is a right-side edge portion of the rectangular slot 39 is swingably fitted to the lock portion 32a of the first support portion 32 of the terminal body 30. Similarly, the straight pivot portion 43 of the second movable member 37 is swingably fitted to the lock portion 33a of the second support portion 33. As a result, a compressive force is lengthwisely generated in the second movable member 37, and a tensile force is lengthwisely generated in the first movable member 36. 
     Therefore, as shown in FIG. 1, when the first movable member 36 is located above the pivot portion 43 the end portions 36a and 37a of the movable contact plate 35 are urged in the left upward direction by the tensile force of the curved portion 40 of the second movable member 37, so that the movable contact 38 is kept in contact with the fixed contact 29 on the closed side with a certain contact pressure. A base end portion 44 of the first movable member 36 is adapted to be contacted with a control member 45 provided in the casing 22. In this way, a switch section is composed of the movable contact plate 35 with the movable contact 38, the fixed contact 26 on the open side, and the fixed contact 29 on the closed side. 
     As shown in FIG. 4, two notches 40a are formed between the curved portion 40 and the end portion 37a to facilitate flexure of the curved portion 40. 
     Next, the operation of the first embodiment will be described. 
     In FIG. 1, the end portions 36a and 37a of the movable contact plate 35 are normally applied with an urging force in the left upward direction from the curved portion 40 of the second movable member 37 that exerts a spring force, so that the movable contact 38 is kept in contact with the fixed contact 29 on the closed side by an upward component of the urging force. In this state, when a knob (not shown) provided in an upper section of the casing 22 is controlled to depress the control member 45 downward, the base end portion 44 of the first movable member 36 of the movable contact plate 35 deforms and curves downward. When the base end portion 44 of the first movable member 36 comes below the lock position (corresponding to the lock portion 43) at which the pivot portion 43 of the second movable member 37 is fitted to the second support portion 33, the end portions 36a and 37a of the movable contact plate 35 are applied with an urging force in the left downward direction from the curved portion 40 of the second movable member 37 that exerts a tensile spring force. Consequently, the end portions 36a and 37a move quickly downward to cause a snap action, whereby the movable contact 38 separates from the fixed contact 29 on the closed side and comes to contact with the fixed contact 26 on the open side, leading to the state shown in FIG. 2. On the contrary, when the depressive force of the knob is removed from the control member 45, the first movable member 36 of the movable contact plate 35 recovers by virtue of its spring force, and the base end portion 44 comes above the pivot portion 43 of the second movable member 37. As a result, the end portions 36a and 37a are applied with an urging force in the left upward direction from the curved portion 40 of the second movable member 37 that exerts a tensile force, so that the end portions 36a and 37a move quickly upward to cause a snap action, whereby the movable contact 38 separates from the fixed contact 26 on the open side and comes to contact with the fixed contact 29 on the closed side, restoring it to the state shown in FIG. 1. When the movable contact 38 comes in contact with the fixed contact 26 on the open side, the motor of the window regulator is energized, so that a window is moved up or down. When such contact is removed, the window stops. 
     The foregoing first embodiment has the following advantages. The width W 3  of the slot 39 of the first movable member 36 may be decreased as much as possible. This suppressing a decrease in the capacity of current resulting from the presence of the slot 39. Therefore, the switch device can have a large current capacity despite its size without increasing the width W 1  of the movable members 36 and 37. 
     The width of the curved portion 40 of the second movable member 37 cannot be limited by the width W 3  of the slot 39 of the first movable member 36, but may be made identical with the width W 1 , for example. Therefore, the contact pressure of the movable contact 38 with respect to the fixed contacts 26 and 29 can be made sufficiently large. Further, since the width of the curved portion 40 which tends to heat up upon current flowing can be increased, its temperature rise can be suppressed. 
     Since the terminal body 30 has the first and second support portions 32 and 33 which are fabricated by bending a conductive plate into a substantial U-shape, the pivot portions 42 and 43 of the first and second movable members 36 and 37 can be kept in line contact with the lock portions 32a and 33a of the first and second support portions 32 and 33; therefore, contrarily to the prior art, the amount of heating due to current concentration can be decreased. 
     Compared to the case in which the first and second movable members 36 and 37 are combined into a single body after being separately fabricated, the fabrication of the movable contact plate is easy and the number of parts is small. The conductivity in the end portions 36a and 37a of the first and second movable members 36 and 37 is enhanced; therefore, the amount of heating due to current concentration can be reduced. 
     Although the first embodiment shows the first and second movable members 36 and 37 being connected together by the connecting portion 41 in the form of a single elongate body, as shown in FIG. 7, the first and second movable members 36 and 37 may be arranged side by side and connected together by the connecting portion 41 in accordance with a second embodiment of the present invention. 
     Further, the present invention has been described as being applied to the switch device of a window regulator, but it can be applied to various types of switch devices. 
     A third embodiment of the present invention will be described with reference to FIGS. 8 through 16. 
     In this embodiment, the first and second movable members 36 and 37 are independently fabricated from separate leaf spring materials. That is, the first movable member 36 has a long slot 52 and a short slot 54 adjacent thereto and a connecting portion 56 therebetween. This connecting portion 56 corresponds with the control member 45. The end portion 36a of the first movable member 36 and the end portion 37a of the second movable member 37 are superposed and secured together by the movable contact 38 which is a rivet. 
     The second movable member 37 is substantially identical in width with the first movable member 36, and has a pair of notches 40a formed in a middle portion thereof as is the case of the first embodiment. The pivot portion 43 of the second movable member 37 is narrower than the long slot 52. Since the second movable member 37 is fabricated independently of the first movable member 36, it may be made of a different material, and its thickness may be made thicker than the first movable member 36. 
     To prevent the first and second movable members 36 and 37 from rotating separately about the movable contact 38, a coupling means 60 is provided in the end portions 36a and 37a. Specifically, the coupling mean 60 includes folded portions 57 and 58 which are formed by partly cutting the end portions 36a and 37a of the first and second movable members 36 and 37 along shear faces 57a and 58a and then folding under to a state in which the end portion 36a is superposed on the end portion 37a. Consequently, the folded portions 57 of the first movable member 36 are engaged with the shear faces 58a of the second movable member 37. Therefore, even when an external force is applied to the movable members 36 and 37, tending to cause them to rotate about the movable contact 38 separately in the directions of the arrow R (FIG. 12), the folded portions 57 are blocked by the shear faces 58a, preventing separate rotation of the movable members 36 and 37. That is, the first and second movable members 36 and 37 are clamped together by the folded portions 57 and 58. 
     FIGS. 13 through 15 show the process of fabricating the first and second movable members 36 and 37. As shown in FIG. 13, the first movable member 36 is fabricated by subjecting a leaf spring material 62 to stamping to form the long slot 52, the short slot 54, and the circular hole 38a for the movable contact, and for punching out U-shaped slits 64 and 66 as well as positioning circular holes 68 and 70. Here, the first movable member 36 is still connected with the leaf spring material 62 via connecting portions 72 and 74 left between the slits 64 and 66. 
     On the other hand, (see FIG. 14) the second movable member 37 is fabricated by punching out the circular hole 38b for the movable contact, a substantially U-shaped slit 77, and positioning circular holes 78 and 79 in a different leaf spring material 76. Here, the second movable member 37 is still connected with the leaf spring material 76 via a connecting portion 80. These movable members 36 and 37 are successively formed in the leaf spring materials 62 and 76, respectively, at certain intervals as shown in FIG. 15. 
     Then, the leaf spring materials 62 and 76 are superposed as shown in FIG. 15 such that the positioning circular holes 68 and 70 correspond to the positioning holes 78 and 79, respectively, leading to the superposed relationship of FIG. 9. A punch 82 (see FIG. 15) is used to form the shear faces 57a and 58a in the two movable members 36 and 37 and provide the folded portions 57 and 58 for clamping. Then, the movable contact 38 is caulked to the circular holes 38a and 38b, and the connecting portions 72, 74 and 80 are cut off, leading to the state of FIG. 9. 
     In the foregoing process of fabrication, the steps of forming the folded portions 57 and 58, securing the movable contact 38, and cutting off the connecting portions 72, 74 and 80 may be performed in a different order, or performed simultaneously if allowable. The number of folded portions 57, 58 may be changed to one or three or more. Further, the coupling means 60 may be embodied by a combination of protrusions (provided on one of the two movable members 36 and 37) and recesses (formed in the other) instead of the folded portions 57 and 58. 
     As shown in FIG. 12, the pivot portion 43 of the second movable member 37 may have projecting portions 86 by which the second movable member 37 is reliably supported on the terminal body 30. Specifically, the projecting portions 86 extend from either end of the pivot portion 43, which are adapted to be engaged with stepped portions 87 formed at either edge of the support portion 33 of the terminal body 30. 
     FIG. 17 shows the partly assembled state in which the first and second movable members 36 and 37 are connected together by the movable contact 38, the second movable member 37 has the curved portion 40, the edge portion (the pivot portion) of the short slot 54 of the first movable member 36 is fitted to the lock portion 32a of the support portion 32 of the terminal body 30. Leading to the assembled state of FIG. 8, the pivot portion 43 of the second movable member 37 is fitted to the lock portion 33a of the support portion 33 of the terminal body 30, so that the movable contact 38 faces upward. The casing 22 is then placed on the base member 21 and secured thereto, so that the movable contact 38 is pressed downward. 
     In the thus completely assembled state, since the projection portions 86 are always engaged with the stepped portions 87 of the support portion 33, the second movable member 37 is never detached from the terminal body 30. 
     FIG. 18 shows a fourth embodiment of the present invention, in which a projecting portion 90 extends from a laterally central portion of the pivot portion 43, which is adapted to be inserted into a rectangular slit 92 formed in the support portion 33 of the terminal body 30. Therefore, similar to the third embodiment, the second movable member 37 is reliably supported on the terminal body 30. The present invention should not be limited to the foregoing engaging mechanism, and the mechanism of reliably engaging the first and second movable members 36 and 37 with the terminal body 30 may be embodied by other means.