Abstract:
An electromagnetic device for use in, for example, the diaphragm control of a camera. The electromagnetic device includes an electromagnet, an armature, an armature shaft and a restricting member for inclining the armature with respect to the armature shaft, whereby even if the armature shaft is not parallel with the attraction face of the electromagnet, holding the armature attraction by the electromagnet is certain.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an electromagnetic device for use in, for example, the diaphragm control of a camera. 
     2. Description of the Prior Art 
     An example of a conventional device of this kind is shown in FIGS. 1 to 5, including an armature 1, a yoke 2, a pair of coils 3, and an armature shaft 4 with a flange 5 mounted on an armature lever 7. The shaft 4 has a pair of short diameter portions 4c on either side of a large diameter portion 4b about which the armature 1 is pivotable in the directions of arrows D (see FIG. 2) to allow intimate contact of a reactive surface 1a of the armature 1 with attraction surfaces 2a of the yoke 2 over the entire area thereof. An E type retainer ring 6 is pressed into an annular groove 4a of the shaft 4 after the armature 1 has been installed on the shaft 4. The armature lever 7 is pivotally mounted about a pin (not shown) in a fitted hole 7a and is urged by a spring 8, in most cases, in a counterclockwise direction. Reference numeral 9 identifies a charge member, and 10 identifies a member to be driven, for example, identifies diaphragm stop member in the shutter priority camera. 
     As the spring 8 usually sets the armature lever 7 in the initial or most counterclockwise position where the armature 1 is separated from the yoke 2, after the charge member 9 moves the armature lever 7 in the clockwise direction of arrow A (see FIG. 1) until the armature 1 contacts the yoke 2, when the coils 3 are supplied with current, the electromagnetic force exerted in the yoke 2, despite the return of the charge member 9 to the initial position of FIG. 1, must hold the armature 1 in contact with the yoke 2. In desired timing, the current supplied to the coils 3 is then cut off, permitting the armature lever 7 to turn in a counterclockwise direction by the bias force of the spring 8, whereby the member 10 moves. By the way, in FIG. 2, the reactive surface 1a of the armature 1 and the attraction face 2a of the yoke 2 show a parallel or ideal relationship. With the electromagnetic device installed in such a relationship, when the armature 1 is brought into mechanical contact with the yoke 2, the reactive surface 1a of the armature 1 arrives at the upper and lower edges 2b and 2c of the yoke 2 simultaneously. Therefore, a stable attraction can be established when the coils 3 are energized. 
     Due to the tolerances of the parts, however, it is very rare that the spatial relationship of FIG. 2 is set up. In most cases, the plane of the armature lever 7 tilts either clockwise or counterclockwise so that the reactive surface of the armature 1 and the attraction surface 2a of the yoke 2 are not parallel with each other as shown in FIGS. 3A and 4A. In FIG. 3A where the axis of the shaft 4 is inclined clockwise from the parallel position with the attraction surface 2a, or the distance from the reactive surface 1a to the upper edge 2b is longer than that to the lower edge 2c, when the armature lever 7 is turned clockwise in FIG. 1 (to the left in FIG. 3A), the reactive surface 1a first contacts with the lower edge 2c, and, as the lever 7 is pushed further, the armature 1 is then pivoted about the edge 2c in the direction of arrow B until the reactive surface 1a rests on the entire area of the attraction surface 2a. Then, when the coils 3 are energized, the armature 1 can be reliably held in the position of FIG. 3B by attraction. It should be noted here that a point G on the axis of the shaft 4 does not shift vertically during the time between before and after the attraction or the positions of FIGS. 3A and 3B. This implies that the armature lever 7 does not distort, because the pivotal arrangement of the armature 1 about the large diameter portion 4b of the shaft 4 absorbs the discrepancy of the actual angular position of the lever 7 from the ideal position of FIG. 3A. 
     In FIG. 4A, on the other hand, the reactive surface 1a first contacts with the upper edge 2b of the yoke 2. For perfect contact to be established, the armature 1 must then turn about a line 0 perpendicular to the paper (in contact with the upper edge 2b) in a clockwise direction of arrow C (see FIG. 4A). But this is not permitted, because the bottom surface 1b of the armature 1 rests on the flange 5. As the lever 7 is pushed further, therefore, twisting of the lever 7 takes place, as shown by the difference in the height h of a point G before and after perfect contact is reached or the positions of FIGS. 4A and 4B respectively. The electromagnetic force is generally not strong enough to overcome the recovering force of the twisted lever 7. Therefore, soon after the charge lever 9 has moved away from the lever 7, the armature 1 turns backward about the line 0, assuming the attitude of FIG. 4A with its upper end only in contact with the yoke 2 at the upper edge 2b. The resultant attracting state is very unstable so that when any shock takes place, such an imperfect contact will be broken easily. 
     From the above it will appear that the abovedescribed problem can be solved if all the parts are assembled to one-sided spatial relationships, as typically represented by the position of FIG. 3A by taking into account the tolerances of the parts. Even when the electromagnetic device has such a characteristic, however, when turned upside down (for example, the camera employing it is held with its bottom pointing upward), the position of FIG. 3A turns to a position of FIG. 5, where similar to the position of FIG. 4A, the reactive surface 1a contacts only the upper edge of the yoke 2 (or the lower edge 2c as viewed in FIG. 3A), and the clockwise movement of the armature 1 about the edge 2c is barred by the retainer ring 6. 
     It should be recognized that if only setting up the armature lever 7 to the clockwise orientation is relied upon, it is impossible to assure proper holding of the armature 1 by the yoke 2 in all angular positions of the electromagnetic device. 
     An object of the present invention is to provide an electromagnetic device capable of maintaining the attraction in a state stable condition in all angular positions. 
     SUMMARY OF THE INVENTION 
     An electromagnetic device includes an electromagnet having an attraction surface, an armature having a reactive surface to be attracted to the attraction surface of the electromagnet, an armature shaft supporting the armature in such a way as to be able to incline with respect to the axis, and a regulating member for inclining the armature with respect to the armature shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of the conventional electromagnetic device. 
     FIG. 2 is a side sectional view of the device of FIG. 1 where the armature and the electromagnet are in an ideal spatial relation. 
     FIG. 3A is similar to FIG. 2 except that the armature shaft inclines clockwise. 
     FIG. 3B is similar to FIG. 3A except that the contact position is illustrated. 
     FIG. 4A is similar to FIG. 2 except that the armature shaft inclines counterclockwise. 
     FIG. 4B is similar to FIG. 4A except that the contact position is illustrated. 
     FIG. 5 is similar to FIG. 3A except that the reversed position is illustrated. 
     FIGS. 6A and 6B are side sectional views of an embodiment of an electromagnetic device according to the present invention. 
     FIG. 7A is a side sectional view of another embodiment of the invention. 
     FIG. 7B is similar to FIG. 7A except that the reversed position is illustrated. 
     FIG. 8 is an exploded perspective view of the device of FIGS. 7A and 7B. 
     FIG. 9A is a side sectional view of still another embodiment of the invention. 
     FIG. 9B is similar to FIG. 9A except that the reversed position is illustrated. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is next described in conjunction with embodiments thereof. In FIGS. 6A and 6B there is shown an embodiment of the invention in which the same reference numerals have been employed to identify the parts similar to those shown in FIGS. 1 to 5. In this embodiment, as shown in FIG. 6A, the armature lever 7 has been previously inclined clockwise, and an E type snap ring 11 pressed into a groove 4a of the armature shaft 4 by utilizing its resilient property. On the lower surface of the ring 11 at the point closest to the electromagnet is formed as a unit a protuberance 11a for keeping the armature 2 in an inclined state with respect to the armature shaft 4 so that the upper edge 2c as viewed in FIG. 6B does not first contact the reactive surface of the armature 1 when the electromagnetic device is used in the reversed position of FIG. 6B, or, generally speaking, the distance between the attraction surface 2a and the reactive surface 1a is not short at the upper end and great at the lower end, as viewed from the direction of gravity. 
     In the erected position of FIG. 6A, owing to setting of the armature lever 7 in a clockwise inclination, similar to the above-mentioned position of FIG. 3A, the reactive surface 1a of the armature 1 first contacts the lower edge 2c of the yoke 2. Subsequently, therefore, perfect contact is established to assure stable attraction. In the upside down position of FIG. 6B also, that half of the armature 1 which is nearer to the electromagnet is lifted upward by the protuberance 11a of the E type snap ring 11. That is, when reversed in position, the reactive surface 1a of the armature 1 is prevented from inclining counterclockwise beyond the parallel position of the attraction surface 2a by the protuberance 11a. In the reversed position also, it is the lower edge 2b of the yoke 2 that the reactive surface 1a first contacts. Thus, the electromagnetic device can perform its attracting operation with high reliability no matter what attitude is taken when it is used. 
     FIGS. 7A, 7B and 8 illustrate another embodiment of the invention, wherein when assembling the parts, an armature lever 12 is not inclined to any direction, and, therefore, the complete device is assumed to have its armature lever 12 inclined either clockwise or counterclockwise with respect to the direction of gravity, depending on the total sum of the tolerances of the parts used therein. This embodiment is different from the first embodiment of FIGS. 6A and 6B in that a resilient retaining member 13 is provided with two protuberances 13a and 13b at respective points closest to the electromagnet so that when in the erected position of FIG. 7A, the protuberance 13b lifts the armature 1 upward at the side closest to the yoke 2, and when in the upside down position, the other protuberance 13a does it. In any case, the inclination of the armature 1 is restricted so that the reactive surface 1a does not first contact the upper edge of the yoke 2 (2b in FIG. 7A, or 2c in FIG. 7B). 
     According to the embodiments of FIGS. 6A to 8, the E type snap ring 11 or the &#34;U&#34; shaped resilient retaining member 13 is provided with the protuberance 11a or the protuberances 13a and 13b formed as a unit therewith to regulate the inclination of the armature 1 so that the gap between the attraction surface 2a of the yoke 2 and the reactive surface 1a of the armature 1 is never shorter at the upper end than at the lower end. Because there is no possibility of occurrence contact of the reactive surface 1a first with the upper edge of the yoke 2, a stable attracting condition can be established in any angular position. 
     FIGS. 9A and 9B illustrate still another embodiment of an invention wherein the armature lever 15 is intentionally inclined counterclockwise as viewed in FIG. 9A, and is provided with a protuberance 15a formed as a unit therewith at the nearest side to the electromagnet, so that when the electromagnetic device is used in the erected position of FIG. 9A, the reactive surface 1a of the armature 1 and the upper edge 2b of the yoke 2 do not first contact each other. In other words, the gap between the attraction surface 2a and the reactive surface 1a does not become narrower at the upper end and wider at the bottom end. 
     In the erected position of FIG. 9A, though the armature lever 15 is set up with a counterclockwise inclination, the armature 1 is inclined clockwise by the above identified protuberance 15a so that the reactive surface 1a of the armature 1 never inclines from the parallel position with the attraction surface 2a of the yoke 2 to permit the reactive surface 1a to first contact the lower edge 2c of the yoke 2. Therefore, the armature 1 can be brought into stable attraction with the yoke 2. 
     In the reversed position of FIG. 9B, the reactive surface 1a of the armature 1 first contacts with the lower edge 2b of the yoke 2. Therefore, the stable attracting condition can be established no matter what attitude may be taken when in use. 
     Though the foregoing embodiments have been described in connection with the unified formation of the protuberance 11a, or 13a (13b), or 15a with the E type snap ring 11, 13, or armature lever 15, the protuberance may be formed otherwise as a unit on the upper end of the armature shaft 4, or a regulating member may be solely mounted and used on the armature shaft 4. Also, though the retaining member is in the form of an E type snap ring 11 or 13 utilizing the resilient property as the fastening force, another form may be employed so that fastening accomplished by caulking means. 
     The present invention is applicable to another type of electromagnetic device in which the yoke is made of permanent magnet. Even in this example of application, a similar advantage to that described in connection with the foregoing embodiments is obtained. It is to be noted in this connection that in this type of electromagnetic device, when the coil is de-energized, the yoke attracts the armature, and when the coil is energized, the attraction of the yoke to the armature is released by the force of a bias spring. 
     Also, though, in the foregoing embodiments, the attractive surface of the yoke is taken as a reference for regulating the inclination of the armature, the inclination of the yoke may be controlled otherwise in reference to the armature, thereby a similar advantage can be obtained. 
     As has been described above, according to the present invention, use is made of a regulating member for inclining the armature with respect to the armature shaft so that the gap between the attraction surface of the electromagnet and the surface to be attracted of the armature is wider at the upper end than at the lower end as viewed from the direction in which gravity works, thereby giving an advantage that in any angular position, the armature can be brought into and maintained stable in contact with the electromagnet without producing any stress in the armature shaft and the armature lever.