Rotary Type Photoelectric Switch

1. Field of the Invention

This invention relates to a photoelectric switch, and more particularly to a rotary type photoelectric switch which is operated by the clockwise and counterclockwise rotation of a shaft.

2. Discussion of the Related Art

There are well known photoelectric switches which contain a light emitting element, a light receiving element, and a light interrupting element slidably provided therebetween. Referring to a conventional photoelectric switch shown in FIG. 1, a push button 1 is pressed against a return spring 2, so that a movable piece 3 pulled by a coil spring 4 acts downwardly in a snap movement. A light interrupting element 5 coupled with movable piece 3 vertically passes down such that a window 6 of the interrupting element 5 moves to the point where a light emitting from an LED 7 is received by a photo-diode 8, thus completing a switch circuit. The switch circuit is broken by releasing push button 1.

However, as denoted by A to D in FIG. 1, many pivots and connections are required to perform such a snap movement, which causes wear or abrasion of contacting parts at such connections, shortening the life of the conventional photoelectric switch.

It is an object of the present invention to provide a photoelectric switch which incorporates a rotary mechanism therein so that the number of connections and moving parts can be reduced, and the life of the switch can be extended.

Another object of the invention is the provision of stoppers for a rotary shaft which are disposed remote from the central axis of a rotary shaft so as to easily and accurately regulate the stroke range of the rotary shaft.

A further object of the invention is the provision of a coil spring the bases of which are so arranged that the spring will expand and contract in a wavy manner, thus preventing a malfunction of a switch caused by the bouncing or rebounding action of a light-interrupting plate.

An alternative object is to provide a magnet on the housing to also reduce bounce.

According to one form of the invention, there is provided a rotary type photoelectric switch comprising a rotary shaft rotated by external force, a light-interrupting plate coupled to the rotary shaft, a light-emitting element for emitting light, and a light-receiving element for receiving the light from the light-emitting element, wherein the light-interrupting plate by the rotary movement thereof enters into and exits from the lightpath formed between the light-emitting element and the light-receiving element. Finally, a wavy spring or a magnet is provided to reduce bounce.

The above and other objects and advantages of the rotary type photoelectric switch according to the instant invention will become apparent from the following description taken together with the accompanying drawings, wherein:

FIG. 1 is a side view showing a prior form of a photoelectric switch;

FIG. 2 is a side view showing the appearance of a rotary type photoelectric switch of the instant invention;

FIG. 3 is a sectional view of one form of the rotary type photoelectric switch of FIG. 2 in which the switch is in the Free position (FP);

FIG. 4 is a sectional view of the rotary type photoelectric switch of FIG. 3 in which the switch is in the Total Travel Position (TTP);

FIG. 5 is an exploded-perspective view of the rotary type photoelectric switch of FIG. 3;

FIG. 6 is an electric circuit diagram of FIG. 2;

FIG. 7 is a graph illustrating the magnitude of spring load in relation to the stroke of the light-interrupting plate ranging from the Free Position to the Total Travel Position;

FIG. 8 is a sectional view of an alternative form of the switch shown in FIG. 2 in the Free Position;

FIG. 9 is a sectional view of the switch of FIG. 8 in the Total Travel Position; and

FIG. 10 is an exploded perspective view of the switch of FIG. 8.

A first embodiment of this invention will now be described with reference to FIG. 2, FIG. 3, FIG. 4, FIG. 5 and FIG. 6.

FIG. 2 is a side view of a rotary type photoelectric switch according to this invention, in which a lever 10 is linked to a rotary shaft 15, the shaft being rotated by the lever 10. Referring to FIGS. 3, 4, and 5, there are shown internal components housed in a switch case 12 of the photoelectric switch. Among the components housed in switch case 12 are a light-emitting diode 13 (LED), a phototransistor 14, the rotary shaft 15, a light-interrupting plate 16 connected to rotary shaft 15, a coil spring 17 for returning light-interrupting plate 16 to its original position, a plurality of leads 18, 19 and 20, a plurality of terminals 21, 22, and 23, and a switch cover 24 which covers these components. Cover 24 has a resilient leg 24a which is designed to spring-into a recess 12a having a holding notch 12b cooperating with an upturned segment 24b on leg 24a.

One end of rotary shaft 15 extends exterior of switch case 12 and coupled to lever 10. Another end 15a of rotary shaft is fixed to light-interrupting plate 16 at 16a such that a light-interrupting portion 25 formed at the tip of plate 16 will swing together with rotary shaft 15 so as to enter into and exit from the lightpath 28 formed between LED 13 and phototransistor 14.

The light-interrupting portion 25 formed by bending the tip of light-interrupting plate 16 is slidably engaged in a circular groove 27, a portion of which is cut to provide the lightpath 26. As light-interrupting plate 16 swings, the portion 25 slides along the circular groove 27.

Normally, the photoelectric switch is in an off-state as shown in FIG. 3, wherein light-interrupting plate 16 is biased by coil spring 17 so as to be in a position wherein the light of LED 13 is prevented by light-interrupting portion 25 from reaching phototransistor 14. Coil spring 17 is pressurized between an upper spring base 30 formed at one end of light-interrupting plate 16 and a lower spring base 31 formed on switch case 12.

As light-interrupting plate 16 rotates against the spring force in response to the external force applied to lever 10, light-interrupting portion 25 rotates clockwise so that the light emitted from LED 13 is received by phototransistor 14 to bring the switch into an on-state as shown in FIG. 4.

As shown in FIG. 6, LED 13 is electrically connected between an input lead 20 and an output lead 19, while phototransistor 14 is connected between an input lead 18 and an output lead 19. Actually, as the leads of LED 13 and phototransistor 14 are too thin to directly connect with leads 18, 19, and 20, terminals 21, 22, and 23 are provided therebetween which merely serve as relay terminals for relaying a signal from input leads 18 and 20 to the thin leads and from the thin leads to said output lead 19.

The light-interrupting plate 16 also acts as a lever for regulating the range of stroke thereof. The clockwise and counterclockwise rotation of light-interrupting plate 16 is interrupted by a stopper 28 at free position (FP) and a stopper 29 at total travel position (TP).

Stoppers 28 and 29 may be formed integrally with switch case 12. These stoppers are provided remote from rotary shaft 15 and are respectively disposed to come into contact with each side of the end of light-interrupting plate 16 close to interrupting portion 25. It should be noted that the accuracy of stroke range between FP and TTP at the position of the tip of lever 10 can be improved by providing stoppers 28 and 29 as far from the central axis of rotary shaft 15 as possible.

Referring to FIGS. 3 and 4, each end of coil spring 17 is so supported by upper spring base 30 and lower spring base 31 such that the spring 17 will "meander" or expand and contract in a wavy or non-straight line, light-interrupting plate 16 rotates in both directions. More specifically, upper spring base 30 is provided to face in a different direction with respect to the direction to which lower spring base 31 faces.

Thus, as coil spring 17 expands to rotate light-interrupting plate to its Free Position, the expansion force does not concentrate into a single direction, thereby reducing the torque of light-interrupting plate 16 around rotary shaft 15. As a result, sharp contact between light-interrupting plate 16 and FP stopper 28 does not occur so that malfunction of the photoelectric will not be caused by bouncing action of plate 16. The expansion and contraction of coil spring 17 is guided by switch case 12 and switch cover 24.

FIG. 7 shows the relationship between the spring load of coil spring 17 and the stroke of light-interrupting plate 16 ranging from FP to TTP. In general, the spring load increases as plate 16 comes close to TTP. In this invention, however, the spring load is kept almost constant over the range of the stroke because coil spring 17 "meanders," whereby undesirable bouncing of plate 16 can be eliminated.

Referring to FIGS. 8-10, an alternative embodiment is illustrated. Like numbers refer to like parts.

The cover 24 includes a second leg 24c with a downturned segment 24d cooperating with a complimentary holding notch 12c, on casing 12, the reverse of 12b. A third leg 24e has an opening 24f therein to engage a projection (not shown) on the bottom of casing 12. All legs are resilient and snap-in to complementary projections or notches on the casing 12.

Also seen mounted on the inner surface of cover 24 is a permanent magnet 32. Magnet 32 is positioned very close to FP stopper 28. The purpose of the magnet is essentially the same as spring 17 in FIGS. 3-5, thus permitting the use of a different spring 17', if desired, in FIGS. 8-10. When force is exerted on actuator/lever 10', the lever follows the arrow in FIG. 9 and moves from the position seen in FIG. 8. When force is removed from lever 2, the restoring spring 17' moves the plate 16 back from the position in FIG. 9 to that in FIG. 8. Under normal conditions the speed of the plate 16 increases as it moves close to the FIG. 8 position. Thus, bouncing can occur and yield false signals. By placing the magnet 32 close to stopper 28 in the position seen in FIG. 8, a magnetic force will be exerted on the metal plate to generally hold it in place and prevent, or at least greatly diminish, bouncing.

While several embodiments of the invention have been described, it will be understood that it is capable of further modifications, and this application is intended to cover any variations, uses, or adaptations of the invention, following in general the principles of the invention and including such departures from the present disclosure as to come within knowledge or customary practice in the art to which the invention pertains, and as may be applied to the essential features hereinbefore set forth and falling within the scope of the invention or the limits of the appended claims.