Linear oscillating actuator

The present invention is directed to a linear oscillating actuator with an oscillator movably supported to a stator assembly by means of a spring link.

EP 0 674 979 A discloses a linear oscillating actuator utilized for driving inner cutters of a dry shaver. The actuator is composed of a stator assembly carrying an electromagnet, and an oscillator carrying a permanent magnet. The oscillator is movably supported to reciprocate in a linear path relative to the stator assembly by an interaction with the electromagnet and the permanent magnet. The stator assembly includes a stator core and a frame which projects on top of the stator core for suspending the oscillator upwardly of the stator core with a magnetic gap therebetween. In order to suspend and also to movably support the oscillator, leaf springs are utilized to connect the oscillator to the frame. Although the leaf springs are sufficiently resilient to allow the movement of the oscillator along the linear path, they are rigid in directions other than along the linear path. In view of that the linear movement of the oscillator may sometimes accompany minor displacements in the directions other than along the linear path, the leaf spring are likely to suffer from undue stresses resulting from the displacements. In this sense, the above actuator is found not satisfactory to absorb incidental vibrations associated with such displacements.

In view of the above problem, the present invention has been accomplished to provide a linear oscillating actuator which is capable of giving a smooth reciprocator movement with a minimum of incidental vibrations or stresses. The actuator in accordance with the present invention includes an oscillator carrying a permanent magnet as well as an output shaft which is adapted to be connected to drive a load, and a stator assembly carrying an electromagnet. The electromagnet generates a magnetic field which interacts with the permanent magnet to reciprocate the oscillator relative to the stator assembly in a linear path. A spring link is provided to resiliently support the oscillator to the stator assembly with a gap distance left therebetween for allowing the oscillator to reciprocate in the linear path. The spring link is configured to deform resiliently also in a direction other than along the linear path so as to allow the oscillator to move to and away from the stator assembly or to twist relative to the stator assembly about a gap axis running along the gap distance. Thus, the spring link can absorb incidental stresses or displacements from which the oscillator may suffer in the directions other than along the linear path, assuring to give a smooth reciprocatory movement to the oscillator with a minimum of fatigue accumulated in the spring link.

This is particularly advantageous when the oscillator is lifted above the stator assembly by means of the spring link. For instance, when the two spring links are provided to connect opposite ends of the oscillator respectively to the stator assembly, the two spring links project upwardly from the stator assembly to lift the oscillator above the stator assembly. In this case, the spring link is susceptible to a compressive or torsional force from the oscillator accompanied with the linear reciprocatory movement, and can absorb such incident stresses for smooth reciprocatory movement.

Preferably, the spring link is configured to deform resiliently in a gap direction of varying the gap distance for absorbing the compressive stress which may act on the spring link during the reciprocatory movement of the oscillator.

For this purpose, the sprig link may be shaped into a bow strip connected at its opposite ends to the oscillator and the stator assembly. Also, the spring link may be in the form of a strip of which width is greater towards its opposite ends than at its center. Further, the spring link may be formed at its connection to the oscillator with a resilient section responsible for resilient deformation in the gap varying direction. Alternatively, the spring link may be formed at its intermediate portion between the opposite ends thereof with a folded section responsible for the resilient deformation in the gap varying direction.

The spring link may be molded together with a molded part of the oscillator for reducing the number of components.

In case a parallel pair of oscillators are supported commonly to the stator assembly to reciprocate in a reverse phase relation with each other, the oscillators are interconnected to each other by means of a coupler spring for assisting the reverse phase relation. The coupler spring is resiliently deformed along the linear path as well as the gap varying direction for giving the function of absorbing the incidental stresses also by the coupler spring. In this version, the spring link and the coupler spring may be integrally molded together with a molded part of the oscillator for minimizing the number of components.

Further, the spring link may be configured to twist resiliently about its lengthwise axis for absorbing the torsional stresses acting on the spring link during the reciprocatory movement of the oscillator.

These and still other advantageous features of the present invention will become more apparent from the following description of the preferred embodiments when taken in conjunction with the attached drawings.

FIG. 1 is a perspective view of a linear oscillating actuator in accordance with a preferred embodiment of the present invention;

FIG. 2 is a front view of the actuator;

FIG. 3 is an exploded perspective view of the actuator;

FIG. 4 is a partial view of the actuator;

FIGS. 5 to 8 are front views respectively showing the actuators in accordance with other preferred embodiments of the present invention

FIGS. 9 to 11 are perspective views respectively showing the actuators in accordance with still other preferred embodiment of the present invention;

FIGS. 12 and 13 are perspective views respectively showing modifications of coupler springs applicable to the embodiment of FIG. 11 ; and

FIG. 14 is a perspective view of a portion of the actuator in accordance with a further embodiment of the present invention.

Referring now to FIGS. 1 to 3 , there is shown a linear oscillating actuator in accordance with a preferred embodiment of the present invention. The actuator includes two oscillators 30 commonly supported to a single stator assembly 10 to reciprocate in a reverse phase relation with each other, although the present invention is not limited thereto and may includes a single or more than two oscillators common to the one stator assembly 10 .

The stator assembly 10 carries an electromagnet 20 , while each oscillator 30 carries a permanent magnet 40 as well as an output shaft 36 for connection to a load to be driven to reciprocate in a linear path. For instance, the actuator may be incorporated in a dry shaver to reciprocate inner cutters relative to an outer cutter. The electromagnet 20 includes an E-shaped stator having a center core 22 and a pair of side cores 23 . A coil 24 is wound around the center core 22 to magnetize pole ends at the respective upper ends of the center and side cores to opposite polarity upon being energized.

Each oscillator 30 is molded with a plastic material into a horizontally extending bar 31 having the output shaft 36 extending from its top center. The permanent magnet 40 is backed-up by a magnetic yoke 42 secured to the bottom of the bar 31 . Each oscillator 30 is movably supported to the stator assembly 10 by means of spring links 50 so as to position the permanent magnet 40 just above the cores of the electromagnet 20 with a small magnetic gap therebetween. Upon being supplied with an alternating current, the electromagnet 20 generates an alternating magnetic field which interacts with the permanent magnets 40 for reciprocating the oscillator 30 relative to the stator assembly 10 in the respective linear paths. The permanent magnets 40 , each in the form of a horizontally extending flat bar, are magnetized to opposite directions so that the oscillators 30 are driven in a counter reciprocating manner, i.e., in the reveres phase relation with each other.

The spring links 50 depend respectively from the opposite lengthwise end of the bar 31 and are fixed at their lower ends to flanges 26 integrally projecting from the side cores 23 , whereby the oscillator 30 is lifted above the stator assembly 10 and is allowed to reciprocate in the linear path by resiliently deforming the spring links 50 . The spring link 50 is molded into a single integrated structure composed of a vertical strip 51 and upper and lower bridges 52 and 53 extending horizontally from the upper and lower ends of the strip 51 . The upper bridge 52 is bonded to the lengthwise end of the bar 31 , while the lower bridge 53 terminates at a thickened mount 54 fastened to the flange 26 by pins 28 . The strip 51 and the bridges 52 and 53 are responsible for imparting resiliency to the spring link 50 with respect to the direction along the linear path as well as along a gap distance between the permanent magnet and the electromagnet 20 , as best shown in FIG. 4 . Thus, the spring link 50 can absorb the incidental displacement of the oscillator 30 which may be associated with the reciprocatory movement thereof.

Described hereinafter are other embodiments in which the spring links are configured to deform resiliently for absorbing the incidental displacement as well. Like parts are designated by like reference numerals and no duplicate explanation is deemed necessary.

In the embodiment of FIG. 5 , the spring link 50 A includes a vertical strip 51 A which is configured to give a thickness which is smaller toward its lengthwise center than at the opposite lengthwise ends.

In the embodiment of FIG. 6 , the spring link is shaped into an L-shaped member 50 B with a like vertical strip 51 B and a upper bridge 52 B. In this embodiment, the flange 26 B of reduced thickness projects from each side core 23 B to be integrated into the lower end of the vertical strip 51 B, and is cooperative with the vertical strip 51 B and the upper bridge 52 B to give resilient deformability with respect to the gap distance in addition to the linear path.

In the embodiment of FIG. 7 , the sprig link is shaped into a bow strip 50 C.

In the embodiment of FIG. 8 , the spring link 50 D is shaped to have a folded section 56 at its intermediate portion between the opposite lengthwise ends. With the inclusion of the folded section 56 , the spring link is given capability of being resiliently deformed in its lengthwise direction, i.e., along the direction of the gap distance to a greater extent for absorbing the compressive stresses acting on the oscillator, even without relying upon the deformations of the upper and lower bridges 52 D and 53 D.

In the embodiment of FIG. 9 , the spring link 50 E is shaped to have a width which is narrower towards its lengthwise center than at the opposite lengthwise ends.

FIG. 10 illustrates a further embodiment in which the spring links 50 F are molded integrally with the bar 31 F of the oscillator 30 for reducing the number of components.

FIG. 11 illustrates a still further embodiment in which the two oscillators 30 are interconnected by means of coupler springs 60 which assist the reverse phase relation between the two oscillators. The coupler spring 60 is configured to resiliently deform, in response to the linear movement of the one of the oscillators, so as to add a resulting bias to the other oscillator moving in the opposite direction for driving the load at an optimum maximum output efficiency. The coupler spring 60 is molded from a plastic material into a U-shaped structure having legs 61 connected by a web 62 , and is welded to the adjacent lengthwise ends of the oscillators 30 at joints 64 respectively formed at the upper ends of the legs 61 . With the U-shaped structure, the coupler spring 60 is given resilient deformability which allows the oscillators 30 to move relative to each other in a lengthwise direction of the oscillator as well as the vertical direction. Thus, the oscillators 30 can move along the linear path as well as the gap varying direction without being restricted by the coupler springs 60 . Preferably, the coupler springs 60 are integrally molded together with the spring links 50 and with the bars 31 of the oscillators 30 .

FIG. 12 illustrates a modified coupler spring 60 G which may be equally utilized to interconnect the two oscillators 30 with an added feature of absorbing a twisting displacement possibly acting over the two oscillators. For this purpose, each leg 61 is connected to the joint 64 by means of horizontal beam 65 of reduced thickness which permits the joints 64 and therefore the oscillators 30 to move laterally relative to each other. Thus, the coupler spring 60 is given a capability of affording the lateral displacement between the oscillators, in addition to the vertical displacement therebetween, thereby enabling to absorb the twisting displacement in combination of the lateral and vertical displacements, while permitting the two oscillators 30 to move towards and away from each other.

Further, as shown in FIG. 13 , the coupler spring 60 H may be shaped to have twisted beams 66 at the connection of the legs 61 to the joints 64 in order to effectively absorb any possible unintended displacement between the two oscillators 30 . The twisted beam 66 is configured to have a reduced thickness with respect to the length as well as width directions of the oscillator to have the resilient deformability in both of the directions, and is cooperative with the given deformability in the vertical direction to absorb the unintended displacements acting between the two oscillators 30 .

FIG. 14 illustrates a still further embodiment of the present invention in which the spring link is in the form of a torsion spring 50 J which exhibits resilient torsional deformability about its lengthwise axis as indicated by an arrow in the figure, allowing the oscillator 30 to pivot about an axis along the gap distance to some extent relative to the stator assembly 10 . Whereby, possible torsional displacement of the oscillator can be absorbed at the spring link 50 J for assuring smooth reciprocatory movement of the oscillator 30 .