NTN: Patent Issued for Link Actuation Device
Resource from: NTN Likes:255
Jul 16,2015
NTN CORPORATION (Osaka, JP) has been issued patent number 9073204, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.
The patent's inventors are Isobe, Hiroshi (Iwata, JP); Ozaki, Takayoshi (Iwata, JP).
This patent was filed on May 11, 2011 and was published online on July 7, 2015.
From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention relates to a link actuating device that may be used in a link mechanism such as, for example, a parallel link mechanism or a robot articulated joint which executes a work such as a complicated processing or article handling in a three dimensional space at high speed and with precision.
"One example of processing machines utilizing a parallel link mechanism is disclosed in the patent document 1 listed below. The processing machine disclosed therein is of a type in which the movement and the change in posture of a movable part are effected by means of the parallel link mechanism, and the movable part thereof has mounted thereon a tool as an end effecter, an electric generator for generating an electric power used to actuate the tool, a servomotor for supplying a motive power to the electric generator and so on."
Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "In view of the foregoing, the present invention is intended to address to the provision of a link actuating device that is structured as a two-degree-of-freedom mechanism having a movable part movable in two axial directions perpendicular to each other, which movable part has a large range of movement, is lightweight and can be positioned accurately.
"The link actuating device designed in accordance with the present invention a link actuating device for connecting an output member relative to an input member through three or more sets of link mechanisms for alteration in posture, which actuating device includes each of the link mechanisms comprising end portion link members on an input side and an output side each member having an one end thereof rotatably connected respectively with the input member and the output member, an intermediate link member to which the other ends of the respective end portion link members on the input side and the output side are rotatably connected, a geometrical model, in which each of the link members is expressed by a line, representing a shape that an input side portion and an output side portion of the intermediate link member relative to a center portion of the intermediate link member are symmetrical with each other. The link actuating device of the present invention also includes a link mechanism drive source provided in two or more sets of link mechanisms in the three or more sets of the link mechanisms for actuating each of the link mechanisms of the two or more sets to control the posture of the output member and a flexible wire passed inside an arrangement of the three or more sets of the link mechanisms and having a flexibility and operable to transmit a rotational force in a direction along a direction of arrangement of the input member and the output member. The output member referred to above is, for example, provided with a driven device adapted to be driven by a rotational force transmitted from the flexible wire. A drive mechanism of the driven device may be either a rotary mechanism or a direct acting mechanism.
"Also, the link actuating device of the present invention can be rephrased as follows. That is, the link mechanism is employed in three or more sets, in which mechanism the end link members are rotatably connected with the input member and the output member, which are provided on the input side and the output side, and the end portion link members on the input side and the output side, respectively are rotatably connected with the intermediate link member; with respect to a transverse sectional plane at a center portion of each of the link mechanisms, the input side and the output side of the link mechanism are made geometrically symmetrical to each other; of revolve pairs of each of the link mechanisms connected with the input member, two or more sets of the link mechanisms are provided with link mechanism drive sources for controlling the posture of the output member arbitrarily; and the flexible wire having a flexibility and capable of transmitting the rotational force from the input side to the output side is provided having been passed inside each of the link mechanisms.
"According to the above described construction, a two-degrees-of-freedom mechanism, in which a movable section comprised of the output member and others is movable in two axis directions perpendicular to each other, is constituted by the three or more sets of the link mechanisms and the link mechanism drive source provided in two or more sets of the link mechanisms. This two-degrees-of-freedom mechanism is such that the large range of movement of the movable section can be obtained. By way of example, the maximum working angle between the center axis of the input member and the center axis of the output member can take about .+-.90.degree. and the angle of turn of the output member relative to the input member can be set to a value within the range of 0 to 360.degree.. Since, of the revolve pairs of each of the link mechanisms that are connected with the input member, two or more sets of the link mechanism are provided with a link mechanism drive source for controlling the posture of the output member arbitrarily, the output member can be easily set to an arbitrary posture. The reason that the revolve pair of the link mechanisms which are provided with the link mechanism drive sources, respectively, is chosen in two or more sets is because it is essential for the pasture of the output member relative to the input member to be fixed.
"If the flexible wire having a flexibility is provided through the inside of each of the link mechanisms and the rotational force is transmitted from the input side to the output side through this flexible wire, the driven device provided in the movable section can be driven with no need to provide the drive source in the movable section. For this reason, the weight of the movable section can be reduced. As a result, the inertia moment acting on the link actuating device is reduced and compactization of the drive source for driving the link actuating device can be easily achieved. Also, if the movable section is lightweight, handing is easy and the positioning accuracy of the movable section is increased. In addition, where the driven device is provided in the movable section, this driven device and the drive source for the driven device can be installed at respective places distant from each other and, therefore, it is easy to keep the driven device in a clean condition.
"Since the flexible wire has a flexibility, it is possible to assuredly transmit the rotational force from the input side to the output side even though the posture of each of the link mechanisms is changed to control the position of the movable section. In case the end portion link members on the input side and the output side of each of the link mechanisms are made of spherical surface link mechanisms, respective spherical surface link centers of each of the link mechanisms coincide with each other, and the distances from those centers to associated end portion link members remain the same. Accordingly, even though the posture of each of the link mechanisms changes, the distances between the spherical surface link centers on the input side and the output side do not change and, therefore, no excessive axial force (tensile force) does not act on the flexible wire and the rotational force can be assuredly transmitted.
"In the present invention, a throughhole is preferably provided in each of the input member and the output member, in which case the flexible wire is passed through those throughholes in the input and output members. If the flexible wire is passed through respective throughholes in the input member and the output member, the flexible wire extends inside of each of the link mechanisms at all times even though each of those link mechanisms assumes any posture. Accordingly, an undesirable contact of the flexible wire with an extra member is prevented.
"In the present invention, the flexible wire is preferably guided by a wire guide member fixed to the intermediate link member and positioned inside each of the link mechanisms. Regardless of the posture each of the link mechanisms, the intermediate link members in at least two link mechanisms out of the three or more link mechanisms pass along a single circular trajectory. For this reason, if the flexible wire is guided by the wire guide member positioned inside each of the link mechanisms and fixed to the intermediate link members, interference between the flexible wire and an external member such as, for example, the intermediate link member and/or the end link members can be avoided.
"The wire guide member referred to above may have a center thereof provided at a position coinciding with a center of the circular trajectory of the intermediate link member. Since the center of the circular trajectory of the intermediate link member always lies on a straight line connecting between respective spherical surface link centers on the input side and the output side and the distance between the spherical link centers is constant even when the posture of each of the link members changes, positioning of the wire guide member in the manner described above makes it possible to arrange the flexible wire with the smallest distance at a position where no change in distance occurs.
"In the present invention, the flexible wire is recommended to have a flexible outer tube, a flexible inner wire having its opposite ends defining an input end and an output end for respective rotations and rotatably supported within the outer tube by means of a plurality of rolling bearings, and a spring elements provided between the neighboring rolling bearings for applying a preload to the rolling bearing. If the inner wire, which forms a rotary shaft of the flexible wire, is provided inside the outer tube, the inner wire can be protected. The use of the spring elements for rotatably supporting the inner wire through a plurality of rolling bearings and positioned between the neighboring rolling bearings is effective to prevent the natural frequency of the inner wire from being lowered, allowing the inner wire to be rotated at a high speed.
"The spring element referred to above includes preferably an inner ring spring element for applying the preload to an inner ring of the rolling bearing and an outer ring spring element for applying the preload to an outer ring, in which case the inner ring spring element and the outer ring spring element are to be alternately arranged in a direction lengthwise of the inner wire. Positioning the inner ring spring element and the outer ring spring element alternately in the direction lengthwise of the inner wire permits the spring elements to be provided without the diameter of the outer tube being unduly increased.
"A rotary drive source for rotating the inner wire may be provided on an input end side of the flexible wire and connected with the input end of the inner wire. The provision of the rotary drive source is effective to efficiently apply a torque to the inner wire.
"A reduction gear for reducing the rotation of the inner wire may be provided on an output end side of the flexible wire and connected with the output end of the inner wire. The provision of the reduction gear on an output end side of the flexible wire is effective to allow a high torque to be generated even though the torque to be transmitted by the inner wire is low. For this reason, when the driven device having a rotary mechanism is installed on the output side of the reduction gear, a large rotation torque can be obtained, and meanwhile, when the driven device having a direct acting mechanism is provided on the output side of the reduction gear, a large thrust force can be obtained. Since against the friction occurring in the rotary mechanism and/or the direct acting mechanism a force necessary to overcome such friction can be generated, stick slip phenomenon will hardly occur even though the torsional rigidity of the inner wire is low. Also, the provision of the reduction gear makes it possible to use a thin inner wire and, with a compactized structure, the flexible wire having a further high flexibility can be realized. In addition, as the rotation drive source to be installed on the input side of the flexible wire, a compact and an inexpensive motor can be employed.
"In addition, where the operating position of the drive mechanism for the rotary mechanism or the direct acting mechanism for the driven device is controlled by a feedback scheme, the following functions and effects can be obtained. Specifically, since the speed of the driving force is reduced by the reduction gear before the driving force is transmitted to the output side, influences brought about by twisting of the inner wire, which appear on an output shaft of the reduction gear, are minimized and the positioning resolution of the operating position of the drive mechanism is high, thereby to achieve a high level feedback control.
"Since the link actuating device of the present invention has the functions and the effects both described above, it is suitable for use in medical equipments.
"By designing a remote controlled robot of a kind, in which an actuating device that can be driven by the rotational force transmitted from the flexible wire is provided in the output member of the link mechanism, this driven device can be operated by remote control."
(NTN)
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1.The news above mentioned with detailed source are from internet.We are trying our best to assure they are accurate ,timely and safe so as to let bearing users and sellers read more related info.However, it doesn't mean we agree with any point of view referred in above contents and we are not responsible for the authenticity. If you want to publish the news,please note the source and you will be legally responsible for the news published.
2.All news edited and translated by us are specially noted the source"CBCC".
3.For investors,please be cautious for all news.We don't bear any damage brought by late and inaccurate news.
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