Expansible chamber devices – Collapsible chamber wall portion – Wall portion formed of flexible material
Reexamination Certificate
2002-11-18
2004-08-10
Lazo, Thomas E. (Department: 3745)
Expansible chamber devices
Collapsible chamber wall portion
Wall portion formed of flexible material
Reexamination Certificate
active
06772673
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flexible actuator that can be used for driving a robot capable of gripping, pinching, or pushing and a pet robot that acts like an animal.
2. Description of the Related Art
As described in Japanese Patent Laid-Open No. 5-172118 and Japanese Patent Laid-Open No. 5-164112, known actuators for gripping an object include a cylindrical elastic body having a plurality of pressure chambers therein and adjust a fluid pressure applied to each pressure chamber to curve and deform the cylindrical elastic body (hereinafter referred to as the first prior art).
Further, as described in Japanese Patent Laid-Open No. 2-17204, an actuator different from the first prior art is also known in which a driving source and a pump are integrated into a hydraulic cylinder (hereinafter referred to as the second prior art).
An actuator that operates as a robot finger of a robot must bend like a human finger, and enclose to grip a soft object such as a fruit or a paper cup, pinch a small object such as a screw with its tip, or bend to push a switch with its tip. In gripping the paper cup with the entire robot finger, a substantially even bending force is desirably produced throughout the finger. On the other hand, in pinching the object with the tip, a bending force proportional to a distance from the tip is desirably produced in terms of moment. Reducing the bending force at the tip saves power for bending.
However, in the first prior art, the actuator entirely bends with a predetermined curvature to grip the object, and do not have a structure in which an appropriate bending force is produced at each part. Thus, it is difficult to configure an actuator capable of performing various operations such as enclosing to grip the soft object, pinching the small object, or pushing the switch with the tip, with appropriate gripping forces like the human finger.
The second prior art is of the piston type, and requires many actuators and associated sensors or mechanisms to configure a flexible actuator, so that it is difficult to cause the actuator to operate as a robot finger.
Even if the actuators according to the first prior art and the second prior art are to be manufactured as pet robots that finely act like animals, many sensors and complex mechanisms must be provided to cause complex appearances.
Further, in the first prior art and the second prior art, an operating fluid must be supplied to the pressure chamber, or a pump that discharges the operating fluid from the pressure chamber must be placed outside via a fluid tube (referred to as an operating tube in the specification of the prior art) which cannot provide a small actuator. Thus, it is difficult to use the actuator as the pet robot that finely acts like an animal.
When a liquid is used as the operating fluid of the first prior art and the second prior art, a reservoir that stores the liquid is placed outside together with the pump. Between when the reservoir is above the pressure chamber (hereinafter referred to as a main liquid chamber) and when the reservoir is below the main liquid chamber, amounts of liquid supplied and discharged to and from the main liquid chamber by gravity change depending on changes in positions of the cylindrical elastic body. Thus, each change in the position of the cylindrical elastic body tends to cause a change in an amount of bending deformation.
The present invention has been achieved to solve the above described problems in the prior art, and has an object to provide a flexible actuator capable of gripping a soft object like a human finger and finely acting like an animal, and also avoiding a change in an amount of liquid moving between a reservoir and a main liquid chamber by gravity even if a liquid is used as an operating fluid, and keeping a constant amount of bending deformation even if the actuator changes its position.
SUMMARY OF THE INVENTION
To solve the problems, a flexible actuator according to the invention has the following configuration. Specifically, the flexible actuator according to the invention includes: a long movable part that is bent by a liquid moving toward a main liquid chamber; a reservoir where the liquid moves to and from the main liquid chamber; a pump that moves the liquid between the reservoir and the main liquid chamber; and a pump driving unit that controls the pump, wherein the movable part includes a long tube that forms the main liquid chamber, a plurality of frame members aligned at predetermined intervals along a length of the tube, and a resilient core member that holds the alignment of the frame members, the tube is made of a flexible elastic material, and includes a plurality of flat expanded hollow portions provided at predetermined intervals along the length and a narrow hollow portion that communicates between the expanded hollow portions, the plurality of frame members are formed by flat members and longitudinally hold the plurality of expanded hollow portions by the narrow hollow portion of the tube inserted into recesses or holes provided on sides abutting the core member, the movable part has a first bending portion that produces a large bending force and a second bending portion that produces a small bending force, the expanded hollow portion placed in the first bending portion has a large transverse cross sectional area, and the expanded hollow portion placed in the second bending portion has a small transverse cross sectional area.
According to the invention, the expanded hollow portion placed in the first bending portion has the large transverse cross sectional area, and the expanded hollow portion placed in the second bending portion has the small transverse cross sectional area, so that the first bending portion produces the large bending force and the second bending portion produces the small bending force simply by a fluid flowing into the tube to increase capacities of the expanded hollow portions, thus allowing operations different from those of a conventional actuator.
The flexible actuator may be used as a robot finger or the like, and the expanded hollow portion at a base of the movable part as the first bending portion may have a largest transverse cross sectional area, with transverse cross sectional areas of the expanded hollow portions gradually decreasing toward a tip of the movable part, and the expanded hollow portion at the tip of the movable part as the second bending portion may have a smallest transverse cross sectional area.
When the flexible actuator with such a configuration is used as the robot finger, the base of the movable part that is a root of the robot finger produces a large bending force, and the tip of the movable part that is a tip of the robot finger produces a small bending force to bend. This allows the actuator to reliably enclose to grip a soft object, pinch a small object, or push a switch with the tip, and act like a human finger.
The transverse cross sectional area of the expanded hollow portion placed in the second bending portion may be 30% to 80% of the transverse cross sectional area of the expanded hollow portion placed in the first bending portion.
In this way, providing the second bending portion at the base prevents a large force to fold the base from being applied in gripping the object, thus allowing the object to be properly gripped. Further, an average sectional area at the tip that requires no large bending force is small, thus a total amount of hydraulic fluid required for bending decreases to allow quick bending and extension.
The core member may be a member having gradually decreasing resilience from the base toward the tip of the movable part. Alternatively, the core member may be a tapered plate material in which a base has a large width, with widths gradually decreasing toward a tip, and the tip has a smallest width.
This exerts no influence on bending displacement of the movable part. When the movable part bends under a no-load or light-load condition, the core member having the large width at the base prevents the
Seto Takeshi
Takagi Kunihiko
Lazo Thomas E.
Oliff & Berridg,e PLC
Seiko Epson Corporation
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