Electricity: motive power systems – Positional servo systems
Reexamination Certificate
2000-09-05
2001-12-18
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Positional servo systems
C318S568100, C318S568110, C318S568210, C414S749200, C414S752100, C414S755000, C414S760000
Reexamination Certificate
active
06331758
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electric hand in which a pair of jaw members for grasping a workpiece are opened and closed by an electric motor and more specifically to an electric hand with a cushioning function in which application of impact to a motor drive shaft is prevented when the jaw members stop at opening and closing ends, grasping positions of the workpiece, and the like.
PRIOR ART
A hand for grasping a workpiece between a pair of jaw members that can be opened and closed is generally formed such that the jaw members are opened and closed by an air cylinder.
However, because a prior-art hand with such a structure requires accompanying equipment such as air piping for the air cylinder and a direction selector valve for controlling supplying/discharging of compressed air to and from the piping and the number of parts constituting the hand itself increases. Therefore, miniaturization of the hand is difficult and it is also difficult to make an entire system compact, the system including the accompanying equipment for allowing operation of the hand.
To solve the above problems, the present inventors proposed an electric hand in which a pair of jaw members for grasping a workpiece were opened and closed by an electric motor (Japanese Patent Application No. 10-357778). In this electric hand, a converting mechanism for which a cam is used is provided between a drive shaft of the electric motor and the jaw members and a reciprocating rotating motion of the drive shaft is converted to opening/closing motions of the jaw members by the converting mechanism.
In such an electric hand, a motor with a speed reducer having a plurality of gears is used as the electric motor in order to increase force for grasping the workpiece by the jaw members. If such a motor with gears is used, a large inertial force due to a rotor of the motor acts when the jaw members stop at opening and closing ends, grasping positions of the workpiece, and the like and the gears of the speed reducer may be damaged by impact.
DISCLOSURE OF THE INVENTION
It is a technical object of the present invention to provide an electric hand in which jaw members for grasping a workpiece are opened and closed by a motor, wherein an inertial force applied to a motor drive shaft when the jaw members stop at opening and closing ends, grasping positions of the workpiece, and the like can be absorbed and damage to motor parts such as gears due to impact is prevented.
To achieve the above object, an electric hand of the present invention comprises a pair of jaw members that are for grasping a workpiece and can be opened and closed, an electric motor having a rotating drive shaft, and a converting mechanism disposed between the drive shaft and the jaw members for converting a reciprocating rotating motion of the drive shaft to opening/closing motions of the jaw members, wherein the converting mechanism has a cam member mounted to the drive shaft of the electric motor, a pair of cam grooves formed in the cam member, and pins respectively mounted to the respective jaw members, respectively fitted into the respective cam grooves, and displaced in the cam grooves in an opening/closing direction of the jaw members by reciprocating rotation of the cam member, and cushioning means for absorbing impact that acts on the drive shaft when the cam member stops at swinging ends is provided between the drive shaft and the cam member.
According to a concrete embodiment of the invention, the cushioning means includes an inner cylinder member with a small diameter that is mounted to the drive shaft, an outer cylinder member with a large diameter that is provided to the cam member and fitted with the inner cylinder member such that the outer cylinder member can rotate with respect to the inner cylinder member, and an elastic body that is engaged with the inner cylinder member and the outer cylinder member between both the members and has a function of connecting both the members and a function of absorbing impact.
More specifically, arc-shaped depressions are formed in a plurality of positions facing each other on an inner face of the outer cylinder member and an outer face of the inner cylinder member and the elastic body having a columnar shape is housed in each of the depressions. In this case, it is preferable that each the depression in the inner cylinder member has a larger radius of curvature than each the depression in the outer cylinder member and edge portions of each the depression in the inner cylinder member are rounded.
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patent: 2000-23391A (2000-08-01), None
Kanda Koichiro
Miyachi Hiroshi
Takanashi Seiji
Nappi Robert E.
Oblon, Spivak, McClelland, Maier & Neustadt PC.
SMC Corporation
Smith Tyrone
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