Geometrical instruments – Distance measuring – Scale reading position sensor
Reexamination Certificate
2000-04-24
2001-10-30
Hirshfeld, Andrew H. (Department: 2859)
Geometrical instruments
Distance measuring
Scale reading position sensor
C033S706000, C033S783000, C033S811000, C033SDIG002
Reexamination Certificate
active
06308431
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an air chuck for gripping a workpiece by a plurality of jaw components which are opened and closed by the action of an air pressure. More specifically, the invention relates to an air chuck with a measuring function capable of measuring the dimension, shape, and the like of a workpiece gripped.
PRIOR ART
An air chuck for gripping a workpiece by a plurality of jaw components which are opened and closed by the action of an air pressure is conventionally well known. For example, Japanese Registered Utility Model Publication No. 3023059 discloses an air chuck of this kind in which a pair of parallel piston rods which extend/contract synchronously with each other in the opposite directions by the action of an air pressure are provided in a casing having a rectangular parallelepiped shape, a jaw component is attached to the tip of each of the piston rods protruding from end faces of the opposite sides of the casing, and a workpiece is gripped by the pair of jaw components which are opened and closed according to the extension/contraction of the piston rods. In the air chuck, for a smooth opening/closing operation of the jaw components, a pair of guide rods which synchronously extend and contract in the opposite directions by a rack-and-pinion mechanism are mounted in the casing, the tips of the guide rods are connected to the jaw components, and the opening/closing operation of the jaw components is guided by the guide rods.
Since the interval between the jaw components, the opening/closing stroke, and the like are set to relatively large values, the air chuck has an advantage such that workpieces having different dimensions can be certainly gripped. Although the air chuck can grip workpieces of various dimensions, the air chuck cannot recognize the dimension of a workpiece gripped. Consequently, the air chuck cannot select workpieces of different dimensions by its dimension and cannot center the workpiece.
If an opening/closing stroke of the jaw components is measured by an electric or magnetic means, the dimension of a workpiece can be measured. When dedicated measuring means is assembled, however, the structure of the chuck is complicated and the size is also enlarged.
DISCLOSURE OF THE INVENTION
A technical subject of the invention is to provide an air chuck having a simple, rational design structure capable of measuring the dimension of a workpiece gripped.
In order to achieve the above subject, according to the invention, there is provided an air chuck comprising: a casing having therein a pair of cylindrical holes and a pair of guide holes; pistons slidably housed in the above cylindrical holes and synchronously driven in opposite directions; a pair of piston rods which are integrally connected to the pistons and whose tips are protruded in opposite directions from both end faces of the casing; a pair of guide rods which are slidably inserted in the guide holes and whose tips are protruded in opposite directions from both end faces of the casing; racks formed in the above guide rods; a pinion which meshes with each of the racks; a pair of jaw components commonly attached to the tips of the piston rods and the tips of the guide rods on both end faces of the casing; a magnetic scale which is formed on a side face of one of the guide rods; and a sensor unit for reading the magnetic scale.
The air chuck of the invention having the above construction can measure the dimension of a workpiece gripped by the pair of jaw components by reading the magnetic scale on the guide rod which slides together with the jaw components by a sensor unit. By gripping a workpiece at a plurality of sites to measure the dimensions at the gripped positions, the shape of the workpiece can also be determined.
When the air chuck is provided with the dimension measuring mechanism, by providing the magnetic scale on the guide rod as guiding means for making the opening/closing operation of the jaw components smooth, the guide rod is used as a part of the dimension measuring mechanism, so that it is unnecessary to separately provide a rod dedicated to the magnetic scale. Consequently, the air chuck with the dimension measuring mechanism can have a very simple and rational design structure. Moreover, the air chuck is prevented from being enlarged by attaching the dimension measuring mechanism.
According to an embodiment of the invention, the casing has a substantially rectangular parallelepiped shape, the pair of guide rods and the pair of pistons and piston rods are arranged in upper and lower stage in the casing, the top face of the casing serves as an attaching face to be attached to a robot arm, and the sensor unit is attached in a position corresponding to the guide rod with the magnetic scale on the side face of the casing, at a height at which the sensor unit is not protruded upward from the top face of the casing.
Consequently, the dimension measuring mechanism can be easily assembled in the air chuck without largely modifying a known air chuck and without causing a problem such that the sensor unit becomes an obstruction when the air chuck is attached to a robot arm.
According to another embodiment of the invention, the sensor unit comprises: a read head having a sensor for reading the magnetic scale in a sensor case; and an amplifying unit having an amplifying circuit for amplifying a read signal from the read head in an amplification case. The above read head is fixed in a head attaching hole formed in the casing, and the amplifying unit is fixed in the casing in order to cover the whole read head with the amplification case in a state where a waterproof seal is interposed between the amplification case and the casing.
By attaching the sensor unit to the casing in such a mode, the read head is completely protected from moisture by the amplification case and the waterproof seal. Consequently, even when the air chuck is used in a high-moisture environment, it is prevented that moisture enters the read head and exerts an adverse influence on measurement. Thus, high measurement accuracy can be maintained.
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Hagiwara Katsumi
Kanda Kouichirou
Takanashi Seiji
Guadalupe Yaritza
Hirshfeld Andrew H.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
SMC Corporation
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