Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Patent
1998-11-24
2000-11-28
Allen, Stephone B.
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
2502221, 356375, 414737, 29407, G01N 2186, B66C 100, B23Q 1722
Patent
active
061538876
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an attraction object detection apparatus and an attraction object detection method which can detect whether or not an attraction object is present, and more particularly to an attraction object detection apparatus and an attraction object detection method suitable for use with an IC test handler which has an attracting transport arm.
BACKGROUND ART
Conventionally, an attraction object to be transported by an attracting transport arm is detected using, for example, a pressure sensor or a transmission type sensor.
Therefore, an attraction object detection apparatus which employs a pressure sensor is shown in (a) and (b) of FIG. 1 while another attraction object detection apparatus which employs a transmission type sensor is shown in FIG. 2, and their constructions and operations are described.
The apparatus shown in FIG. 1 is constructed such that it includes an arm 2 having a suction opening and movable in a horizontal direction and a vertical direction and air around the suction opening of the arm 2 is sucked into a vacuum source (not shown) via a pressure sensor 3. In the present apparatus, whether or not an attraction object 1 is present is discriminated by a pressure sensor 3 when the arm 2 is moved down to a location at which the attraction object 1 is to be placed. In particular, if the attraction object 1 is not present when the arm 2 is moved down, since the suction opening of the arm 2 remains in a leaking condition, a drop of pressure is not detected by the pressure sensor 3, but if the attraction object 1 is present, then there is no leak from the arm 2 and a drop of pressure is detected by the pressure sensor 3. From this, whether or not the attraction object 1 is present can be discriminated.
Meanwhile, in the apparatus shown in FIG. 2, a transmission type sensor is disposed at a location at which an attraction object 1 is to be placed. In the transmission type sensor, rays of light which go across the location at which the attraction object 1 is to be placed are formed from a pair of light emitting elements 4 and a pair of light receiving elements 5. In the apparatus of the type just described, whether or not an attraction object 1 is present can be discriminated as the attraction object 1 intercepts rays of light between the pair of light emitting elements 4 and the pair light receiving elements 5 of the transmission type sensor.
However, such an apparatus as shown in FIG. 1 is disadvantageous in that whether or not an attraction object is present cannot be discriminated unless the arm is moved down to the location at which the attraction object is to be placed. The apparatus is disadvantageous also in that it may possibly discriminate in error that an attraction object is present because of an error in adjustment of the pressure sensor.
On the other hand, such an apparatus as shown in FIG. 2 is disadvantageous in that it cannot be used where the sensor cannot be mounted in horizontal and oblique directions with respect to an attraction object. The apparatus is disadvantageous also in that, where it is intended to discriminate whether or not an attraction object is present at each of a large number of attraction points, a large number of sensors are required.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide an attraction object detection apparatus and method which is superior in throughput to the constructions of the prior art described above, can detect with certainty whether or not there is present an attraction object, and in which the required space is reduced and is simple in construction.
In order to attain the object described above, the present invention presupposes an attraction object detection apparatus for detecting whether or not an attraction object to be attracted and transported by an attracting transport arm which is movable in vertical and horizontal directions is present at a predetermined location of a stage. And, a first aspect of the present invention is characterized by the following points. In
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Advantest Corporation
Allen Stephone B.
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