Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2002-12-05
2004-08-10
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S239000, C340S555000
Reexamination Certificate
active
06774352
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a multi-beam photoelectric sensor and its mount.
2. Discussion of the Related Art
Multi-beam photoelectric sensors disclosed in U.S. Pat. No. 6,166,371, International Publication No. WO 00/54077 and Japanese Patent Laid-Open Publication No. 2000-251595 each include units of paired light emitters and photo detectors to make a protective fence, typically called a light curtain, of a desired size by using one or more units of light emitters and photo detectors. Multi-beam photoelectric sensors of this type are widely used for prohibiting intrusion of any part of a worker's body or any other object into a prohibited zone around a work area with a machine tool, press machine, etc.
Multi-beam photoelectric sensors typically need positioning of light emitters and photo detectors in an opposed relation upon their initial setup, and need adjustment of optical axes between light emitters and photo detectors. Adjustment of optical axes includes rotation of light emitters and/or photo detectors about their own axes. Light emitters and/or photo detectors can be adjusted in rotational orientation by appropriate amounts of rotation.
FIG.
1
and
FIG. 2
show examples of existing mount for multi-beam photoelectric sensors. In each of these examples, the multi-beam photoelectric sensor
1
includes a plurality of through holes
3
aligned in a single row in equal intervals on the light emitting or detecting surface that is the front surface of a body
2
. The multi-beam photoelectric sensor
1
exchanges equally spaced light beams through these holes.
The multi-beam photoelectric sensor
1
is fixed on a support (not shown), which is an external structure like a frame of a press machine, via a bracket
4
. In the example of
FIG. 1
, the bracket
4
includes a base member
5
and a plate member
6
. The plate member
6
is firmly fixed to the base member
5
by bolts
7
. The bracket
4
defines a shaft hole between the base member
5
and the plate member
6
to receive a shaft
17
having a circular section and axially extending from top and bottom ends of the sensor body
2
. When the bolts
7
are rotated in the fastening direction, the multi-beam photoelectric sensor
1
is fixed to the bracket
4
and prevented from relative rotation. When the bolts
7
are loosened, the multi-beam photoelectric sensor
1
can rotate about the axis.
In the example of
FIG. 2
, the bracket
4
is a member having an L-shaped section, which includes a base portion
8
for engagement with the support and a sensor mount portion
9
extending perpendicularly to the base portion
8
. The base portion
8
has elongate holes
10
longer in the axial direction of the multi-beam photoelectric sensor
1
to enable adjustment of the multi-beam photoelectric sensor
1
in its axial position.
The sensor mount portion
9
of the bracket
4
has a round hole
11
for receiving the shaft
17
of the sensor
1
, and a plurality of elongated arcuate holes about the round hole
11
. The sensor
1
is fixed to the bracket
4
by bolts (not shown) inserted through the arcuate holes
12
.
In the existing example shown in
FIG. 2
, when the bolts in the arcuate holes
12
are rotated in the releasing direction, the sensor
1
is permitted to rotate about its axis. When the bolts are rotated in the fastening direction, the sensor
1
is fixed no to be rotatable about the axis. That is, the sensor
1
is fixed in rotational orientation.
In any of the existing examples shown in
FIGS. 1 and 2
, when a plurality of multi-beam photoelectric sensors
1
are used together in straight or angled connection to make a large light curtain, it is practically impossible to make a light curtain without a large gap between the nearest light beams of every two adjacent sensors
1
,
1
. That is, it is practically impossible to place the adjacent sensors
1
,
1
such that the pitch between the extreme light beam of one sensor
1
and the nearest light beam of another sensor
1
equals the pitch of the light beams within each sensor
1
.
Additionally, the existing example of
FIG. 2
involves the problem that the adjustable extent of the sensor
1
in its rotating direction is substantially limited by the length of each arcuate hole
12
. Therefore, the sensor
1
can be adjusted in rotational orientation only within a limited range.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a multi-beam photoelectric sensor and its mount of a scheme different from existing ones.
A further object of the invention is to provide a multi-beam photoelectric sensor and its mount that are capable of connecting a plurality of multi-beam photoelectric sensors substantially in direct contact and suitable for placing a plurality of multi-beam photoelectric sensors such that the pitch of light beams between adjacent multi-beam photoelectric sensors equals the pitch of light beams within each multi-beam photoelectric sensor.
A still further object of the invention is to provide a multi-beam photoelectric sensor and its mount that are designed to facilitate enlargement of the rotatable angle of the multi-beam photoelectric sensor, that is, the adjustable extent of its rotational orientation.
Those objects of the invention can be accomplished by various aspects of the invention.
According to an aspect of the invention, there is provided a multi-beam photoelectric sensor comprising:
a light emitter having a plurality of light emitting elements aligned in equal intervals in the lengthwise direction of an elongate casing inside the elongate casing;
a photo detector having a plurality of photo detector elements aligned in the same equal intervals as those of the light emitting elements in the lengthwise direction of an elongate casing inside the elongate casing;
a cable connected to at least one of lengthwise ends of the casing of the light emitter to supply an electric power and/or transmit a signal;
a cable connected to at least one of lengthwise ends of the casing of the photo detector to supply an electric power and/or transmit a signal;
a light emitter mounting means for mounting the casing of the light emitter to a support, said light emitter mounting means being positioned on a back surface of the casing of the light emitter opposite from a light emitting surface from which the light emitting elements emit light beams; and
a photo detector mounting means for mounting the casing of the photo detector to a support, said photo detector mounting means being positioned on a back surface of the casing of the photo detector opposite from a photo-detecting surface where the photo detector elements receive light beams.
In the multi-beam photoelectric sensor summarized above, at least one of the light emitter mounting means and the photo detector mounting means preferably includes means for adjusting the corresponding elongate casing in rotational angular position about a lengthwise axis thereof. Adjustment of optical axes is to adjust relative orientations of the light emitter and the photo detector, and it can be accomplished by adjusting at least one of the light emitter and the photo detector in its orientation.
According to another aspect of the invention, there is provided a multi-beam photoelectric sensor comprising:
a light emitter having a plurality of light emitting elements aligned in equal intervals in the lengthwise direction of an elongate casing inside the elongate casing;
a photo detector having a plurality of photo detector elements aligned in the same equal intervals as those of the light emitting elements in the lengthwise direction of an elongate casing inside the elongate casing;
a light emitter mounting means for mounting the casing of the light emitter to a support, said light emitter mounting means being positioned on a back surface of the casing of the light emitter opposite from a light emitting surface from which the light emitting elements emit light beams;
a photo detector mounting means for mounting the casing of the photo detector
Koyama Masatoshi
Sakaguchi Tomikazu
Allen Stephone B.
Keyence Corporation
Kilyk & Bowersox, P.L.L.C
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