Radiant energy – Photocells; circuits and apparatus – Signal isolator
Reexamination Certificate
2001-06-25
2002-12-10
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Signal isolator
C250S221000
Reexamination Certificate
active
06492650
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a sensor unit which is suitable for use in a multiple sensor unit array of a main body unit for an optical fiber type photoelectric sensor, a proximate sensor having a separate sensor head, an ultrasonic sensor having a separate sensor head or the like, and in particular to a sensor unit which is suitable for performing a bi-directional optical data communication between the adjacent sensor units.
BACKGROUND OF THE INVENTION
Various sensors such as photoelectric sensors, proximate sensors and ultrasonic sensors are used for detecting the presence or position of an object as a part of factory automation (FA). In particular, optical fiber type photoelectric sensors that have separate sensor heads are widely used in compact and high-density machines which are required to be controlled because such sensors can be mounted in a limited space. The term “sensor” as used herein includes those producing a switching output by comparing a detected value with a threshold value as well as those for producing the detected value as an analog or a digital value.
In the case of a sensor having a separate sensor head as is the case with an optical fiber type photoelectric sensor, the sensor head and the main body unit are joined by a cable (consisting of an optical fiber cable in the case of a photoelectric sensor, or an electric cable in the case of a proximate sensor or an ultrasonic sensor). The main body unit is sometimes called as an amplifier unit in the industry. The main body unit is called in the following description as a “sensor unit”.
The housing of a sensor unit accommodates various circuits such as a drive circuit for driving a sensor head and a signal processing circuits for processing the signal from the sensor head and generating an output signal of a desired form. In other words, the sensor unit housing accommodates a sensing circuit system which achieves a desired sensing function in cooperation with the sensor head.
Conventionally, sensor units for use in a multiple sensor unit array have been developed with the aim to accommodate a large number of sensor units in a console board or the like. Such a sensor system incorporating a large number of sensor units closely one next to another is illustrated in FIG.
14
. The illustrated sensor units each consist of a main body unit (often called as an amplifier unit) of an optical fiber type photoelectric sensor.
As shown in the drawing, this sensor system comprises a DIN rail
301
placed inside a control console or the like, and a plurality of sensor units
300
,
300
, . . . which are adapted to be used in a multiple sensor unit array and mounted on the DIN rail
301
closely one next to another. In other words, each sensor unit
300
is mounted on the DIN rail
301
in alignment with other sensor units by fitting a DIN rail mount groove
302
formed in the bottom surface of the housing onto the DIN rail
301
.
A pair of optical fiber cables consisting of an outgoing optical fiber cable
303
and an incoming optical fiber cable
304
extend from the rear surface of the housing of each sensor unit
300
, and the free ends of these optical fiber cables
303
and
304
are connected to sensor heads
303
a
and
304
a
which are placed in a detection region.
An electric cable (or cord)
305
extends from the front surface of the sensor unit
300
to produce a switching output or a signal indicating the intensity of the received light which is generated by the sensing circuit system (not shown in the drawing) inside the unit housing. This electric cable
305
is connected to external control equipment such as a programmable logic controller (PLC) which is not shown in the drawing.
As the presence or position of an object is detected by the sensor heads
303
a
and
304
a
of the optical fiber cables
303
and
304
according to the change in the transmitted or reflected light, by virtue of the prescribed operation of the sensing circuit system of the sensor unit
300
, a detection signal (a switching output or a signal indicating the intensity of the received light) is forwarded to control equipment such as a programmable logic controller (PLC) via the cable
305
.
Thus, according to the sensor system described above, because the outer profile of the housing of each sensor unit
300
has a flat configuration with its small side aligned with the direction of the array, and is provided with a DIN rail mount groove
302
in its bottom surface, if the control console is provided with a DIN rail
301
, a large number of such independent sensor units
300
can be mounted on the DIN rail
301
closely one next to another in a highly compact fashion.
In recent years, the sensing circuit system incorporated in the sensor unit is given with a progressively higher functionality and performance so that the sensor unit may be adapted to a greater variety of objects and a wider range of detecting conditions. Therefore, there is a growing need to set up the conditions for a larger number of data items for each sensor unit and to monitor the sensor unit to place the sensor unit in an optimum condition for detecting a greater variety of objects and a wider range of detecting conditions.
Such set-up work has been conventionally performed manually by manipulating small set-up keys provided on outer surface of each sensor unit housing while viewing a display unit which is typically difficult to read. Therefore, such work has been known to be irritating and time-consuming.
The sensor unit housing is made smaller and smaller because of the growing demand for more compact design. This trend severely hampers the effort to solve the problems associated with the inconvenience in manipulating the set-up keys on the sensor unit housing and the difficulty in reading the display on the sensor unit.
The inventors have conducted a research to the end of eliminating such problems of the prior art, and have conceived the idea that if each pair of adjacent sensor units in a sensor unit array can transfer data between them in both directions, it will become possible to provide a data set-up unit of good manipulability at an end of the sensor unit array which is easily accessible, and to transfer the data from the data set-up unit to each sensor unit. Also, it will become possible to transfer the data of each sensor unit to the sensor unit at an end of the array so that the data may be monitored on a data display device which provides a favorable visibility.
Implementation of such an idea requires an arrangement which allows a bi-directional data transfer between each pair of adjacent sensor units. However, in the technical field of sensor systems, no appropriate prior art is available that serves this purpose.
For instance, Japanese patent laid open publication (kokai) No. 9-64712 discloses a detection switch system in which a female connector and a male connector are provided on opposing surfaces of each pair of adjacent detection switches (which correspond to the sensor units of the present invention), and are joined together electrically so that the control circuit board of each detection switch may be supplied with electric power for the adjacent detection switch, and the light emission timing may be suitably varied from one detection switch to another by passing an external synchronization signal from the upstream detection switch to the downstream detection switch with a suitable time delay.
However, to achieve such a bi-directional data transfer system contemplated by the inventors, it is necessary to arrange a large number of sensor units, typically from 16 to 64 sensor units, in a series. Therefore, when a contact type connector is used for signal transfer means between each pair of adjacent sensor units as shown in the above publication, the signal transmission path contains so many contact points which may become faulty that such an arrangement would be too unreliable for any practical purpose.
Because the synchronization signal in this prior patent publication is intended for delaying the timing of light emiss
Gondo Kiyohiko
Imai Kiyoshi
Inoue Hiroyuki
Kamei Takashi
Osako Kazunori
Foley & Lardner
Le Que T.
Omron Corporation
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