Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-07-17
2003-11-11
Hjerpe, Richard (Department: 2674)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S297000, C250S239000, C345S046000, C345S051000, C345S052000, C345S156000, C235S462200, C235S462240, C235S462250, C340S691600
Reexamination Certificate
active
06646251
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoelectric switch of the separate type, which is formed with a head and a main body, for detecting an object in a predetermined detection area.
2. Description of the Related Art
Photoelectric switches have been used for detecting objects in production lines of factory. The photoelectric switch projects light to within a predetermined detection area, receives light returned from an object, and determines whether or not an object to be detected is present within the detection area by receiving light returned from the object.
In the photoelectric switch of the transmission type, when an object to be detected does not exist within a detection area, light projected from a light projecting section enters a light receiving section. In this case, when a level of the amount of received light in the light receiving section is lower than a predetermined threshold value, it is determined that an object to be detected is present there. In the photoelectric switch of the reflection type, when an object to be detected is present, light projected from the light projecting section is reflected by the object and enters the light receiving section. In this case, when a level of the amount of received light in the light receiving section exceeds a predetermined threshold value, it is determined that the object is present there. A sensitivity of the photoelectric switch is adjusted by varying the threshold value.
One of those photoelectric switches is of the separate type in which the photoelectric switch is separated into a head and a main body. The head contains mainly a light projecting section for projecting light and a light receiving section for receiving light returned from an object to be detected. The main body contains mainly a control unit for controlling the light projecting section and the light receiving section, and a power supply circuit. Further, it contains a display unit for displaying the amount of the received light in the head and a threshold value, and a switch for adjusting the threshold value. The display unit of the main body displays a tolerance level of the light-receiving amount with respect to the threshold value.
The photoelectric switch of the separate type may be used such that when a broad space does not exist near the object to be detected, only the head is located near the object while the main body is located farther from the object.
In installing the photoelectric switch of the separate, reflection type, to prevent noise from giving rise to error, a position of the head must be adjusted, for example, in such a manner that when an object to be detected exists within the detection area, the light-receiving amount is sufficiently high with respect to the threshold value, and when the object does not exist within the detection area, the light-receiving amount is sufficiently low with respect to the threshold value.
In this type of the photoelectric switch, however, when the main body is located far from the head, it is impossible that the operator adjusts the head position while checking a display by the display portion in the main body. This makes it difficult to accurately adjust the head position and impairs workability in adjusting the head position.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a photoelectric switch of the separate type which can accurately and easily check information on a process carried out in the main body even when the main body is located far from the head.
Another object of the present invention is to provide a photoelectric switch of the separate type which can accurately and easily adjust a position of the head even when the main body is located far from the head.
These objects can be achieved by a photoelectric switch of the separate type, according to a first aspect of the present invention, which projects light to a detection area and detects the presence or absence of an object to be detected within the detection area by receiving light returned from the detection area. The photoelectric switch comprises: a head that includes at least a light receiver for outputting a light reception signal based on a light receiving state of light returned from the detection area; and a main body, connected to the head by a signal line, for receiving a light reception signal output from the light receiver through the signal line. In the photoelectric switch the main body includes a processor for detecting the presence or absence of an object to be detected within the detection area by use of the light reception signal received through the signal line from the head, and the head includes an indicator for displaying information on the process carried out by the processor by the main body. The information on the process carried out by the processor is information regarding the detection of the presence of the object executed by the processor.
In the photoelectric switch of the invention, the light receiving section of the head outputs a light reception signal based on a light receiving state of light returned from the detection area, and the light reception signal is applied through the signal line to the main body. In the main body, the processor detects the presence or absence of an object to be detected within the detection area by use of the light reception signal received through the signal line from the head. In the head, the indicator displays information on the process carried out by the processor in the main body.
Thus, the indicator of the head displays information on the process in the main body. Therefore, when the main body is located farther from the head, the operator/user checks information on the process by the processor while watching a display by the indicator of the head.
In the photoelectric switch of the invention, it is preferable that the processor includes: a generator for producing a process signal based on a light reception signal, which is received from the head through the signal line in order to detect the presence or absence of an object to be detected within the detection area; a setting unit for setting a reference value used for determining if the object to be detected is present within the detection area; a detecting unit for determining if the object to be detected is present within the detection area by comparing a process signal produced by the generator with a reference value set by the setting unit; and a calculator for calculating a relative value of the process signal produced by the generator to the reference value set by the setting unit in the form of a tolerance level, wherein an indicator displays a tolerance level calculated by the calculator as information on the process by the processor.
In this case, in the main body, the generator produces a process signal based on a light reception signal, which is received from the head through the signal line in order to detect the presence or absence of an object to be detected within the detection area. The setting unit sets a reference value used for determining whether or not the object to be detected is present within the detection area. The detecting unit determines if the object to be detected is present within the detection area by comparing the process signal produced by the generator with the reference value set by the setting unit. The calculator calculates the relative value of the process signal produced by the generator to the reference value set by the setting unit in the form of a tolerance level. In the head, the indicator displays a tolerance level thus calculated by the calculator as information on the process by the processor.
Thus, the tolerance level is displayed by the indicator of the head. Therefore, even when the main body is installed at a position located far from the head, the operator/user may adjust a position of the head while watching a display by the indicator of the head. Accordingly, the operator/user can accurately and easily adjust a position of the head so that a tolerance level is sufficie
Abdulselam Abbas
Hjerpe Richard
Keyence Corporation
Kilyk & Bowersox P.L.L.C.
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