Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – In combination with or also constituting light responsive...
Reexamination Certificate
2001-03-29
2002-10-01
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
In combination with or also constituting light responsive...
C257S099000
Reexamination Certificate
active
06459099
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a photointerrupter used or detecting a desired object or desired part of an object. It also relates to a case used for such a photointerrupter.
BACKGROUND ART
A typical prior art photointerrupter, which is disclosed in JP-U-6-50365 for example, has such a structure as shown in
FIGS. 12 and 13
of the accompanying drawings. The illustrated photointerrupter B comprises an LED lamp
7
, a photodetector
8
and a case
9
. The LED lamp
7
as a light emitting element comprises an LED chip
70
sealed in a transparent resin
71
. The LED lamp has two leads
72
. The photodetector
8
comprises a light receiving element sealed in a transparent resin
81
. The photodetector has two leads
82
. The case
9
includes a pair of receiving portions
90
for receiving the LED lamp
7
and the photodetector
8
, respectively, and a plurality of walls for defining the receiving portions.
Each of the receiving portions
90
has an opening
91
at the bottom. The plurality of walls include a pair of opposite walls
92
A each of which is formed with a slit
94
for allowing light emitted from the LED lamp
7
to travel toward the photodetector
8
. When an object to be detected (not shown) exists between the slits
94
, the object blocks light from the LED lamp
7
. As a result, light cannot be received by the photodetector
8
so that signal output from the two leads
82
stops. In this way, the presence or absence of an object is checked.
The case
9
further includes another pair of walls
92
B each of which is formed with a projection
95
having an increasing thickness toward its upper end. The upper end of each projection
95
partially extends into the corresponding receiving portion
90
. With this structure, the upper end of each projection
95
is brought into engagement with the resin
71
of the LED lamp
7
or the resin
81
of the photodetector
8
, thereby fixing the LED lamp
7
or the photodetector
8
in the corresponding receiving portion
90
. In the photointerrupter B, therefore, the LED lamp
7
and the photodetector
8
need not be press-fitted into the receiving portions
90
, so that deformation of the LED lamp
7
and the photodetector
8
due to such press fit can be avoided. Moreover, since a lid which is separate from the case
9
need not be provided to fix the LED lamp and the photodetector
8
, it is possible to reduce the number of parts of the photointerrupter.
However, the above-described prior art apparatus has the following problems.
In the prior art apparatus, the slits
94
for light transmission are provided in the walls
92
A of the case
9
, whereas the projections
95
are provided in the walls
92
B which are separate from the walls
92
A. Therefore, in forming the case
9
by resin molding, large openings
99
for forming the projections
95
are provided in the walls
92
B. Specifically, as shown in
FIG. 14
, when the case
9
is formed by using a mold
4
C comprising an upper mold member
48
and a lower mold member
49
, portions
48
a
of the upper mold member
48
need to be disposed above clearances
95
′ for forming the projections
95
in the case
9
. As is clear from the configuration of the projections
95
shown in
FIG. 12
, part of the upper mold member
48
needs to extend on both sides of the corresponding clearance
95
′ for forming the projection
95
. Accordingly, the case is correspondingly formed with openings
99
.
Since each of the walls
92
B of the case
9
is formed with an opening
99
, disturbing external light is likely to enter the corresponding receiving portion
90
at the opening
99
. In the prior art apparatus, therefore, disturbing external light is received by the photodetectors
8
, which leads to malfunction of the apparatus.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a photointerrupter and a case for a photointerrupter which are capable of eliminating or reducing the problems of the above-described prior art apparatus.
In accordance with a first aspect of the present invention, there is provided a photointerrupter comprising a light source, a photodetector, and a case. The case includes a pair of receiving portions each of which is open at one end for receiving the light source or the photodetector, and a plurality of walls defining the pair of receiving portions. The plurality of walls of the case include a pair of first walls each of which is formed with a respective elongated slit. The case further includes a pair of projections each of which projects into a respective one of the receiving portions for preventing the light source or the photodetector from coming out of the receiving portion. Each projection is connected to a respective one of the first walls on an extension line of the respective slit.
Preferably, each projection may be connected to a longitudinal end edge of the respective slit.
Preferably, the case may be made of a synthetic resin, and the pair of projections may be integral with the plurality of walls.
Preferably, each projection may include a base end connected to the respective first wall and a tip end projecting into the respective receiving portion for engagement with one of the light source and the photodetector.
Thus, according to the present invention, in forming the case of the photointerrupter by resin-molding using a mold, part of the mold for forming the slit can be utilized for forming the projection. Therefore, unlike the prior art apparatus, the case of the present invention is not formed with a large opening at portions other than the first walls at which the slits are formed. Therefore, disturbing external light is less likely to enter the receiving portions, which enhances reliability of detection by the photointerrupter.
Preferably, each projection may be elastically deformable for allowing movement of the tip end toward the respective first wall.
With this structure, each of the light source and the photodetector can be easily inserted into the corresponding receiving portion by pushing the tip end of the corresponding projection by the light source or the photodetector toward the corresponding first wall. After the light source and the photodetector are inserted into the respective receiving portions, the tip end of each projection projects into the corresponding receiving portion due to the elastic recovery. Thus, fixing of the light source and the photodetector can also be performed easily.
Preferably, a rounded connection may be provided between the base end of each projection and the respective first wall.
With this structure, a gradually curving outer configuration is provided at the connection between the base end of each projection and the corresponding first wall. Therefore, even when a force is applied to the tip end of each projection and the base end is subjected to a bending stress, it is possible to prevent a stress concentration on a particular portion of the base end. Accordingly, even when a pulling force (a force to pull out the light source or the photodetector from the corresponding receiving portion through the opening) is generated and each of the projection is pressed by the light source or the photodetector, it is possible to prevent the projection from easily breaking. Thus, the light source and the photodetector can be reliably fixed.
Preferably, each of the light source and the photodetector may include a bottom surface facing the opening of the respective receiving portion and a side surface facing the respective first wall, and the tip end of each projection may include a first surface and a second surface for engagement with the bottom surface and the side surface, respectively.
With this structure, since the second surface of each projection engages the side surface of the light source or the photodetector, the projection is prevented from rotating in a direction in which the second surface faces toward the side surface of the light source or the photodetector. Therefore, even when a pulling force is exerted on the light source or the photo
Bednarek Michael D.
Chaudhuri Olik
Rohm & Co., Ltd.
Shaw Pittman LLP
Wille Douglas A.
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