Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-10-27
2003-02-18
Mullen, Thomas (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C073S037000, C200S0830SA
Reexamination Certificate
active
06522252
ABSTRACT:
TECHNICAL FIELD
The present invention relates to pressure sensors and door opening/closing monitoring systems, and more particularly to sensors suitable for detecting door opening/closing.
BACKGROUND ART
Various types of sensors for detecting opening/closing of doors are known including switch-type, optical-type and infrared type sensors. All of these sensors are subjected to a certain limitation; for example, they must be installed near a door to be detected, as they directly monitor a condition and a position of the door to be detected. In addition, as an installation of the sensor is readily noticeable by a third person, if it is employed in a security system for detecting an intruder, for example, a counter measure can be easily taken. Further, as only one door can be detected by one sensor, for the detection of opening/closing of a plurality of doors, a plurality of sensors corresponding to the number of the doors is required.
On the other hand, to solve the problem as described above, a sensor for detecting opening/closing of a door based on pressure change caused by the opening/closing of the door is disclosed in the publication of Japanese Utility Model Registration No. 3039782 entitled “Sensor for Automatic Security System”, for example. In addition, Japanese Utility Model Registration No. 3039783 entitled “Automatic Security System” discloses a system employing the same.
As shown in
FIG. 1A
, a sensor disclosed in these publications includes an opening
1
a
at one end of a cylindrical casing
1
, a screen
3
, an opposite electrode
4
and an amplifying circuit
5
arranged in this order from the side of opening
1
a
in casing
1
and acting as pressure receiving surfaces. Further, in a back side of casing
1
, a partition wall
6
having a through hole
6
a
is arranged and a chamber
7
is formed between partition wall
6
and the back surface of casing
1
, thus a differential-type fine differential pressure gauge is formed. The sensor senses with the pressure receiving surfaces a change in pressure in a space in which it is installed if there is a change and outputs a voltage as shown in
FIG. 1B
as a sensor output.
Thus, when, for example, the door is not opened nor closed and the pressure in the room is maintained at a constant level, the sensor output does not change (being maintained at a standard level), whereas when the door is opened or closed and the pressure in the room changes, the change in pressure in the room is reflected in a change in the sensor output, whereby the opening/closing of the door can be detected. In Japanese Utility Model Registration No. 3039783 “Automatic Security System”, it is shown that the opening/closing of the door is monitored based mainly on an output from a differential-type fine differential pressure sensor, with one sensor as described above and one infrared sensor installed in the room.
The conventional sensor as described above (Japanese Utility Model Registration No. 3039782), however, is of a mechanical type and bulky. In addition, as an actual pressure change accompanying the opening/closing of the door is very small, a highly sensitive sensor is required. To increase the detectivity, a ratio of a depth L of casing
1
to a depth t of chamber
7
must be increased, which further increases the size and the shape of the sensor.
In addition, as the sensor is formed as a differential-type fine differential pressure gauge, the function is limited to the detection of the change in pressure and it cannot be known whether the change represents the opening or the closing of the door.
Further, according to the automatic security system, if there is a plurality of doors in the room, it is impossible to determine which door is opened. In addition, if the sensor itself has a trouble, the sensor output will be held at the standard level and determined to represent that there is no intruder. In other words, no function for detecting the failure of the sensor is provided. Thus various problems exist.
The present invention is made in view of the above described background and an object of the invention is to provide a pressure sensor and a door opening/closing monitoring system which will solve the problems as described above, is small and capable of detecting the opening/closing of the door with high sensitivity, allowing a detection of an operation condition, that is, whether the door is opened or closed, is subjected to less limitation in an installation position thereof and can be installed such that the sensor is not readily noticeable from outside, and allowing a determination on which door is opened/closed with a small number of sensors when a plurality of doors exists.
SUMMARY OF THE INVENTION
According to the present invention a pressure sensor is provided. The pressure sensor includes a pressure receiving side located in a gas; a reference pressure side located in the same gas as the pressure receiving side; a device for changing the speed of transmission of a change in pressure of the gas to said performance side. The pressure receiving side and the reference pressure side are subject to the same pressure during steady state conditions during which there is no gas flow.
In alternative embodiment of the present invention, a monitoring system for detecting the opening and closing of a door to a room is provided. The system includes a pressure sensor located in the room. The sensor includes a pressure receiving side located in a gas, a reference pressure side located in the same gas as the pressure receiving side, and a device for changing the pressure of the gas provided to the reference pressure side. The pressure sensor is configured to produce an output when the position of the door changes in response to a measured pressure difference between the reference pressure side and the pressure receiving side.
According to the present invention a monitoring system for determining which door among a plurality of doors in a room is opened or closed is provided. The system includes a plurality of pressure sensors positioned in the room; wherein each pressure sensor includes a pressure receiving side and a reference pressure side, both of the sides being exposed to the pressure in the room. Each pressure sensor includes a device for delaying the speed of transmission of a change in the pressure of the room to the reference pressure side. Each pressure sensor is configured to produce an output corresponding to a measured pressure difference between the pressure receiving side and the reference pressure side. The system further includes a means for determining which door opened or closed based on the difference between the production of outputs by each of said plurality of pressure sensors.
The present invention further includes a pressure sensing apparatus including a stem bonded to a cap to form a package. A sensor is positioned within the package. The sensor includes a reference pressure side and a received pressure side. The stem includes a first opening for supplying a gas to the received pressure side and the cap includes a second opening for supplying the gas to the reference pressure side. The apparatus further includes a device for changing the speed of transmission of a pressure change in the gas to the reference pressure side.
The present invention also includes a method of detecting the opening and closing of a door. The method may include the steps of positioning pressure sensors in a room containing the door, each of the sensors having a pressure receiving side and a reference pressure side, both of the sides being exposed to the pressure in the room; receiving a change in the pressure in the room associated with opening or closing the door on the pressure receiving side of each sensor; delaying the receipt of the pressure change on the reference pressure side of each sensor; measuring the pressure difference between the pressure receiving side and the reference pressure in each sensor; producing an output from each sensor corresponding to the measured pressure difference; and determining the position of the door bas
Horibe Koji
Sasaki Syo
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