JPH0473756B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention measures the distance to a measurement target by transmitting electromagnetic waves through an antenna and detecting reflected electromagnetic waves from the measurement target. This invention relates to a distance detection device for a continuous unloader using a distance detection device from the bottom of a ship's hold.

[Conventional technology]

It is widely known that a bucket elevator type continuous unloader is used to unload cargo such as earth and sand, coke, etc. loaded in a ship's hold onto a cargo handling quay. This continuous unloader is loaded into a cargo hold prior to unloading work, and can unload the cargo continuously by raising and lowering the cargo and by circulating the bucket elevator. However, during unloading operations, the lower end of the bucket elevator is always directed towards the bottom of the hold, and it descends as the layer of cargo decreases. There is a risk of collision. Therefore, mutual contact and
In order to prevent accidents caused by collisions, it is common practice for workers to enter the cargo hold and constantly monitor the thickness of the cargo layer before unloading operations.

On the other hand, it is also known to attach a distance detection device equipped with a magnetic sensor or a mechanical sensor to the lower end of a bucket elevator, and to automatically perform measurement work using this distance detection device. A distance detection device equipped with a magnetic sensor detects the distance between the bottom of a ship's hold and the bottom of a ship's hold by utilizing the effect that the change in magnetic flux of a detection coil provided opposite to the bottom of the ship's hold increases as the distance approaches the bottom of the hold. (Japanese Patent Application Laid-Open No. 58-207224). In addition, the distance detection device equipped with a mechanical sensor monitors the distance from the bottom of the cargo hold using a detection rod attached to the bottom end of the bucket elevator so that it can move up and down, and outputs a warning signal when a dangerous distance is reached. (Utility Model Kai 61-151931, Utility Model Kai 53-37182).

[Problem that the invention seeks to solve]

However, when using the conventional distance detection device, the following problems and drawbacks are pointed out.

Distance detection devices equipped with magnetic sensors have a short detection distance, so they are unsuitable for applications where it is necessary to detect distance over a relatively wide range, such as in unloaders. Distance detection devices equipped with mechanical sensors require the detection rod to be inserted into the cargo, resulting in problems with the durability of the detection rod and damage to the bottom of the hold due to contact between the detection rod and the bottom of the hold. It was hot.

SUMMARY OF THE INVENTION In view of the above-mentioned problems and drawbacks, an object of the present invention is to provide a highly practical distance detection device that can improve work efficiency, has a long detection distance, has high reliability, and is highly practical.

That is, it is an object of the present invention to provide an apparatus for detecting the distance between a continuous unloader and the bottom of a ship's hold, which is not affected by the surface reflection of the cargo interposed between the object to be measured, that is, the bottom of the ship's hold.

[Means for solving problems]

According to the present invention, in the distance detection device for a continuous unloader that uses a bucket elevator to unload a cargo placed on the bottom of a cargo hold, the device contacts the cargo and the radiation direction is directed to the bottom of the cargo hold. An antenna attached to the lower end of the bucket elevator is used to direct the antenna to the bottom of the cargo hold, and by transmitting electromagnetic waves through the antenna and detecting reflected electromagnetic waves from the bottom of the cargo hold, the distance to the bottom of the cargo hold can be determined. a sensor section for measuring, and the antenna includes a metal waveguide;
There is obtained a distance detecting device for a continuous unloader from the bottom of a ship's hold, characterized in that it has a rod made of polystyrene extending from the waveguide.

〔Example〕

Hereinafter, the basic structure and operation of the distance detection device used in the present invention will be explained with reference to FIGS. 4 and 5.

As shown in the schematic configuration diagram of FIG. 4, this type of distance detecting device includes a modulation section 40 that performs predetermined modulation on a carrier wave, and an output signal (defined as a modulated wave) of the modulation section 40.
It has a transmission amplification section 41 that amplifies the power to a predetermined power value. The output signal (transmission wave) of the transmission amplification section 41 is passed through a circulator 4 that allows signals to pass only in a certain direction.
2 and is sent out via the antenna 43 in the form of electromagnetic waves. The circulator 42 may be replaced by a directional coupler.

On the other hand, the transmitted electromagnetic waves are reflected by the object to be measured, and the reflected electromagnetic waves are transmitted to the antenna 43.
The signal is extracted and converted into transmission power, and guided to the reception amplification section 43 via the circulator 42. In the reception amplification section 43, this weak reception power is amplified to an appropriate value. The amplified received power is guided to the demodulation section 44, where it is demodulated into the original signal, that is, the modulated wave component (referred to as a demodulated wave). aerial line 43
The other portions may be referred to as the sensor section 4.

By the way, since electromagnetic waves propagate at a constant speed, there is a time difference between the modulated wave and demodulated wave that corresponds to the propagation distance, and by detecting this time difference, the distance to the object to be measured can be determined. Can be measured.

FIG. 5 shows a characteristic diagram of modulation/demodulation waves in a commonly used continuous wave radar type distance detection device that continuously transmits electromagnetic waves. FIG. 5 is a characteristic diagram when, for example, a carrier wave in the 4 GHz band is frequency-modulated with a triangular wave whose wavelength is longer than or about the same as the maximum measurement distance. Of course, a similar characteristic diagram can be formed when phase modulation is performed. As can be seen from Figure 5, between the modulation and demodulation waves,
A frequency beat Δf corresponding to the propagation distance of the electromagnetic wave occurs. This Δf and the distance h to the object to be measured
The following relational expression holds true between .

Δf=4・fm・B/v・h... However, fm: Modulation repetition frequency B: Frequency deviation v: Propagation speed of electromagnetic wave in the medium When the equation is modified, h=v/4・fm・B・Δf... ... Therefore, by detecting this Δf, the distance to the object to be measured can be measured.

Incidentally, as shown in FIG. 5, the distance can also be detected by detecting the shift time t of any one point of the modulated wave. This is based on the fact that the following relational expression holds true: t=2.h/v...h=t.v/2...

Next, one embodiment of the present invention will be described with reference to FIGS. 1 to 4.

The distance detection device according to the first embodiment of the present invention is equipped with an antenna 43 (FIG. 4) suitable for measuring the distance between the unloader and the bottom of the ship's hold.

Referring to FIG. 1a, the antenna in one embodiment of the present invention is connected to a coaxial cable feed line 14 that supplies high frequency power, one end of which is open, and the other end of which is connected to a predetermined distance from the core wire of the coupled feed line 14. A circular metal tube waveguide 11 short-circuited at a distance, and a polystyrene rod 13 extending from the open end.
have. The circular metal tube waveguide 11 has a shape that allows impedance matching between the feed line 14 and the polystyrene rod 13, and specifically, the tube wavelength λg and the free space wavelength shown in FIG. It is determined based on λ. A tuning stub 10 is provided on the side of the circular metal tube waveguide 11 to assist in the impedance matching. The polystyrene rod 13 has a length of 6λ in the extending direction from the open end of the circular metal pipe waveguide 11, and its diameter is 0.5λ to 0.3λ from the open end to a length of 3λ.
It tapers to a circular rod with a diameter of 0.3λ. Here λ is the free space wavelength of the carrier wave.

If the antenna 1 is configured as described above, the high frequency signal supplied from the coaxial cable feeder line 14 is converted into an electromagnetic wave, guided by the polystyrene rod 13, and radiated with maximum energy in the extending direction. Ru. A directional characteristic diagram of the antenna 1 constructed as described above is shown in FIG. 1b.

In this embodiment, as described above, the distance detection device for the unloader to the bottom of the cargo hold is formed using an antenna equipped with a rod made of a material that has unidirectional characteristics and can withstand contact with cargo. This allows the distance to be measured with the antenna in contact with the cargo, preventing the spread of electromagnetic waves in the air, improving the S/N ratio, and saving transmission power. Furthermore, since the rod is made of polystyrene, which is inexpensive and easy to process, a highly practical distance detection device with a wide range of applications can be realized. Furthermore, since the antenna has unidirectionality as described above, there is no need to insert the antenna deeply into the cargo, and damage to the bottom of the ship can be prevented. On the other hand, since the antenna is provided with a rod made of a strong material that can withstand contact with the cargo, damage to the antenna can also be prevented.

Next, a case in which the distance detecting device using the above-mentioned antenna is used as a distance detecting device to the bottom of a cargo hold of a continuous unloader will be described in more detail. As shown in FIGS. 2 and 3, the distance detection device from the bottom of the ship's hold has, for example, a configuration in which the antenna 1 having the above-described structure is fixed to the support member 3 attached to the lower end of the bucket elevator 2. aerial line 1
is electrically connected to the sensor section 4. The antenna 1 has an electromagnetic wave radiated toward the bottom of the hold. The sensor section 4 has the configuration already described based on FIG. 4. The support member 3 is configured such that an insulator supporting the antenna 1 is attached so as to be expandable and contractible in the extending direction of the polystyrene rod 13, and the amount of expansion and contraction can be detected.

Based on the above configuration, the operation of the continuous unloader to cargo hold bottom distance detection device will be explained. As shown in FIGS. 2 and 3, before or during the unloading operation, the support member 3 is extended toward the bottom of the hold, and the antenna 1 supported by the support member 3 is brought into contact with the cargo layer 5. In this way, the electromagnetic waves radiated from the antenna do not pass through the air layer, so they are not affected by reflection from the cargo surface 6 due to the difference in dielectric constant between the air layer and the cargo layer 5. Now, as shown in FIG. 3, the distance from the bottom of the hold 7 to the lowest point of the bucket elevator is x, the distance to the contact point of the antenna 1 is y, and the distance to the cargo surface 6 is z. The difference between y and x, which changes due to the expanding and contracting support member 3, can be known when the cargo hold bottom detection device according to this embodiment is installed. Furthermore, if the antenna 1 is brought into contact with the cargo surface 6, z=y.

In this way, since the antenna 1 always sends and receives electromagnetic waves while being in contact with any point within the cargo layer 5,
It is possible to realize a distance-to-ship hold bottom distance detection device that is not affected by diffused reflection from the cargo surface 7 and can measure the distance between the lowest point of the bucket elevator and the hold bottom. Furthermore, since the antenna 1 is made of the inexpensive and easily processed polystyrene rod shown in the first embodiment, a highly practical distance detecting device from the bottom of a ship's hold can be realized.

The distance detection device according to the present invention can also be applied to port cargo handling devices such as stackers and reclaimers, or cargo handling devices in food warehouses such as silos.

〔effect〕

As described above, according to the present invention, it is possible to provide a distance detection device that improves work efficiency, has a long detection distance, and is equipped with a highly reliable and highly practical electromagnetic wave sensor.

Further, according to the present invention, it is possible to provide a distance detecting device that is not affected by surface reflections of cargo or the like interposed between the object to be measured, that is, the bottom of the cargo hold.

[Brief explanation of the drawing]

Fig. 1a is a cross-sectional diagram of an antenna having a polystyrene rod, Fig. 1b is a directional characteristic diagram of the antenna, and Fig. 2 is a side view of a continuous unloader equipped with a distance detection device to the bottom of the cargo hold. 3 is a front view of the same, FIG. 4 is a schematic configuration diagram of a distance detection device equipped with an electromagnetic wave sensor, and FIG. 5 is a diagram showing the characteristics of modulation and demodulation waves in a continuous wave radar type distance detection device. In the figure, 1... antenna having a polystyrene rod, 3... support member, 4... distance detection section, 10...
... Tuning stub, 11 ... Circular metal tube waveguide, 13
...Polystyrene rod, 14...Coaxial cable feeder line.

Claims (1)

[Claims] 1. In a distance detection device for a continuous unloader that uses a bucket elevator to carry out a cargo placed on the bottom of a cargo hold, the device contacts the cargo and directs the radiation direction toward the bottom of the cargo hold, By transmitting electromagnetic waves through an antenna attached to the lower end of the bucket elevator and detecting reflected electromagnetic waves from the bottom of the hold,
a sensor section for measuring the distance to the bottom of the cargo hold, and the antenna includes a metal waveguide and a rod made of polystyrene extending from the waveguide. Hold bottom distance detection device.