RU2536089C2 - Sounding lead level meter - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: sounding lead level meter comprises a pulley, a load, a sensor of the lower and upper load position. Also the first stepper motor is mounted, which shaft the pulley is mounted on. A thread is wound on the pulley, passing through the unit and the tube-rod, freely movable vertically in the guide tube. At the end of the tube-rod the magnet of the sensor of the upper load position is mounted, on the free end of the thread the load is attached. The value of the measured level is determined by the number of pulses given to the stepper motor between the time of reaction of the sensors of the upper and lower position of the load. The wound thread is pressed against the surface of the pulley by the springy clamp.

EFFECT: simplification of the device.

2 cl, 2 dwg

Description

FIELD OF THE INVENTION

The invention relates to the field of industrial automation and can be used to measure the level of the product in silo-type storage facilities (elevators, silos), including hazardous industrial facilities.

State of the art

When measuring the level of the product using the lot, a cord is used, to the end of which a load is attached. The load is lowered into the container until it touches the level of the product. The moment of touch is determined by the tension of the cord of the lot. The measurement result is determined by the length of the cord from the reference point of the level to the load. The length of the cord is determined by the number of revolutions of the pulley shaft on which the cord was originally wound. The error of such a device is determined by the fact that when winding the cord, the diameter of the coil "randomly" depends on the number of turns. Therefore, to increase accuracy, a tape is used instead of the cord. When winding the tape, you can accurately predict the dependence of the diameter of the coil on the number of turns. Many industrial lot level meters are built on this principle. However, the use of non-metallic tape leads to a violation of the principles of ensuring electrostatic intrinsic safety, according to which the area of non-metallic objects in an explosive zone according to GOST R 52274-2004 cannot exceed 100 sq. Cm, therefore a metal tape is usually used. A metal tape with a typical length of 30 m has a weight of several kilograms, which requires the use of a powerful engine with a powerful control device to lift it and cargo at the end of the tape, which leads to a complication and cost of the device.

To prevent falling asleep during loading of the silo, electronic locking systems are used.

When using a cable in a lot meter, which is wound "in bulk" in known devices (see, for example, http://www.evroprylad.com.ua/catalog/item/78/), an encoder is used to determine the cable length, rotation to which is transmitted from a pulley that rotates through a cable passing through it. The disadvantage of this device is also its high complexity, high weight, dimensions and price.

Closest to the proposed device is the device INNOLevel LOT http://rusautomation.ru/lotovye/elekttromehanicheskie/innolevel_lot, consisting of a coil on which a metal tape is wound, a motor and an encoder for counting the number of revolutions of the motor shaft, as well as belt tension sensors and sensors top position of the load.

The principle of operation of the device is based on the calculation of the number of encoder pulses, which corresponds to the number of revolutions of the pulley mounted on the motor shaft. The beginning of the count is determined by the sensor of the upper position of the load, the end of the count is determined by the belt tension sensor, which weakens when the load touches the product. To ensure explosion safety, the electrical and mechanical parts of the device are located in different compartments of the device case, and steel is used as the material of the tape.

A common disadvantage of the known devices is the complexity, high weight and high power consumption, which leads to a high cost of the devices.

Disclosure of invention

The technical result of the invention is to simplify the device, subject to the requirements of intrinsic safety.

The technical result is achieved by the fact that in the proposed device, instead of a metal tape, a non-metallic thread with a thickness of 100 μm or less is used, which ensures compliance with the requirements of the standards for electrostatic intrinsic safety, and instead of a motor with an encoder, a stepper motor is used, the number of revolutions of the shaft of which is calculated by the number of pulses applied to stepper motor and measured between the moments of operation of the sensors of the lower and upper position of the load.

The sensor of the upper position of the load is made in the form of a tube-rod, which freely moves in the vertical direction inside the guide tube. When the cargo reaches its upper position, it pushes the rod-tube, on the second end of which a magnet is fixed, the magnet approaches the reed switch, the triggering moment of which is the moment the sensor detects the upper position of the load.

Due to the small thickness of the thread, “winding” the thread winding weakly affects the measurement error, and due to the small weight of the thread it became possible to use a light weight load and a low-power stepper motor, which significantly reduces the complexity, weight, power consumption and device price (up to 10 times). The technical feasibility of the device is ensured by the use of commercially available filaments with a thickness of 0.1 mm or less with a breaking force of 4 kg, for example, Berkley FireLine braided fishing line.

The invention is based on the idea of using the latest material - ultra-thin and ultra-strong yarn instead of a metal tape. This allowed for “winding in” winding to provide a low error in calculating the number of pulley revolutions in the length of the thread and at the same time simplify the device by eliminating the encoder from it and reducing the power and weight of the engine and control circuit by about 10 times.

A further improvement of the proposed device is the use of a thread-to-turn thread stacker in it, which increases the measurement accuracy by about 10 times. The use of the stacker became possible because the use of a thin thread made it possible to lay it in one row. For example, to measure the level up to 30 m with a thread thickness of 0.1 mm, it is enough to use a pulley with a diameter of 3 cm and a width of 3 cm, which ensures the simplicity of the device.

Brief Description of the Drawings

Figure 1 - structural diagram of the proposed device (side view). Here 1 is the pulley on which the thread is wound; 2 - thread; 3 - cargo; 4 - tube; 5 - tube-rod; 6 - magnet; 7 - reed switch; 8 - block; 9 - thread tension sensor; 10 - spring clip; 11 - the body of the device; 12 - stepper motor.

Figure 2 is a structural diagram of the proposed device with a stacker (top view). Here 1 is the pulley on which the thread is wound; 2 - thread; 12 - stepper motor; 17 - the second stepper motor; 13 - threaded rod; 16 - a rectangular nut with a guide 15; 14 - block; 4 - tube-rod.

The implementation of the invention

In the initial state, the load 3 touches the lower end of the tube 4, the tube-rod 5 is in the upper position, the magnet 6 touches the reed switch 7, the thread is completely wound on the pulley 1. To measure the level, the stepper motor 12 rotates the pulley 1, the magnet moves away from the reed switch 7. Signal with a reed switch is a signal to start counting pulses supplied to the stepper motor. The load drops down under its weight and when the product level in the silo is touched, the thread tension drops sharply, which triggers the sensor 9. The signal from it is a signal for the end of the pulse count and a signal for changing the direction of rotation of the stepper motor shaft 12. After lifting the load, it picks up the tube -Stock 5, at the second end of which a magnet 6 is fixed, which touches the reed switch 7, the signal from which is the signal for the end of the measurement process. Spring clip 10 provides a tight winding of the thread and prevents the sliding of its coils. The tube 4 prevents dust from entering the device case, since the dust does not have the property of diffusion.

A further improvement of the invention is the use of a stacker (figure 2), which allows to lay the thread "turn to turn", which increases the accuracy of level measurements by about 10 times. A second stepper motor 4 is introduced into the device, which rotates a threaded rod 5 with a thread along which the rectangular nut 6 moves. The lower part of the rectangular nut touches the device body, which prevents the nut from turning, that is, ensures its forward movement, excluding rotational. A guide with a hole for passing the thread is attached to the nut 6, which moves the thread as the nut moves along the stud. The ratio of the speeds of the pulley 1 and the guide 7 is selected so that the thread is laid "turn to turn".

The meter is controlled as in analogs by a microprocessor.

According to the authors, the essence of the claimed invention does not follow explicitly from the prior art for a specialist, since none of the lot meters on the market uses the described idea of using ultra-thin filaments to increase accuracy, ensure intrinsic safety and simplify the device. From the current level of technology it follows that for the reliability of the device, instead of a thread, it is necessary to use a strong cable. The cable has traditionally been used to measure the depths of the sea and is still used in lot level meters.

For the first time, we guessed that in a closed volume, which is a silo-type storage, there are no mechanical influences that could lead to a break in the thread. To prevent the product falling asleep and the thread breaking at this moment, both in the known devices, and we use electronic locking of measurements for the time of filling the silo.

Application of the described idea allowed to reduce the cost of the product by about 10 times compared with analogues.

The present invention has shown high technical characteristics and is currently prepared for mass production.

Claims (2)

1. A lot level meter comprising a pulley, a load, a lower and upper load position sensor, characterized in that a first stepper motor is introduced, on the shaft of which a pulley is fixed, a thread is wound on the pulley passing through the block and the rod-tube freely moving in a vertical direction inside the guide tube, the magnet of the upper load position sensor is fixed at the end of the tube-rod, the load is fixed at the free end of the thread, the measured level is determined by the number of pulses applied to the stepper motor between the moment amps of operation of the sensors of the upper and lower position of the load; the winding thread is pressed against the surface of the pulley by a spring clip. 2. The device according to claim 1, characterized in that a second stepper motor is introduced, on the shaft of which a stud with a thread is fixed, on which there is a nut that moves along the thread along the stud, a guide with a hole for thread passing is fixed on the nut; the ratio of the speeds of the pulley and the rectangular nut is chosen so that the thread is laid round to round.

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