RU2194215C2 - Draw-bar load sensing mechanism - Google Patents

Abstract

FIELD: automatization of heat and power generating installations. SUBSTANCE: invention specifically refers to automatization of control processes in steam and hot-water boilers. Draw-bar load sensing mechanism has smoke-removing conduit, bimetal sensitive element, switching element and element setting mechanism in operational condition. Switching element comes in the form of microswitch and lever is employed as element setting mechanism in operational condition. Adjustment screw setting driving member in working position between operational and emergency positions of bar is put on free end of bimetal sensitive element. EFFECT: expanded functional potential of draw-bar load sensing mechanism thanks to widened range of operational currents and voltages, increased sensitivity and possibility of its adjustment. 1 cl, 1 dwg

Description

 The invention relates to the field of automation of heat power plants, in particular to the automation of control processes in steam and hot water boilers.

 The well-known "Device for monitoring the operation of a heat generator" (A.S. SU 1014346, F 23 N 5/24, publ. 09/22/80; "Device for monitoring a heat generator", AS. SU 1217039, F 23 N 5/08, publ. 06.28.84; "The control device of the heat generator", A. S. SU 1374880, F 23 F 5/08, publ. 24.07.85). The devices contain a branch in the chimney, a sensitive element, which is used as a transistor.

The disadvantages of the devices are:
1. Low functional reliability associated with the possibility of failure of the transistor, performing the function of the sensing element, at the time of failure of traction, when the temperature of the exhaust gases can significantly exceed the temperature acceptable for the transistor.

 2. The inability to memorize an emergency.

 Closest to the claimed is the "Traction Sensor" (R.R. Rybakov, "Automation of gasified units", Leningrad, "Nedra", 1984, p. 220-221). The device contains a coupler in the flue duct, a magnet, a reed switch and a button for setting the sensor to working condition. The device allows you to remember an emergency.

The disadvantages of the device are:
1. The inability to adjust the sensitivity of the sensor.

 2. The inability to achieve maximum sensitivity, which would be limited only by the parameters of the bimetallic sensor used. The reason for this is the presence of friction between the free end of the bimetallic plate and the stop.

 3. Restrictions on the use of the sensor due to the fact that a reed switch is used as a switching element.

The objectives of the claimed device are:
Expanding the functionality of the device by expanding the range of operating currents and voltages; increasing the sensitivity of the sensor and providing the possibility of its regulation.

 The solution to this problem is achieved by the fact that in the device containing the smoke exhaust channel, a bimetallic sensing element, a switching element and an element for setting the sensor to working condition, a microswitch is installed as a switching element, and a lever is used as an element for setting the sensor in working condition. At the same time, a tuning screw is installed on the free end of the bimetallic sensing element with the possibility of both mechanical impact and changing the position of the point of application of this impact on the sensor installation element in the operating state and the microswitch button.

In this case, the expansion of the functionality of the sensor is achieved:
- the use of a microswitch as a switching element,
- using as an element of the sensor in the operating state of the lever,
- using a tuning screw mounted on the free end of the sensing element, with the possibility of both mechanical impact and changing the position of the point of application of this impact on the sensor installation element in working condition and the microswitch button.

 Using a microswitch as a switching element allows expanding the range of operating currents and voltages in comparison with the prototype.

 In addition, the use of a microswitch allows you to implement the function of storing an emergency without the use of any special structural elements, as this, for example, is implemented in the prototype. The ability to memorize an emergency in the inventive device is achieved by using the hysteresis of the button position of the microswitch when it is turned on and off.

 The use of a lever as an element of setting the sensor in the operating state of the lever allows you to move along the lever the point of application of the mechanical impact of the setting screw relative to the position of the microswitch button and thereby widely control the reaction time of the sensor to an emergency in case of traction violation. Removing the point of application of mechanical action to the lever - the element that sets the sensor in working condition from the button of the microswitch increases the working stroke of the free end of the sensitive element and accordingly reduces the sensitivity of the sensor, increases its reaction time to an emergency. And vice versa, approaching the point of application of mechanical action on the sensor installation element to the operating state to the button of the microswitch reduces the working stroke of the sensitive element and, as a result, increases the sensor sensitivity. In the general case, it is desirable to achieve the maximum possible sensitivity of the sensor and thereby minimize its reaction time to an emergency. At the same time, in order to achieve the sensor's resistance to mechanical vibrations and to prevent false alarms of the sensor, it is necessary to be able to reduce its sensitivity. Accordingly, the ability to control a sensor’s response to an emergency over a wide range by moving the point of application of the mechanical action of the tuning screw to the sensor’s setting element and the microswitch button expands the functionality of the device.

Installing the adjustment screw on the free end of the sensor with the possibility of mechanical action on the sensor installation element in the operating state and the microswitch button allows:
- fine-tune the sensitivity of the sensor without changing the position of the point of application of mechanical stress to the element of the installation of the sensor in working condition;
- realize the ability to memorize an emergency by selecting the operating position of the microswitch button between the points of its on and off.

The combined use of the first and third factors in the device allows us to achieve a sensor sensitivity that is several times higher than that of the prototype. High sensitivity of the sensor and, accordingly, a short response time to an emergency in the inventive device is achieved by:
- the absence of any mechanical effect that impedes the movement of the free end of the sensitive element (in the prototype, friction between the end of the sensitive element and the stop affects the mobility of the free end of the sensitive element),
- the ability to set the adjustment screw to a position in which the microswitch is in a state arbitrarily close to the point of changing its state from working to emergency.

Thus, the use of the inventive traction sensor:
- microswitches as a switching element,
- a lever as an element for setting the sensor in working condition,
- a tuning screw mounted on the free end of the sensing element with the possibility of both mechanical impact and changing the position of the point of application of this impact on the installation element of the sensor in working condition and the button of the microswitch,
provides enhanced functionality of the device, including:
- increase in the operating range of currents and voltages;
- regulation over a wide range of sensitivity and, accordingly, the response time of the device to an emergency,
- an increase in sensitivity and, accordingly, a decrease in the response time of the sensor to an emergency.

 The design of the device is shown in the drawing.

 The draft sensor contains a flue channel 1, a bimetallic sensing element 2, a micro switch 3, a lever 4 — an element for setting the sensor to working condition, a set screw 5, a free end 6 of the sensor 2, a microswitch button 7, a cover 8, a guide 9 of the flue channel 1, base 10.

 The device operates as follows.

 In the initial state, the free end 6 of the sensing element 2 by means of the adjustment screw 5 and by means of the lever 4 acts on the button 7 of the microswitch 3, partially drowning it inside the latter. Using the adjustment screw 5, lever 4, button 7 of microswitch 3 is installed and occupies a state between the operating emergency positions of the draft sensor.

 In case of draft failure in the chimney of the heat generating unit, the flue gases enter the flue channel of the sensor formed by the base 10, the cover 8 and the guide of the flue channel 9. The flue gases heat the bimetal sensor 2, the free end of which 6 moves to the side of the micro switch 3. The button 7 of the micro switch 3 is released from the mechanical impact of the free end 6 of the sensing element 2 and puts the micro switch in the state corresponding to the accident.

 According to the alarm “No draft”, the boiler unit is switched off, the temperature of the flue gases decreases to the temperature at which the sensor was set up for operation. The free end 6 of the sensing element 2 is returned to its original state, in which the button 7 of the micro switch 3 occupies the initial state, however, the micro switch remains in emergency condition. In order to set the sensor in working condition, it is necessary to press the lever 4. Under its action, button 7 of microswitch 3 lowers to the lower position, as a result of which the contacts of the microswitch assume a position corresponding to the operating state.

 The draft sensor is made using the following components and materials.

- bimetallic sensing element - from tape TB 138/80 0,8x200-0-M-A,
- switching element - micro-switch MI-3A, (micro-switch MI-3A is equipped with a lever),
- the free end of the sensor, the base of the sensor cover is made of sheet steel with a thickness of 1.5 mm.,
- tuning screw - M3x20 screw.

The inventive device provides:
- expanding the range of operating values of currents and voltages by at least 25%,
- provides increased sensitivity and, accordingly, reduced response time of the sensor to an emergency situation - not less than 2 times,
- provides the ability to configure the response time of the sensor to an emergency from 2 to 30 s.

Claims (1)

 A draft sensor containing a smoke exhaust channel, a bimetallic sensing element, a switching element and an element for setting the sensor in working condition in the form of a lever, characterized in that a micro switch with a driving element (button) is installed as a switching element, and a screw is installed on the free end of the bimetallic sensor element settings setting the operating position of the drive element between the operating and emergency positions of the traction sensor.