Novel silicon carbide ceramic surface grinding device

Abstract

A novel silicon carbide ceramic surface grinding device comprises a current transformer, a bottom plate, an electric linear sliding table, an electric telescopic rod, a motor speed reducing mechanism, a linear bearing, a rack and an electric grinding machine body and further comprises an electric clamping mechanism and a detection circuit. The bottom plate, the electric linear sliding table, the electric telescopic rod, the motor speed reducing mechanism, the linear bearing, the rack, the electric grinding machine body and the electric clamping mechanism are installed together, and the current transformer and the detection circuit are installed in the element box. According to the electric grinding machine, a silicon carbide ceramic product needing to be ground can be clamped or loosened in an electric mode, the electric grinding machine body can be driven to grind the surface of the silicon carbide ceramic product in the front or back, left or right, up or down and different circumferential directions by operating the power switch, convenience is brought to workers, and the working efficiency is improved. The probability that workers make contact with dust generated after polishing is reduced, the overall working current of equipment can be monitored in real time, and when the current is too large, the buzzer can make sound to prompt the workers to shut down and overhaul in time in real time.

Description

Technical Field

[0001] The utility model relates to the technical field of grinding equipment, in particular to a novel surface grinding and repairing device for silicon carbide ceramics. Background Art

[0002] Products prepared from silicon carbide (SiC) ceramics (such as silicon carbide bricks, silicon carbide cantilever paddles, silicon carbide beams, silicon carbide structural ceramic shafts, silicon carbide plates, silicon carbide ceramic tubes, silicon carbide air ducts, silicon carbide rod protection tubes, etc., which are not listed one by one) have the advantages of high strength, high hardness, high temperature resistance, corrosion resistance, good thermal conductivity, low density, excellent thermal shock resistance, low thermal expansion, oxidation resistance, etc., and are therefore widely used in the field of industrial ceramics.

[0003] In the actual production of silicon carbide ceramic products, due to production equipment and processes, improper operation of staff, or terminal application requirements, there is a need to grind (repair) the corresponding end faces of the silicon carbide ceramic products after production. In the prior art, when grinding the corresponding end faces of silicon carbide ceramic products, they are fixed in a fixture, and then the staff holds an electric grinder, and the grinding head driven by a motor is used to grind the corresponding surface. Although the existing grinding method meets the production needs to a certain extent, due to structural limitations, there are still the following technical problems. First: During the entire grinding process, the staff needs to hold the electric grinder by hand for grinding, which brings inconvenience to the staff and increases their labor intensity. Second: The staff is too close to the grinding operation area, and the dust generated during grinding is likely to have an adverse impact on the respiratory health of the staff. Third: The staff needs to manually operate to control the chuck of the fixture to clamp or separate from the workpiece, which also brings inconvenience to the staff. In summary, it is very necessary to provide a surface grinding and repairing device for silicon carbide ceramics that can bring convenience to the staff and reduce the adverse impact on the physical health of the staff. Summary of the Utility Model

[0004] In order to overcome the disadvantages of the existing grinding equipment for silicon carbide ceramic products due to structural limitations as described in the background art, the utility model provides a novel surface grinding and repairing device for silicon carbide ceramics. Under the combined action of relevant mechanisms, it can conveniently clamp or loosen the product to be ground in an electric manner, and by simply operating the power switch, the grinding head of the electric grinder body can grind the product in the front or rear, left or right, up or down, and different circumferential directions, which brings convenience to the staff, reduces the probability of the staff coming into contact with the dust generated after grinding, can play a good role in protecting the respiratory health of the staff, and can monitor the working current of the whole equipment in real time. When the electric grinder body and other components cause an excessive current due to a fault, it can prompt the staff to shut down and repair in time, reducing the damage caused by the expansion of equipment failures.

[0005] The technical solution adopted by the utility model to solve its technical problems is as follows:

[0006] A novel surface grinding and repairing device for silicon carbide ceramics includes a current transformer, a bottom plate, an electric linear slide, an electric telescopic rod, a motor reduction mechanism, a linear bearing, a frame, and an electric grinding machine body. It is characterized in that it also has an electric clamping mechanism and a detection circuit; there are multiple sets of the electric linear slides, and two sets of the electric linear slides are respectively installed on both sides of the upper end of the bottom plate. The lower end of the frame is installed on both side ends of the bottom plate. The upper ends of the electric telescopic rod and the linear bearing are respectively installed on both sides of the upper end of the frame, and the lower ends of the electric telescopic rod and the linear bearing are respectively installed on the upper end of the housing of the third set of electric linear slides; the motor reduction mechanism is vertically installed on the lower side of the sliding block of the third set of electric linear slides; the upper end of the housing of the electric grinding machine body is installed on the lower end of the rotating shaft of the electric reduction mechanism; the electric clamping mechanism is installed on the upper parts of the sliding blocks of two sets of the electric linear slides, and the detection circuit and the current transformer are installed in the power supply box.

[0007] Furthermore, the electric clamping mechanism includes a motor, a lead screw, a fixed shell, a fixed block, and a movable block. The lower end of the fixed shell is respectively installed on the upper parts of the sliding blocks of two sets of the electric linear slides. There are three horizontally distributed chutes on the upper side of the fixed shell. One side end of the fixed shell is installed with a bearing. The motor is installed on the other side end of the fixed shell. The lower end of the fixed block is installed on one end of the fixed shell. The lower end of the movable block is installed with three guide rods, and the lower end of the middle guide rod has a threaded hole. The three guide rods of the movable block are respectively slidably located in the right ends of the three chutes. The middle of the lead screw and the threaded hole at the lower end of the middle guide rod of the movable block are connected by threads. One end of the lead screw is installed in the inner ring of the bearing, and the other end of the lead screw is installed together with the side end of the motor rotating shaft.

[0008] Furthermore, limit blocks are respectively installed at the lower ends of the two guide rods at the front and rear parts of the movable block.

[0009] Furthermore, the detection circuit includes a resistor, a triode, a buzzer, a capacitor, a bridge rectifier, and a variable resistor that are electrically connected, and is electrically connected to the current transformer. The phase wire input end of the electric grinding machine body passes through the central hole of the current transformer. The secondary side power output end of the current transformer and the two power input ends of the bridge rectifier are respectively connected. The positive power output end of the bridge rectifier is connected to the positive pole of the capacitor and one end of the variable resistor. One end of the resistor is connected to the base of the triode and the other end of the variable resistor. The collector of the triode is connected to the negative power input end of the buzzer. The emitter of the triode is connected to the negative pole of the capacitor and the other end of the resistor.

[0010] The beneficial effects of the present utility model are as follows: (1) Based on the electric grinding machine body, the present utility model can conveniently clamp or loosen the silicon carbide ceramic product to be ground through the electric clamping mechanism and in an electric manner, and by simply operating the power switch, the three sets of electric linear slides, electric telescopic rods, and motor reduction mechanisms can drive the grinding head of the electric grinding machine body forward or backward, left or right, up or down, and in different circumferential directions to grind the surface of the silicon carbide ceramic product, which brings convenience to the staff. Since there is no need to hold the electric grinding machine body by hand, the probability of the staff coming into contact with the dust generated after grinding is correspondingly reduced, which can play a good role in protecting the respiratory health of the staff (the component box can also not be installed on the bottom plate, and the staff can operate at a relatively farther place, which can further reduce the adverse impact of dust on their health); (2) The detection circuit cooperates with the current transformer to monitor the working current of the whole device in real time. When the current of the electric grinding machine body and other components is too large due to a fault, it can emit a sound through the buzzer in real time to prompt the staff to shut down and repair in time, reducing the probability of the device being damaged due to the expansion of the fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present utility model will be further described below with reference to the drawings and embodiments.

[0012] Figure 1 It is a schematic diagram of the overall structure of the present utility model.

[0013] Figure 2 It is a schematic diagram of the partial structure of the present utility model.

[0014] Figure 3 It is a circuit diagram of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] Figure 1 、 2, as shown in FIGS. 3, the new type of surface grinding and repairing device for silicon carbide ceramics includes a power supply module W1, a power switch, a current transformer T, a bottom plate 1, an electric linear slide, an electric telescopic rod M3, a motor reduction mechanism M5, a linear bearing 2, a frame 3, an electric grinding machine body M4, and also has an electric clamping mechanism and a detection circuit 5; there are three sets of electric linear slides, and the lower ends of the shells of two sets of electric linear slides M1 are longitudinally distributed at left and right intervals and are respectively installed on both sides of the upper end of the bottom plate 1 through bolts. The lower ends of both sides of the "Π"-shaped frame 3 are respectively welded to both side ends of the bottom plate 1. There are two sets of electric telescopic rods and linear bearings respectively. The push rods of the two sets of electric telescopic rods M3 are respectively welded to the front part of the left end and the rear part of the right end inside the upper end of the frame 3. The upper ends of the bearing seats of the two sets of linear bearings 2 are respectively welded to the rear part of the left end and the front part of the right end inside the upper end of the frame 3; the upper ends of the left and right sides of the shell of the third set of electric linear slide M2 (its slider faces downward) are respectively longitudinally welded with a connecting plate 6. The lower ends of the cylinders of the two sets of electric telescopic rods M3 are respectively welded to the front and rear parts of the two connecting plates 6. The lower ends of the shafts of the two sets of linear bearings 2 are respectively welded to the rear and front parts of the two connecting plates 6; the motor reduction mechanism M5 is vertically distributed and the upper end of its shell is installed on the lower side of the slider of the third set of electric linear slide M2 through bolts; the middle part of the upper end of the shell of the electric grinding machine body M4 is welded to the lower end of the rotating shaft of the electric reduction mechanism M5; the electric clamping mechanism is installed on the upper parts of the sliders of two sets of electric linear slides M1. The power supply module W1, the power switch, the detection circuit 5, and the current transformer T are installed on the circuit board in the power supply box 7. The component box 7 is installed on the left end of the bottom plate 1.

[0016] Figure 1 , 2, as shown in Figures 3, the electric clamping mechanism includes a motor M6, a lead screw 81, a hollow fixed housing 82, a fixed block 83, and a movable block 84. The lower left and right sides of the fixed housing 82 are respectively welded to the upper parts of the sliding blocks of two sets of electric linear slides M1. The front, rear, and middle parts of the upper side of the fixed housing 82 are respectively provided with a horizontally distributed rectangular chute 85. The middle parts of the left and right sides of the fixed housing 82 respectively have an opening. A bearing 86 is welded in the right end opening. The motor M6 is installed in the middle of the left end of the fixed housing 82 through bolts, and its rotating shaft is introduced into the fixed housing 82 through the left opening (the inner diameter of the opening is greater than the outer diameter of the rotating shaft). The lower end of the fixed block 83 is longitudinally welded to the upper part of the left end of the fixed housing 82. Three guide rods 87 are vertically welded at intervals at the lower end of the movable block 84, and a screw hole 88 is provided at the lower end of the middle guide rod. The three guide rods 87 of the movable block are respectively slidably located in the right ends of the three chutes 85. The middle part of the lead screw 81 is threadedly connected to the screw hole 88 at the lower end of the middle guide rod of the movable block. The right end of the lead screw 81 is tightly sleeved in the inner ring of the bearing 86. The left end of the lead screw 81 is welded to the right end of the rotating shaft of the motor M6. At the lower ends of the front and rear parts of the lower end of the movable block 84, a limiting block 89 with a front and rear width greater than the front and rear width of the chute is respectively welded. The front and rear width of the guide rod 87 is slightly smaller than the front and rear width of the chute 85. The upper end of the limiting block 89 is in sliding contact with the lower end of the chute 85. The detection circuit includes a resistor R1, a triode Q1, a buzzer B, a capacitor C1, a bridge rectifier W2, and a variable resistor RP1 connected by circuit board wiring, and is connected to a current transformer T through a wire. The power input end of the power supply module W1 and the phase wire input end of the electric grinding machine body M4 pass through the central hole of the current transformer T. The secondary side power output end of the current transformer T and the power input ends 1 and 2 of the bridge rectifier W2 are respectively connected through wires. The positive power output end 3 of the bridge rectifier W2 is connected to the positive electrode of the capacitor C1 and one end of the variable resistor RP1. One end of the resistor R1 is connected to the base of the triode Q1 and the other end of the variable resistor RP1. The collector of the triode Q1 is connected to the negative power input end of the buzzer B. The emitter of the triode Q1 is connected to the negative electrode of the capacitor C1 and the other end of the resistor R1.

[0017] Figure 1 , 2As shown in Figures 2 and 3, the power input end of the electric grinding machine body M4 is connected in series through a wire by the first power switch S4, and the power input ends 1 and 2 of the power module W1 and the two poles of the AC 220V power supply are respectively connected through wires. The power output ends 3 and 4 of the power module W1, the power input end of the detection circuit, the positive power input end of the buzzer B, the emitter of the triode Q1, and the power input ends 1 and 2 of the other five power switches are respectively connected through wires. The power output ends 3, 4, 5, and 6 of the second power switch S and the positive and negative and negative and positive power input ends of two sets of electric linear slides M are respectively connected through wires. The power output ends 3, 4, 5, and 6 of the third power switch S1 and the positive and negative and negative and positive power input ends of the third set of electric linear slides M2 are respectively connected through wires. The power output ends 3, 4, 5, and 6 of the fourth power switch S2 and the positive and negative and negative and positive power input ends of two sets of electric telescopic rods M3 are respectively connected through wires. The power output ends 3, 4, 5, and 6 of the fifth power switch S3 and the positive and negative and negative and positive power input ends of the motor reduction mechanism M5 are respectively connected through wires. The power output ends 3, 4, 5, and 6 of the sixth power switch S5 and the positive and negative and negative and positive power input ends of the motor M6 of the electric clamping mechanism are respectively connected through wires.

[0018] Figure 1 、 2As shown in Figures 1 and 3, the present utility model is based on the electric grinding machine body M4, and the grinding head is driven by the motor of the electric grinding machine body M4 to perform grinding operations on the corresponding surface of the product. After the AC power supply enters the power input terminal of the power supply module W1, the power output terminal of the power supply module W1 outputs a stable DC 24V power supply to enter the power input terminals of the other five power switches and detection circuits. The use process of this new type is as follows. (1): The staff toggles the handle of the power switch S5 of the motor M6 to the left or right, and the 1st, 2nd feet and the 3rd, 4th feet or the 5th, 6th feet of the power switch S5 are respectively connected. In this way, the positive and negative or negative and positive power input terminals of the motor M6 will be powered on; after the positive and negative power input terminals of the motor M6 are powered on, its rotating shaft will drive the lead screw 81 to rotate clockwise. The external thread of the lead screw 81 acts on the guide rod screw hole 88 of the movable block 84. Then, the movable block 84 moves towards the left end and the distance between it and the fixed block 83 decreases, and the silicon carbide ceramic to be ground can be fixed between the movable block and the fixed block (with the grinding surface facing up). After reaching the position, the power switch S5 is turned off; after the negative and positive power input terminals of the motor M6 are powered on, its rotating shaft will drive the lead screw 81 to rotate counterclockwise. The external thread of the lead screw 81 acts on the guide rod screw hole 88 of the movable block 84. Then, the movable block 84 moves towards the right end and the distance between it and the fixed block 83 increases, and the ground silicon carbide ceramic can be taken out. After reaching the position, the power switch S5 is turned off. During specific grinding, after turning on the power switch S4 of the electric grinding machine body M4 (with a power of 2.5KW), the electric grinding machine body M4 is powered on and its motor drives the grinding head to rotate at a high speed. Subsequently, the grinding head grinds the upper grinding surface of the silicon carbide ceramic product. After the staff toggles the handle of the power switch S to the left or right, the 1st, 2nd feet and the 3rd, 4th feet or the 5th, 6th feet of the power switch S are respectively connected. In this way, the positive and negative or negative and positive power input terminals of the motors of two sets of electric linear slides M1 will be powered on; the sliding blocks of the two sets of electric linear slides M1 drive the electric clamping mechanism and the fixed silicon carbide ceramic product to move forward or backward to the position, and are located below the grinding head of the electric grinding machine body M4 for grinding (after reaching the position, the power switch S is turned off). After the staff toggles the handle of the power switch S1 to the left or right, the 1st, 2nd feet and the 3rd, 4th feet or the 5th, 6th feet of the power switch S1 are respectively connected. In this way, the positive and negative or negative and positive power input terminals of the motor of the third set of electric linear slide M2 will be powered on; the sliding block of the third set of electric linear slide M2 drives the electric clamping mechanism and the fixed silicon carbide ceramic product to move left or right to the position, and is located below the grinding head of the electric grinding machine body M4 for grinding (after reaching the position, the power switch S1 is turned off).After the staff toggles the handle of the power switch S2 to the left or right, the 1st and 2nd pins, the 3rd and 4th pins, or the 5th and 6th pins of the power switch S2 are respectively connected. In this way, the positive and negative or negative and positive power input terminals of the motors of the two sets of electric telescopic rods M3 will be powered on; the push rods of the two sets of electric telescopic rods M3 drive the grinding head of the electric grinding machine body M4 to move upward or downward to grind the surface of the silicon carbide ceramic product (turn off the power switch S2 after reaching the position), and the two sets of linear bearings 2 guide the up or down movement of the electric grinding machine body M4. After the staff toggles the handle of the power switch S3 to the left or right, the 1st and 2nd pins, the 3rd and 4th pins, or the 5th and 6th pins of the power switch S3 are respectively connected. In this way, the positive and negative or negative and positive power input terminals of the motor of the motor reduction mechanism M5 will be powered on, and the rotating shaft of the motor reduction mechanism M5 drives the lower end of the grinding head of the electric grinding machine body M4 to rotate clockwise or counterclockwise to the in-place position to grind the corresponding angle of the grinding surface of the silicon carbide ceramic product (turn off the power switch S3 after reaching the position). Through the above, the present invention can conveniently clamp or loosen the silicon carbide ceramic product to be ground by the electric clamping mechanism in an electric manner, and by simply operating the power switch, the three sets of electric linear slides, electric telescopic rods, and motor reduction mechanisms can respectively drive the grinding head of the electric grinding machine body to move forward or backward, left or right, up or down, and in different circumferential directions to grind the surface of the silicon carbide ceramic product, which brings convenience to the staff. Since there is no need for the staff to hold the electric grinding machine body by hand, the probability of the staff coming into contact with the dust generated after grinding is correspondingly reduced, which can play a good role in protecting the respiratory health of the staff (the component box can also not be installed on the bottom plate, and the staff can operate at a relatively farther place, which can further reduce the adverse impact of dust on their health).

[0019] Figure 1 , 2, as shown in Figures 3, after the detection circuit is powered on and working, when the device is working normally and consuming electricity, the greater the current, the greater the current flowing through the current transformer T, and the greater the voltage signal output from the secondary side of the current transformer T to pins 1 and 2 of the bridge rectifier W2 (when the current is large, the voltage will increase). Conversely, the smaller the current flowing through the current transformer T, the lower the voltage signal output from the secondary side of the current transformer T to the bridge rectifier W2 (when the current is low, the voltage will decrease). As the total power consumption load of the device changes, the AC power output from the secondary side of the current transformer T is rectified by the bridge rectifier W2 and converted into DC power, filtered by the capacitor C1, and then enters one end of the adjustable resistor RP1. In actual situations, when the device is working normally and consuming electricity and the current does not exceed the set threshold (for example, does not exceed 15A), the power output from the bridge rectifier W2 is divided by the resistor R1 and the adjustable resistor RP1 and enters the base of the triode Q1, which is lower than 0.7V. The triode Q1 will not conduct, so the buzzer B will not be powered on and make a sound, indicating normal operation. When the current is too large due to a fault in the electric grinding machine body or the like (for example, exceeds 15A), the power output from the bridge rectifier W2 is divided by the resistor R1 and the adjustable resistor RP1 and enters the base of the triode Q1, which is higher than 0.7V. The triode Q1 will conduct, and the collector will output a low level to the negative power input terminal of the buzzer B. In this way, the buzzer B will be powered on and make a sound, indicating abnormal operation. The staff can then shut down the machine for maintenance in a timely manner, reducing the probability of the device being damaged due to the expansion of the fault. Figure 3 Among them, the resistance value of the resistor R1 is 10K; the model of the NPN triode Q1 is 9013; the model of the capacitor C1 is 470μF 50V; the model of the buzzer B is an active continuous sound buzzer alarm of SF24V; the model of the rectifier bridge W2 is KBPC310; the electric linear slides M1 and M2 are finished products of electric screw type linear slides with a power of 150W; the motor reduction mechanism M5 is a finished product of a coaxial motor gear reducer with a power of 120W and a rotation speed of 6 revolutions per minute of the rotating shaft; the power of the motor M6 is 180W; the electric telescopic rod M3 is a finished product of a reciprocating electric push rod with a power of 80W; the resistance value of the adjustable resistor RP1 is 470K (the greater the resistance value adjusted by the technician, the greater the voltage division. Then, when the overall device working current is relatively large, the triode Q1 will conduct, that is, the current detection threshold of this new type is set relatively large; the smaller the resistance value adjusted by the technician, the smaller the voltage division. Then, when the overall device working current is relatively small, the triode Q1 will conduct, that is, the current detection threshold of this new type is set relatively small. Specifically, the technician sets it according to needs); the power supply module W1 is a finished product of an AC 220V to DC 24V power supply module of the Mean Well brand; the current transformer T is a finished product of a small current transformer.

[0020] The foregoing has shown and described the basic principles, main features and advantages of the present utility model. For those skilled in the art, it is obvious that the present utility model is limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic features of the present utility model, the present utility model can be implemented in other specific forms. Therefore, in any regard, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present utility model is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes that fall within the meaning and scope of the equivalent elements of the claims in the present utility model.

[0021] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A new type of silicon carbide ceramic surface grinding device, including a current transformer, a base plate, an electric linear slide, an electric telescopic rod, a motor reduction mechanism, a linear bearing, a frame, and an electric grinding machine body, characterized in that: It also has an electric clamping mechanism and a detection circuit; there are multiple sets of electric linear slides, two of which are respectively installed on both sides of the upper end of the base plate, the lower end of the frame is installed on both sides of the base plate, the upper ends of the electric telescopic rod and the linear bearing are respectively installed on both sides of the upper end of the frame, and the lower ends of the electric telescopic rod and the linear bearing are respectively installed on the upper end of the shell of the third set of electric linear slides; the motor reduction mechanism is vertically installed on the lower side of the sliding block of the third set of electric linear slides; the upper end of the shell of the electric grinder body is installed on the lower end of the rotating shaft of the electric reduction mechanism; the electric clamping mechanism is installed on the upper part of the sliding blocks of two of the electric linear slides, and the detection circuit and the current transformer are installed in the power box.

2. The novel silicon carbide ceramic surface grinding device according to claim 1 is characterized in that: The electric clamping mechanism includes a motor, a lead screw, a fixed shell, a fixed block, and a movable block. The lower end of the fixed shell is respectively installed on the upper part of the sliding blocks of two sets of electric linear slides. The upper side of the fixed shell is provided with three laterally distributed slide grooves. A bearing is installed on one side end of the fixed shell. The motor is installed on the other side end of the fixed shell. The lower end of the fixed block is installed on one end of the fixed shell. Three guide rods are installed on the lower end of the movable block, and the lower end of the middle guide rod has a screw hole. The three guide rods of the movable block are respectively slidably located in the right ends of the three slide grooves. The lower end screw holes of the guide rods in the middle of the lead screw and the middle of the movable block are threadedly connected. One end of the lead screw is installed in the inner ring of the bearing, and the other end of the lead screw is installed together with the side end of the motor shaft.

3. The novel silicon carbide ceramic surface grinding device according to claim 2 is characterized in that: Limiting blocks are respectively installed at the lower ends of two guide rods at the front and rear parts of the movable block.

4. The novel silicon carbide ceramic surface grinding device according to claim 1 is characterized in that: The detection circuit includes an electrically connected resistor, a transistor, a buzzer and a capacitor, a bridge stack, an adjustable resistor, and is electrically connected to a current transformer. The phase line input end of the electric grinder body passes through the center hole of the current transformer, the secondary side power supply output end of the current transformer is respectively connected to the two ends of the power supply input of the bridge stack, the positive power supply output end of the bridge stack is connected to the positive pole of the capacitor and one end of the adjustable resistor, one end of the resistor is connected to the base of the transistor and the other end of the adjustable resistor, the collector of the transistor is connected to the negative power supply input end of the buzzer, and the emitter of the transistor is connected to the negative pole of the capacitor and the other end of the resistor.

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