SU419735A1 - PNEUMATIC CONTROL SYSTEM - Google Patents

Description

one

The invention relates to control systems, mainly machines for casting under low pressure.

A known system for pneumatic control of a machine for low pressure casting. It consists of air preparation devices (water separator, air dryer, oil spray), pressure regulator, air supply valve, throttle, variable section valve connected parallel to the throttle, air distributor, sealed chamber (furnace) for metal, safety interlock devices (safety valves) , pressure relief valve, instrumentation.

When the air supply valve is turned on, the compressed air enters the sealed chamber through the throttle and begins to displace the metal through the metal conduit. The pressure build-up time in the sealed chamber is controlled by the throttle and variable valve, which are activated by the air distributor. At the beginning of the mold filling, the alloy closes the electrical sensor, turns on the air distributor, and the latter actuates the variable cross section valve. At the same time, the alloy with a given acceleration fills the cavity of the mold. However, the fill rate

the metal conductor and the metal mold itself as the production of metal from the hermetic chamber (furnace) decreases. Consequently, the filling time of the form increases. In this case, during the filling of the mold, the metal manages to overcool in it and hardens in thin casting areas. As a result of this, the feeding of the more massive parts of the casting, which are located behind the solidified

plots in relation to the metal pipe. Thus, the subsequent castings have defects in the form of shrink holes and loose, as well as violation of the geometry. In addition, at the end of the production of metal from the hermetic chamber, due to a decrease in the rate of pouring, the productivity of the machine is reduced. The decrease in the speed of the die casting in the described machine occurs due to an increase in the resistance of the metal-static head,

the height of which increases after each cast as the metal is produced from the chamber. In addition, the rate of metal pouring into the mold in this machine is also reduced due to the lower fluidity.

metal in the case where the metal has a lower temperature during casting the mold. The aim of the invention is to create conditions for casting metal with the same speed both at the beginning and at the end of the production of metal from the sealed chamber, as well as when the temperature of the metal in it varies. This is achieved by the fact that a variable volume receiver with a control device made of a series-installed solenoid valve and throttle with a check valve is connected between the two air supply valves. In addition, the control device of the receiver is connected to a time-correcting chain consisting, for example, of series-connected thermocouples, a secondary signaling device and a quadratic signal converter of the secondary device.

The drawing shows a pneumatic control scheme for a low pressure casting installation.

The installation includes a valve 1, air preparation instruments 2, a pressure regulator 3, an air supply valve 4, a control valve 5, a variable volume receiver 6, a receiver’s safety valve 7, a pressure gauge 8, a receiver volume control device consisting of a series-connected valve 9 and throttle with a check valve 10, a valve 11 for draining oil from the receiver, an air supply valve 12 (from the receiver to a sealed chamber), a throttle 13 connected in parallel and a variable section valve 14, an air distributor 15, a check valve 16, ger electric camera (furnace) 17, metal pouring mold 18, electrical sensors 19, level gauges 20, furnace relief valve 21, pressure relief valve 22, pressure relief valve 23, furnace 24, 25 and 26 pressure monitoring and alarm devices, thermocouple 27 , secondary signaling device 28 and quadrant converter 29. The listed devices and equipment are interconnected by communication lines 30-46, control lines 47-49, control lines 50-53 and control lines 54-57.

In the initial state, the valve 1 is open, the valves 11 and 23 are closed. The air supply valve 4, the receiver 6 and the pressure relief valve 22 from the furnace 17 are open. The valve 9 of the regulating device, the valve 12 for supplying air, the valve 14 of irregular section and the air distributor 15 are closed. Let us assume that pressure switch 24 is set at a pressure of 0.05 kg / cm, and pressure switch 26 is set at a pressure of 0.71 kg / cm. If this pressure is exceeded, valve 22 receives a command to open (pressure release). Apparatus 25 is designed to maintain the crystallization pressure of the metal in a form of about 0.7 kg / cm. Safety valve 7 is set to the maximum pressure in the receiver. The safety valve 21 is set to release pressure when it is exceeded in a sealed chamber of more than 7.1 kg / cm.

To start the priming cycle, pressing the button on the control panel (not shown) turns off the air supply valve solenoid 4, and the valve solenoid 22

include As a result, valves 4 and 22 are closed. In so doing, the electromagnets of the valves 9 and 12 are turned on, and the valves themselves open. The valve 9 of the regulating device of the receiver 6 remains open for the time of displacement of a certain portion of oil from the external cavity 58 of the receiver 6 into its internal cavity 59. The time of the displacement of the portion of oil is controlled by the time relay setting

(not shown) of the regulating device of the receiver 6.

The displacement of a portion of oil from the external cavity 58 into the internal cavity 59 is required in order to increase the volume of the receiver 6

for the next compaction of the air in order to preserve the speed of pouring the following form. The increase in the volume of the receiver 6 in this case is necessary to compensate (fill) the volume of the sealed chamber 17, the increased

due to the metal consumption for the previous casting, as well as for overcoming the additional resistances, compared with the first casting, due to the increase in the metal column, which must be raised when

pouring, i.e., to overcome the additional resistances of metallostatic pressure.

The increase in the volume of the receiver occurs after each fill to the production of metal from the sealed chamber. After that, liquid metal is poured into the sealed chamber, and oil from the internal cavity 59 of the receiver 6 is forced out into its external cavity 58 by compressed air by turning the control knob 5 knob. The receiver and the sealed chamber are ready for the next filling cycle.

When metal is poured into the mold, air from the receiver 6 through the open valve 12 and the throttle 13 through pipelines 39, 40, 42, 43 and through the check valve 16 enters the hermetic chamber 17. The air pressure in the chamber increases; and the metal is displaced along the metal conduit 60 into the mold 18. At the beginning of the mold filling, the metal closes the bottom contact 61

electrical sensor 19, which includes the air distributor 15, and the latter includes a valve 14 of variable cross section. Metal with a given acceleration fills the cavity of the mold. At the end of the mold casting, the metal closes the upper contact 62 of the electrical sensor 19, which activates a time relay with a setting for the time that the metal crystallizes in the mold. The air pressure to the sealed chamber continues to increase to a maximum value, in this case, up to 0.7 kg / cm. This pressure is fixed by the device 25, which gives the command to close the air supply valve 12. A portion of the air from the network is fed to the receiver 6 with some

excess to compensate for leaks.

In the event of a pressure drop in the hermetic chamber 17 due to leaks, the device 25 gives a command to reopen valve 12. When a predetermined pressure is reached, the device 25 gives a command to close valve 12,

Thus, the pressure in the impermeable enclosure is held until the crystallization of the metal in the mold is complete.

At the end of the crystallization delay, the time relay issues a command to close valve 12 (if it was open) and open valve 22 to depressurize air from the sealed chamber 17. Pressure is released in the chamber. When the overpressure in the sealed chamber decreases to 0.05 kg / cm, the pressure switch 24 gives a signal to the devices (not shown in the drawing), which carry out the separation of the mold from the hole and the disassembly of the mold. After the assembly of the new form, the cycle is repeated.

If a lower temperature metal was poured into the sealed chamber 17 or the temperature of the metal in the chamber decreased, then when pouring such a metal into the mold, additional resistances appear due to a decrease in its fluidity. In order to maintain the rate of pouring of the metal in this case, the circuit provides a correction chain consisting of thermocouples 27 connected in series, a secondary signaling device 28 and a quadratic converter 29. The pulse from the thermocouple 27 is transmitted to the quadratic converter 29, and the last gives the command to correct the setpoint of the time relay of the regulating device of the receiver 6. The said time relay increases the time of oil displacement from the external cavity 58 of the receiver 6 into the internal cavity 59, if the metal in the hermetic chamber 17 has a reduced temperature relative to the optimum one, and reduces the oil displacement time, if the metal has a higher temperature.

Subject invention

Claims (2)

1. Pneumatic control system, mainly a pressurized casting system, containing successively connected gas preparation devices, pressure regulator, instrumentation, gas supply valves, variable cross-section valve with a throttle connected in parallel adjusting the duration of pressure build-up, variable valve control valve, pressure-tight chamber and safety interlocking and pressure-relief devices, characterized in that In order to improve the quality of the castings, it is equipped with a variable-capacity Receiver of variable volume II installed between two gas supply valves, made of a series-connected solenoid valve and throttles with a non-return valve. 2. The system according to claim 1, characterized in that, in order to preserve the pouring speed with the temperature of the metal, the control device is connected to a time-corrective chain made of a series-connected thermocouple, secondary signaling device and quadratic converter using a receiver. . Fri VV | R / Z) 13 Ksch w " J5 lid W W i 4S 75