KR100449980B1 - An overload preventing apparatus of a mechanical press - Google Patents

Abstract

The present invention relates to an overload protection device of a mechanical press that is easy to set the overload pressure of the mechanical press, and can improve the processing quality by allowing the load acting during the press operation to be measured at any time.

The overload protection device of the mechanical press of the present invention is a mechanical press (1) in which an overload cylinder (15) is formed between the slide (7) on which the upper mold is installed and the ball seat (14) at the bottom of the ball screw (11). A detection unit 20 for measuring a pressure value acting on the overload cylinder 15 and a power supply unit 50 for applying a DC input current to the detection unit 20 input side 38 to measure the pressure value in the detection unit 20. ), An amplifier 70 for amplifying a difference between the current value input to the input side 38 of the detector 20 and the current value output from the output side of the detector 20, and an input from the amplifier 70. And a signal processor 40 for processing the amplified signal to be output as a measured value through the display 44 or the relay 46.

Therefore, according to the present invention, there is no need to restore the original device of the prevention device according to the overload protection, and malfunctions due to pressure or vibration are not generated, and the load applied from time to time can be measured even during operation.

Description

An overload preventing apparatus of a mechanical press}

The present invention relates to an overload protection device, and more particularly, press pressure during operation by measuring the pressing force generated during various plastic working at all times in the hydraulic chamber to monitor whether the press operation is performed within a preset allowable range. The present invention relates to an overload protection device of a mechanical press that predicts and determines quality, thereby precluding failure factors, and preventing damage to the machine itself and the mold against excessive loads exceeding the pressure capacity.

In general, the press is equipped with an overload protection device, which is a device for preventing the damage of the press itself or the mold when the mechanical press is operated in excess of the press capacity, that is, the nominal pressure. In the case of a forging press, a plate-shaped rigid body is inserted between the slide and the connecting rod so that the plate-shaped rigid body is broken when overloaded, so that the press is not overwhelmed.

An example of a press equipped with such a rigid body breakage overload protection device is a press as shown in FIG. 1 as 101. According to the press 101, the lower mold 105 installed on the upper surface of the bed 103 and Ball screw 113 in the power transmission system (not shown) leading to the motor, flywheel, clutch, crankshaft, connecting rod when the workpiece 111 is inserted and processed between the upper mold 109 installed on the lower surface of the slide 107. The energy transmitted to the sheet 117 is transferred to the slide 107 via the ball seat 115 and the seat plate 117 so that the repulsive force between the bed 103 and the slide 107 is greater than the allowable load of the seat plate 117 during processing. In this case, the sheet plate 117 is damaged to protect the press or the mold. By the way, such a rigid body damage overload protection device has the advantage that the price is low, but takes a long time to restore the original condition when an overload occurs, there is a problem that it is difficult to use in a precision press.

In most other cases, there is an overload cylinder between the slide and the connecting rod. When the hydraulic pressure exceeds the set pressure, the pressure switch is operated to stop the press. The pressure capacity of the press is based on the cross-sectional area of the cylinder, which is also referred to as nominal pressure or nominal pressure, which means the press can withstand up to several tons of pressure generation.

This overload cylinder type overload protection device is applied to the mechanical press 201 as shown in Figs. 2a to 2c, so that the motor 202, the flywheel 203, the clutch / brake 204, the first and the second gear reduction unit (209, 210), a lower mold (not shown) installed on the top of the bed 213 along the power transmission system leading to the crank shaft 205, the ball screw 211, the slide 207 and the upper mold installed on the bottom of the slide 207 The reaction force generated when machining the workpiece (not shown) between (not shown) is detected by the pressure magnitude | size inside the overload cylinder 215, ie, cross-sectional area x pressure = reaction force.

At this time, the overload detector 221 for detecting the pressure applied to the overload cylinder 215 can set and control the overload as shown in more detail in Figure 2c, once the air supply source 225 in the air pump 223 30% of the pressure (P _p ; hereinafter referred to as preload pressure) at the time of overloading when the hydraulic pressure P1 on the overload cylinder 215 side and the hydraulic pressure P2 on the control side are generated by using the compressed air as a power source. Set to the level (typically, 70 kg / cm 2) to maintain the equilibrium, and set to the set pressure at the time of overload by the spring 227, the hydraulic piston 229 by the same pressure as the overload cylinder 215 at the time of overload This pushes up and simultaneously pushes up the air piston 231 and the air piston 233. Accordingly, as the switch 235 is short-circuited, the press 201 is stopped, and the oil inside is returned to the tank 239 through the drain pipe 237.

However, such a conventional overload cylinder type overload protection device is difficult to set the overload pressure, and it is difficult to check whether the overload pressure is correctly set without a load measuring device such as a separate load cell. I have a problem that I need. In addition, since the press itself vibrates severely, there is a problem in that malfunction due to spring or pneumatic fluctuations cannot be avoided.

Therefore, the present invention has been proposed to solve the problems of the conventional mechanical press overload protection device as described above, it is easy to set the overload pressure without a separate measuring device, the material during the press work plastic processing by the mold When not only can the pressure be measured continuously at every moment, but it can also predict and determine the defectiveness of the product to be processed in advance in comparison with the optimum pressure set in advance. Its purpose is to store it for use in analyzing the cause of product defects.

1 is a partial schematic cross-sectional view showing a conventional mechanical press with a rigid body overload protection device.

Figure 2 is a view of a conventional mechanical press with a hydraulic overload protection device by an overload cylinder, Figure 2a is a longitudinal sectional view of the press, Figure 2b is an enlarged view of the portion indicated by A of Figure 2a, Figure 2c Magnified view of the portion labeled B in 2b.

Figure 3 is a longitudinal sectional view of the mechanical press with an overload protection device according to the present invention.

Figure 4 is a partial cross-sectional view in detail showing the detection portion of the overload protection device according to the invention.

Figure 5 is a block diagram schematically showing an overload protection device according to the present invention.

* Explanation of Signs of Major Parts of Drawings *

1: mechanical press 3: flywheel

5: crankshaft 7: slide

11: ball screw 13: bed

15: overload cylinder 17,17-1,17-2: hydraulic line

20: detector 21: detector cylinder

40: signal processing unit 50: power supply unit

51: constant voltage output unit 60: alarm signal unit

70: amplification unit

In order to achieve the above object, the present invention provides a detection unit for measuring a pressure value acting on an overload cylinder in a mechanical press in which an overload cylinder is formed between a slide on which an upper mold is installed and a ball seat at a lower end of a ball screw. A power supply unit for applying a DC input current to the detector input side to measure the pressure value in the detector, an amplifier for amplifying the difference between the current value inputted at the input side of the detector and the current value output at the output side of the detector; An overload protection device for a mechanical press including a signal processing unit for processing an amplified signal and outputting it as a measured value through a display or a relay.

Hereinafter, the overload prevention apparatus of the mechanical press according to the embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The mechanical press to which the overload protection device of the present invention is applied is the same as the conventional mechanical presses as shown in FIGS. 3 and 4, the motive motor 2, the flywheel 3, the clutch / brake 4, the first and the second. The gear reduction parts 9 and 10, the crankshaft 5, the ball screw 11, the slide 7, the bed 13, etc. make a basic structure.

Therefore, the slide 7 and the bed with the pressing force transmitted to the ball screw 11 through the flywheel 3 and the gear reduction parts 9 and 10 by the driving force generated in the motor 2 as in the conventional general mechanical press. The workpiece | work (not shown) between the upper and lower metal mold | die (not shown) provided in each of 13 is press-processed.

4 and 5, the overload cylinder 15 formed between the ball seat 14 and the slide 7 coupled to the bottom of the ball screw 11 maintains the preload pressure which is the preset pressure. In order to detect an overload and to control and display the detected pressure, the overload protection device of the present invention is connected to the overload protection device according to the present invention. The overload protection device of the present invention includes a detector 20, an amplifier 70, and a signal processor 40. ), A power supply unit 50, an alarm signal unit 60, and the like.

At this time, the detection unit 20 is composed of a detector cylinder 21 of the hydraulic cylinder type as shown in Figs. 4 and 5, the detector cylinder 21 and the overload cylinder 15 through the hydraulic line 16 Is connected to the oil tank 18 through the hydraulic line 17 branched in the middle of the hydraulic line 16, the cylindrical cylinder body 29, which forms the outer body as shown, the control side in the body 29 The detector piston 22 which forms the oil pressure, the adjustment knob 24 which finely adjusts the control side oil pressure, and the strain gauges 31, 32, 33, 34 attached to the outer peripheral surface of the detector piston 22 are comprised.

Here, the detector piston 22 of the detection unit 20 is configured to form the control side hydraulic pressure together with the inner surface of the cylinder 21 by the front hydraulic surface 23 as shown, and for this purpose, the front and rear outer peripheral surfaces are sealed. A plurality of O-rings 26 are wound around each other, and the cutouts 27 are processed in a dumbbell shape between the front and rear O-rings 26. And one strain gauge pair 31-1, 31-2 arranged back and forth is attached to the inner side of the cutout 27 of the piston 22, and the front strain gauge 31-1 has a right angle with the axis line. In the forming direction, the rear strain gauges 31-2 are each arranged in a direction parallel to the axis line. At this time, each strain gauge 31, 32, 33, 34 is connected to form a whole Wheatstone bridge circuit as shown in FIG.

In addition, the adjustment knob 24 is screwed in the rear side of the cylinder 21, the push rod 28 is in close contact with the rear surface opposite the hydraulic surface 23 of the piston 22 as shown in FIG. It is to adjust the control side hydraulic pressure formed by the piston 22 while moving forward and backward by forward and reverse rotation, push rod 28 has a tip portion in contact with the rear surface of the piston 22 to reduce the pressure deviation It is rounded.

The hydraulic line 17 branched from the hydraulic line 16 and connected to the oil tank 18 is connected to the two hydraulic lines 17-1 and 17-2 from the oil tank 18 side as shown in FIG. Branching again, one line 17-1 is equipped with a pneumatic-driven hydraulic pump 36 in the middle to receive air from the air supply source 35 to supply the elevated pressure at the input side to the hydraulic line 17-1. The hydraulic pressure in the line 16 is increased by applying it to the hydraulic line 16. A check valve 37-1 is attached to the front and rear of the pneumatically driven hydraulic pump 36. As shown in FIG. In the middle of the other line 17-2, a drain actuating valve 37-2 is installed between the oil tank 18 as shown, and the actuating valve 37-2 has an overload cylinder 15 It is to operate when the overload is detected in the to drain the hydraulic pressure in the overload cylinder (15).

As shown in FIG. 5, in the detector 20 configured to detect the pressure applied to the overload cylinder 15 as described above, the constant voltage output unit 51 of the power supply unit 50 is connected to the input side 38. The amplifiers 70 are connected to the amplification units 70, respectively, where the constant voltage output unit 51 converts the AC input power into a DC current of 10 V and applies the input to the input side 38 of the detection unit 20. Accordingly, the current output from the output side 39 of the detection unit 20 is compared with the input current, and the difference is converted by the signal processing unit 40 of FIG. 5 to detect the load value of the press. In addition, the amplifying unit 70 is configured to amplify the micro-signal input from the output side 39 to be transmitted to the signal processing unit 40, the signal processing unit 40 as shown in Figure 5 A / D converter 41 , A microprocessor 43, a display 44, an interface 45, and a relay 46. Here, the microprocessor 43 again includes a CPU 47, a RAM 48, a ROM 49, and the like, and includes an A / D converter 41, a microprocessor 43, a display 44, and an interface. It is connected with the 45 and the relay 46, respectively, and is also connected with the alarm signal part 60 through the relay 46. As shown in FIG.

Now, the operation of the overload protection device of the mechanical press 1 according to the present invention configured as described above will be described with reference to FIGS. 3 to 5.

The mechanical press 1 to which the overload protection device of the present invention is applied is also designed to process a workpiece by an upper mold installed below the slide 7 and a lower mold installed above the bed like a general press. An overload protection device is connected to the overload cylinder 15 to set and maintain the preload pressure, as shown by the overload cylinder 15 between the slide 14 and the slide 7 to detect the overload occurring during the press operation. In addition to stopping the operation of the press during overload detection, it also serves to detect the pressing force in the middle of the work process.

Among these, the process of detecting the overload occurring during operation by the mechanical press 1 will first be described. When the overload cylinder 15 is overloaded along the power transmission system as described above, the pressure in the overload cylinder 15 is increased. Ascending, the hydraulic pressure on the control side in the detector cylinder 21 connected to the overload cylinder 15 by the hydraulic line 16 also rises together. As the control side hydraulic pressure is increased in this manner, the detector piston 22 is retracted in the detector cylinder 21 by the O-ring 26 to be kept airtight, and finally, the adjustment knob 24 as shown in FIG. 4. ) Is pressed against the rounded portion of the tip of the push rod 28. Accordingly, the maximum stress is generated at the notch portion of the notch 27 of the piston 22, and the generated stress is composed of a plurality of strain gauges 31, 32, 33, 34 attached to the notch 27. Measured by the detector 20, the strain gauge resistance change value according to the magnitude of the stress is the difference between the voltage of the output side 39 according to the voltage of the input side 38 of the detector 20, which is usually 10V in the amplifier 70. After being amplified to a level, the signal processing unit 40 converts the ratio of the cross-sectional area of the overload cylinder 15 and the detector cylinder 21 into proportional calculations to convert the data into a load value of the press.

At this time, in order to set the preload pressure of the overload cylinder 15 to maintain the preload pressure inside the overload cylinder 15, first, the pneumatic drive hydraulic pump 36 is driven to draw air from a supply source such as a compressor. By supplying hydraulic pressure to the hydraulic line 17-1, the hydraulic pressure of the hydraulic line 17 is increased through the check valve 37-1. As a result, when the hydraulic pressure in the detector cylinder 21 and the hydraulic pressure in the overload cylinder 15 become the same, the load in which the signal value is set in advance by an external key switch or the like in the signal processing unit 40 (usually 30 of the press capacity). %) And outputs the set pressure value R2 through the relay 46 so that the hydraulic pump 36 is stopped by a separate control means such as a magnet and predetermined by a key input to the display 44. This completes the setting of the preload pressure. At this time, the adjustment of the minute load can be performed by the adjustment knob 24.

In addition, when a pressure drop occurs in the overload cylinder 15 due to internal leakage, a predetermined range up to about 80% of the preload set pressure is set using a key switch or the like, and when a pressure drop occurs to the set range, the relay 46 Outputs a pressure value (R1), and the reason why the pressure drop occurs at this time is that even if the O-ring or the packing is used, the internal sealing cannot be achieved 100%.

Therefore, according to the overload cylinder 15 set as described above, when the detected load reaches the load (usually 120% of the press capacity) set in advance in the overload cylinder 15, the pressure value corresponding to the detected load is measured by the signal processor. The microprocessor 43 microprocessor 43 microprocesses the data value, and then compares with the preset values in the CPU 47, the RAM 48, and the ROM 49 to determine the pressure value R4 in the relay 46. ) Then, by operating the brake of the press 1 by a separate control means such as a magnet or the like, the operation of the press is quickly stopped, and at the same time, the drain operating valve 37-2 is operated to reduce the hydraulic pressure in the overload cylinder 15. The oil tank 18 is drained.

In addition, when it is necessary to determine whether there is a defect for predicting the quality of the press work during the press work, the necessary load is set in advance, and when the work load reaches the set load during the press process, the pressure value corresponding to the work load is determined by a microprocessor ( After data is converted into 43, the CPU 47, the RAM 48, and the ROM 49 of the signal processing unit 40 make a comparison with the set value and output the pressure value R3 from the relay 46 to output the alarm signal unit ( In (60), a worker may be made aware through a buzzer or a lamp.

As described above, according to the overload protection device of the mechanical press according to the present invention, as in the sheet plate breakage type overload protection method, it is not necessary to suffer the original recovery measures due to the breakage of the seat plate. In addition, as in the conventional pneumatic overload prevention method, it is possible to completely overcome the occurrence of micro clearance due to the slide up and down, and to prevent the difficulty of setting the overload pressure of the pneumatic type and malfunction due to vibration of the press. In addition, it can be applied to almost all kinds of mechanical presses equipped with an overload cylinder, and the load in the working process can be easily measured without additional equipment, thereby improving the quality of the press work.

Claims (3)

In the mechanical press (1) in which an overload cylinder (15) is formed between the slide (7) on which the upper mold is installed and the ball seat (14) at the bottom of the ball screw (11), A cylinder body 29 forming an outer body, a detector piston 22 inserted in a forward and backward direction to form a control side hydraulic pressure in the body 29, and a plurality of strain gauges 31 attached to the piston 22. A detection unit (20) comprising a detector cylinder (21) composed of 32, 33, and 34, for measuring a pressure value acting on the overload cylinder (15); A power supply unit (50) for applying a DC input current to the detection unit (20) input side (38) to measure the pressure value in the detection unit (20); An amplifier 70 which amplifies the difference between the current value input to the input side 38 of the detector 20 and the current value output from the output side of the detector 20; A signal processing unit 40 for processing the amplified signal input from the amplifying unit 70 and outputting it as a measured value through the display 44 or the relay 46; . According to claim 1, And an alarm signal unit (60) connected to the signal processing unit (40) through the relay (46) to emit a warning or an alarm. According to claim 1, The detector cylinder (21), the overload protection of the mechanical press, characterized in that further comprising an adjustment knob (24) for fine-adjusting the control side hydraulic pressure while being in contact with or spaced from the piston (22).