Air control circuit with safety function

Abstract

An air control circuit with safety function is constituted only by an air circuit. The air control circuit with safety function has: a main air pipe (4) for controlling an air device (3) by simultaneously opening and closing two electromagnetic valves (5a, 5b) of an external pilot type; a pilot air pipe (6) for supplying pilot air to the electromagnetic valves (5a, 5b); and a pilot control pipe (7) for switching the pilot air pipe (6) to a supply state and a discharge state, discharging air of the air device (3) through the electromagnetic valve of the other side which is switched to the closed position when a failure occurs in one of the two electromagnetic valves (5a, 5b) and is not switched to the closed position, thereby recovering the air device (3), and switching the pilot air pipe (6) to the discharge state with the pilot control pipe (7), thereby preventing the re-start of the two electromagnetic valves (5a, 5b).

Description

TECHNICAL FIELD

[0001] The present application relates to an air control circuit with a safety function for safely controlling an air device such as a cylinder. BACKGROUND

[0002] An air control circuit with a safety function for safely controlling an air device such as a cylinder is known as shown in Fig. 1, for example. The known air control circuit is configured by connecting two internal pilot type and spring return type 3-port electromagnetic valves 43, 44 in series in an air pipe 42 connecting an air source 40 and a cylinder 41, and even in the case where one of the electromagnetic valves 43 or 44 fails to normally operate in the operation of the cylinder 41, the residual air in the cylinder 41 is certainly exhausted by closing the other electromagnetic valve 44 or 43. Figure 11

[0003] However, in the known air control circuit, it is necessary to detect the failure of one of the electromagnetic valves 43 or 44 by an electric signal, and to control the closing of the other electromagnetic valve by a control device 45 such as a sequence generator by the electric signal, and so it is necessary to use an electromagnetic valve provided with a limit switch 46 that detects the operating position of the electromagnetic valves 43, 44 to output an electric signal, and it is also necessary to provide the sequence generator and its control program, and there are problems of high equipment cost, and the necessity of a technician skilled in the safety function and the sequence generator program. SUMMARY

[0004] PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] The technical problem of the present application is to provide an air control circuit with a safety function for safely controlling an air device that can be configured only by an air circuit without using an electromagnetic valve provided with a limit switch, a sequence generator, and the like.

[0006] SOLUTION TO THE PROBLEM

[0007] In order to solve the problem, the air control circuit of the present application has: a main air pipe connecting two external pilot type electromagnetic valves in series; a pilot air pipe supplying pilot air to the two electromagnetic valves; and a pilot control pipe switching the pilot air pipe between a supply state of supplying pilot air to the two electromagnetic valves and an exhaust state of exhausting the pilot air of the two electromagnetic valves.

[0008] ​The two solenoid valves of the main air pipe are two-position valves having a first position at the time of closing and a second position at the time of opening, and are connected in such a manner that, when both of the solenoid valves are in the first position, the air source and the air device are cut off and air of the air device is exhausted via one of the solenoid valves, when both of the solenoid valves are in the second position, the air source and the air device are connected to supply air from the air source to the air device, and when one of the solenoid valves is in the first position and the other is in the second position, the air source and the air device are cut off and air of the air device is exhausted via the solenoid valve in the first position.

[0009] An air operation valve having a first position in which the pilot air pipe becomes the supply state and a second position in which the pilot air pipe becomes the exhaust state is connected to the pilot air pipe.

[0010] Further, the pilot control pipe is configured to be connected to or cut off from the air source by the two solenoid valves, when both of the solenoid valves are in the first position and when both of the solenoid valves are in the second position, the air operation valve is maintained in the first position in which the pilot air pipe becomes the supply state by being cut off from the air source, and when one of the solenoid valves is in the first position and the other is in the second position, the air operation valve is switched to the second position in which the pilot air pipe becomes the exhaust state by being connected to the air source via the two solenoid valves to supply control air from the air source.

[0011] In the present application, it is preferable that the air operation valve has a lock pin mechanism that maintains the air operation valve in the second position and a release button that releases the maintenance of the lock pin mechanism.

[0012] The air control circuit of the present application can also be configured such that a pilot check valve that permits forward flow and reverse flow of the control air from the air source toward the air operation valve within the pilot control pipe when pilot air from the pilot air pipe acts on the pilot check valve and blocks the reverse flow of the control air when the pilot air does not act on the pilot check valve, a manual pressure relief valve that switches the pilot control pipe from a conductive state in which the control air is flowable to an open state in which the control air is exhausted to the outside by manual operation, and the air operation valve are connected to the pilot control pipe.

[0013] In addition, the air control circuit of the present application can also be configured such that an air tank that accumulates control air supplied from the air source and supplies the control air to the air operation valve is connected to the pilot control pipe.

[0014] Further, in the air control circuit of the present application, the two solenoid valves can also be 5-port valves having an input port, a first output port and a second output port, and a first exhaust port and a second exhaust port, and the two solenoid valves are composed of a first solenoid valve connected to the air source side of the main air pipe and a second solenoid valve connected to the air equipment side of the main air pipe, the input port of the first solenoid valve is connected to the air source, the first output port of the first solenoid valve is connected to the input port of the second solenoid valve, the second output port of the first solenoid valve is connected to the second exhaust port of the second solenoid valve, the first exhaust port and the second exhaust port of the first solenoid valve are open to the outside, the first output port of the second solenoid valve is connected to the air equipment, the second output port of the second solenoid valve is connected to the pilot control pipe, and the first exhaust port of the second solenoid valve is open to the outside.

[0015] In addition, in the air control circuit of the present application, a delay mechanism for delaying the start of the air equipment can also be connected to the main air pipe.

[0016] In this case, the delay mechanism is preferably composed of a switching valve operated by air and a throttle valve for limiting the flow of air, when the two solenoid valves are both open to connect the air source and the air equipment, the air with limited flow is circulated to the main air pipe via the throttle valve, and when a part of the air output from the main air pipe to the air equipment is fed back to the switching valve, the switching valve is switched in a manner that the air from the air source is circulated to the main air pipe in a free flow state.

[0017] Effects of the Invention

[0018] According to the present application, the air control circuit with safety function is composed of only an air circuit without using solenoid valves with limit switches, sequence generators, etc., so the structure is very simple and the equipment cost is low, and it is also unnecessary to ensure technicians skilled in safety function and sequence generator programs. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a circuit diagram showing a first embodiment of the air control circuit to which the present application pertains.

[0020] Figure 2 is a circuit diagram showing a different operation state of the air control circuit.

[0021] Figure 3 is a circuit diagram showing a further different operation state of the air control circuit.

[0022] Figure 4 is a circuit diagram showing further different operation states of the air control circuit.

[0023] Figure 5 is a diagram when a manual pressure relief valve is operated.

[0024] Figure 6 is a connection diagram showing different examples of the manual pressure relief valve.

[0025] Figure 7 is a circuit diagram showing a second embodiment of the air control circuit to which the present invention pertains.

[0026] Figure 8 is a circuit diagram showing a third embodiment of the air control circuit to which the present invention pertains.

[0027] Figure 9 is a diagram showing different operation states of the delay mechanism in Figure 8

[0028] Figure 10 is a connection diagram showing different examples of the delay mechanism.

[0029] Figure 11 is a circuit diagram showing a known air control circuit. DETAILED DESCRIPTION

[0030] Figures 1-5 A first embodiment of the air control circuit with a safety function to which the present invention pertains is shown. The air control circuit 1A connects an air source 2 and an air device 3, controls the air device 3 by supplying air from the air source 2 to the air device 3 or discharging air of the air device 3 to the outside, and has: a main air pipe 4 that connects two external pilot type electromagnetic valves 5a, 5b in series; a pilot air pipe 6 that supplies pilot air to the two electromagnetic valves 5a, 5b; and a pilot control pipe 7 that switches the pilot air pipe 6 to a supply state of supplying pilot air to the two electromagnetic valves 5a, 5b and a discharge state of discharging pilot air of the two electromagnetic valves 5a, 5b.

[0031] Further, in the present embodiment, the air device 3 is a cylinder, and the cylinder 3 is a single-acting cylinder that reciprocally drives a piston 3a and a rod 3b by air supplied to a pressure chamber 3c and a return spring 3d.

[0032] ​The two solenoid valves 5a, 5b have the same structure as each other, and are configured to switch to a first position 12 at the time of closing and a second position 13 at the time of opening by supplying and discharging pilot air and a return spring 11 by opening and closing operation of one solenoid spool 10. Therefore, the solenoid valves 5a, 5b can be single-spool and spring-return type two-position valves.

[0033] In addition, the solenoid valves 5a, 5b are five-port valves having one input port 14, two output ports, i.e., a first output port 15a and a second output port 15b, and two exhaust ports, i.e., a first exhaust port 16a and a second exhaust port 16b.

[0034] One of the two solenoid valves 5a, 5b, i.e., the solenoid valve 5a, is a first solenoid valve 5a connected on the air source 2 side of the main air passage 4, and the other solenoid valve 5b is a second solenoid valve 5b connected on the cylinder 3 side of the main air passage 4. Further, the input port 14 of the first solenoid valve 5a is connected to the air source 2 via an input passage 4a, the first output port 15a of the first solenoid valve 5a is connected to the input port 14 of the second solenoid valve 5b via a first relay passage 4b, the second output port 15b of the first solenoid valve 5a is connected to the second exhaust port 16b of the second solenoid valve 5b via a second relay passage 4c, and the first exhaust port 16a and the second exhaust port 16b of the first solenoid valve 5a are respectively opened to the outside via mufflers 17. In addition, the first output port 15a of the second solenoid valve 5b is connected to the pressure chamber 3c of the cylinder 3 via an output passage 4d, the second output port 15b of the second solenoid valve 5b is connected to one end of the pilot control passage 7, and the first exhaust port 16a of the second solenoid valve 5b is opened to the outside via a muffler 17.

[0035] The air device is controlled by simultaneously performing opening and closing operation of the two solenoid valves 5a, 5b connected to the main air passage 4 at all times by a control device not shown, and operates as follows.

[0036] First, as Figure 1As shown, when both of the solenoid valves 5a, 5b are closed and in the first position 12, the air source 2 and the cylinder 3 are cut off from each other, and the air in the pressure chamber 3c of the cylinder 3 is exhausted to the outside via the solenoid valve 5b on one side. That is, the input pipe 4a from the air source 2 is connected to the second relay pipe 4c through the first solenoid valve 5a, but the second relay pipe 4c is cut off by the second solenoid valve 5b, and the output pipe 4d connecting the first output port 15a of the second solenoid valve 5b and the cylinder 3 is open to the outside via the first exhaust port 16a of the second solenoid valve 5b, and the air from the cylinder 3 is exhausted. Thus, the piston 3a and the rod 3b of the cylinder 3 are retracted to the initial position by the restoring spring 3d.

[0037] At this time, the pilot control pipe 7 is open to the outside from the second output port 15b and the input port 14 of the second solenoid valve 5b via the first relay pipe 4b, the first output port 15a and the first exhaust port 16a of the first solenoid valve 5a.

[0038] On the other hand, as shown in FIG. 2, when both of the solenoid valves 5a, 5b are switched to the second position 13, the air source 2 and the cylinder 3 are connected to each other. That is, the input pipe 4a from the air source 2, the first relay pipe 4b, and the output pipe 4d are sequentially communicated via the first solenoid valve 5a and the second solenoid valve 5b, and the pressure chamber 3c of the cylinder 3 is supplied with air from the air source 2. Thus, the piston 3a and the rod 3b of the cylinder 3 are advanced toward the operating position. Figure 2 At this time, the pilot control pipe 7 is open to the outside from the second output port 15b and the second exhaust port 16b of the second solenoid valve 5b via the second relay pipe 4c, the second output port 15b and the second exhaust port 16b of the first solenoid valve 5a.

[0039] Next, in the case where both of the solenoid valves 5a, 5b are closed to return the air control circuit 1A and the cylinder 3 to the state of FIG. 1, in the case where a failure occurs in one of the solenoid valves and the solenoid valves are not switched to the first position 12, the air source 2 and the air device 3 are cut off, and the air in the pressure chamber 3c of the cylinder 3 is exhausted via the solenoid valve 5a or 5b returned to the first position 12, as described below.

[0040] Figure 1 First, as shown in FIG. 3, when the first solenoid valve 5a is closed and the second solenoid valve 5b is opened, the air source 2 and the cylinder 3 are cut off from each other, and the air in the pressure chamber 3c of the cylinder 3 is exhausted to the outside via the second solenoid valve 5b.

[0041] First, as shown in FIG. 3, when the first solenoid valve 5a is closed and the second solenoid valve 5b is opened, the air source 2 and the cylinder 3 are cut off from each other, and the air in the pressure chamber 3c of the cylinder 3 is exhausted to the outside via the second solenoid valve 5b. Figure 3 ​As shown, in the case where the first solenoid valve 5a is malfunctioning and left at the second position 13 and the second solenoid valve 5b is normally operating and returned to the first position 12, the input pipe 4a from the air source 2 is connected to the pilot control pipe 7 from the first solenoid valve 5a via the first relay pipe 4b and the second solenoid valve 5b, so that the pilot control pipe 7 is supplied with control air. In contrast, the output pipe 4d to the cylinder 3 is cut off from the air source 2, and is open to the outside via the first output port 15a and the first exhaust port 16a of the second solenoid valve 5b, so that the air of the cylinder 3 is exhausted via the second solenoid valve 5b, and the cylinder 3 is returned to the initial position.

[0042] Further, as shown in Fig. 2, the air operation valve 20 is a three-port valve which is switched to two positions by the action of the control air supplied via the pilot control pipe 7 and a return spring 22. Figure 4 As shown, in the case where the first solenoid valve 5a is normally operating and returned to the first position 12 and the second solenoid valve 5b is malfunctioning and left at the second position 13, the input pipe 4a from the air source 2 is connected to the pilot control pipe 7 from the second solenoid valve 5b via the second relay pipe 4c and the second solenoid valve 5b, so that the pilot control pipe 7 is supplied with control air. In contrast, the output pipe 4d is cut off from the air source 2, and is open to the outside from the second solenoid valve 5b via the first relay pipe 4b, the first output port 15a and the first exhaust port 16a of the first solenoid valve 5a, so that the air of the cylinder 3 is exhausted via the first solenoid valve 5a, and the cylinder 3 is returned to the initial position.

[0043] Returning to Figure 1 , the pilot air pipe 6 branches from a position between the air source 2 and the first solenoid valve 5a of the main air pipe 4, and is connected to the pilot ports 21 of the first solenoid valve 5a and the second solenoid valve 5b, respectively, via an air operation valve 20 connected to the pilot air pipe 6.

[0044] Further, in the following description, the input side (the side connected to the air source 2) of the air operation valve 20 is referred to as the primary side, and the output side (the side connected to the solenoid valves 5a, 5b) is referred to as the secondary side. Therefore, the portion of the pilot air pipe 6 from the air source 2 to the air operation valve 20 is a primary side pipe 6a, and the portion from the air operation valve 20 to the two solenoid valves 5a, 5b is a secondary side pipe 6b.

[0045] The air operation valve 20 is a three-port valve which is switched to two positions by the action of the control air supplied via the pilot control pipe 7 and the return spring 22. The air operation valve 20 is normally closed, as shown in Fig. 2. Figure 1 and Figure 2As shown, when the control air does not act by the pilot control pipe 7 being cut off from the air source 2, by switching to the 1st position 20a with the restoring spring 22, the pilot air pipe 6 is maintained in a supply state with the primary side pipe 6a and the secondary side pipe 6b being open, as shown Figure 3 and Figure 4 As shown, when the control air acts by the pilot control pipe 7 being connected to the air source 2, by switching to the 2nd position 20b with the control air, the primary side pipe 6a and the secondary side pipe 6b of the pilot air pipe 6 are cut off, and the secondary side pipe 6b is opened to the outside to become a discharge state.

[0046] In the pilot control pipe 7, from the 2nd electromagnetic valve 5b side toward the air operated valve 20 side, a pilot check valve 23, a manual pressure relief valve 24, and an air tank 25 are connected in series, and, in a display pipe 7a branching from a position between the manual pressure relief valve 24 and the air tank 25, a display lamp 26 that displays that control air is being supplied to the pilot control pipe 7 is connected.

[0047] The pilot check valve 23 allows the pilot control pipe 7 to be open in both directions when pilot air from the pilot air pipe 6 acts, and allows the pilot control pipe 7 to be open in only one direction when the pilot air does not act. That is, the pilot check valve 23 allows the forward flow of control air from the air source 2 toward the air operated valve 20 and the reverse flow of control air from the air operated valve 20 side toward the air source 2 side in the pilot control pipe 7 when the pilot air acts, and allows only the forward flow of control air and prevents the reverse flow when the pilot air does not act.

[0048] The manual pressure relief valve 24 is a 3-port valve that is switched to 2 positions by an operation lever 27 and a restoring spring 28. The manual pressure relief valve 24, as shown Figure 1 maintains the pilot control pipe 7 in an open state in which control air can flow through when switched to the 1st position 24a by the restoring spring 28, maintains the pilot control pipe 7 in an open state in which control air is discharged to the outside when switched to the 2nd position 24b of FIG. 5 by the operation lever 27, and returns to the 1st position 24a by the restoring spring 28 when the operation lever 27 is released.

[0049] The air tank 25 supplies control air supplied from the air source 2 to the air operated valve 20 after accumulating the control air, for stabilizing the supply of control air.

[0050] Next, the operation of the air control circuit 1A as a whole will be described.

[0051] Figure 1 is a state where both the first solenoid valve 5a and the second solenoid valve 5b are closed and in the first position 12, and the main air pipe 4 cuts off the air source 2 and the cylinder 3.

[0052] At this time, the air in the pressure chamber 3c of the cylinder 3 is exhausted to the outside via the second solenoid valve 5b from the output pipe 4d, so the cylinder 3 is in the initial position where the rod 3b is retracted. In addition, the control air from the air source 2 is not supplied to the pilot control pipe 7, so the air operated valve 20 is in the first position 20a to keep the pilot air pipe 6 in the supply state. Therefore, the pilot air from the air source 2 is supplied to the first solenoid valve 5a and the second solenoid valve 5b via the pilot air pipe 6. Further, the pilot operated check valve 23 makes the pilot control pipe 7 conductive in both directions by the action of the pilot air.

[0053] When the first solenoid valve 5a and the second solenoid valve 5b are simultaneously opened and switched to the second position 13 from this state, as shown in Figure 2 , the air source 2 and the pressure chamber 3c of the cylinder 3 are communicated via the input pipe 4a, the first solenoid valve 5a, the first relay pipe 4b, the second solenoid valve 5b, and the output pipe 4d. Therefore, by supplying air to the pressure chamber 3c from the air source 2, the rod 3b of the cylinder 3 is advanced toward the working position.

[0054] At this time, the pilot control pipe 7 is cut off from the air source 2.

[0055] After the working procedure using the cylinder 3 is finished, by simultaneously closing the first solenoid valve 5a and the second solenoid valve 5b, the air control circuit 1A returns to the operating state shown in Figure 1 , so the cylinder 3 also returns to the initial position.

[0056] However, in the case where one of the two solenoid valves 5a, 5b fails and does not return to the first position 12, as explained below, the air of the cylinder 3 is exhausted via the returned solenoid valve 5a or 5b, so that the cylinder 3 returns to the initial position, and at the same time, the pilot air of the first solenoid valve 5a and the second solenoid valve 5b is automatically exhausted, so that the first solenoid valve 5a and the second solenoid valve 5b are prevented from being restarted.

[0057] First, as shown in Figure 3As shown, when the second solenoid valve 5b is closed and switched to the first position 12, and the first solenoid valve 5a malfunctions and is in the second position 13, the output pipe 4d to the cylinder 3 is opened to the outside via the second solenoid valve 5b, so the air in the cylinder 3 is vented through the second solenoid valve 5b, and the cylinder 3 returns to its initial position.

[0058] At this time, the pilot control pipe 7 is connected to the air source 2 via the first solenoid valve 5a and the second solenoid valve 5b, so control air is supplied to the pilot control pipe 7 from the air source 2. This control air, after being accumulated in the air tank 25 via the pilot check valve 23 and the manual pressure relief valve 24, is supplied from the air tank 25 to the air-operated valve 20, switching the air-operated valve 20 to the second position 20b. As a result, the primary side pipe 6a and the secondary side pipe 6b of the pilot air pipe 6 are cut off, and the secondary side pipe 6b is opened to the outside to become an exhaust state. Therefore, the pilot air of the first solenoid valve 5a and the second solenoid valve 5b is vented, and as a result, the first solenoid valve 5a and the second solenoid valve 5b can no longer be activated.

[0059] Moreover, after the pilot air in the secondary side pipe 6b is vented, the pilot air will not act on the pilot check valve 23, so the pilot check valve 23 performs its original check function, preventing the control air from flowing back from the air-operated valve 20 side to the air source 2 side in the pilot control pipe 7.

[0060] Additionally, when control air is supplied to the pilot control conduit 7, the indicator light 26 illuminates, notifying the operator that either of the solenoid valves 5a or 5b has malfunctioned.

[0061] On the other hand, such as Figure 4 As shown, when the first solenoid valve 5a is closed and switched to the first position 12, and the second solenoid valve 5b malfunctions and is in the second position 13, the output pipe 4d to the cylinder 3 opens to the outside from the second solenoid valve 5b via the first relay pipe 4b and the first solenoid valve 5a, so that the air in the cylinder 3 is exhausted, and the cylinder 3 returns to its initial position.

[0062] Even in this case, the pilot control conduit 7 is connected to the air source 2 via the second solenoid valve 5b and the first solenoid valve 5a, supplying control air to the pilot control conduit 7, so that... Figure 3 Similarly, the pilot air of the first solenoid valve 5a and the second solenoid valve 5b is vented by the air-operated valve 20 to prevent the restart of the first solenoid valve 5a and the second solenoid valve 5b. The pilot-operated check valve 23 and the indicator light 26 also operate in the same manner as described above.

[0063] By such an action of the air control circuit 1A, the danger of sudden start of the air cylinder 3 due to reactivation of the electromagnetic valves 5a, 5b in the check of the failure is avoided.

[0064] Further, in the state where the failure of the electromagnetic valve 5a or 5b is recovered, in order to make the air control circuit 1A into a state where it is possible to reactivate, as shown in Fig. 6, the manual pressure relief valve 24 is switched to the second position 24b by manually operating the operation lever 27 of the manual pressure relief valve 24. Thereby, the pilot control pipe 7 becomes an open state and the control air in the air tank 25 is discharged to the outside, so the air operated valve 20 is switched to the first position 20a by the restoring spring 22, making the pilot air pipe 6 into a supply state. Thereby, the pilot air from the air source 2 is supplied to the first electromagnetic valve 5a and the second electromagnetic valve 5b, so the first electromagnetic valve 5a and the second electromagnetic valve 5b become into a state where it is possible to reactivate. In addition, the pilot check valve 23 makes the pilot control pipe 7 conductive in both the forward direction and the reverse direction by the action of the pilot air. Figure 3 and Figure 4 Figure 5

[0065] After the operation of the operation lever 27 is released, the manual pressure relief valve 24 is restored to the first position 24a by the restoring spring 28.

[0066] In the embodiment, the air tank 25 is connected to the pilot control pipe 7, but the air tank 25 does not necessarily have to be provided.

[0067] In addition, the manual pressure relief valve 24 is a 3-port valve, but a 2-port valve can also be used. Figure 6 A connection example in the case where a manual pressure relief valve 24 constituted by a 2-port valve is used is shown. In this example, the manual pressure relief valve 24 is connected to a pressure relief pipe 7b branched from the pilot control pipe 7.

[0068] The manual pressure relief valve 24 is normally in the first position 24a and cuts off the pressure relief pipe 7b, but when the operation lever 27 is operated, it is switched to the second position 24b and the pressure relief pipe 7b is opened to the outside via the muffler 18, so the control air in the pilot control pipe 7 is discharged to the outside.

[0069] Figure 7 ​​FIG. 2 is a view showing a second embodiment of the air control circuit to which the present application is applied. The air control circuit IB of the second embodiment differs from the air control circuit IA of the first embodiment in that the air operation valve 20 connected to the pilot air pipe 6 is provided with a latch mechanism 50 for holding the air operation valve 20 in the second position 20b and a release button 51 for releasing the holding by the latch mechanism 50.

[0070] The latch mechanism 50 has a variable member 50a which is displaced integrally with the air operation valve 20 and a latching member 50b with which the variable member 50a is latched after the air operation valve 20 is switched to the second position 20b by the control air from the pilot control pipe 7, so that the air operation valve 20 is held in the second position 20b.

[0071] In addition, the release button 51 releases the latching of the latching member 50b against the variable member 50a by pressing the release button 51, so that the air operation valve 20 is displaced toward the first position 20a by the urging force of the return spring 22.

[0072] The latch mechanism 50 is provided for the reason that, in a state where one of the solenoid valves 5a, 5b fails to switch normally, the air operation valve 20 is switched to the second position 20b by the action of the control air supplied from the pilot control pipe 7, and in the case where the control air no longer acts on the air operation valve 20 due to the reason that air is not sufficiently held in the tank 25, etc., the air operation valve 20 is returned to the first position 20a by the return spring 22, the pilot air pipe 6 becomes a supply state to supply the pilot air to the solenoid valves 5a, 5b, so that the solenoid valves 5a, 5b are prevented from becoming a restartable state.

[0073] The structure and action of the air operation valve 20 of the air control circuit IB other than the air control circuit IB are the same as those of the air control circuit IA of the first embodiment, so that the same reference numerals are added to the main identical structural parts of the two, and the description thereof is omitted.

[0074] Further, the release button 51 can be configured to act in conjunction with the pressing operation of the operation lever 27 of the manual pressure relief valve 24.

[0075] In this case, in the case where the air operation valve 20 is held in the second position 20b by the latch mechanism 50, the air operation valve 20 is returned to the first position 20a by the release button 51. Figure 7When the manual pressure relief valve 24 is switched to position 24b by pressing the operating lever 27, the release button 53 is activated in conjunction with it, and the air-operated valve 20 is switched to position 1 20a. As a result, the pilot control pipe 7 becomes open, venting control air to the outside, and the pilot air pipe 6 becomes supplied, supplying pilot air to the solenoid valves 5a and 5b.

[0076] After the operating lever 27 is released, the manual pressure relief valve 24 returns to the first position 24a via the return spring 28, and the air-operated valve 20 maintains the first position 20a via the return spring 22.

[0077] Figure 8 This is a diagram illustrating a third embodiment of the air control circuit according to the present invention. The air control circuit 1C of this third embodiment differs from the air control circuit 1A of the first embodiment in that a delay mechanism 30 for delaying the start-up of the cylinder 3 is connected to the main air duct 4.

[0078] The delay mechanism 30 consists of a switching valve 31 that can be switched to two positions by air and a return spring 32, and a throttle valve 33 that limits the flow of air, and is connected between the air source 2 and the first solenoid valve 5a.

[0079] The switching valve 31 is a three-port valve, having a first port 34 connected to the input pipe 4a of the main air pipe 4, a second port 35 connected to a branch pipe 4e branching from the input pipe 4a, and a third port 36 connected to the input port 14 of the first solenoid valve 5a by a third relay pipe 4f. It switches to the original position via feedback air from the output pipe 4d connecting the second solenoid valve 5b and the cylinder 3 via the feedback pipe 37 and the return spring 32. Figure 8 Position 1, 31a and Figure 9 Position 2, 31b.

[0080] In addition, the throttle valve 33 is a variable throttle valve with an adjustable flow path cross-sectional area.

[0081] In the air control circuit 1C, as follows Figure 8 When the switching valve 31 is in position 31a, both the first solenoid valve 5a and the second solenoid valve 5b are open and switched to position 13 (see reference). Figure 2 When the air source 2 and the cylinder 3 are connected via the throttle valve 33, the air from the air source 2 is supplied to the cylinder 3 in a state where the flow rate is limited by the throttle valve 33, so the cylinder 3 starts slowly.

[0082] After that, when a portion of the air is fed back to the switching valve 31 from the output pipe 4d via the feedback pipe 37, as shown in Fig. 6, the switching valve 31 is switched to the second position 31b, the branch pipe 4e connected to the throttle valve 33 is shut off and the input pipe 4a is connected to the third relay pipe 4f, so the air from the air source 2 flows into the air cylinder 3 in a free flow state, whereby the rod 3b of the air cylinder 3 advances at a normal speed. Figure 9

[0083] The structure and action of the delay mechanism 30 of the air control circuit 1C other than the above are the same as those of the air control circuit 1A of the first embodiment, so the same parts of the two are given the same reference numerals and the explanation thereof is omitted.

[0084] Further, the switching valve 33 of the delay mechanism 30 is a 3-port valve, but a 2-port valve can also be used. In this case, as shown in Fig. 8, the switching valve 31 and the throttle valve 33 are connected in parallel between the input pipe 4a and the third relay pipe 4f. Thereby, at the time of starting the air cylinder 3, the switching valve 31 is in the first position 31a and the flow path is shut off, so the air from the input pipe 4a flows to the third relay pipe 4f in a state where the flow is restricted by the throttle valve 33. Also, when the air is fed back to the switching valve 31 via the feedback pipe 37, the switching valve 31 is switched to the second position 31b, so the air from the input pipe 4a flows to the third relay pipe 4f in a free flow state via the switching valve 31. Figure 10

[0085] Further, even in the air control circuit 1C of the third embodiment, the air operation valve 20 can have the latch mechanism 50 and the release button 51 as in the air control circuit 1B of the second embodiment.

[0086] In the illustrated embodiment, the air cylinder is shown as an example of the air device 3, but the air device 3 can also be a device other than the air cylinder, for example, it can also be another pilot electromagnetic valve that controls the air cylinder and the like. In this case, by connecting the output pipe 4d of the main air pipe 4 to the pilot pipe of the pilot electromagnetic valve, at the time of emergency, it is possible to perform control such as discharging the pilot air of the pilot electromagnetic valve and resetting the air device.

[0087] As detailed above, the air control circuits 1A, 1B, 1C are composed only of air circuits, so compared to the conventional examples using electromagnetic valves with limit switches, sequence generators and the like, they have the advantages that the structure is very simple and the equipment cost is low, and it is not necessary to secure a technician skilled in safety functions and sequence generator programs. ​​

[0088] Reference Signs List

[0089] 1A, 1B, 1C: air control circuit; 2: air source; 3: air device (cylinder); 4: main air pipe; 5a: 1st solenoid valve; 5b: 2nd solenoid valve; 6: pilot air pipe; 7: pilot control pipe; 12: 1st position; 13: 2nd position; 14: input port; 15a: 1st output port; 15b: 2nd output port; 16a: 1st exhaust port; 16b: 2nd exhaust port; 20: air operated valve; 23: pilot check valve; 24: manual pressure relief valve; 25: air tank; 30: delay mechanism; 31: switching valve; 33: throttle valve; 50: lock pin mechanism; 50a: variable member; 50b: locking member; 51: release button.

Claims

1. An air control circuit with safety function, characterized in that, has: a main air pipe connecting two external pilot electromagnetic valves in series; a pilot air pipe supplying pilot air to the two electromagnetic valves; and a pilot control pipe switching the pilot air pipe between a supply state of supplying pilot air to the two electromagnetic valves and a discharge state of discharging the pilot air of the two electromagnetic valves, the two electromagnetic valves of the main air pipe are two-position valves having a first position at the time of closing and a second position at the time of opening, and are connected in such a manner that, when both of the two electromagnetic valves are in the first position, an air source and an air device are cut off and air of the air device is discharged via one of the electromagnetic valves, when both of the two electromagnetic valves are in the second position, the air source and the air device are connected to supply air from the air source to the air device, and when one of the two electromagnetic valves is in the first position and the other is in the second position, the air source and the air device are cut off and air of the air device is discharged via the electromagnetic valve in the first position, an air operation valve is connected to the pilot air pipe, and has a first position in which the pilot air pipe is in the supply state and a second position in which the pilot air pipe is in the discharge state, the pilot control pipe is configured to connect or disconnect the two electromagnetic valves to / from the air source, and when both of the two electromagnetic valves are in the first position and in the second position, the air operation valve is maintained in the first position in which the pilot air pipe is in the supply state by being disconnected from the air source, and when one of the two electromagnetic valves is in the first position and the other is in the second position, the air operation valve is switched to the second position in which the pilot air pipe is in the discharge state by being connected to the air source via the two electromagnetic valves to supply control air from the air source.

2. The air control circuit according to claim 1, wherein the air operation valve has a lock pin mechanism that maintains the air operation valve in the second position and a release button that releases the maintenance of the lock pin mechanism.

3. The air control circuit according to claim 1, wherein a pilot check valve, a manual pressure relief valve, and the air operation valve are connected to the pilot control pipe, the pilot check valve permits forward flow and reverse flow of the control air from the air source toward the air operation valve within the pilot control pipe when pilot air from the pilot air pipe acts on the pilot check valve, and blocks the reverse flow of the control air when the pilot air does not act on the pilot check valve, the manual pressure relief valve switches the pilot control pipe from a conduction state in which the control air is flowable to an open state in which the control air is discharged to the outside by manual operation.

4. The air control circuit according to claim 3, wherein an air tank that accumulates control air supplied from the air source and supplies the control air to the air operation valve is connected to the pilot control pipe.

5. The air control circuit according to claim 1, wherein the two electromagnetic valves are 5-port valves having an input port, a first output port and a second output port, and a first exhaust port and a second exhaust port, in addition, the two electromagnetic valves are constituted by a first electromagnetic valve connected to the air source side of the main air pipe, and a second electromagnetic valve connected to the air device side of the main air pipe, the input port of the first electromagnetic valve is connected to the air source, the first output port of the first electromagnetic valve is connected to the input port of the second electromagnetic valve, the second output port of the first electromagnetic valve is connected to the second exhaust port of the second electromagnetic valve, the first exhaust port and the second exhaust port of the first electromagnetic valve are open to the outside, the first output port of the second electromagnetic valve is connected to the air device, the second output port of the second electromagnetic valve is connected to the pilot control pipe, and the first exhaust port of the second electromagnetic valve is open to the outside.

6. The air control circuit according to any one of claims 1 to 5, wherein a delay mechanism for delaying the start of the air device is connected to the main air pipe.

7. The air control circuit according to claim 6, wherein the delay mechanism is constituted by a switching valve operated by air, and a throttle valve that restricts the flow of air, when both of the two electromagnetic valves are open to connect the air source and the air device, air that restricts the flow is made to flow to the main air pipe via the throttle valve, and when a part of the air output from the main air pipe to the air device is fed back to the switching valve, the switching valve is switched so that air from the air source flows to the main air pipe in a free flow state.

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