Pneumatic circuit for conveying equipment and control method thereof

Abstract

The present invention provides a pneumatic circuit for a conveying apparatus capable of reducing energy consumption compared to conventional techniques by more effectively utilizing the generated negative pressure. The control valve mechanism includes a three-way valve and a two-way valve controlled to be in an open state during the suction operation and in a closed state during the release operation. Further, a three-way valve in the control valve mechanism is controlled to be in a first state in which negative pressure generated by the vacuum generator is supplied to the one or more suction cups during the suction operation, and in a second state in which negative pressure generated by the vacuum generator is supplied to the one or more suction cups during the release operation. And a second state in which supply of negative pressure generated by the vacuum generator is blocked to arrange a negative pressure limiting section between the three-way valve and the two-way valve and to lead the inside of the one or more suction cups to the atmosphere, and during a suction operation in the next delivery operation, the three-way valve is controlled to change from the second state to the first state, the negative pressure in the negative pressure limiting section and the negative pressure generated by the vacuum generator are used in combination.

Description

Technical Field

[0001] The present invention relates to a pneumatic circuit for a conveying device and a control method thereof. The pneumatic circuit is used to control the supply of negative pressure to one or more suction cups arranged at a conveying head. Background Art

[0002] Japanese Patent No. 4,653,984 discloses an apparatus for removing one or more shaped products. The apparatus includes a pneumatic circuit for a conveying device, the pneumatic circuit comprising: one or more suction cups disposed at a chuck (conveying head) for conveying one or more shaped products (the conveyed product or products); a conduit line disposed between the one or more suction cups and a vacuum generator; and a negative pressure control section disposed in the conduit line having a negative pressure maintaining valve (control valve). The negative pressure maintaining valve is configured to supply negative pressure generated by the vacuum generator to the one or more suction cups when the one or more suction cups are sucking the conveyed products, and to release the negative pressure within the conduit line to atmosphere when the conveyed products are released from the one or more suction cups. When moving from a standby position to a removal position, the apparatus generates vacuum pressure in the chuck and controls the negative pressure in the chuck so that the suction pressure is reached just as the chuck reaches the removal position. Therefore, compared with the prior art in which negative pressure is generated in the chuck in advance when the chuck returns to the standby position and the negative pressure in the chuck reaches the suction pressure when the chuck reaches the removal position, since the suction start signal is output only at the moment when the negative pressure in the chuck reaches the suction pressure when the chuck reaches the removal position, it has the advantage of reducing the consumption of compressed air.

[0003] Related technical literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 4,653,984 (March 16, 2011) Summary of the Invention

[0006] Technical issues

[0007] In conventional devices, when one or more conveyed products are released from one or more suction cups, the negative pressure inside the catheter line is released to atmosphere by opening both the negative pressure retaining valve and the vacuum generator. During the next suction operation, the interior of the catheter line must be restored to a stored negative pressure state. In conventional methods, the need to maintain negative pressure inside the catheter line each time results in significant energy consumption. The longer the catheter line, the greater the energy consumption, as described above.

[0008] The object of the present invention is to provide a pneumatic circuit for a conveying device which is capable of reducing energy consumption by utilizing the negative pressure generated more effectively than with conventional technology.

[0009] Solution to the problem

[0010] The pneumatic circuit for a conveying device of the present invention comprises: one or more suction cups, the one or more suction cups being arranged at a conveying head to convey one or more conveyed products; a conduit line, the conduit line being arranged between the one or more suction cups and a vacuum generator; and a control valve mechanism, the control valve mechanism comprising two or more control valves arranged in the conduit line, the control valve mechanism supplying negative pressure generated by the vacuum generator to the one or more suction cups during a suction operation, wherein the one or more conveyed products are sucked by the one or more suction cups during the suction operation. , the control valve mechanism allows the interior of the one or more suction cups to be vented to the atmosphere and forms a negative pressure restriction section during a release operation, wherein the negative pressure is restricted in a rear conduit section of the conduit line, the rear conduit section being positioned closer to the vacuum generator than the front conduit section of the conduit line. In the release operation, the one or more conveyed products are released from the one or more suction cups, and the two or more control valves are arranged to use both the negative pressure in the negative pressure restriction section and the negative pressure generated by the vacuum generator when suctioning in the next conveying operation.

[0011] According to the present invention, a portion of the negative pressure generated during the suction operation is stored in the negative pressure limiting section, and the negative pressure stored in the negative pressure limiting section and the negative pressure generated by the vacuum generator are used in combination in the next conveying operation. Therefore, since a portion of the negative pressure is reused without wasting the generated negative pressure, energy consumption can be reduced more than that in conventional technology.

[0012] Preferably, the control valve mechanism includes a three-way valve provided in the front conduit section and a two-way valve provided in the rear conduit section, the two-way valve being controlled to be in an open state during the suction operation and in a closed state during the release operation. Furthermore, the three-way valve of the control valve mechanism 6' is controlled to be in a first state during the suction operation, in which the negative pressure generated by the vacuum generator is supplied to the one or more suction cups, and in a second state during the release operation, in which the supply of the negative pressure generated by the vacuum generator is blocked to form the negative pressure limiting section between the three-way valve and the two-way valve, and to allow the interior of the one or more suction cups to be vented to the atmosphere. During the suction operation in the next conveying operation, the three-way valve is controlled to change from the second state to the first state, so that the negative pressure in the negative pressure limiting section and the negative pressure generated by the vacuum generator are used in combination. According to the above-described control valve mechanism, the number of port valves used can be minimized.

[0013] Furthermore, the control valve mechanism may include a first two-way valve and a second two-way valve, respectively, disposed at one end and the other end of the rear conduit section, and a third two-way valve disposed in the front conduit section. In this case, the first two-way valve and the second two-way valve are each in an open state during the suction operation, and both are in a closed state during the release operation to form the negative pressure restriction section between the first two-way valve and the second two-way valve. Furthermore, the first two-way valve and the second two-way valve are both in an open state during the suction operation in the next transfer operation to supply the negative pressure in the negative pressure restriction section and the negative pressure supplied from the vacuum generator to the one or more suction cups. Thus, the third two-way valve is in a first state during the suction operation, enabling the negative pressure generated by the vacuum generator to be supplied to the one or more suction cups, and in a second state during the release operation, venting the interiors of the one or more suction cups to atmosphere. The valve is controlled to change from the second state to the first state before the suction operation in the next transfer operation is performed. According to the above-described control valve mechanism, the suction operation and the negative pressure limiting operation can be performed by providing the third two-way valve without being affected by a time delay in the operations of the first two-way valve and the second two-way valve.

[0014] It should be noted that the multiple suction cups are disposed on the delivery head, and the catheter line may include multiple branch conduits and a common conduit, each branch conduit being connected to the multiple suction cups, and the common conduit connecting the multiple branch conduits to the vacuum generator. In this manner, an additional three-way valve may be provided in at least one of the multiple branch conduits to allow the interior of the at least one branch conduit to vent to the atmosphere. In this case, the multiple suction cups can be released individually.

[0015] The pneumatic circuit for a conveying device of the present invention can be adapted to a device for removing formed products.

[0016] The present invention may also relate to a method for controlling a pneumatic circuit for a conveying device. Specifically, the method relates to a method for controlling a pneumatic circuit for a conveying device, the pneumatic circuit comprising: one or more suction cups disposed at a conveying head for conveying one or more conveyed products; a conduit line disposed between the one or more suction cups and a vacuum generator; and a control valve mechanism comprising two or more control valves disposed in the conduit path, the control valve mechanism supplying negative pressure generated by the vacuum generator to the one or more suction cups during a suction operation, wherein the one or more conveyed products are sucked by the one or more suction cups, and the control valve mechanism venting the interiors of the one or more suction cups to atmosphere during a release operation, wherein the one or more conveyed products are released from the one or more suction cups. In the method of the present invention, the control valve mechanism controls the two or more control valves to form a negative pressure limiting section, in which the negative pressure is limited to the rear conduit section, and the rear conduit section is positioned closer to the vacuum generator than the front conduit section of the conduit line, and the control valve mechanism also controls the two or more control valves to supply both the negative pressure in the negative pressure limiting section and the negative pressure generated by the vacuum generator to the one or more suction cups during the suction operation in the next delivery operation.

[0017] According to the method of the present invention, a portion of the negative pressure generated during the suction operation is stored in the negative pressure limiting section, and the negative pressure stored in the negative pressure limiting section and the negative pressure generated by the vacuum generator are used in combination during the next delivery operation. Therefore, since a portion of the negative pressure is reused without wasting the generated negative pressure, energy consumption can be further reduced compared to energy consumption in conventional technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 11 is a schematic diagram showing an example in which the pneumatic circuit for the conveying apparatus of the present embodiment is adapted to a suction cup provided at a take-out head for a molded product (a conveying head for a molded product).

[0019] Figure 2 It is shown for Figure 1 A diagram showing the configuration of a specific example of a pneumatic circuit for a conveying device according to the illustrated embodiment.

[0020] Figure 3 It is shown that in the first operation of taking out the product and the second operation of taking out the product, Figure 2 A diagram showing the temporal variation of the operation of a pneumatic circuit for a conveying device and the variation of the suction pressure of a suction cup is shown.

[0021] Figure 4A is a diagram showing a time axis for suction pressure changes in a conventional pneumatic circuit for a delivery device having no negative pressure limiting section, Figure 4B : is a diagram showing a time axis for changes in suction pressure in a pneumatic circuit for a conveying device having a negative pressure limiting section in this embodiment.

[0022] Figure 5 : is a diagram showing the configuration of a specific example of a pneumatic circuit for a conveying apparatus used in the second embodiment of the present invention.

[0023] Figure 6 1 and 2 are graphs showing temporal changes in the operation of a pneumatic circuit for a conveying device and changes in suction pressure of a suction cup in a first operation of taking out a product according to the second embodiment and a second operation of taking out a product according to the second embodiment.

[0024] Figure 7 It is a diagram for explaining a modified example. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of a pneumatic circuit for conveying equipment and a control method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

[0026] First embodiment

[0027] Figure 1: This is a schematic diagram showing an example of adapting the pneumatic circuit for the conveying device 1 of this embodiment to one or more suction cups 2 provided at the removal head 3 of the device for extracting or removing a formed product. The pneumatic circuit for the conveying device 1 includes one or more suction cups 2 provided at the removal head 3, and the one or more suction cups 2 are used to remove one or more formed products or molded products as one or more conveyed products. The pneumatic circuit for the conveying device 1 also includes a conduit line 5 arranged between the one or more suction cups 2 and the vacuum generator or vacuum generator 4, and a control valve mechanism 6 arranged in the conduit line 5. The control valve mechanism 6 includes a first two-way valve 7, a second two-way valve 8, and a third two-way valve 9, which will be described separately later. A negative pressure limiting section 10 is formed between the first two-way valve 7 and the second two-way valve 8. A pressure sensor 11 for measuring the negative pressure generated by the vacuum generator 4 is arranged in the portion of the conduit line 5 positioned between the removal head 3 and the third two-way valve 9. The control device 12 includes a function of applying a control command to control the opening and closing of the first two-way valve 7, the second two-way valve 8 and the third two-way valve 9 based on the output of the pressure sensor 11, a function of applying an operation command to the vacuum generator 4 based on a predetermined operation sequence, and a function of applying a drive command to the conveying mechanism 13 of the device for removing the molded product based on a predetermined operation sequence to execute the movement of the head 3 for removing the molded product.

[0028] Figure 2 It is shown for Figure 1 FIG. 1 is a diagram showing a specific example of the configuration of the pneumatic circuit of the conveying device 1 of the embodiment shown. Figure 2 As specifically shown in FIG. 4 , the vacuum generator 4 includes an air inlet 4A, a ventilation opening 4B, a supply inlet 4C containing positive pressure generated by a pump in the factory, and a two-way valve 4D including a solenoid valve disposed at the supply inlet 4C. A first two-way valve 7 is disposed in a conduit section near the air inlet 4A of the vacuum generator 4, and a second two-way valve 8 is disposed in a conduit section near the suction cup 2. A third two-way valve 9 is disposed between the suction cup 2 and the second two-way valve 8. In this specification, the conduit section between the first two-way valve 7 and the second two-way valve 8 is referred to as the rear conduit section of the conduit line, and the conduit section between the rear conduit section and the suction cup 2 is referred to as the front conduit section of the conduit line. Furthermore, in this embodiment, the control valve mechanism 6 comprises the first two-way valve 7 (control valve), the second two-way valve 8 (control valve), and the third two-way valve 9 (control valve).

[0029] The two-way valves 4D, 7, 8, and 9 each have two ports, IN and OUT, and each valve simply closes or opens one path. In this embodiment, the first two-way valve 7 and the second two-way valve 8 are controlled to be in an open state during the suction operation and in a closed state during the release operation. In this embodiment, the third two-way valve 9 is provided at the branch conduit line 5A connected to the front conduit section of the conduit line. The third two-way valve 9 is controlled to be in a first state during the suction operation, in which the negative pressure generated by the vacuum generator 4 is applied to the suction cup 2, and in a second state during the release operation, in which the interior of the suction cup 2 is exposed to the atmosphere.

[0030] exist Figure 2 In the illustrated state, the valve bodies of two-way valves 4D, 7, and 8 have been removed from the path, leaving the path open. Since the valve body of third two-way valve 9 closes the atmospheric release port of branch conduit line 5A, the interior of conduit line 5 is normally exposed to the atmosphere through air inlet 4A of vacuum generator 4, resulting in negative pressure inside the conduit line and inside suction cup 2. In this specification, this state is defined as the "supply negative pressure" generated by vacuum generator 4.

[0031] The shaped product (conveyed product) is conveyed by the suction cup 2 during the suction operation. Then, during the operation to release the shaped product (conveyed product) from the suction cup 2 at a predetermined conveying position, the interior of the suction cup 2 is opened to the atmosphere by opening the atmospheric release port (a second state). Substantially simultaneously with the atmospheric release operation of the third two-way valve 9, the first two-way valve 7 and the second two-way valve 8 are closed, and the two-way valve 4D in the vacuum generator 4 is closed via the valve body, stopping the supply of positive pressure to the vacuum generator 4. While the vacuum generator 4 is generating negative pressure (the first state), when the first two-way valve 7 and the second two-way valve 8 are closed, the negative pressure is reliably stored in the negative pressure restriction section 10. As described in detail later, during the next conveying operation, the negative pressure stored in the negative pressure restriction section 10 is combined with the negative pressure generated by the vacuum generator 4. Specifically, the negative pressure stored in the negative pressure restriction section 10 is added to the negative pressure generated by the vacuum generator 4, and this combined negative pressure is then supplied to the suction cup 2. Therefore, according to the present embodiment, a portion of the negative pressure generated during the suction operation is stored in the negative pressure limiting section 10, and the negative pressure stored in the negative pressure limiting section 10 and the negative pressure generated by the vacuum generator 4 are used in combination in the next conveying operation. Therefore, since a portion of the negative pressure is reused without wasting the generated negative pressure, energy consumption can be reduced more than that in conventional technology.

[0032] Figure 3 It is shown that in the first operation for taking out the product and the second operation for taking out the product, Figure 2The operation of the pneumatic circuit for the conveying device 1 and the change in the suction pressure of the suction cup 2 are shown over time. It should be noted that Figure 3 In order to ensure data collection, a suction pressure sensor 11 for measurement is arranged at a position close to the suction cup 2. First, the suction cup 2 is moved close to the molded product, and air suction is performed using the vacuum generator 4 to start the suction operation (P1). When the suction cup 2 is in close contact with the molded product, suction is started and the suction pressure (negative pressure) is increased. When the removal head 3 is moved to the release position (P2), the suction is saturated (at the same time, the inside of the catheter line is almost a vacuum), and a release command is output when the movement is completed. When the release command is output, the first two-way valve 7 and the second two-way valve 8 are closed, and then the path of the third two-way valve 9 becomes open due to the cessation of the operation of the vacuum generator 4, thereby allowing the inside of the suction cup 2 to be exposed to the atmosphere and completing the release of the molded product. Note that, in Figure 3 The dotted line DL1 shown during the opening duration in the first operation for removing the product and the second operation for removing the product shows the change in suction pressure when the first two-way valve 7, the second two-way valve 8 and the third two-way valve 9 are not used when using a conventional pneumatic circuit for a conveying device.

[0033] In such Figure 3 In the case of the second operation of taking out the product shown, since the negative pressure in the negative pressure limiting section 10 is also used together with the negative pressure generated by the vacuum generator, the negative pressure rises in a short time. Figure 3 The dashed line DL2 shown when the suction operation is started in the second operation for taking out the product shows the change in suction pressure when a conventional pneumatic circuit for a conveying device without the negative pressure limiting section 10 is used. Figure 4A The change in suction pressure when using a conventional pneumatic circuit for a conveying device without the negative pressure limiting section 10 is shown. Figure 4B The change in suction pressure in the case of using the pneumatic circuit for a conveying device having the negative pressure limiting section 10 of the present embodiment is shown. Figure 4A and Figure 4B As can be clearly seen from the figures explained above, according to this embodiment, in the second operation of removing the product and in the operations after the second operation, the time period for the start of suction and the time period for the completion of release are significantly shorter than before.

[0034] Second embodiment

[0035] Figure 5 1 ' is a diagram showing a specific example of the configuration of a pneumatic circuit for a conveying device 1 ' used in a second embodiment of the present invention. The second embodiment differs from the first embodiment in that Figure 2Compared to the pneumatic circuit for the conveying device of the first embodiment shown, the second two-way valve 8 is not present, and a three-way valve or a three-port valve 9 ′ is used instead of the third two-way valve 9 .

[0036] In this embodiment, the control valve mechanism 6' includes a three-way valve 9' provided at the front conduit section of the catheter line and a two-way valve 7 provided at the rear conduit section of the catheter line. The two-way valve 7 is controlled to be open during the suction operation and closed during the release operation. Thus, during the suction operation, the three-way valve 9' of the control valve mechanism 6' is controlled to be in a first state, in which the negative pressure generated by the vacuum generator 4 is supplied to the suction cup 2. During the release operation, the three-way valve 9' is controlled to be in a second state, which blocks the supply of negative pressure generated by the vacuum generator 4 and opens the interior of the suction cup 2 to the atmosphere (via a branch path), thereby forming a negative pressure restriction section 10 between the three-way valve 9' and the two-way valve 7. Furthermore, during the next delivery operation, during the suction operation, the three-way valve 9' is controlled to switch from the second state to the first state, thereby combining the negative pressure within the negative pressure restriction section 10 with the negative pressure generated by the vacuum generator 4. This control valve mechanism 6' minimizes the number of port valves used.

[0037] Figure 6 is a graph showing the time-dependent change in the operation of the pneumatic circuit for the conveying device 1 ′ and the change in the suction pressure of the suction cup 2 in the first operation of removing the product of the second embodiment and in the second operation of removing the product of the second embodiment, and Figure 3 As shown in Figure 6 It is understood that the same effects as those of the first embodiment are obtained even in the second embodiment.

[0038] Variation examples

[0039] Figure 7 1 is a diagram for explaining a modified example in the case where a plurality of suction cups 21 and 22 are provided at a take-out head (conveying head) for a plurality of products. Figure 7 The illustrated modified example provides multiple suction cups 21 and 22, and the conduit line includes multiple branch conduit lines 51 and 52 connected to the multiple suction cups 21 and 22, respectively, and a common conduit line 5 connecting the multiple branch conduit lines 51 and 52 to the vacuum generator 4. Furthermore, in this modified example, a pressure sensor 11 for detecting the pressure in the conduit line 5 during suction operation is arranged on the suction cup side rather than on the three-way valve 9' side. Therefore, an additional three-way valve 14 is provided in at least one of the multiple branch conduit lines 51 and 52, which opens the interior of the conduit line 51 to the atmosphere. In this way, the suction cups 21 and 22 can be opened individually.

[0040] Industrial Applicability

[0041] According to the present invention, a portion of the negative pressure generated during the suction operation is stored in the negative pressure limiting section, and the negative pressure stored in the negative pressure limiting section and the negative pressure generated by the vacuum generator are used in combination in the next conveying operation. Therefore, since a portion of the negative pressure is reused without wasting the generated negative pressure, energy consumption can be reduced more than that in conventional technology.

Claims

1. A pneumatic circuit for conveying equipment, comprising: one or more suction cups provided at the conveying head for conveying the one or more conveyed products, a conduit line disposed between the one or more suction cups and a vacuum generator, and A control valve mechanism comprising two or more control valves arranged in the conduit line, wherein the control valve mechanism supplies the negative pressure generated by the vacuum generator to the one or more suction cups during a suction operation in which the one or more conveyed products are sucked by the one or more suction cups, and wherein the control valve mechanism allows the interior of the one or more suction cups to be vented to the atmosphere and forms a negative pressure restriction section during a release operation in which the one or more conveyed products are released from the one or more suction cups, in which the negative pressure is restricted in a rear conduit section of the conduit line, the rear conduit section being positioned closer to the vacuum generator than the front conduit section of the conduit line, and wherein the two or more control valves are arranged to use both the negative pressure in the negative pressure restriction section and the negative pressure generated by the vacuum generator during suction in the next conveying operation.

2. The pneumatic circuit for conveying equipment according to claim 1, wherein: The control valve mechanism includes a three-way valve arranged in the front conduit section and a two-way valve arranged in the rear conduit section. The two-way valve is controlled to be in an open state during the suction operation and in a closed state during the release operation; as well as The three-way valve is controlled to be in a first state during the suction operation, in which the negative pressure generated by the vacuum generator is supplied to the one or more suction cups, and to be in a second state during the release operation, in which the supply of the negative pressure generated by the vacuum generator is blocked to form the negative pressure limiting section between the three-way valve and the two-way valve, and to allow the interior of the one or more suction cups to be open to the atmosphere, and during the suction operation in the next conveying operation, the three-way valve is controlled to change from the second state to the first state so that the negative pressure in the negative pressure limiting section and the negative pressure generated by the vacuum generator are used in combination.

3. The pneumatic circuit for conveying equipment according to claim 1, wherein: The control valve mechanism includes a first two-way valve and a second two-way valve respectively provided at one end and the other end of the rear conduit section, and a third two-way valve provided in the front conduit section. The first two-way valve and the second two-way valve are respectively in an open state during the suction operation, and the first two-way valve and the second two-way valve are both in a closed state during a release operation to form the negative pressure limiting section between the first two-way valve and the second two-way valve, and the first two-way valve and the second two-way valve are both in an open state during the suction operation in the next conveying operation to supply the negative pressure in the negative pressure limiting section and the negative pressure supplied from the vacuum generator to the one or more suction cups, and The third two-way valve changes to a first state capable of supplying the negative pressure generated by the vacuum generator to the one or more suction cups during the suction operation, and changes to a second state of opening the interior of the one or more suction cups to the atmosphere during the release operation, and is controlled to change from the second state to the first state before performing the suction operation in the next conveying operation.

4. The pneumatic circuit for conveying equipment according to claim 2, wherein: The plurality of suction cups are arranged on the delivery head, The catheter line has a plurality of branch catheters and a common catheter, each branch catheter is connected to the plurality of suction cups, and the common catheter connects the plurality of branch catheters with the vacuum generator, and An additional three-way valve is provided in at least one branch conduit among the plurality of branch conduits, so that the interior of the at least one branch conduit is open to the atmosphere.

5. The pneumatic circuit for conveying equipment according to claim 3, wherein: The plurality of suction cups are arranged on the delivery head, The catheter line has a plurality of branch catheters and a common catheter, each branch catheter is connected to the plurality of suction cups, and the common catheter connects the plurality of branch catheters with the vacuum generator, and An additional three-way valve is provided in at least one branch conduit among the plurality of branch conduits, so that the interior of the at least one branch conduit is open to the atmosphere.

6. A device for removing formed products, comprising the pneumatic circuit for a conveying device according to any one of claims 1 to 5.

7. A method of controlling a pneumatic circuit for a conveying device, the pneumatic circuit comprising: one or more suction cups provided at the conveying head for conveying the one or more conveyed products, a conduit line disposed between the one or more suction cups and a vacuum generator, and a control valve mechanism including two or more control valves arranged in a conduit path, the control valve mechanism supplying negative pressure generated by the vacuum generator to the one or more suction cups during a suction operation in which the one or more conveyed products are sucked by the one or more suction cups, and the control valve mechanism venting the interior of the one or more suction cups to atmosphere during a release operation in which the one or more conveyed products are released from the one or more suction cups, wherein the control valve mechanism controls the two or more control valves to form a negative pressure limiting section in which negative pressure is limited in a rear conduit section that is located closer to the vacuum generator than a front conduit section of the conduit line, and The control valve mechanism also controls the two or more control valves to supply both the negative pressure in the negative pressure limiting section and the negative pressure generated by the vacuum generator to the one or more suction cups during a suction operation in a next conveying operation.

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