Patent Application
20220250208
This application is based on Japanese Patent Application No. 2021-018341 filed with Japan Patent Office on Feb. 8, 2021, the entire contents of which are hereby incorporated by reference.
The present disclosure relates to a blasting apparatus and a volumetric feeder.
Blasting that performs surface treatment by projecting a solid-gas two-phase flow consisting of an abrasive and gas toward an object to be processed by an injection nozzle has been widely known. Blasting is used for scale removal, flow line erasure, rust stripping, coating film removal, and surface preparation of a casting, for example. In recent years, blasting is also used for applications in which a high treatment accuracy is required such as microfabrication and smooth finish of an electronic component.
One requirement for realizing a high treatment accuracy is that the abrasive is stably supplied to the nozzle in a constant quantity. In Japanese Unexamined Patent Publication No. H07-328924, a blasting apparatus including a volumetric feeder that supplies a constant quantity of an abrasive to a nozzle is described. The blasting apparatus has a configuration in which a screw is provided in a lower portion of a tank in which the abrasive is stored, and the abrasive discharged from a screw pump is temporarily housed in a buffer and then is supplied to the nozzle via an abrasive supplying path.
In the blasting apparatus disclosed in Japanese Unexamined Patent Publication No. H07-328924, by the buffer, fluctuation of the negative pressure generated in the nozzle for blasting and the fluctuation of the screw are absorbed, and the performance of supplying of the abrasive to the nozzle in a certain amount is improved. The negative pressure is a suction power of sucking the abrasive. However, in this blasting apparatus, the pressure loss of the path for supplying the abrasive becomes high. Therefore, there is a need to increase the negative pressure. The negative pressure depends on the pressure of the compressed air supplied to the nozzle. Therefore, compressed air of which pressure is higher than that of the conventional art inevitably needs to be supplied. The pressure of the supplied compressed air is normally set in accordance with a surface state that is the target of the blasting. When the pressure of the compressed air is set in accordance with the suction power of the abrasive, the target surface state may not be obtained by the blasting. Conversely, when the pressure of the compressed air is set in accordance with the blasting for obtaining the target surface state, the supply amount of the abrasive to the nozzle may become insufficient or the supply amount of the abrasive may not be stable. In other words, in the blasting apparatus disclosed in Japanese Unexamined Patent Publication No. H07-328924, there is a risk that a constant quantity of the abrasive necessary to obtain the target surface state cannot be projected. Thus, the present disclosure provides a technology capable of suppressing the increase and decrease of the amount of an abrasive that is projected when a constant quantity of the abrasive is projected in a blasting apparatus.
A blasting apparatus according to one aspect of the present disclosure includes a storage container, a volumetric feeder, and a nozzle for blasting. The storage container defines a storage chamber storing an abrasive in the storage chamber. The volumetric feeder supplies the abrasive to an outside of the storage container from the storage chamber. The nozzle projects, together with compressed air, the abrasive supplied from the volumetric feeder. The volumetric feeder has a casing and a screw. The casing extends along a horizontal direction and defines a space on an inside. The casing has an introduction port causing the space and the storage chamber to communicate with each other, and a supply port opened toward a lower side in a position separated from the introduction port in the horizontal direction. The screw has a rotational shaft housed in the casing and extending along the horizontal direction. The screw carries the abrasive in the space toward the supply port from the introduction port by rotating about the rotational shaft. The screw is housed in the casing in such a way as not to overlap the supply port in a vertical direction.
In the blasting apparatus, the abrasive is introduced to the casing of the volumetric feeder from the storage chamber defined in the storage container. In the volumetric feeder, the abrasive is carried toward the supply port opened toward the lower side of the casing by the rotation of the screw. In the supply port, the supply port and the screw do not overlap in the vertical direction, and hence the abrasive accumulated on the screw does not fall down to the supply port. The abrasive that has fallen down from the supply port is projected from the nozzle for blasting together with compressed air. The “nozzle for blasting” may be hereinafter simply referred to as a “nozzle”. The supply port is opened toward the lower side of the casing, and hence the distance from the supply port to the nozzle can be reduced. As a result, the loss of the projecting pressure due to the transfer of the abrasive can be suppressed. Therefore, when the blasting apparatus projects a constant quantity of abrasive, the blasting apparatus can suppress the increase and decrease of the amount of the abrasive that is projected and satisfactorily perform the blasting.
In one embodiment, the blasting apparatus may further include an air supplying member. The air supplying member may be housed in the storage chamber, connected to an air source, and have a plurality of air holes supplying air from the air source provided therein. In this case, air is supplied to the abrasive stored in the storage container and the abrasive is fluidized. The blasting apparatus can suppress bridging in which the abrasive adheres to the inner wall of the storage container. Bridging is also referred to as scaffolding.
In one embodiment, the blasting apparatus may further include a connection pipe. The connection pipe may connect the nozzle and the supply port of the casing to each other. The nozzle may be provided in such a way as to cause a relative positional relationship with the casing to be fixed. In this case, the attitude of the nozzle is limited to the position of the casing, and hence the connection pipe is not deformed in accordance with the nozzle. Therefore, the blasting apparatus can avoid a case where the flow of the abrasive changes in accordance with the deformation of the connection pipe. Therefore, the blasting apparatus can suppress the increase and decrease of the amount of the abrasive that is projected.
In one embodiment, the nozzle may include a nozzle body, an air nozzle, and an injection nozzle. The nozzle body may be coupled to a path through which the abrasive is transferred toward the nozzle from the volumetric feeder. The air nozzle may introduce the compressed air into the nozzle body and generate an air flow sucking the abrasive into the nozzle body. The injection nozzle may project, together with the compressed air, the abrasive transferred into the nozzle body. The nozzle may be disposed in such a way as to cause a pressure loss generated in accordance with the generation of the air flow to be 0.1 kPa or less.
In one embodiment, the blasting apparatus may further include a restriction plate. In the restriction plate, an opening passing through the restriction plate in a thickness direction may be formed. The restriction plate may be disposed between a distal end of the screw and the supply port in such a way as to partition an inside of the casing. In this case, the abrasive that has been carried by the screw is pressed against the restriction plate. As a result, the abrasive that has passed through the opening of the restriction plate is compressed to a predetermined bulk density. Therefore, the blasting apparatus can cause the bulk density of the abrasive that is sent out to the nozzle to be stable.
In one embodiment, the blasting apparatus may further include a restriction plate. The restriction plate may be fixed to a distal end of the screw in such a way as to form a gap between the restriction plate and an inner wall of the casing. In this case, the abrasive that has been carried by the screw is pressed against the restriction plate. As a result, the abrasive that has passed through the gap formed between the restriction plate and the inner wall of the casing is compressed to a predetermined bulk density. Therefore, the blasting apparatus can cause the bulk density of the abrasive that is sent out to the nozzle to be stable.
In one embodiment, the blasting apparatus may further include a movement mechanism. The storage container, the volumetric feeder, and the nozzle may configure a unit, and the movement mechanism may relatively move the unit with respect to an object to be processed. The blasting apparatus can perform blasting on the object to be processed in a state in which the nozzle and the volumetric feeder are unitized.
A volumetric feeder according to another aspect includes a casing and a screw. The casing extends along a horizontal direction and defines a space on an inside. The casing has an introduction port for introducing the abrasive to the space, and a supply port opened toward a lower side in a position separated from the introduction port in the horizontal direction. The screw has a rotational shaft housed in the casing and extending along the horizontal direction. The screw carries the abrasive in the space toward the supply port from the introduction port by rotating about the rotational shaft. The screw is housed in the casing in such a way as not to overlap the supply port in a vertical direction.
In the volumetric feeder, the abrasive is carried toward the supply port opened toward the lower side of the casing by the rotation of the screw. In the supply port, the supply port and the screw do not overlap in the vertical direction, and hence the abrasive accumulated on the screw does not fall down to the supply port. The abrasive that has fallen down from the supply port is projected from the nozzle for blasting together with compressed air. Therefore, the volumetric feeder can suppress the increase and decrease of the amount of the abrasive when a constant quantity of abrasive is supplied to the blasting apparatus.
According to the technology according to the present disclosure, the increase and decrease of the amount of the abrasive that is projected can be suppressed and the blasting can be satisfactorily performed.
An embodiment of the present disclosure will be described below with reference to the drawings. In the description below, the same or equivalent elements are denoted by the same reference characters, and overlapping description is not repeated. Dimension ratios of the drawings do not necessarily match with those described. Terms “up”, “down”, “left”, and “right” are based on the illustrated states and are for convenience.
[Configuration of Blasting Apparatus]
The volumetric feeder 20 is an apparatus that sends out the abrasive M stored in the storage container 10 to the outside. The volumetric feeder 20 is a screw feeder, for example, and continuously sends out the abrasive M stored in the storage container 10 by a constant quantity. The volumetric feeder 20 is disposed on the lower side of the storage container 10. A part of the volumetric feeder 20 may be housed in a lower portion of the storage container 10. The volumetric feeder 20 includes a casing 21 and a screw 24 housed in the casing 21.
The casing 21 is a hollow-cylinder-shaped member extending along the horizontal direction. In the casing 21, a space V is defined. The casing 21 has an introduction port 22 that causes the storage chamber S of the storage container 10 and the space V to communicate with each other. The introduction port 22 is opened toward the upper side, for example. The abrasive M is introduced into the space V of the volumetric feeder 20 from the storage chamber S of the storage container 10 via the introduction port 22. The casing 21 has a supply port 23 in a position separated from the introduction port 22 in the horizontal direction. The supply port 23 is opened toward the lower side of the casing 21. The supply port 23 is formed in a lower portion of the casing 21 in such a way as to cause the abrasive M carried by the screw 24 to fall down. The supply port 23 causes the abrasive M to fall down and sends the abrasive M to the nozzle 30.
The screw 24 is housed in the space V in the casing 21. The screw 24 has a rotational shaft 24a and blades 24b. The rotational shaft 24a is housed in the casing 21 and extends along the horizontal direction. The blades 24b are helicoidally fixed to an outer peripheral surface of the rotational shaft 24a in such a way as to cause two blades 24b adjacent to each other to be arranged at a predetermined interval. The screw 24 is rotatably supported by a first bearing portion 26a and a second bearing portion 26b. The first bearing portion 26a and the second bearing portion 26b are members including a bearing and a support portion of the bearing. The screw 24 is coupled to a motor 25 and is rotationally driven about the rotational shaft 24a. The abrasive M that has come between the adjacent two blades 24b is carried to the supply port 23 of the casing 21 by the rotational driving of the screw 24.
The screw 24 is housed in the casing 21 in such a way as not to overlap the supply port 23 in the vertical direction. For example, when the screw 24 is rotatably supported by the first bearing portion 26a and the second bearing portion 26b in a cantilever manner near the introduction port 22, the screw 24 extends toward the supply port 23 from the introduction port 22 to a position that does not overlap the supply port 23 in the vertical direction. In other words, the screw 24 does not exist above the supply port 23.
The supply port 23 of the casing is connected to the nozzle 30 via a connection pipe 31. The connection pipe 31 transfers the abrasive M sent out from the supply port 23 to the nozzle 30. The connection pipe 31 defines a flow path capable of transferring the abrasive M on the inside. The connection pipe 31 is a hose made of resin, or a pipe made of metal, for example.
The nozzle 30 projects, together with compressed air, the abrasive M supplied from the connection pipe 31. The nozzle 30 includes a nozzle body 30a, an air nozzle 30b inserted from one end side of the nozzle body, and an injection nozzle 30c inserted into the other end side of the nozzle body. The compressed air is supplied into the nozzle body 30a from an air pipe 32 connected to the air nozzle 30b. By an ejector phenomenon by the compressed air projected from the air nozzle 30b, a negative pressure is generated in the nozzle body 30a. The negative pressure generated in the nozzle body 30a generates an air flow in the connection pipe 31 connected to the nozzle body 30a. The abrasive M is transferred to the nozzle body 30a from the supply port 23 by the air flow generated in the connection pipe 31. The transferred abrasive M is mixed with the compressed air in the nozzle body 30a. By the injection nozzle 30c, the abrasive M is projected onto a workpiece W as a solid-gas two-phase flow with the compressed air.
The workpiece W is an object to be processed that is the target of blasting. As one example, the workpiece W is a hard brittle material such as glass, silicon, and ceramics, various metals, or composite materials such as a carbon fiber reinforced plastics (CFRP) material and glass fiber reinforced plastics (GFRP). The workpiece W is placed on a table 33.
The table 33 is a board on which the placed workpiece W is fixed during the blasting. For example, the table 33 has a placing surface that adsorbs the workpiece W. The table 33 is disposed in such a way as to intersect with the projecting direction of the nozzle 30. The table 33 may move the position of the workpiece W relative to the nozzle 30.
A treatment container 3 defines a processing chamber P on the inside and houses the nozzle 30, the workpiece W, and the table 33. The blasting is performed in the processing chamber P. The abrasive M projected onto the workpiece W as a solid-gas two-phase flow of compressed air falls down to a lower portion of the processing chamber P with swarf of the workpiece W. The abrasive M and the swarf of the workpiece W that have fallen down to the lower portion of the processing chamber P are collected by a collection pipe 12. The collection pipe 12 connects the processing chamber P of the treatment container 3 and a classification mechanism 11 to each other.
The classification mechanism 11 collects the abrasive M and the swarf of the workpiece W that have fallen down to the lower portion of the processing chamber P through the collection pipe 12. The classification mechanism 11 separates the abrasive M and the swarf of the workpiece W that have been collected. The classification mechanism 11 is a cyclone-type classification machine, for example. The classification mechanism 11 separates the abrasive M that can be reused, and the abrasive M and the swarf of the workpiece W that cannot be reused. The abrasive M that can be reused is returned to the storage container 10. The abrasive M and the swarf of the workpiece W that cannot be reused are collected in a dust collector 2.
The dust collector 2 is an apparatus that collects the abrasive M and the swarf of the workpiece W that cannot be reused. The dust collector 2 is connected to the classification mechanism 11. The dust collector 2 generates a negative pressure. The negative pressure of the dust collector 2 generates an air flow in the classification mechanism 11 and the collection pipe 12 connected to the classification mechanism 11. The abrasive M and the swarf of the workpiece W that cannot be reused travel on the air flow and are sucked into the dust collector 2. The abrasive M and the swarf of the workpiece W having been sucked that cannot be reused are collected in the dust collector 2 by a filter, for example.
The blasting apparatus 1 is controlled by a control device 4. The control device 4 is configured as a programmable logic controller (PLC), for example. The control device 4 may be configured as a computer system including a processor such as a central processing unit (CPU), a memory such as a random access memory (RAM) and a read only memory (ROM), an input-output device such as a touch screen, a mouse, a keyboard, and a display, and a communication device such as a network card. The control device 4 realizes a function of the control device 4 by causing each hardware to operate under the control of the processor based on a computer program stored in the memory. For example, the control device 4 controls the pressure of the compressed air supplied from the air pipe 32. The control device 4 controls the amount of the abrasive M that the volumetric feeder 20 sends out. The control device 4 may control at least any one of the projecting amount of the abrasive, the pressure by which the abrasive M is projected, and the positional relationship between the nozzle 30 and the workpiece W.
As above, according to the blasting apparatus 1 and the volumetric feeder 20 according to the embodiment, the abrasive M is introduced to the casing 21 of the volumetric feeder 20 from the storage chamber S defined in the storage container 10. In the volumetric feeder 20, the abrasive M is carried toward the supply port 23 opened toward the lower side of the casing 21 by the rotation of the screw 24. In the supply port 23, the supply port 23 and the screw 24 do not overlap in the vertical direction, and hence the abrasive M accumulated on the screw 24 does not fall down to the supply port 23. The abrasive M that has fallen down from the supply port 23 is projected from the nozzle 30 for blasting together with compressed air. Therefore, the blasting apparatus 1 and the volumetric feeder 20 can suppress the increase and decrease of the amount of the abrasive that is projected.
The blasting apparatus 1 of the present disclosure may be variously omitted, replaced, and changed.
[Modified Example of Connection Between Volumetric Feeder and Nozzle]
A pressure loss is generated in a path through which the abrasive M is transferred to the nozzle 30 from the supply port 23 of the casing 21. The pressure loss is a friction loss generated between the connection pipe 31 forming the flow path and the air flow flowing through the flow path. The flow amount of the abrasive M transferred in the connection pipe 31 by the air flow changes in accordance with the pressure loss. The pressure loss changes in accordance with the entire length and the shape of the flow path. When the entire length of the flow path extends or when the flow path is curved, the pressure loss increases. For example, when the relative positional relationship between the nozzle 30 and the casing 21 changes, the entire length and the shape of the flow path changes in accordance with the relative positional relationship between the nozzle 30 and the casing 21. In this case, by the increase and decrease of the pressure loss, the flow amount of the abrasive M transferred to the nozzle 30 fluctuates. As a result of the relative positional relationship between the nozzle 30 and the casing 21 being fixed, a case where the flow path through which the abrasive M is transferred between the supply port 23 of the casing 21 and the nozzle 30 is deformed is avoided, and the flow amount of the abrasive M transferred to the nozzle 30 becomes stable.
If the pressure loss of the path is large when the abrasive to be projected from the injection nozzle is drawn from the volumetric feeder, there are cases where the abrasive cannot be sufficiently sucked. When the nozzle 30 is disposed in a position in which the pressure loss becomes large, the pressure of the compressed air introduced to the nozzle 30 may be further increased in order to obtain a negative pressure, that is, a suction power with which the abrasive M can be sufficiently sucked. However, the pressure by which the abrasive M is projected also increases, and hence the performance of the blasting also inevitably improves. As a result, the blasting may become an excessive treatment for the surface state that is the target. Therefore, the nozzle 30 needs to be disposed in such a way as to cause a negative pressure with which the abrasive M is sufficiently sucked to be obtained. In order to do so, the position in which the nozzle 30 is disposed may be adjusted in such a way as to cause the pressure loss to be 0.1 kPa or less.
In the blasting apparatus illustrated in
The blasting apparatus illustrated in
As above, in the blasting apparatus illustrated in
[Modified Example of Storage Container and Volumetric Feeder]
The air supplying member 40 is a member that causes the abrasive M stored in the storage container 10 to easily flow to the introduction port 22. The air supplying member 40 is connected to an air source 41 and a plurality of air holes that supply air from the air source 41 is provided. As one example, the air supplying member 40 is sintered metal and is a porous member. The air source 41 is an air blowing machine, a compressing machine, or a blower, for example.
The fluidity of the abrasive M stored in the storage container 10 may increase by air supply from the air supplying member 40. The fluidity of powder is the ease of flow of powder. Powder of which fluidity is high exhibits a behavior close to a liquid phase. Powder of which fluidity is low exhibits a behavior close to a solid phase. The fluidity of powder is determined on the basis of the amount of air that the powder includes, the particle diameter configuring the powder, the physical property of the particle, and the like. In the storage container 10, air may be supplied to the abrasive M from the air holes of the air supplying member 40, and the fluidity of the stored abrasive M may improve. The blasting apparatus can suppress the adhesion of the abrasive M to the inside of the storage container 10.
The blasting apparatus illustrated in
A constant quantity of the abrasive M out of the abrasive M stored in the storage container 10 is introduced into the casing 21 from the introduction port 22. The abrasive M is carried toward the supply port 23 by the rotation of the screw 24. When the abrasive M reaches the restriction plate 50, the abrasive M that has been carried by the screw 24 is pressed against the restriction plate 50. As a result, the abrasive M that has passed through the opening of the restriction plate 50 is compressed to a predetermined bulk density. Therefore, the blasting apparatus 1 can cause the bulk density of the abrasive M that is sent out to the nozzle 30 to be stable.
[Another Modified Example of Restriction Plate]
The blasting apparatus 1 may include the restriction plate 50 fixed to the distal end of the screw 24 in such a way as to form a gap between the restriction plate 50 and an inner wall of the casing 21. In this case, an opening does not necessarily need to be formed in the restriction plate 50. The abrasive M that has been carried by the screw 24 is pressed against the restriction plate 50. As a result, the abrasive M that has passed through the gap formed between the restriction plate 50 and the inner wall of the casing 21 is compressed to a predetermined bulk density. Therefore, the blasting apparatus 1 can cause the bulk density of the abrasive that is sent out to the nozzle 30 to be stable.
The nozzle 30 does not necessarily need to be connected to the supply port 23 in such a way as to cause the relative positional relationship with the introduction port 22 of the casing 21 to be fixed. The storage container 10, the volumetric feeder 20, and the nozzle 30 do not necessarily need to configure the unit 5. The blasting apparatus 1 does not necessarily need to include the movement mechanism 60 that causes the unit 5 to move relative to the workpiece W.
The blasting apparatus 1 does not necessarily need to include the air supplying member 40 which is housed in the storage container 10 and connected to the air source 41 and in which the plurality of air holes that supply air from the air source 41 is provided. The blasting apparatus 1 does not necessarily need to include the restriction plate 50 in which the opening passing therethrough in the thickness direction is formed and which is disposed between the distal end of the screw 24 and the supply port 23 in such a way as to partition the inside of the casing 21. The blasting apparatus 1 does not necessarily need to include the restriction plate 50 fixed to the distal end of the screw 24 in such a way as to form a gap between the restriction plate 50 and the inside of the casing 21.
The blasting apparatus 1 may be a direct-pressure-type blasting apparatus. The blasting apparatus 1 may be a wet-type blasting apparatus. When the abrasive M is not reused, the blasting apparatus 1 does not necessarily need to include the classification mechanism 11 and the dust collector 2. In this case, an operator may supply the abrasive M to the storage container 10.
The movement mechanism 60 is not limited to an orthogonal robot. The movement mechanism 60 may be an articulated robot, a parallel link robot, and a SCARA robot, for example.
[Verification of Arrangement and Blast Condition of Nozzle]
The arrangement and the blast condition of the nozzle 30 with which the pressure loss in the path when the abrasive is induced from the volumetric feeder becomes 0.1 kPa or less was examined.
A blasting apparatus 1A illustrated in
In the blasting apparatus 1A illustrated in
Table 1 is a table showing the measurement results of the pressure loss. As shown in Table 1, it was confirmed that the pressure loss became 0.1 kPa or less when the projecting pressure was in the range of 50 kPa to 600 kPa in the example. When the projecting pressure was 50 kPa, the projecting amount of the abrasive M became 500 g/min and the pressure loss became 0.1 kPa or less. In other words, it was confirmed that the abrasive M was stably projected even at an extremely low pressure because the pressure loss was small in the example. It was confirmed that the pressure loss was more than 0.1 kPa when the projecting pressure was in the range of 150 kPa to 600 kPa in the comparative example. When the projecting pressure was 150 kPa, the projecting amount of the abrasive M became 150 g/min and the pressure loss became more than 0.1 kPa. This indicates that the projecting of the abrasive M caused pulsation at an extremely low pressure and the lowest usable pressure became high because the pressure loss was large in the comparative example. Therefore, it was confirmed that the abrasive M was not stably projected under a low-pressure condition and only a small amount was stably projected even at the lowest usable pressure in the comparative example.
1 . . . Blasting apparatus, 10 . . . Storage container, 20 . . . Volumetric feeder, 21 . . . Casing, 22 . . . Introduction port, 23 . . . Supply port, 24 . . . Screw, 24a . . . Rotational shaft, 30 . . . Nozzle, 30a . . . Nozzle body, 30b . . . Air nozzle, 30c . . . Injection nozzle, 31 . . . Connection pipe, 40 . . . Air supplying member, 41 . . . Air source, 50 . . . Restriction plate, 60 . . . Movement mechanism, M . . . Abrasive, S . . . Storage chamber, V . . . Space.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-018341 | Feb 2021 | JP | national |
