Patent Grant
6874997
This application is based on and claims the benefit of prior Japanese Patent Application No. 2002-118247, filed on Apr. 19, 2002, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a pump system for transferring a target fluid via a pump camber using reciprocating flexible members such bellows and diaphragms. In particular, it relates to a pump system using a control fluid to drive a switching valve mechanism for an actuating fluid.
2. Description of the Related Art
A bellows pump is known as a liquid injection pump for use in semiconductor processes and so forth in the art. It employs fluororesin bellows for sucking and discharging a liquid. The bellows pump includes a pump head containing a valve unit; a pair of bellows located at both sides of the pump head to form pump chambers inside these bellows; and a case for covering the outside of the bellows to form a pair of air chambers. When an air is supplied alternately into the air chambers to extend and contract the bellows, a target fluid such as a liquid can be transferred as it is sucked into and discharged from the pump chamber.
The air is supplied from an air source, switched at a switching valve mechanism such as a magnetic valve and fed as an actuating fluid alternately to the pair of air chambers. As for switching control of the switching valve mechanism, proximity switches are located at both ends of the case to detect a moving end of each bellows. The use of the proximity switches requires metals and wires arranged in the sensor sections. Generally, inside the pump chamber is a first liquid-contact section and the air chamber is a second liquid-contact section that is a liquid-free section. The proximity switch may be often located in the second liquid-contact section. In the case of a pump for transferring a metal-corrosive target fluid, however, it is desired to avoid the use of metals and metallic wires in the second liquid-contact section as far as possible.
In known bellows pumps of an all air type, a switching valve mechanism is switched under pressure of a fluid (control fluid) branched from the actuating fluid (U.S. Pat. No. 5,893,707 and U.S. Pat. No. 5,558,506).
The above-described bellows pumps of the all air type include one that houses a switching mechanism for switching the switching valve mechanism in a pump case as disclosed in U.S. Pat. No. 5,893,707. This rises a problem because of the poor maintenance ability for the switching mechanism and no compatibility with a switching mechanism of the proximity switch type. In the bellows pump disclosed in U.S. Pat. No. 5,558,506, as a part of a switching mechanism for switching the switching valve mechanism, a piston is fixed to a reciprocating shaft. Accordingly, the switching mechanism can not be detached and attached individually. This also rises a problem because of the poor maintenance ability for the switching mechanism and no compatibility with a switching mechanism of the proximity switch type.
The use of the proximity switch has merits because: (1) the number of reciprocating strokes of the pump can be converted into a discharged flow amount; and (2) the pump halting due to some trouble can be detected from an electric signal. Therefore, it is greatly significant to replace the switching mechanism of the all air type for the proximity switch type.
The present invention has been made in consideration of the above situation and accordingly has an object to provide a pump system excellent in the maintenance ability and compatibility.
According to the present invention, a pump system comprises a pump and a switching valve mechanism. The pump includes a pump head having an inlet and an outlet for a target fluid to be transferred and including a valve unit for routing the target fluid from the inlet to the outlet, a shaft passing through the pump head for reciprocating therethrough, a first and a second flexible members linked to both ends of the shaft to form a first and a second pump chambers at both sides of the pump shaft for introducing the target fluid through the valve unit, a first and a second cases for housing the first and second flexible members individually to form a first and a second actuating fluid chambers for introducing an actuating fluid into spaces outside the first and second flexible members, and a first and second switching mechanisms detachably attached to the cases from outside and located in the axial direction at both sides of the shaft, having flow paths formed therein for branching part of the actuating fluid and including movable members reciprocating together with the shaft in a state not fixed to the shaft, in which the movable member opens the flow path to branch part of the actuating fluid as a control fluid when the shaft reaches one of limits of reciprocation. The switching valve mechanism alternately distributes an actuating fluid supplied from an actuating fluid source to the pair of actuating fluid chambers using the control fluid branched at the switching mechanisms. The actuating fluid is alternately introduced into the pair of actuating fluid chambers to drive the shaft back and forth in opposite phases to suck and discharge the target fluid.
According to the present invention, in the pump system of the type that employs the control fluid branched from the actuating fluid to switch the switching valve mechanism, the switching mechanism for branching the actuating fluid is detachably attached to the case from outside. In addition, the movable member reciprocating together with the shaft is not fixed to the shaft. Therefore, it is easy to remove the switching mechanism entirely from the case. This is effective to improve the maintenance ability. It is also possible to remove the switching mechanism entirely to replace for a switching mechanism of a proximity switch type. This is effective to improve the compatibility.
In an embodiment of the present invention, the switching valve mechanism includes a switching valve mechanism body having a distribution chamber formed therein for distributing the actuating fluid, and a switching valve capable of reciprocating and located inside the distribution chamber in the switching valve mechanism body. The switching valve mechanism body has an introduction orifice formed for introducing the actuating fluid from the actuating fluid source into the distribution chamber, a first and a second actuating fluid orifices formed for discharging the actuating fluid introduced into the distribution chamber to the pump and introducing the actuating fluid discharged from the pump into the distribution chamber, a first and a second discharge orifices formed for discharging the actuating fluid discharged from the pump, and a first and a second control fluid orifices formed for introducing and discharging a control fluid branched from the actuating fluid. The switching valve is operative to switch between a first state and a second state when the control fluid drives the switching valve back and forth. In the first state the introduction orifice is communicated with the first actuating fluid orifice and the second actuating fluid orifice with the second discharge orifice. In the second state the introduction orifice is communicated with the second actuating fluid orifice and the first actuating fluid orifice with the first discharge orifice.
In an embodiment of the present invention, the pump system further comprises a first main conduit for connecting the first actuating fluid orifice in the switching valve mechanism with the first actuating chamber; a second main conduit for connecting the second actuating fluid orifice in the switching valve mechanism with the second actuating chamber; a first control fluid introduction path for introducing part of the actuating fluid as a control fluid into a flow path in the first switching mechanism; a second control fluid introduction path for introducing part of the actuating fluid as a control fluid into a flow path in the second switching mechanism; a first control fluid conduit for introducing the control fluid discharged from the flow path in the first switching mechanism into the first control fluid orifice in the switching valve mechanism; and a second control fluid conduit for introducing the control fluid discharged from the flow path in the second switching mechanism into the second control fluid orifice in the switching valve mechanism.
In an embodiment of the present invention, the switching mechanism includes a cylinder detachably fixed to the case from outside and having a discharge orifice for the control fluid formed at a side, and a rod serving as the movable member for reciprocating along with the shaft within the cylinder, having an introduction orifice for the actuating fluid or the control fluid formed at an end, and a discharge orifice for the control fluid formed in communication with the introduction orifice at a side. The discharge orifice in the rod communicates with the discharge orifice in the cylinder when the rod reaches one of limits of reciprocation thereof.
In another embodiment of the present invention, the switching mechanism includes a movable member case detachably fixed to the case from outside and having a discharge orifice for the control fluid formed at a side, a rod serving as the movable member for reciprocating within the movable member case, the rod having a tip protruded from the movable member case and contacted with the flexible member, an introduction orifice for the control fluid formed in the tip contacted with the flexible member, and a discharge orifice for the control fluid formed in communication with the introduction orifice at a certain location, and a resilient member for driving the rod toward the flexible member. The tip of the rod separates from the flexible member and the discharge orifice in the rod communicates with the discharge orifice in the cylinder when the shaft reaches in the vicinity of one of limits of reciprocation thereof.
In yet another embodiment of the present invention, the switching mechanism includes a ball valve case detachably fixed to the case from outside and having an introduction orifice for the control fluid formed at an end and a discharge orifice for the control fluid formed at a side, a rod serving as the movable member for reciprocating within the ball valve case and having a tip protruded from the ball valve case, in which the rod contacts with the flexible member and moves back when the flexible member reaches in the vicinity of a limit of reciprocation, and a ball valve housed in the ball valve case, in which the ball valve is opened to communicate the introduction orifice with the discharge orifice for the control fluid when the rod moves back and the rear end of the rod pushes the rod.
The flexible member may comprise a bellows or diaphragm. Preferably, the switching mechanism is composed of a ceramic or resin.
The present invention will be more fully understood from the following detailed description with reference to the accompanying drawings, in which:
Preferred embodiments of the present invention will be described below based on the drawings.
This pump system employs switching mechanisms of a cylinder type and comprises a pump 1 and a switching valve mechanism 2 for distributing an air as an actuating fluid into the pump 1.
The pump 1 includes a pair of cylindrical bellows 13a, 13b composed of flexible members to form pump chambers 12a, 12b at both sides of a pump head 11. These bellows 13a, 13b have movable end plates 14a, 14b linked together via a shaft 15 that passes through the pump head 11. The bellows 13a, 13b are individually housed in cylindrical cases 16a, 16b located at both sides of the pump head 11 to form air chambers 17a, 17b between the inner walls of the cases 16a, 16b and the outer walls of the bellows 13a, 13b. The cases 16a, 16b have stationary ends or opened edges 18a, 18b fitted in recessed portions in the pump head 11, of which outer surfaces are secured on the pump head 11 when fixing rings 19a, 19b are screwed in the pump head 11. The bellows 13a, 13b have stationary ends or opened edges 20a, 20b fitted in recessed portions in the pump head 11. The outer surfaces thereof are liquid-tightly secured on the pump head 11 when they are pressed beneath the inner steps of the edges 18a, 18b of the cases 16a, 16b. The cases 16a, 16b have main air orifices 21a, 21b for introducing and discharging airs into and from the air chambers 17a, 17b.
The pump head 11 includes an inlet 26 and an outlet 27 on a side of the pump head body 25 for a target fluid to be transferred, as shown in
The cases 16a, 16b have closed ends, to which switching mechanisms 40a, 40b are detachably attached. The switching mechanisms 40a, 40b include cylindrical cases 41a, 41b fixedly and detachably screwed to the cases 16a, 16b from outside; cylinders 42a, 42b coaxially housed in these cylindrical cases 41a, 41b; and rods 43a, 43b capable of reciprocating in the axial direction within these cylinders 42a, 42b. The cylindrical cases 41a, 41b have pilot air orifices 44a, 44b, 45a, 45b at ends and sidewalls for introducing and discharging pilot airs or control fluids. The cylinders 42a, 42b have openings at both ends and holes 46a, 46b in the sidewalls to communicate with the pilot air orifices 45a, 45b in the cylindrical cases 41a, 41b. The rods 43a, 43b have tips, passing through the cases 16a, 16b, facing to the air chambers 17a, 17b and contacting with the end plates 14a, 14b of the bellows 13a, 13b, and can reciprocate along with the reciprocation of the end plates 14a, 14b. The rods 43a, 43b have bores 47a, 47b formed in the axial direction extending from the base ends to the tips. The bores 47a, 47b have top portions communicating with holes 48a, 48b formed in the sidewalls. The holes 48a, 48b communicate with the holes 46a, 46b at certain locations immediately before the rods 43a, 43b move back most within the cylinders 42a, 42b. The cylindrical cases 41a, 41b have air escaping holes 49a, 49b formed therein and branched from the pilot air orifices 45a, 45b. The cases 16a, 16b have lip seals 51a, 51b formed at the parts that slidably contact with the tip sides of the rods 43a, 43b. Cylindrical spaces are formed between the inner walls of the cylinders 42a, 42b and the outer circumferences of the tips of the rods 43a, 43b. The cylindrical spaces are in communication with air escaping holes 52a, 52b formed in the cases 16a, 16b.
The switching valve mechanism 2 includes a switching valve mechanism body 62 that contains an air distribution chamber 61 formed therein. It also includes a spool (switching valve) 63 located in the switching valve mechanism body 62 so that it can reciprocate within the distribution chamber 61. In the switching valve mechanism body 62, an air introduction orifice (introduction orifice) 64 is formed to introduce an air into the distribution chamber 61. Main air orifices (actuating fluid orifices) 65a, 65b are formed to discharge the air once introduced into the distribution chamber 61 to the pump 1 and introduce the air discharged from the pump 1 into the distribution chamber 61. Main air discharge orifices 66a, 66b are formed to discharge the air discharged from the pump 1 and introduced into the distribution chamber 61. Pilot air orifices (control fluid orifices) 67a, 67b are formed to introduce and discharge pilot airs. The spool 63 has three large-diameter portions formed at a certain interval in the axial direction, which are employed to selectively close holes arrange around the portions to switch airflow paths between first and second states. The first state is such a mode that a pilot air is introduced through the pilot air orifice 67a. In this mode, the air introduction orifice 64 is in communication with the main air orifice 65a and the main air orifice 65b in communication with the main air discharge orifice 66b. The second state is such a mode that a pilot air is introduced through the pilot air orifice 67b. In this mode, the air introduction orifice 64 is in communication with the main air orifice 65b and the main air orifice 65a in communication with the main air discharge orifice 66a.
An air source 71 is employed to supply an air, which is introduced via a regulator 72 and an air introduction conduit 73 into the air introduction orifice 64 in the switching valve mechanism 2. The main air orifice 65a in the switching valve mechanism 2 is connected to the main air orifice 21a in the case 16a via a main air conduit (main conduit) 74a. The main air orifice 65b in the switching valve mechanism 2 is connected to the main air orifice 21b in the case 16b via a main air conduit (main conduit) 74b. The main air conduits (main conduits) 74a, 74b are connected to pilot air-pressure introduction conduits (introduction path) 75a, 75b, which pilot air-pressure introduction conduits 75a, 75b are connected to the pilot air orifices 44a, 44b in the switching mechanisms 40a, 40b. At the connected points between the pilot air orifices 44a, 44b and the pilot air-pressure introduction conduits 75a, 75b, throttles 76a, 76b are located to adjust amounts of the pilot airs introduced into the switching mechanisms 40a, 40b. The pilot air orifices 45a, 45b in the switching mechanisms 40a, 40b are connected to pilot air orifices 67a, 67b in the switching valve mechanism 2 via pilot air conduits (control fluid conduits) 77a, 77b. Air pools 50a, 50b are formed in the pilot air conduits 77a, 77b at the sides near the pilot air orifices 45a, 45b.
Operations of the pump system thus configured according to this embodiment will be described next.
In
Immediately before the bellows 13b reaches the terminal position in the suction process, the hole 48b in the rod 43b communicates with the bore 46b in the cylinder 42b. As a result, the compressed pilot air is introduced into the switching valve mechanism 2 via the pilot air conduit 77b to move the spool 63 toward the right side in the figure and shift the system to the second state.
In the second state, the air supplied from the air source 71 is introduced via the main air conduit 74b into the air chamber 17b in the pump 1 at the right side in the figure. As a result, the bellows 13b contracts to move the shaft 15 toward the left side in the figure. Accordingly, the bellows 13a extends to discharge the air in the air chamber 17a to external via the main air conduit 74a, the main air orifice 65a and the air discharge orifice 66a. Consequently, the target fluid is introduced into the pump chamber 12a via the inlet 26 and the target fluid in the pump chamber 12b is discharged to external via the outlet 27. At the same time, the pilot air is introduced into the switching mechanism 40a via the pilot air-pressure introduction conduit 75b branched from the main air conduit 74b to elevate the pressure inside the bore 47a in the rod 43a. Immediately before the bellows 13a reaches the terminal position in the suction process, the hole 48a in the rod 43a communicates with the bore 46a in the cylinder 42a. As a result, the compressed pilot air is introduced into the switching valve mechanism 2 via the pilot air conduit 77a to move the spool 63 toward the left side in the figure and the system returns to the first state.
Through the repetition of the above operations to extend and contract the bellows 13a, 13b, the liquid can be transferred continuously.
Annular spaces are present in between the tips of the rods 43a, 43b and the cylinders 42a, 42b in the switching mechanisms 40a, 40b. In relation to the presence of the lip seals 51a, 51b, these annular spaces are pressurized/evacuated in accordance with reciprocation of the rods 43a, 43b. The occurrence of such the pressurization/evacuation prevents the rods 43a, 43b from smoothly moving back and forth. The air escaping holes 52a, 52b are thus formed in the cases 16a, 16b to allow the spaces between the tips of the rods 43a, 43b and the cylinders 42a, 42b to communicate with external. This is effective to smoothly move the rods 43a, 43b back and forth.
If the pilot air has an excessive amount, air leakage through clearances between the cylinders 42a, 42b and the rods 43a, 43b may possibly cause a malfunction in the switching valve mechanism 2. If the pilot air has an excessive amount, when pressures inside the bores 47a, 47b in the rod 43a, 43b elevate, air leakage may possibly cause a malfunction in the switching valve mechanism 2. This air leakage is caused during a transient time from the communication state between the holes 48a, 48b in the rods 43a, 43b and the holes 46a, 46b in the cylinders 42a, 42b to the non-communication state after the rods 43a, 43b move. In this embodiment, the throttles 76a, 76b are located at the pilot air orifices 44a, 44b in the switching mechanisms 40a, 40b to limit amounts of the compressed airs from the pilot air-pressure introduction conduit 75a, 75b. This is effective to stabilize operations. The above malfunction may be prevented by the air pools 50a, 50b located in the pilot air conduits 77a, 77b to delay the introduction of the pilot air. In this embodiment, to prevent a malfunction in the switching valve mechanism 2 due to residual air pressures in the pilot air conduits 77a, 77b, the air escaping holes 49a, 49b are employed to remove the residual pressures.
According to the pump system, all components can be composed of non-metallic materials such as resins for the pump head 11, cases 16a, 16b and bellows 13a, 13b and ceramics for the shaft 15 and switching mechanisms 40a, 40b. Thus, it is possible to provide a pump system that is excellent in anti-corrosion and available even in an environment for transferring a corrosive chemical liquid. The switching mechanisms 40a, 40b can be removed entirely by screwing off because the rods 43a, 43b are not coupled to the end plates 14a, 14b of the bellows 13a, 13b. Thus, it is possible to provide a pump system that is excellent in the maintenance ability and easy to replace and repair the switching mechanisms 40a, 40b.
The pump system according to this embodiment comprises a pump 3 and a switching valve mechanism 2. Switching mechanisms 80a, 80b detachably attached to the pump 3 are different from the switching mechanisms 40a, 40b in the first embodiment. The pump system according to the first embodiment is operative to turn on one of the switching mechanisms 40a, 40b having the rods 43a, 43b pressed by the bellows 13a, 13b immediately before the end of the suction process to supply the pilot air to the switching valve mechanism 2. To the contrary, the second embodiment is operative to turn on one of the switching mechanisms 80a, 80b having rods pressing the bellows 13a, 13b from behind immediately before the end of the suction process to supply the pilot air to the switching valve mechanism 2.
The switching mechanisms 80a, 80b are detachably attached to the closed ends of the cases 16a, 16b. The switching mechanisms 80a, 80b include cylindrical cases 81a, 81b fixedly and detachably screwed to the cases 16a, 16b from outside; cylinders 82a, 82b coaxially housed in these cylindrical cases 81a, 81b; and rods 83a, 83b capable of reciprocating in the axial direction within these cylinders 82a, 82b. The cylindrical cases 81a, 81b have main air orifices 84a, 84b at the ends for introducing and discharging main airs or actuating fluids and pilot air orifices 85a, 85b in sidewalls for introducing and discharging pilot airs or control fluids. The cylinders 82a, 82b have openings at both ends and holes 86a, 86b in the sidewalls to communicate with pilot air orifices 85a, 85b in the cylindrical cases 81a, 81b. The rods 83a, 83b have tips, passing through the cases 16a, 16b, facing to the air chambers 17a, 17b and contacting with the end plates 14a, 14b of the bellows 13a, 13b, and can reciprocate along with the reciprocation of the end plates 14a, 14b. The rods 83a, 83b have bores 87a, 87b formed in the axial direction extending from the base ends to the tips. The bores 87a, 87b have mid-portions and top portions communicating with holes 88a, 88b and 89a, 89b formed in the sidewalls at the mid-portions and top portions. The holes 88a, 88b communicate with the holes 86a, 86b at certain locations immediately before the rods 83a, 83b advance most within the cylinders 82a, 82b. The holes 89a, 89b are located inside the air chambers 17a, 17b. The cases 16a, 16b have lip seals 51a, 51b formed at the parts that slidably contact with the tip sides of the rods 83a, 83b. Cylindrical spaces are formed in between the inner walls of the cylinders 82a, 82b and the outer circumferences of the tips of the rods 83a, 83b. The cylindrical spaces are in communication with air escaping holes 52a, 52b formed in the cases 16a, 16b. The cylindrical cases 81a, 81b have air escaping holes 90a, 90b formed therein and branched from the pilot air orifices 85a, 85b.
This embodiment is not provided with the pilot air-pressure induction conduits 75a, 75b employed in the first embodiment. Instead, the main air conduits 74a, 74b are connected to the main air orifices 84a, 84b in the switching mechanisms 80a, 80b.
This embodiment places the main air orifices 65a, 65b and the air discharge orifices 66a, 66b in the switching valve mechanism 2 in a positional relation opposite to the previous embodiment.
Operations of the pump system thus configured according to this embodiment will be described next.
In
Immediately before the bellows 13a reaches the terminal position in the discharge process, the hole 88a in the rod 83a communicates with the hole 86a in the cylinder 82a. As a result, the pilot air branched from the main air is introduced into the switching valve mechanism 2 via the pilot air conduit 77a to move the spool 63 toward the left side in the figure and shift the system to the second state.
In the second state, the air supplied from the air source 71 is introduced via the main air conduit 74b and the holes 87b, 89b formed in the rod 83b in the switching mechanism 80b into the air chamber 17b in the pump 1 at the right side in the figure. At the same time, the pressure of the main air drives the rod 83b forward. The pressure of the main air contracts the bellows 13a to move the shaft 15 toward the left side in the figure. Accordingly, the bellows 13a extends to discharge the air in the air chamber 17a to external via the holes 89a, 87a in the rod 83a in the switching mechanism 80a, the main air conduit 74a, the main air orifice 65a and the air discharge orifice 66a. Consequently, the target fluid is introduced into the pump chamber 12b via the inlet 26 and the target fluid in the pump chamber 12a is discharged to external via the outlet 27. Immediately before the bellows 13b reaches the terminal position in the discharge process, the hole 88b in the rod 83b communicates with the hole 86a in the cylinder 82a. As a result, the compressed pilot air is introduced into the switching valve mechanism 2 via the pilot air conduit 77b to move the spool 63 toward the right side in the figure and shift the system back to the first state.
Through the repetition of the above operations to extend and contract the bellows 13a, 13b, the liquid can be transferred continuously.
In this embodiment, to prevent a malfunction in the switching valve mechanism 2 due to residual air pressures in the pilot air conduits 77a, 77b, the air escaping holes 90a, 90b are employed to remove the residual pressures.
The pump system according to this embodiment comprises a pump 4 and a switching valve mechanism 2. Switching mechanisms 100a, 100b detachably attached to the pump 4 are different from the switching mechanisms 40a, 40b, 80a, 80b in the first and second embodiments. In the pump system according to the first and second embodiments, the switching mechanisms 40a, 40b, 80a, 80b are of cylinder types. To the contrary, in the third embodiment, they are of types using springs.
The switching mechanisms 100a, 100b are detachably attached to the closed ends of the cases 16a, 16b. The switching mechanisms 100a, 100b include cylindrical cases 110a, 101b fixedly and detachably screwed to the cases 16a, 16b from outside. Spring retaining screws 102a, 102b are fastened to the base end of these cylindrical cases 110a, 101b. Rings 103a, 103b are housed in the cylindrical cases 101a, 101b movably in the axial direction. Springs 104a, 104b are located in between the spring retaining screws 102a, 102b and the rings 103a, 103b to always drive the rings 103a, 103b toward the bellows 13a, 13b. Rods 105a, 105b are secured in the rings 103a, 103b to move back and forth together with the rings 103a, 103b. The rods 105a, 105b have tips facing to the air chambers 17a, 17b and bores 106a, 106b extending in the axial direction to communicate with the tips. The bores 106a, 106b have base ends in communication with holes 107a, 107b formed in the sidewalls of the rings 103a, 103b. Pilot air orifices 108a, 108b are formed in the sidewalls of the cylindrical cases 101a, 101b for introducing and discharging pilot airs or control fluids. They communicate with the holes 107a, 107b in the rings 103a, 103b when the rods 105a, 105b protrude most. The cylindrical cases 101a, 101b have air escaping holes 109a, 109b formed therein and branched from the pilot air orifices 108a, 108b. The springs 104a, 104b may be made of stainless steel and covered with a PFA or PTFE tube or applied with fluorine coating to possibly improve anti-corrosion.
This embodiment is not provided with the pilot air-pressure induction conduits 75a, 75b employed in the first embodiment. This embodiment places the pilot air orifices 67a, 67b in the switching valve mechanism 2 in a positional relation opposite to the previous embodiments.
Operations of the pump system thus configured according to this embodiment will be described next.
In
Immediately before the bellows 13a reaches the terminal position in the discharge process, the tip of the rod 105a separates from the end plate 14a of the bellows 13a. As a result, the hole 106a at the tip of the rod 105a is opened Then, the compressed air in the air chamber 17a is introduced into the switching valve mechanism 2 via the holes 106a, 107a, the pilot air orifice 108a and the pilot air conduit 77a to move the spool 63 toward the left side in the figure and shift the system to the second state.
In this second state, the air supplied from the air source 71 is introduced via the main air conduit 74b into the air chamber 17b in the pump 1 at the right side in the figure. As a result, the bellows 13b contracts to move the shaft 15 toward the left side in the figure. Accordingly, the bellows 13a extends to discharge the air in the air chamber 17a to external via the main air conduit 74a, the main air orifice 65a and the air discharge orifice 66a. Consequently, the target fluid is introduced into the pump chamber 12a via the inlet 26 and the target fluid in the pump chamber 12b is discharged to external via the outlet 27.
Immediately before the bellows 13b reaches the terminal position in the discharge process, the tip of the rod 105b separates from the end plate 14b of the bellows 13b. As a result, the hole 106b at the tip of the rod 105b is opened. Then, the compressed air in the air chamber 17b is introduced into the switching valve mechanism 2 via the holes 106b, 107b, the pilot air orifice 108b and the pilot air conduit 77b to move the spool 63 toward the left side in the figure and shift the system back to the first state.
Through the repetition of the above operations to extend and contract the bellows 13a, 13b, the liquid can be transferred continuously.
In this embodiment, the cylindrical cases 101a, 101b are pressurized/evacuated in accordance with reciprocation of the rings 103a, 103b. The air escaping holes 52a, 52b are thus formed in the cases 16a, 16b and air escaping holes 110a, 110b are also formed in the retaining screws 102a, 102b to prevent such the pressurization/evacuation from occurring.
The pump system according to this embodiment comprises a pump 5 and a switching valve mechanism 2. This embodiment employs bellows in switching mechanisms 120a, 120b while the previous embodiment employs the springs 104a, 104b in the switching mechanisms 100a, 100b.
The switching mechanisms 120a, 120b are detachably attached to the closed ends of the cases 16a, 16b. The switching mechanisms 120a, 120b include cylindrical cases 121a, 121b fixedly and detachably screwed to the cases 16a, 16b from outside. Bellows retaining screws 122a, 122b are fastened to the base end of these cylindrical cases 121a, 121b. Rings 123a, 123b are housed in the cylindrical cases 121a, 121b movably in the axial direction. Bellows 124a, 124b are located in between the retaining screws 122a, 122b and the rings 123a, 123b to always drive the rings 123a, 123b toward the bellows 13a, 13b. Rods 125a, 125b are secured in the rings 123a, 123b to move back and forth together with the rings 123a, 123b. The rods 125a, 125b have tips facing to the air chambers 17a, 17b and bores 126a, 126b extending in the axial direction to communicate with the tips. The bores 126a, 126b have base ends in communication with holes 127a, 127b formed in the sidewalls of the rings 123a, 123b. Pilot air orifices 128a, 128b are formed in the sidewalls of the cylindrical cases 121a, 121b for introducing and discharging pilot airs or control fluids. They communicate with the holes 127a, 127b in the rings 123a, 123b when the rods 125a, 125b protrude most. The cylindrical cases 121a, 121b have air escaping holes 129a, 129b formed therein and branched from the pilot air orifices 128a, 128b.
Detailed operations are almost similar to those of the third embodiment and accordingly omitted to describe the contents. It is required to always fill the bellows 124a, 124b with air compressed under an appropriate pressure. Holes 130a, 130b are thus formed in the retaining screws 122a, 122b. In addition, the air supplied from the air source 71 is pressurized at a bellows-pressurizing regulator 78 to supply a pressurizing air to the bellows 124a, 124b via bellows-pressurizing conduits 79a, 79b and the holes 130a, 130b.
The pump system according to this embodiment comprises a pump 6 and a switching valve mechanism 2. Switching mechanisms 140a, 140b detachably attached to the pump 6 are of a ball valve type.
The switching mechanisms 140a, 140b are detachably screwed to the cases 16a, 16b from outside and include cylindrical cases 141a, 141b. Ball-valve retaining screws 142a, 142b are fastened to the base end of these cylindrical cases 141a, 141b. Ball valves 143a, 143b are housed in the cylindrical cases 141a, 141b and secured by the retaining screws 142a, 142b. Rods 144a, 144b are housed in the front portions of the cylindrical cases 141a, 141b and move back and forth. The rods 144a, 144b have tips facing to the air chambers 17a, 17b and base ends for opening/closing the ball valves 143a, 143b. Pilot air introduction orifices 145a, 145b are formed in the retaining screws 142a, 142b to communicate with the air introduction side of the ball valves 143a, 143b. Formed in the sidewalls of the cylindrical cases 141a, 141b are pilot air orifices 146a, 146b in communication with the air discharge side of the ball valves 143a, 143b and air escaping holes 147a, 147b branched from the pilot air orifices 146a, 146b.
Pilot air discharge orifices 151a, 151b are formed in the sidewalls of the cases 16a, 16b in the pump 6. These pilot air discharge orifices 151a, 151b are connected to the pilot air introduction orifices 145a, 145b via pilot air introduction conduits 152a, 152b.
Operations of the pump system thus configured according to this embodiment will be described next.
In
Immediately before the bellows 13b reaches the terminal position in the suction process, the base end of the rod 144b pushes up the ball in the ball valve 143b to open the ball valve 143b. As a result, the compressed pilot air introduced into the switching mechanism 140b is introduced into the switching valve mechanism 2 via the pilot air orifice 146a and the pilot air conduit 77b to move the spool 63 toward the right side in the figure and shift the system to the second state.
Similarly, in the second state, the pilot air compressed through the switching mechanism 140a is introduced into the switching valve mechanism 2 via the pilot air conduit 77a to move the spool 63 toward the left side in the figure and shift the system back to the first state.
Through the repetition of the above operations to extend and contract the bellows 13a, 13b, the liquid can be transferred continuously.
Also in this embodiment, to prevent a malfunction in the switching valve mechanism 2 due to residual air pressures in the pilot air conduits 77a, 77b, the air escaping holes 147a, 147b are employed to remove the residual pressures.
In this embodiment, if it takes a long time until the ball valves 143a, 143b are closed after the introduction of the pilot air into the switching mechanisms 140a, 140b from the pilot air introduction conduits 152a, 152b, leakage of the pilot air may cause a malfunction. Therefore, the pilot air introduction conduits 152a, 152b are connected to the main air conduits 74a, 74b not directly but once through the air chambers 17a, 17b. This is operative to cause a primary delay in the pilot air toward the switching mechanisms 140a, 140b to prevent the leakage of the pilot air. The above malfunction may be prevented by the air pools 50a, 50b located in the pilot air conduits 77a, 77b to delay the introduction of the pilot air.
This embodiment employs a pump 7 of a diaphragm type instead of the pump 1 of the bellows type of the embodiment shown in FIG. 1.
The pump 7 employs diaphragms 161a, 161b as flexible members instead of the bellows 13a, 13b in the pump 1 of FIG. 1. Except for this point, other arrangement is same as that of the pump 1 and accordingly omitted to describe in detail.
As obvious from the above, according to the present invention, in the pump system of the type that employs the control fluid branched from the actuating fluid to switch the switching valve mechanism, the switching mechanism for branching the actuating fluid is detachably attached to the case from outside. In addition, the movable member reciprocating together with the shaft is not fixed to the shaft. Therefore, it is easy to remove the switching mechanism entirely from the case. This is effective to improve the maintenance ability. It is also possible to remove the switching mechanism entirely to replace for a switching mechanism of a proximity switch type. This is effective to improve the compatibility.
Having described the embodiments consistent with the invention, other embodiments and variations consistent with the invention will be apparent to those skilled in the art. Therefore, the invention should not be viewed as limited to the disclosed embodiments but rather should be viewed as limited only by the spirit and scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-118247 | Apr 2002 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20030198561 A1 | Oct 2003 | US |
