Patent Application
20110318207
The present invention relates to a bellows pump which is suitable as liquid transporting means for pure water or medical solution and to be used in equipment or apparatus for producing a semiconductor or liquid crystal.
A bellows pump is configured by: a pump body which comprises a suction path and discharge path for a to-be-transported fluid; a bellows which is placed in a state where one end is airtightly fixed to the pump body to form a closed space with respect to the pump body; and an actuation plate which is attached to the other end of the bellows so as to cause the bellows to expand and contract with respect to the pump body. As examples of such a bellows pump, a single-bellows type disclosed in Patent Literature 1, and a double-bellows type (reciprocating pump) disclosed in Patent Literature 2 are known.
In a bellows pump which is a displacement pump, it is known that, in the timing of switching between suction due to the expansion of a bellows and discharge due to contraction of the bellows, a large pressure change (pressure rise) is momentarily produced. In the case where the fluid is liquid such as water, the change is shock vibration which is also called “water hammer”. Vibration caused by the large pressure change is transmitted to an apparatus or a pipe, thereby producing a possibility that inconveniences such as that particles are generated, and that various portions are broken (for example: a quartz-made tank which is connected to the pump through a pipe cracks or breaks) may occur.
Conventionally, therefore, countermeasures that the flow rate in the pipe is reduced to suppress vibration, and that an accumulator or the like is added to absorb generated vibration, thereby relaxing vibration are taken. However, the former vibration suppressing means is in summary to reduce the discharge amount of the pump, and hence there is a disadvantage that the performance is lowered, and, in the case of the latter vibration relaxing means, problems such as that the installation place is made large, and that the cost is increased occur.
As described above, in the proposed countermeasures for suppressing or eliminating shock vibration which is generated because of the structure of a bellows pump in the timing of switching between suction and discharge, without causing performance reduction and increases of the installation place and the cost, there remains room for further improvement.
It is an object of the invention to develop and provide a bellows pump which is further improved so that, without causing or while suppressing performance reduction and increases of the installation place and the cost, shock vibration which is generated in the timing of switching between suction and discharge can be suppressed or eliminated.
The invention set forth in claim 1 is characterized in that a bellows pump has: a pump body 1 comprising a suction path 12 and discharge path 13 for a to-be-transported fluid; a bellows 2 which is placed in a state where one end 2a is airtightly fixed to the pump body 1 to form a closed space 11 with respect to the pump body 1; and an actuation plate 15 which is attached to another end 2c of the bellows 2 so as to cause the bellows 2 to expand and contract with respect to the pump body 1, wherein an airtight-like space portion 19 is formed between the other end 2c of the bellows 2 which is made of a fluorine resin, and the actuation plate 15, and a space-facing portion 20 which faces the space portion 19 in the other end 2c is elastically deformably configured so as to enable the space portion 19 to expand and contract.
The invention set forth in claim 2 is characterized in that, in the bellows pump according to claim 1, the other end 2c is formed into a plate-like portion in which a center portion is recessed so as to be opened toward the actuation plate, and which exhibits a substantially bottomed cylindrical shape, and a recessed portion in the other end 2c is configured as the space portion 19 by the actuation plate 15 in the other end 2c or sealing means 18 placed in an annular tip end face 17.
The invention set forth in claim 3 is characterized in that, in the bellows pump according to claim 1, the bellows pump is configured as a reciprocating pump in which the bellows 2 is airtightly fixed to each of end portions of the pump body 1, and the actuation plates 15 which are attached respectively to the bellows 2 are coupled to each other so that the pair of bellows 2, 2 that are opposed to each other complementarily expand and contract, by coupling rods 22 which are placed outside the bellows 2.
The invention set forth in claim 4 is characterized in that, in the bellows pump according to any one of claims 1 to 3, the bellows 2 is made of PTFE.
According to the invention of claim 1, although its detail will be described in the paragraph of embodiments, the space-facing portion which faces the space portion in the other end of the bellows is elastically deformable so that the airtight-like space portion formed between the other end of the bellows and the actuation plate can expand and contract. In the transmission (water hammer phenomenon) of vibration due to a pressure rise generated by sudden stop of the fluid, therefore, the internal capacity of the bellows is increased by elastic deformation of the space-facing portion synchronized with the generation of the pressure rise, to absorb the pressure rise, whereby the vibration can be reduced. This causes transmission of the vibration to other apparatuses to be reduced or avoided, and inconveniences such as that apparatuses are broken, and that particles are generated can be suppressed or eliminated. Moreover, it is not necessary to reduce the flow rate of the fluid, the original performance of the pump can be sufficiently provided, and an additional buffer apparatus is not required. As a result, it is possible to provide a bellows pump which is further improved so that, without causing or while suppressing performance reduction and increases of the installation place and the cost, shock vibration which is generated in the timing of switching between suction and discharge can be suppressed or eliminated. Furthermore, the bellows is made of a fluorine resin, and therefore a bellows pump can be provided that is suitable in, for example, a semiconductor washing step in which cleanness is required, or a medical solution supplying line in which high resistance to erosion is required.
According to the invention of claim 2, the recessed portion is disposed in the thick plate-like other bellows end, and the space portion is formed between the other end and the actuation plate. Therefore, there is an advantage that rational and economical means in which only a change of the bellows is requested and any other change is not necessary can attain the above-mentioned effects of the invention of claim 1. Moreover, the invention has another advantage that replacement of the bellows enables the bellows pump to be applied to an existing apparatus.
According to the invention of claim 3, it is possible to provide a bellows pump in which the structure is suitable for a high capacity pump, and shock vibration in a reciprocating pump in which also vibration tends to be large can be effectively suppressed or eliminated, and which has practical great advantages.
According to the invention of claim 4, PTFE is used as the fluorine resin, and the following effects can be attained. Although PTFE (polytetrafluoroethylene) is a general-purpose fluorine resin and a material which is relatively easily available, PTFE has excellent characteristics such as a wide working temperature range, a chemical resistance, an electrical insulation property, a low frictional property, a nonadhesive property, a weather resistance, and a fire retardancy, and is a material which is more suitable for a bellows pump.
Hereinafter, embodiments of the bellows pump of the invention will be described with reference to the drawings.
As shown in
Hereinafter, the pumping function will be briefly described. The air is complementarily introduced and discharged with respect to air supplying/discharging ports a, a which are disposed on the axis P of the end cases 5, 5, from an air supplying/discharging apparatus that is not shown, thereby causing the pair of air cylinders 3, 3 to complementarily expand and contract, so that a fluid such as medical solution which is sucked from a fluid sucking port ri that is placed in a side of the pump body 1 can be substantially continuously discharged from a fluid discharging port ro that is placed above the fluid sucking port. Namely, the pump has a structure where the pair of the bellows 2, 2 are complementarily expandingly and contractingly moved (expandingly and contractingly driven), and, during a period when one of the bellows 2 operates to discharge the fluid, the other bellows 2 operates to suck the fluid, so that, although having the reciprocating structure, the pump can continuously discharge the fluid.
Next, the structures of the portions will be described. As shown in
Circular holes 6b, 7b for passage of the fluid are formed in tip end portions of the valve cases 6A, 7A which are disposed in a state of projecting into pump chambers (an example of a closed space) 11 that are internal spaces of the bellows 2. In the pump body 1, a suction path 12 for communicating the pair of suction check valves 6, 6 with the fluid sucking port ri, and a discharge path 13 for communicating the pair of discharge check valves 7, 7 with the fluid sucking port ri are formed. In
As shown in
The head portion 2c is formed into a plate-like portion in which a center portion is recessed so as to be opened toward the actuation plate 15, and which exhibits a substantially bottomed cylindrical shape, and the recessed portion in the head portion 2c is configured as a space portion 19 by placing an O-ring (an example of sealing means) 18 on an annular tip end face 17 which is in contact with the actuation plate 15. In a structure where the head portion 2c is made of an elastic material such as rubber, sealing is performed simply by pressingly contacting the annular tip end face 17 with the actuation plate 15. In this case, the annular tip end face 17 itself functions as the sealing means. The existence of the space portion 19 which is a large-diameter hole causes the head portion 2c to be formed into a reduced-thickness portion (an example of a space-facing portion) 20 which has a small thickness, excluding its outer peripheral portion. Since the bellows 2 is made of a fluorine resin, preferably, PTFE, the reduced-thickness portion 20 can be elastically film-transferred. The bellows 2 may be formed by a material which is plastically and elastically deformable.
Namely, the airtight-like space portion 19 is formed between the head portion 2c of the bellows 2 and the actuation plate 15, and the reduced-thickness portion 20 which faces the space portion 19 in the head portion 2c is elastically deformably configured so as to enable the space portion 19 to expand and contract (expansion and contraction). The head portion 2c is formed into a plate-like portion in which a center portion is recessed so as to be opened toward the actuation plate 15, and which exhibits a substantially bottomed cylindrical shape, and it is configured as the space portion 19 in the head portion 2c by placing the O-ring 18 which is sealing means, on the annular tip end face 17 which is in the head portion 2c, and which is in contact with the actuation plate 15. Because of the existence of the space portion 19, shock buffering means (vibration relaxing means) B which suppresses and relaxes shock vibration (water hammer) generated in the timing of switching between suction and discharge (or discharge and suction) of the fluid is configured.
The bellows 2 is made of a fluorine resin, preferably, PTFE (polytetrafluoroethylene), and formed not by blow molding, but by performing a cutting process on a cylindrical member made of PTFE by a lathe with using a stick cutting tool, a knife, or the like. As shown in
The thickness in the apex portion of the crest portion 32 and the deepest portion of the valley portion 33, i.e., the minimum thickness of the crest portion 32 and the valley portion 33 in the bellows diameter direction is set to be equal to the thickness of the side face portion 34 in the bellows axis direction. Preferably, the thickness may be set to be equal to or larger than it. More preferably, the inner peripheral face (the inner face of the bellows 2) of the crest portion 32, and the outer peripheral face (the outer face of the bellows 2) of the valley portion 33 may be configured by a curved face having a predetermined angle R or a radius R so that an acute portion is not produced. According to the configuration, when the bellows 2 expands in the axial direction, the side face portion 34 actively flexes, and, because of the flexure, stresses which are mainly generated in the inner face side of the curved face are dispersed in the minimum thickness portions of the crest portion 32 and the valley portion 33 or in the vicinities thereof, and stress concentration is relaxed.
Particularly, the ratio of the thickness of the side face portion 34 to the minimum thickness portions of the crest portion 32 and the valley portion 33 is preferably set to be in the range of 1.2 to 2.5. According to the configuration, even when the thicknesses of the crest portion 32 and the valley portion 33 are not wastefully made large, stress concentration in the portions can be effectively relaxed. When the minimum thickness of the crest portion 3 and the valley portion 33 is 1.4 mm and the thickness of the side face portion 34 is 3.0 mm, for example, the above-described ratio is about 2.1, and set to be in the adequate thickness range. When the ratio is smaller than 1.2, stress relaxation may be insufficient, and, when the ratio is larger than 2.5, the diameter of the bellows is increased so as to be contrary to the compactness.
The right and left actuation plates 15, 15 are loosely fitted into passing holes 4a, 4a of the intermediate cases 4, 4, movably passed through the basal end side annular plates 9, and screwingly fixed to the both ends of the coupling rods 22 which are passed in a liquid-tight state through a seal bearing 21 that is fitted into the pump body 1. The coupling rods 22 are disposed in a plural number (for example, four) at regular angular intervals about the axis P. The seal bearing 21 is pressingly inserted or fitted into a through hole la formed in the stepped recess annular grooves 1A, and inner and outer Orings 23, 24 are attached thereto. As described above, the right and left actuation plates 15, 15 are configured so as to be integrally moved in the direction of the axis P by the coupling rods 22, and the complementary expansion and contraction of the pair of the bellows 2, 2 can be surely performed.
Next, the function and effect of the shock buffering means B will be described. Usually, when a fluid suction check valve and fluid discharge check valve which are incorporated in a bellows pump are switched, or when various valves which exist in a piping system, such as an opening/closing valve, a stop valve, and a check valve are switched, a valve element butts against (or separates from) a valve seat, and therefore an abrupt pressure rise due to sudden acceleration or deceleration of a fluid is generated, thereby producing a disadvantage that shock vibration is generated in the piping system. In the bellows pump A of the invention, there is an advantage that generation of such shock vibration is relaxed or eliminated by the shock buffering means B which is disposed in the head portion 2c by using the actuation plate 15.
The water hammer will be described in a further detail. In the case where one of the bellows expands and the fluid enters the bellows through the fluid suction check valve which is incorporated in the bellows pump, even when the expansion movement of the bellows is stopped, the fluid is caused by inertia to try to still enter the bellows through the fluid suction check valve, and hence the pressure in the bellows temporarily abruptly rises. Then, the fluid suction check valve is suddenly closed (suddenly interrupted), and, at this time, the fluid which tries to enter the bellows through the fluid suction path is abruptly interrupted, thereby producing a water hammer. Shock and vibration due to by the water hammer transmit through the piping, and cause a damage such as a crack to be produced in a quartz-made tank or the like. Basically, a water hammer is produced by suddenly closing a check valve. When an abrupt pressure rise in a bellows which causes sudden valve closing is absorbed so that sudden valve closing does not occur, it is possible to prevent a water hammer from being generated. As an example of means for the purpose, it may be contemplated that the expansion/contraction moving rate (stroke speed) of a bellows is reduced to prevent sudden valve closing from occurring. In this case, however, the flow amount cannot be ensured, with the result that it is difficult to realize the above. According to the means in which the reduced-thickness portion 20 is disposed in the head portion 2c as in the invention, the elastic deformation of the reduced-thickness portion 20 absorbs an abrupt pressure rise in the bellows, and a water hammer can be avoided or reduced. Moreover, an excellent effect that it is not necessary to reduce the expansion/contraction moving rate of the bellows and a predetermined flow amount can be ensured can be realized.
When a large pressure rise occurs, namely, the space portion 19 functions as an air bag and the reduced-thickness portion 20 is elastically deformed in the direction along which the capacity is reduced, as indicated by the phantom lines in
In the transmission of vibration or so-called the water hammer phenomenon due to a pressure rise generated by sudden stop of the fluid (kinetic energy), the internal capacity of the bellows is increased by elastic deformation of the reduced-thickness portion 20 synchronized with the generation of the pressure rise, to absorb the pressure rise, whereby the vibration can be reduced. This causes transmission of the vibration to other apparatuses to be reduced (or avoided), and inconveniences such as that apparatuses are broken, and that particles are generated can be suppressed (or eliminated). Moreover, since it is not necessary to reduce the flow rate of the fluid, the original performance of the pump can be sufficiently provided, and an additional buffer apparatus is not required. Also an effect that the footprint and the cost are reduced can be expected.
As shown in
In
As shown in
Although not illustrated also, the shock buffering means B may be configured so that a spherical member which can perform only elastic contraction is placed inside the bellows 2. For example, the spherical member may be an air-filled rubber ball in which the outside is covered by a woven metal wire mesh, and, when a large pressure rise such as a water hammer occurs, the rubber ball contracts to absorb and relax the pressure. Even when a negative pressure acts, the ball does not expand beyond the size which is defined by the woven metal wire mesh. Therefore, this is convenient.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-040673 | Feb 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/051406 | 2/2/2010 | WO | 00 | 8/11/2011 |
