Bellows pump

A bellows pump with a case member that forms an axial space therein, closed-bottomed cylindrical bellows that are arranged in the space in an axially extendable/contractable manner and axially separate the space into a pump chamber and an operation chamber, suction valves that are provided on a suction side of the pump chamber and guide a fluid to be transferred to the pump chamber, and discharge valves that are provided on a discharge side of the pump chamber and discharge the fluid to be transferred from the pump chamber, and which extends/contracts the bellows by introducing a working fluid into the operation chamber to discharge the working fluid from the operation chamber, wherein each of the bellows is configured by alternately forming mountain portions and valley portions along the axial direction and having, on a predetermined position in the axial direction, annular ring portion integrally formed therewith.

TECHNICAL FIELD

The present invention relates to a bellows pump that performs a pump operation using bellows separating a pump chamber and an operation chamber.

BACKGROUND ART

A bellows pump has a structure in which a bellows divides an enclosed region into a pump chamber and an operation chamber. Then the bellows pump operates to compress and extend the pump chamber by introducing and discharging a working fluid into and from the operation chamber. Known examples of such a bellows pump are, for example, those disclosed in Patent Document 1 and Patent Document 2 listed below.

The bellows pumps disclosed in Patent Document 1 and Patent Document 2 have a configuration in which the bellows has an optimized shape to reduce a problem, such as deformation of a bellows100shown inFIG. 4due to stress concentration caused by an operating pressure as shown by the arrows inFIG. 4. The bellows deformation arises if the pressure exceeds the limit of the bellows' pressure resistance performance or the temperature of the bellows increases too high. The problem has been addressed, therefore, by increasing the pressure resistance by changing the bellows shape as described above or increasing the bellows' wall thickness.

RELATED ART DOCUMENTS

Patent Documents

Patent Document 1: Examined Japanese Patent Application Publication No. JP 2001-193836 A

Patent Document 2: Examined Japanese Patent Application Publication No. JP 2001-193837 A

SUMMARY OF THE INVENTION

Problem to be solved By the Invention

Unfortunately, increasing the pressure resistance performance by changing the bellows shape as described above or increasing the wall thickness will restrict the motion of the bellows itself or increase the operating resistance, thus adversely affecting the discharge amount of a fluid to be transferred. Then, more force is needed to expand and contract the bellows to eliminate the affect on the discharge amount, thereby reducing the operating efficiency.

The present invention was accomplished in light of the above problems. It is an object of the invention to provide a bellows pump having a bellows that has good temperature characteristics and that may improve the pressure resistance performance without decreasing the operating efficiency.

Means for solving the Problem

A first bellows pump according to the present invention comprises: a case member that forms an axial space therein; closed-bottomed cylindrical bellows that are arranged in the space in an axially extendable/contractable manner and axially separate the space into a pump chamber and an operation chamber; suction valves that are provided on a suction side of the pump chamber and guide a fluid to be transferred to the pump chamber; and discharge valves that are provided on a discharge side of the pump chamber and discharge the fluid to be transferred from the pump chamber, wherein the bellows are extended/contracted by introducing a working fluid into the operation chamber and discharging the working fluid from the operation chamber, thus transferring the fluid to be transferred, and wherein each of the bellows is configured by alternately forming mountain portions and valley portions along the axial direction, and having, on a predetermined position in the axial direction, an annular ring portion integrally formed therewith.

A second bellows pump according to the present invention comprises: a pump head; a pair of bottom-closed cylindrical bellows provided on respective opposite sides of the pump head with their opening sides being opposed, each bellows forming a pump chamber therein and being axially extendable/contractable; a pair of bottom-closed cylindrical cylinders attached to the pump head with their opening portions being opposed, the cylinders being disposed coaxially to the pair of bellows to contain the respective bellows therein, the cylinders forming operation chambers between the cylinders and the pair of bellows; a pair of pump shafts passing through the respective bottoms of the pair of cylinders slidably in an airtight manner along the central axis of the cylinders, the pump shafts having first ends joined to the respective bottoms of the pair of bellows; a joint shaft joining second ends of the pair of pump shafts movably in the axial direction; and a valve unit attached to the pump head in the pump chambers, the valve unit introducing a fluid to be transferred from a suction opening of the fluid to be transferred to the pump chamber and introducing the fluid to be transferred from the pump chamber to a discharge opening of the fluid to be transferred, the pair of bellows being extended/contracted by introducing a working fluid into the operation chamber and discharging the working fluid from the operation chamber, thus transferring the fluid to be transferred, and each of the pair of bellows being configured by alternately forming mountain portions and valley portions along the axial direction and having, on a predetermined position in the axial direction, an annular ring portion integrally formed therewith.

In one preferred embodiment, the ring portion is formed, for example, in a plurality at a predetermined interval in the axial direction.

In another embodiment, the bellows comprises, for example, fluororesin.

EFFECTS OF THE INVENTION

The present invention may provide a bellows pump having a bellows that has good temperature characteristics and that may improve the pressure resistance performance without decreasing the operating efficiency.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

With reference to the accompanying drawings, the embodiments of a bellows pump according to the present invention will be described in more detail.

FIG. 1is a cross-sectional view of a bellows pump according to one embodiment of the present invention and a schematic view of its peripheral mechanism. Note that although the bellows pump according to this embodiment will be described with respect to, by way of example, a bellows pump of a so-called multi-barrel type of a reciprocating pump structure, a bellows pump of a so-called single barrel type is also applicable.

The bellows pump is configured as follows. A pump head1is centrally disposed. Bottom-closed cylindrical cylinders2aand2b, which are case members, are coaxially disposed on the respective opposite sides of the pump head1. The cylinders2aand2bcomprise a pair of spaces formed therein. The spaces comprise respective bottom-closed cylindrical bellows3aand3bcoaxially disposed therein.

The bellows3aand3bhave opening ends secured to the pump head1and have respective shaft fixing plates4aand4bsecured on their bottoms. The bellows3aand3bcomprises, for example, fluororesin. The bellows3aand3bseparate the inside spaces of the cylinders2aand2binto inside pump chambers5aand5band outside operation chambers6aand6b, respectively.

Each of the bellows3aand3bhas a structure that comprises mountain portions12aand valley portions12b, which are alternately formed in the axial direction, and an annular ring portion12integrally formed around an intermediate position in the axial direction. The bellows3aand3bhave the same shape as a usual bellows without the ring portion12. The number of mountain portions12aand valley portions12bare set to provide the same wall thickness and the same operating resistance as a usual bellows.

Shafts7aand7bextending coaxially have first ends secured to the respective shaft fixing plates4aand4b. The shafts7aand7bhave second ends passing through the bottom centers of the cylinders2aand2bin an airtight manner via seal members8to the outside of the cylinders2aand2b, respectively. Joint plates9aand9bare secured to the second ends of the shafts7aand7bvia nuts10.

The joint plates9aand9bare joined together by joint shafts11aand11bat positions above and below the cylinders2aand2b. Each of the joint shafts11aand11bis secured to the joint plates9aand9bvia bolts15.

The pump head1comprises a suction opening16and a discharge opening17for a fluid to be transferred, the openings16and17being at positions facing the side surfaces of the pump. In addition, the pump head1comprises suction valves18aand18bat positions in a path from the suction opening16to the pump chambers5aand5b, and discharge valves19aand19bat positions in a path from the pump chambers5aand5bto the discharge opening17.

Meanwhile, a working fluid such as an air from a working fluid source such as a not-shown air compressor is regulated to a predetermined pressure by a regulator26and supplied to a solenoid valve27.

It is assumed here that the operation chamber6ais in an exhaust state, the operation chamber6bis in an air-introducing state, the pump chamber5ais in an expansion process, and the pump chamber5bis in a contracting process. Then, the suction valve18aand the discharge valve19bare in an open state and the suction valve18band the discharge valve19aare in a closed state. The liquid to be transferred is thus introduced from the suction opening16to the pump chamber5aand discharged from the pump chamber5bvia the discharge opening17.

The bellows3aand3brepeat the expansion and contraction in the axial direction to achieve the operation by the expansion and contraction of the pump chambers5aand5bas described above. Then, even if the transfer pressure or the operating pressure is increased to transfer more fluid to be transferred or the temperature inside the pump increases during the operation, the ring portion12may provide high pressure resistance without using a large wall thickness, thus preventing the deformation or damage. In other words, each of the bellows3aand3bhas a structure that may provide higher pressure resistance than a bellows without the ring portion12if they are set to have the same operating efficiency as the bellows without the ring portion12.

Therefore, the bellows pump according to this embodiment may have better temperature characteristics and higher pressure resistance performance without reducing the operating efficiency than a conventional bellows pump comprising a bellows without the ring portion12. Note that the bellows3aand3bmay be configured as follows.

FIG. 2shows another example of the bellows3aand3bof the bellows pump.FIG. 3shows still another example of the bellows3aand3bof the bellows pump. With reference toFIG. 2andFIG. 3, each of the bellows3aand3bcomprises the mountain portions12aand the valley portion12bas well as two or three ring portions12formed at a predetermined interval in the axial direction, for example. In this way, the bellows3aand3bcomprising a plurality of ring portions12may also improve the pressure resistance as inFIG. 1. Note that the ring portions12are not necessarily provided at regular intervals.

EXAMPLES

The applicants performed the following burst test and operating resistance test to check the characteristics of the above bellows3aand3b. In these tests, all the bellows were made of fluororesin and had a wall thickness of 2 mm and 12 mountain portions12a. In addition, the ring portion12had an axial direction thickness of 10 mm. The example 1 is for one ring portion12, the example 2 is for two ring portions12, the example 3 is for three ring portions12, and the comparative example is for zero ring portion12.

With reference toFIG. 4, the burst test was performed by applying external pressure to the bellows, and the operating resistance test was performed by pulling the bellows in the axial direction with a predetermined load. Table 1 below shows the burst test results. Table 2 below shows the operating resistance test results. Note that in the burst test, the temperature (ambient temperature) of the bellows was set to 180° C.

Table 1 shows that in the burst test, the bellows burst pressure (MPa) was 0.286 in the comparative example, while 0.298 in the example 1, 0.389 in the example 2, and 0.376 in the example 3, which all exceed the result in the comparative example. This proves that the pressure resistance is improved.

Meanwhile, table 2 shows that in the operating resistance test, the axial free length of the bellows was 175.5 mm in the comparative example, while 187.4 mm in the example 1, 199 mm in the example 2, and 212.7 mm in the example 3. In addition, the length under a load of 10 kgf was 181.3 mm in the comparative example, while 193.6 mm in the example 1, 205 mm in the example 2, and 219 mm in the example 3.

Therefore, the elongation of the bellows was 5.8 mm in the comparative example, while 6.2 mm in the example 1, 6 mm in the example 2, and 6.3 mm in the example 3. This result shows almost the same operating resistance in the comparative example and the examples 1, 2, and 3. This proves that the operating resistance remains unchanged regardless of the presence or absence of the ring portion12.

As described above, in the bellows pump according to the present invention, the bellows3aand3bcomprising the ring portion12may have good temperature characteristics and improve the pressure resistance performance without decreasing the operating efficiency.

DESCRIPTION OF REFERENCE NUMERALS