Duplex reciprocating pump

Abstract

A duplex reciprocating pump includes: a case member forming a pair of spaces; a movable partitioning member that partitions insides of these spaces into a first and second pump chamber and a first and second actuation chamber; a first switch valve mechanism provided with a first valve mechanism that switches supply of an actuation fluid to the first actuation chamber; a second switch valve mechanism provided with a second valve mechanism that switches supply of the actuation fluid to the second actuation chamber; a first switching mechanism that switches supply to the first switch valve mechanism of a control fluid; and a second switching mechanism that switches supply to the second switch valve mechanism of the control fluid, the first and second switching mechanisms switching supply so as to have an overlap period in which compression steps of the first and second pump chambers partially overlap.

Description

TECHNICAL FIELD

The present invention relates to a duplex reciprocating pump that transfers a transfer fluid by a pair of pump chambers formed by a pair of movable partitioning members such as bellows.

BACKGROUND ART

A duplex reciprocating pump and bellows pump have conventionally been known (see Patent Documents 1 and 2 listed below). These kinds of pumps have a pair of movable partitioning members such as bellows. Moreover, a pair of closed spaces are demarcated into a pump chamber and an actuation chamber by this pair of movable partitioning members.

By alternately introducing an actuation fluid, by means of a switch valve mechanism, into the pair of actuation chambers demarcated in this way, this kind of pump alternately compresses and extends the pump chamber, thereby transferring a transfer fluid. Note that in this kind of pump, generally, a pulsation corresponding to the number of strokes occurs in a discharge flow rate of the transfer fluid.

This pulsation occurs as a result of a pair of suction valves and a pair of discharge valves respectively switching from one pump chamber side to another pump chamber side at an end section of an extension/contraction operation stroke of the bellows, for example. Because such a pulsation causes a variety of difficulties, solutions have been attempted by the duplex reciprocating pumps disclosed in Patent Documents 1 and 2.

PRIOR ART DOCUMENTS

Patent Documents

Patent Document 1: Japanese Patent No. 5315550

Patent Document 2: Japanese Patent No. 3574641

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

However, in the pumps disclosed in the above-listed Patent Documents 1 and 2, there is further room for improvement in achieving a high pulsation reducing effect at a low cost.

The present invention has an object of providing a duplex reciprocating pump that can achieve reduction of pulsation of a transfer fluid, while achieving an overall lowering of cost by having operation of a switch valve mechanism of an actuation fluid switched by a control fluid.

Means for Solving the Problem

A duplex reciprocating pump according to the present invention includes: a case member forming a first space and a second space along an axial direction inside thereof; a movable partitioning member disposed deformably inside the first space and the second space, the movable partitioning member partitioning the first space into a first pump chamber and a first actuation chamber and partitioning the second space into a second pump chamber and a second actuation chamber; a first switch valve mechanism including a first valve mechanism that switches supply of an actuation fluid to the first actuation chamber; a second switch valve mechanism including a second valve mechanism that switches supply of an actuation fluid to the second actuation chamber; a first switching mechanism that switches supply to the first switch valve mechanism of a control fluid for operating the first valve mechanism; and a second switching mechanism that switches supply to the second switch valve mechanism of a control fluid for operating the second valve mechanism, the duplex reciprocating pump being characterized in that the first and second switching mechanisms switch supply to the first and second switch valve mechanisms of the control fluid so as to have an overlap period in which a compression step of the first pump chamber and a compression step of the second pump chamber partially overlap.

In one suitable embodiment of the present invention, the first and second switch valve mechanisms each include a valve mechanism main body in which a distribution chamber of the actuation fluid is formed inside thereof and in which the first or second valve mechanism is disposed reciprocatingly inside the distribution chamber.

In one embodiment of the present invention, the valve mechanism main body includes an actuation fluid introduction port through which the actuation fluid supplied from the actuation fluid source is introduced into the distribution chamber, and an actuation fluid inlet/outlet port through which the actuation fluid that has been introduced into the distribution chamber is discharged to the first or second actuation chamber.

In one embodiment of the present invention, the valve mechanism main body further includes a first control fluid inlet/outlet port and a second control fluid inlet/outlet port for introducing the control fluid into the valve mechanism main body.

In one embodiment of the present invention, the first and second valve mechanisms each include a plurality of large-diameter sections formed with a predetermined interval therebetween in an axial direction and a small-diameter section formed between these large-diameter sections, and the actuation fluid is discharged toward the first or second actuation chamber by the first or second valve mechanism moving whereby the actuation fluid introduction port and the actuation fluid inlet/outlet port communicate via the small-diameter section.

In one embodiment of the present invention, the first and second switching mechanisms each include: a valve body housing case; a valve body that reciprocates inside the valve body housing case and is disposed such that a tip thereof projects from the valve body housing case to be capable of being abutted on by a cooperating member that cooperates with the movable partitioning member; and an elastic member that biases the valve body toward the cooperating member.

Effect of the Invention

The present invention makes it possible to achieve reduction of pulsation of a transfer fluid, while achieving an overall lowering of cost by having operation of an actuation fluid switched by a control fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a configuration of a duplex reciprocating pump according to one embodiment of the present invention.

FIG. 2 is a timing chart showing operation of each section of the duplex reciprocating pump.

FIG. 3 is a view for explaining operation of the duplex reciprocating pump.

FIG. 4 is a view for explaining operation of the duplex reciprocating pump.

FIG. 5 is a view for explaining operation of the duplex reciprocating pump.

FIG. 6 is a view for explaining operation of the duplex reciprocating pump.

EMBODIMENTS OF THE INVENTION

Hereinafter, a duplex reciprocating pump according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a view showing a configuration of a duplex reciprocating pump 1 according to one embodiment of the present invention, and shows a cross section and a peripheral mechanism of the duplex reciprocating pump 1. As shown in FIG. 1, in the duplex reciprocating pump 1, a bottomed cylindrical first cylinder 2a and a bottomed cylindrical second cylinder 2b which are case members are disposed in a state of being fitted such that their opening sections face each other, on both sides of a pump head 1a disposed in a central section.

A pair of spaces are formed along an axial direction on insides of these cylinders 2a, 2b. A bottomed cylindrical first bellows 3a and second bellows 3b, made of a fluororesin, for example, that are capable of extension/contraction in the axial direction, are coaxially disposed, in a state of being affixed to the pump head 1a such that their respective opening sides face each other, inside these pair of spaces.

These bellows 3a, 3b have their opening ends fixed in a liquid-tight manner to the pump head 1a by being screwed into the pump head 1a, for example. Therefore, the bellows 3a, 3b configure a pair of movable partitioning members that partition internal spaces of the cylinders 2a, 2b assuming inner sides of the bellows 3a, 3b to be a first pump chamber 5a and second pump chamber 5b and outer sides of the bellows 3a, 3b to be a first actuation chamber 6a and second actuation chamber 6b.

A shaft fixing plate 4a and shaft fixing plate 4b are fixed to bottom sections of the bellows 3a, 3b by bolts 15a. One end of a coaxially extending shaft 7a and one end of a coaxially extending shaft 7b are fixed to the shaft fixing plates 4a, 4b. The other ends of the shafts 7a, 7b penetrate, in an air-tight manner, via seal members 8, centers of bottom sections of the cylinders 2a, 2b, thereby extending to outer sides of the cylinders 2a, 2b. A coupling plate 9a and coupling plate 9b are fixed to these other ends of the shafts 7a, 7b by nuts 10.

The coupling plates 9a, 9b are coupled in an axial direction by a coupling shaft 11a and coupling shaft 11b at certain positions on outsides of the cylinders 2a, 2b, for example, at positions shown upwardly and downwardly in FIG. 1. Each of the coupling shafts 11a, 11b includes a pair of a shaft section 12 and shaft section 13, and a coil spring 14 which is an extending/contracting member, fitted between these shaft sections 12, 13.

In each of the coupling shafts 11a, 11b, end sections on opposite sides to coil spring 14 sides of the shaft sections 12, 13 are fixed to the coupling plates 9a, 9b by bolts 15. As a result, the bellows 3a, 3b connected via the shafts 7a, 7b and the shaft fixing plates 4a, 4b to each of the coupling plates 9a, 9b are extendably/contractibly coupled, in an axial direction, via the coil spring 14, by each of the coupling shafts 11a, 11b.

In addition, a suction port 16 and a discharge port 17 of a transfer fluid, for example, a liquid, are provided in the pump head 1a at positions facing side surfaces of the pump. A suction valve 18a and suction valve 18b are provided in pathways reaching from this suction port 16 to the pump chambers 5a, 5b, and a discharge valve 19a and discharge valve 19b are provided in pathways reaching from the pump chambers 5a, 5b to the discharge port 17. These suction valves 18a, 18b and discharge valves 19a, 19b configure a valve unit.

A cylinder side inlet/outlet port 2c and cylinder side inlet/outlet port 2d are provided in bottom sections of the cylinders 2a, 2b. These cylinder side inlet/outlet ports 2c, 2d are for an actuation fluid, for example, actuation air supplied from an actuation fluid source such as an unillustrated air compressor, for example, to be introduced into the actuation chambers 6a, 6b or discharged from the actuation chambers 6a, 6b, via a first main pipe 90a connected to an actuation air inlet/outlet port 81a of a first switch valve mechanism 80a and a second main pipe 90b connected to an actuation air inlet/outlet port 81b of a second switch valve mechanism 80b.

The first switch valve mechanism 80a includes a switch valve 86a that switches supply of the actuation air to the actuation chamber 6a. The second switch valve mechanism 80b includes a switch valve 86b that switches supply of the actuation air to the actuation chamber 6b. These switch valves 86a, 86b of the first and second switch valve mechanisms 80a, 80b are operated by a control fluid, for example, control air whose supply is switched by a first and second switching mechanism 20a, 30a configuring a first switching mechanism and a third and fourth switching mechanism 20b, 30b configuring a second switching mechanism that will be mentioned later. The control air is obtained by diverting part of the actuation air from the actuation fluid source.

The first switch valve mechanism 80a includes a first valve mechanism main body 85a that has a distribution chamber 84a of the actuation air formed inside thereof and has the switch valve 86a housed reciprocatingly inside thereof. The second switch valve mechanism 80b includes a second valve mechanism main body 85b that has a distribution chamber 84b of the actuation air formed inside thereof and has the switch valve 86b housed reciprocatingly inside thereof.

The following are formed in the first and second valve mechanism main bodies 85a, namely, an actuation air introduction port 87a and actuation air introduction port 87b by which the actuation air supplied from the actuation fluid source is introduced into the distribution chambers 84a, 84b, via an air pipe 99a and air pipe 99b that have been branched into two branches, and the above-mentioned actuation air inlet/outlet ports 81a, 81b.

The actuation air inlet/outlet ports 81a, 81b are for the actuation air that has been introduced into the distribution chambers 84a, 84b to be discharged to the actuation chambers 6a, 6b via the first and second main pipes 90a, 90b, and for the actuation air that has been discharged from the actuation chambers 6a, 6b to be introduced into the distribution chambers 84a, 84b via the first and second main pipes 90a, 90b.

In addition, the following are formed in the first and second valve mechanism main bodies 85a, 85b, namely an actuation air discharge port 88a and actuation air discharge port 88b for the actuation air that has been introduced into the distribution chambers 84a, 84b after being discharged from the actuation chambers 6a, 6b to be discharged to outside. Note that a later-mentioned first control air inlet/outlet port 82a and second control air inlet/outlet port 83a are formed in the first valve mechanism main body 85a, and a later-mentioned third control air inlet/outlet port 82b and fourth control air inlet/outlet port 83b are formed in the second valve mechanism main body 85b.

The first and second control air inlet/outlet ports 82a, 83a are for the control air to be introduced into and discharged from inside the first valve mechanism main body 85a via first and second control air pipes 92a, 92c. The third and fourth control air inlet/outlet ports 82b, 83b are for the control air to be introduced into and discharged from inside the second valve mechanism main body 85b via third and fourth control air pipes 92b, 92d.

The switch valve 86a of the first switch valve mechanism 80a is reciprocatingly driven by the control air that has been introduced into inside the first valve mechanism main body 85a from the first and second control air inlet/outlet ports 82a, 83a. The switch valve 86b of the second switch valve mechanism 80b is reciprocatingly driven by the control air that has been introduced into inside the second valve mechanism main body 85b from the third and fourth control air inlet/outlet ports 82b, 83b.

The switch valves 86a, 86b include three large-diameter sections 89a, 89b formed with a predetermined interval between them in an axial direction, and two small-diameter sections 98a, 98b formed between these large-diameter sections 89a, 89b. The large-diameter sections 89a, 89b selectively block the actuation air introduction ports 87a, 87b, the actuation air inlet/outlet ports 81a, 81b, and the actuation air discharge ports 88a, 88b formed in the first and second valve mechanism main bodies 85a, 85b. Moreover, the small-diameter sections 98a, 98b, along with inner wall surfaces of the first and second valve mechanism main bodies 85a, 85b, form the distribution chambers 84a, 84b.

The first switching mechanism 20a configuring the first switching mechanism is, for example, detachably fixed to the cylinder 2a in part of a bottom section outer wall surface of the cylinder 2a. Moreover, the second switching mechanism 30a configuring the first switching mechanism is, for example, disposed integrally fixed to the cylinder 2a by the likes of integral molding, on a lower side of a bottom section side outer wall surface of the cylinder 2a. Such first and second switching mechanisms 20a, 30a configuring a pair of the first switching mechanisms are provided for switching supply of the control air to the first switch valve mechanism 80a.

In addition, the third switching mechanism 20b configuring the second switching mechanism is, for example, detachably fixed to the cylinder 2b in part of a bottom section outer wall surface of the cylinder 2b. Moreover, the fourth switching mechanism 30b configuring the second switching mechanism is, for example, disposed integrally fixed to the cylinder 2b by the likes of integral molding, on a lower side of a bottom section side outer wall surface of the cylinder 2b. Such third and fourth switching mechanisms 20b, 30b configuring a pair of the second switching mechanisms are provided for switching supply of the control air to the second switch valve mechanism 80b.

Note that the first switching mechanism 20a and the third switching mechanism 20b may, for example, be disposed integrally fixed to the cylinders 2a, 2b by the likes of integral molding. Moreover, the second switching mechanism 30a and the fourth switching mechanism 30b may, for example, be disposed detachably fixed to the cylinders 2a, 2b.

Note that although detailed description will be mentioned later, the first and second switching mechanisms 20a, 30a and the third and fourth switching mechanisms 20b, 30b operate so as to switch supply of the control air to the first and second switch valve mechanisms 80a, 80b so as to have an overlap period OP (see FIG. 2) in which a compression step of the pump chamber 5a and a compression step of the pump chamber 5b partially overlap.

The first switching mechanism 20a configuring part of the first switching mechanism includes a first housing case 21a fixed by detachably fixing an unillustrated flange section to the cylinder 2a by screws, for example. The third switching mechanism 20b configuring part of the second switching mechanism includes a third housing case 21b fixed by detachably fixing an unillustrated flange section to the cylinder 2b by screws, for example. An introduction port 22a and introduction port 22b of the control air and a discharge port 23a and discharge port 23b of the control air are formed on side surfaces of these first and third housing cases 21a, 21b.

A control air introduction path 91a and control air introduction path 91b are connected to the introduction ports 22a, 22b of the first and third housing cases 21a, 21b, and the first control air pipe 92a and third control air pipe 92b are connected to the discharge ports 23a, 23b of the first and third housing cases 21a, 21b. Note that an escape hole 24a and escape hole 24b that communicate insides and outsides of the first and third housing cases 21a, 21b are formed in certain positions of the first and third housing cases 21a, 21b, for example, in side surfaces in a vicinity of bottom sections of the first and third housing cases 21a, 21b.

In addition, the first switching mechanism 20a includes a first valve body 25a configuring a first valve body, that reciprocates inside the first housing case 21a. The third switching mechanism 20b includes a third valve body 25b configuring a second valve body, that reciprocates inside the third housing case 21b. A spring 26a and spring 26b that bias these first valve body 25a and third valve body 25b toward the coupling plates 9a, 9b are provided inside the first and third housing cases 21a, 21b.

The first valve body 25a is disposed such that its tip section projects toward the coupling plate 9a from the first housing case 21a and can be abutted on by an inner side surface of the coupling plate 9a. The third valve body 25b is disposed such that its tip section projects toward the coupling plate 9b from the third housing case 21b and can be abutted on by an inner side surface of the coupling plate 9b.

The first and third valve bodies 25a, 25b are configured such that when, for example, the bellows 3a, 3b undergo displacement from a position when they have reached a vicinity of a contraction limit position to a position when they have reached the contraction limit position, the tip sections of the first and third valve bodies 25a, 25b abut continuously on the coupling plates 9a, 9b. Moreover, the first and third valve bodies 25a, 25b continue to be pressed into the insides of the first and third housing cases 21a, 21b, against an elastic force of the springs 26a, 26b.

Therefore, a flow diverting path 27a formed between the first housing case 21a and the first valve body 25a and a flow diverting path 27b formed between the third housing case 21b and the third valve body 25b open when the bellows 3a, 3b have reached the vicinity of the contraction limit position and communicate the introduction ports 22a, 22b and the discharge ports 23a, 23b. When the flow diverting paths 27a, 27b have opened, the control air supplied to the first and third switching mechanisms 20a, 20b from the control air introduction paths 91a, 91b passes along the first control air pipe 92a and the third control air pipe 92b to be introduced into the first control air inlet/outlet port 82a and the third control air inlet/outlet port 82b of the first and second switch valve mechanisms 80a, 80b.

Moreover, when the tip sections of the first and third valve bodies 25a, 25b are in a separated state from when they have reached positions immediately before separating from the coupling plates 9a, 9b, the first and third valve bodies 25a, 25b protrude from the first and third housing cases 21a, 21b due to the elastic force of the springs 26a, 26b to close the flow diverting paths 27a, 27b. As a result, the first and third valve bodies 25a, 25b communicate the discharge ports 23a, 23b and the escape holes 24a, 24b by the insides of the first and third housing cases 21a, 21b.

When the flow diverting paths 27a, 27b have closed in this way, the control air that has been discharged via the first and third control air pipes 92a, 92b from the first and third control air inlet/outlet ports 82a, 82b is introduced into insides of the first and third housing cases 21a, 21b via the discharge ports 23a, 23b to be discharged to outside from the escape holes 24a, 24b.

Moreover, the second switching mechanism 30a configuring part of the first switching mechanism includes a second housing case 31a formed integrally with the cylinder 2a. The fourth switching mechanism 30b configuring part of the second switching mechanism includes a fourth housing case 31b formed integrally with the cylinder 2b. An introduction port 32a and introduction port 32b of the control air and a discharge port 33a and discharge port 33b of the control air are formed on side surfaces of these second and fourth housing cases 31a, 31b.

A control air introduction path 91c and control air introduction path 91d are connected to the introduction ports 32a, 32b of the second and fourth housing cases 31a, 31b, and the second control air pipe 92c and fourth control air pipe 92d are connected to the discharge ports 33a, 33b of the second and fourth housing cases 31a, 31b. Note that an escape hole 34a and escape hole 34b that communicate insides and outsides of the second and fourth housing cases 31a, 31b are formed in certain positions of the second and fourth housing cases 31a, 31b, for example, in bottom sections of the second and fourth housing cases 31a, 31b.

In addition, the second switching mechanism 30a includes a second valve body 35a configuring the first valve body, that reciprocates inside the second housing case 31a. The fourth switching mechanism 30b includes a fourth valve body 35b configuring the second valve body, that reciprocates inside the fourth housing case 31b. A spring 36a and spring 36b that bias these second valve body 35a and fourth valve body 35b in a direction that they face each other along their axial directions, specifically, toward an abutting plate 35c and abutting plate 35d provided in the shaft sections 12, 13 of the coupling shaft 11b, are provided inside the second and fourth housing cases 31a, 31b.

The second valve body 35a is disposed such that its tip section projects toward the abutting plate 35c from the second housing case 31a and can be abutted on by the abutting plate 35c. The fourth valve body 35b is disposed such that its tip section projects toward the abutting plate 35d from the fourth housing case 31b and can be abutted on by the abutting plate 35d.

The second and fourth valve bodies 35a, 35b are configured such that when, for example, the bellows 3a, 3b undergo displacement from a position when they have reached a vicinity of an extension limit position to a position when they have reached the extension limit position, the tip sections of the second and fourth valve bodies 35a, 35b abut continuously on the abutting plates 35c, 35d. Moreover, the second and fourth valve bodies 35a, 35b continue to be pressed into the insides of the second and fourth housing cases 31a, 31b against an elastic force of the springs 36a, 36b.

Therefore, a flow diverting path 37a formed between the second housing case 31a and the second valve body 35a and a flow diverting path 37b formed between the fourth housing case 31b and the fourth valve body 35b open when the bellows 3a, 3b have reached the vicinity of the extension limit position and communicate the introduction ports 32a, 32b and the discharge ports 33a, 33b. When the flow diverting paths 37a, 37b have opened, the control air supplied to the second and fourth switching mechanisms 30a, 30b from the control air introduction paths 91c, 91d passes along the second control air pipe 92c and the fourth control air pipe 92d to be introduced into the second control air inlet/outlet port 83a and the fourth control air inlet/outlet port 83b of the first and second switch valve mechanisms 80a, 80b.

Moreover, when the tip sections of the second and fourth valve bodies 35a, 35b are in a separated state from when they have reached positions immediately before separating from the abutting plates 35c, 35d, the second and fourth valve bodies 35a, 35b protrude from the second and fourth housing cases 31a, 31b due to the elastic force of the springs 36a, 36b to close the flow diverting paths 37a, 37b. As a result, the second and fourth valve bodies 35a, 35b communicate the discharge ports 33a, 33b and the escape holes 34a, 34b by the insides of the second and fourth housing cases 31a, 31b.

When the flow diverting paths 37a, 37b have closed in this way, the control air that has been discharged via the second and fourth control air pipes 92c, 92d from the second and fourth control air inlet/outlet ports 83a, 83b is introduced into insides of the second and fourth housing cases 31a, 31b via the discharge ports 33a, 33b to be discharged to outside from the escape holes 34a, 34b.

In the duplex reciprocating pump 1 according to the present embodiment, supply of actuation air to the actuation chamber 6a is switched by switch-operating the switch valve 86a of the first switch valve mechanism 80a by control air from the first and second switching mechanisms 20a, 30a. Moreover, supply of actuation air to the actuation chamber 6b is switched by switch-operating the switch valve 86b of the second switch valve mechanism 80b by control air from the third and fourth switching mechanisms 20b, 30b.

That is, the switch valves 86a, 86b supply the actuation air to the actuation chamber 6a and discharge the actuation air from the actuation chamber 6b by, for example, communicating the actuation air introduction port 87a and the actuation air inlet/outlet port 81a of the first valve mechanism main body 85a and communicating the actuation air inlet/outlet port 81b and the actuation air discharge port 88b of the second valve mechanism main body 85b, so as to have the above-mentioned overlap period OP.

In addition, the switch valves 86a, 86b supply the actuation air to the actuation chamber 6b and discharge the actuation air from the actuation chamber 6a by, for example, communicating the actuation air introduction port 87b and the actuation air inlet/outlet port 81b of the second valve mechanism main body 85b and communicating the actuation air inlet/outlet port 81a and the actuation air discharge port 88a of the first valve mechanism main body 85a, so as to have the above-mentioned overlap period OP. Moreover, providing the overlap period OP makes it possible to configure such that immediately before a final stage of the compression step (discharge step) where discharge pressure drops of one of the pump chambers, of the pump chambers 5a, 5b, a liquid is discharged also from the other of the pump chambers, of the pump chambers 5a, 5b, whereby pulsation of the transfer fluid on a discharge side can be suppressed.

Next, operation of the duplex reciprocating pump 1 configured in this way will be described. During operation of the pump, the first and second switching mechanisms 20a, 30a configuring the pair of first switching mechanisms and the third and fourth switching mechanisms 20b, 30b configuring the pair of second switching mechanisms drive the bellows 3a, 3b switching operation of the first and second switch valve mechanisms 80a, 80b in the following way, for example, so as to have the overlap period OP in which the compression step of one pump chamber 5a and the compression step of the other pump chamber 5b partially overlap.

FIG. 2 is a timing chart for explaining operation of each section of the duplex reciprocating pump 1 according to the present embodiment. In addition, FIGS. 3 to 6 are views for explaining operation of the duplex reciprocating pump 1. Note that in FIG. 2, illustration of a mechanical time lag in operation of each section is omitted. In the present embodiment, actuation air of the actuation fluid source is supplied at all times to the first and second switch valve mechanisms 80a, 80b via the air pipes 99a, 99b, after having been adjusted to a certain pressure by an unillustrated regulator, for example. Moreover, the actuation air is supplied at all times to the first through fourth switching mechanisms 20a, 30a, 20b, 30b via the control air introduction paths 91a-91d branched from the air pipes 99a, 99b.

Note that in the description hereafter, regarding the first and second switch valve mechanisms 80a, 80b, a time when the switch valves 86a, 86b are communicating the actuation air introduction ports 87a, 87b and the actuation air inlet/outlet ports 81a, 81b is assumed to be an “ON state”. Moreover, a time when the switch valves 86a, 86b are communicating the actuation air inlet/outlet ports 81a, 81b and the actuation air discharge ports 88a, 88b is assumed to be an “OFF state”.

Moreover, regarding the first through fourth switching mechanisms 20a, 30a, 20b, 30b, a time when the first through fourth valve bodies 25a, 35a, 25b, 35b are communicating the introduction ports 22a, 32a, 22b, 32b and the discharge ports 23a, 33a, 23b, 33b via the flow diverting paths 27a, 37a, 27b, 37b is assumed to be an “ON state”, and a time when these ports are not communicated is assumed to be an “OFF state”. Note that configuring elements identical to portions already described will be assigned with reference numerals identical to those assigned to the portions already described, hence, hereafter, duplicated descriptions thereof will be omitted.

First, the overlap period OP when, for example, the switch valves 86a, 86b of the first and second switch valve mechanisms 80a, 80b are on a right side in the first and second valve mechanism main bodies 85a, 85b, and the bellows 3a is contracting and the bellows 3b is extending, will be described. Since the switch valve 86a is on the right side in the first valve mechanism main body 85a, the actuation air introduction port 87a communicates with the actuation air inlet/outlet port 81a, and the actuation air that has been supplied from the actuation fluid source to pass along the air pipe 99a passes through the distribution chamber 84a of the first switch valve mechanism 80a to be introduced into the actuation chamber 6a via the first main pipe 90a.

As a result, the bellows 3a moves in a direction that its bottom section approaches the pump head 1a (hereafter, referred to as a “pump head approach direction”) thereby contracting, and the shaft sections 12, 12 of the coupling shafts 11a, 11b similarly move in the pump head approach direction along an axial direction. Moreover, the shaft sections 13, 13 cooperate with the shaft sections 12, 12 of the coupling shafts 11a, 11b slightly later via the coil spring 14, and the coupling plate 9b cooperating with these shaft sections 13, 13 moves in a direction of separating from the pump head 1a (hereafter, referred to as a “pump head separation direction”).

In a state before time point t1 shown in FIG. 2, the bellows 3a continues to contract until it reaches the contraction limit position, and the bellows 3b continues to extend until it reaches the extension limit position. Note that since the switch valve 86b is on the right side in the second valve mechanism main body 85b, the actuation air inlet/outlet port 81b and the actuation air discharge port 88b communicate, and when the bellows 3b is continuing extension, the actuation air in the actuation chamber 6b passes through the distribution chamber 84b of the second switch valve mechanism 80b via the second main pipe 90b and is discharged to outside from the actuation air discharge port 88b.

In this case, since the suction valve 18a and the discharge valve 19b are in a closed state and the suction valve 18b and the discharge valve 19a are in an open state as shown in FIG. 1, the liquid which is the transfer fluid is introduced into the pump chamber 5b from the suction port 16 and discharged via the discharge port 17 from the pump chamber 5a. Since, in the state before time point t1, the pump chamber 5a is during the compression step and the pump chamber 5b is during the extension (expansion) step in this way, the first switch valve mechanism 80a maintains the ON state and the second switch valve mechanism 80b maintains the OFF state as shown in FIGS. 1 and 2.

Then, immediately before time point t1 shown in FIG. 2, when the bellows 3b has reached a vicinity of the extension limit position, the abutting plate 35d provided in the shaft section 13 of the coupling shaft 11b is abutted on by the tip section of the fourth valve body 35b of the fourth switching mechanism 30b disposed in the cylinder 2b. The abutting plate 35d continues to press the fourth valve body 35b causing it to retreat inside the fourth housing case 31b.

As a result, by the introduction port 32b and the discharge port 33b communicating via the flow diverting path 37b, the fourth switching mechanism 30b on a cylinder 2b side attains the ON state as shown in FIG. 2, while the first switch valve mechanism 80a is in the ON state. This ON state of the fourth switching mechanism 30b is maintained by the flow diverting path 37b opening due to the fourth valve body 35b abutting continuously on the abutting plate 35d.

When the fourth switching mechanism 30b on the cylinder 2b side attains the ON state in this way, control air from the control air introduction path 91d passes along the fourth control air pipe 92d via the flow diverting path 37b and is introduced into the fourth control air inlet/outlet port 83b of the second switch valve mechanism 80b. Due to pressure of this control air, the switch valve 86b moves to a left side in the second valve mechanism main body 85b. Then, the actuation air introduction port 87b and the actuation air inlet/outlet port 81b communicate via the small-diameter section 98b and the distribution chamber 84b, and the second switch valve mechanism 80b attains the ON state.

Note that the control air on a third control air inlet/outlet port 82b side in the second valve mechanism main body 85b is discharged from the third control air inlet/outlet port 82b by being pushed out by the switch valve 86b that has moved to the left side. Then, the discharged control air passes along the third control air pipe 92b to be introduced into the third housing case 21b from the discharge port 23b of the third switching mechanism 20b disposed on the cylinder 2b side, and passes through the escape hole 24b to be discharged to outside.

Such a structure results in the switch valve 86b moving smoothly to the left side along the inside of the second valve mechanism main body 85b. In this way, as shown by the arrow curve L1 in FIG. 2, the second switch valve mechanism 80b attains the ON state at time point t1 immediately after the fourth switching mechanism 30b on the cylinder 2b side has attained the ON state. When the second switch valve mechanism 80b attains the ON state, the actuation air introduction port 87b communicates with the actuation air inlet/outlet port 81b, hence actuation air that has been supplied from the actuation fluid source to pass along the air pipe 99b passes through the distribution chamber 84b of the second switch valve mechanism 80b to be introduced into the actuation chamber 6b via the second main pipe 90b.

As a result, the extension step is switched to the compression step in the pump chamber 5b. However, at this time point t1, actuation air is continuing to be supplied via the first switch valve mechanism 80a also to the other actuation chamber 6a, hence the pump chamber 5a also is maintaining the compression step and the overlap period OP in which the compression steps of both of the pump chambers 5b, 5a overlap is started. In the overlap period OP here, the suction valves 18a, 18b are in the closed state and the discharge valves 19a, 19b are in the open state, hence the liquid which is the transfer fluid is discharged from both of the pump chambers 5a, 5b via the discharge port 17, and pulsation is prevented. Note that the coil spring 14 of the coupling shafts 11a, 11b is compressed in order to absorb a change in dimensions between both ends of the bellows 3a, 3b at this time.

When the second switch valve mechanism 80b attains the ON state whereby the extension step is switched to the compression step in the pump chamber 5b, the bellows 3b that has reached the extension limit position contracts so as to move in the pump head approach direction until its bottom section reaches the contraction limit position on an opposite side. Then, the shaft sections 13, 13 of the coupling shafts 11a, 11b similarly move in the pump head approach direction along an axial direction.

On the other hand, when, on a side of the pump chamber 5a that is still during the compression step at a time of time point t1, the bellows 3a has got to a final stage of its compression step to reach the vicinity of the contraction limit position in a state after time point t1 and before time point t2, the coupling plate 9a is abutted on by the tip section of the first valve body 25a of the first switching mechanism 20a disposed on a cylinder 2a side. The coupling plate 9a continues to press the first valve body 25a causing it to retreat inside the first housing case 21a.

As a result, by the introduction port 22a and the discharge port 23a communicating via the flow diverting path 27a, the first switching mechanism 20a on the cylinder 2a side attains the ON state like that shown in FIG. 2 immediately before time point t2 and at or after time point t1, while the first and second switch valve mechanisms 80a, 80b are in the ON state. This ON state of the first switching mechanism 20a is maintained by the flow diverting path 27a opening due to the first valve body 25a abutting continuously on the coupling plate 9a.

When the first switching mechanism 20a on the cylinder 2a side attains the ON state in this way, control air from the control air introduction path 91a passes along the first control air pipe 92a via the flow diverting path 27a and is introduced into the first control air inlet/outlet port 82a of the first switch valve mechanism 80a. Due to pressure of this control air, the switch valve 86a moves to a left side in the first valve mechanism main body 85a and the first switch valve mechanism 80a attains the OFF state.

Note that the control air on the second control air inlet/outlet port 83a side in the first valve mechanism main body 85a is discharged from the second control air inlet/outlet port 83a by being pushed out by the switch valve 86a that has moved to the left side. Then, the discharged control air passes along the second control air pipe 92c to be introduced into the second housing case 31a from the discharge port 33a of the second switching mechanism 30a disposed on the cylinder 2a side, and passes through the escape hole 34a to be discharged to outside.

Such a structure results in the switch valve 86a moving smoothly to the left side along the inside of the first valve mechanism main body 85a. In this way, as shown by the arrow curve L2 in FIG. 2, the first switch valve mechanism 80a attains the OFF state at time point t2 immediately after the first switching mechanism 20a on the cylinder 2a side has attained the ON state. In this way, the overlap period OP is provided between time point t1 and time point t2.

When the first switch valve mechanism 80a attains the OFF state, the actuation air inlet/outlet port 81a communicates with the actuation air discharge port 88a, hence actuation air in the actuation chamber 6a passes through the distribution chamber 84a of the first switch valve mechanism 80a via the first main pipe 90a and is discharged to outside from the actuation air discharge port 88a.

The shaft sections 12, 12 move in the pump head separation direction along an axial direction via the coil spring 14, and the coupling plate 9a cooperating with the shaft sections 12, 12 moves in the pump head separation direction, slightly later than the shaft sections 13, 13 of the coupling shafts 11a, 11b that are moving in the pump head approach direction along an axial direction on the side of the bellows 3b that is already in the compression step in a state after time point t1.

As a result, at time point t2, the compression step is switched to the extension step in the pump chamber 5a. When the pump chamber 5a switches to the extension step, the bellows 3a that has reached the compression limit position extends so as to move in the pump head separation direction until its bottom section reaches the extension limit position on an opposite side. Then, the shaft sections 12, 12 of the coupling shafts 11a, 11b similarly move in the pump head separation direction along an axial direction.

In this way, in a state immediately after time point t2, the duplex reciprocating pump 1 becomes as shown in FIG. 3, for example. That is, the switch valves 86a, 86b of the first and second switch valve mechanisms 80a, 80b are moving to the left side in the first and second valve mechanism main bodies 85a, 85b. Actuation air from the second switch valve mechanism 80b is supplied to inside the actuation chamber 6b as shown by arrow A in FIG. 3, via the second main pipe 90b.

Control air from the control air introduction path 91d is introduced into the second valve mechanism main body 85b as shown by arrow B in FIG. 3, via the fourth control air pipe 92d and the fourth control air inlet/outlet port 83b. Control air in the second valve mechanism main body 85b is introduced into the third switching mechanism 20b and discharged from the escape hole 24b as shown by arrow C in FIG. 3, via the third control air inlet/outlet port 82b and the third control air pipe 92b.

In addition, actuation air in the actuation chamber 6a is introduced into the first valve mechanism main body 85a as shown by arrow D in FIG. 3, via the first main pipe 90a and the actuation air inlet/outlet port 81a, and discharged via the distribution chamber 84a, the small-diameter section 98a, and the actuation air discharge port 88a. Control air from the control air introduction path 91a is introduced into the first valve mechanism main body 85a as shown by arrow E in FIG. 3, via the first control air pipe 92a and the first control air inlet/outlet port 82a. Control air in the first valve mechanism main body 85a is introduced into the second switching mechanism 30a and discharged from the escape hole 34a as shown by arrow F in FIG. 3, via the second control air inlet/outlet port 83a and the second control air pipe 92c.

In a state before time point t3 and at or after time point t2 shown in FIG. 2, the bellows 3a continues to extend until it reaches the extension limit position, and the bellows 3b continues to contract until it reaches the contraction limit position. In this case, since the suction valve 18b and the discharge valve 19a are in the closed state and the suction valve 18a and the discharge valve 19b are in the open state, the liquid which is the transfer fluid is introduced into the pump chamber 5a from the suction port 16 and discharged via the discharge port 17 from the pump chamber 5b. Since, in the state before time point t3 at or after time point t2, the pump chamber 5a is during the extension step and the pump chamber 5b is during the compression step in this way, the first switch valve mechanism 80a maintains the OFF state and the second switch valve mechanism 80b maintains the ON state as shown in FIGS. 2 and 3.

Note that after time point t2, when the coupling plate 9a separates from the first valve body 25a of the first switching mechanism 20a, the first switching mechanism 20a attains the OFF state like that shown in FIG. 2. When this first switching mechanism 20a attains the OFF state, the flow diverting path 27a is closed, whereby the discharge port 23a and the escape hole 24a are communicated.

In addition, after time point t2, when the abutting plate 35d separates from the fourth valve body 35b of the fourth switching mechanism 30b after the first switching mechanism 20a has attained the OFF state, the fourth switching mechanism 30b attains the OFF state like that shown in FIG. 2. When this fourth switching mechanism 30b attains the OFF state, the flow diverting path 37b is closed, whereby the discharge port 33b is communicated with the escape hole 34b.

Then, immediately before time point t3 shown in FIG. 2, when the bellows 3a has reached the vicinity of the extension limit position, the abutting plate 35c provided in the shaft section 12 of the coupling shaft 11b is abutted on by the tip section of the second valve body 35a of the second switching mechanism 30a disposed on the cylinder 2a side. The abutting plate 35c continues to press the second valve body 35a causing it to retreat inside the second housing case 31a.

As a result, by the introduction port 32a and the discharge port 33a communicating via the flow diverting path 37a, the second switching mechanism 30a on the cylinder 2a side attains the ON state like that shown in FIG. 2 immediately before time point t3 at or after time point t2, while the second switch valve mechanism 80b is in the ON state. This ON state of the second switching mechanism 30a is maintained by the flow diverting path 37a opening due to the second valve body 35a abutting continuously on the abutting plate 35c.

When the second switching mechanism 30a on the cylinder 2a side attains the ON state in this way, control air from the control air introduction path 91c passes along the second control air pipe 92c via the flow diverting path 37a and is introduced into the second control air inlet/outlet port 83a of the first switch valve mechanism 80a as shown by arrow G in FIG. 4. Due to pressure of this control air, the switch valve 86a moves to the right side in the first valve mechanism main body 85a as shown by arrow H in FIG. 4. Then, the actuation air introduction port 87a and the actuation air inlet/outlet port 81a communicate via the small-diameter section 98a and the distribution chamber 84a, and the first switch valve mechanism 80a attains the ON state.

Note that the control air on a first control air inlet/outlet port 82a side in the first valve mechanism main body 85a is discharged from the first control air inlet/outlet port 82a by being pushed out by the switch valve 86a that has moved to the right side. Then, the discharged control air passes along the first control air pipe 92a to be introduced into the first housing case 21a from the discharge port 23a of the first switching mechanism 20a on the cylinder 2a side, and passes through the escape hole 24a to be discharged to outside, as shown by arrow I in FIG. 4.

Such a structure results in the switch valve 86a moving smoothly to the right side along the inside of the first valve mechanism main body 85a. In this way, as shown by the arrow curve L3 in FIG. 2, the first switch valve mechanism 80a attains the ON state at time point t3 immediately after the second switching mechanism 30a on the cylinder 2a side has attained the ON state. When the first switch valve mechanism 80a attains the ON state, the actuation air introduction port 87a communicates with the actuation air inlet/outlet port 81a, hence actuation air that has been supplied from the actuation fluid source to pass along the air pipe 99a again passes through the distribution chamber 84a of the first switch valve mechanism 80a to be introduced into the actuation chamber 6a via the first main pipe 90a.

As a result, the extension step is switched to the compression step in the pump chamber 5a. However, at this time point t3, actuation air is continuing to be supplied via the second switch valve mechanism 80b also to the other actuation chamber 6b, hence the pump chamber 5b is also maintaining the compression step and the overlap period OP in which the compression steps of both of the pump chambers 5a, 5b overlap is again started. Even in the overlap period OP here, as mentioned above, the liquid which is the transfer fluid is discharged from both of the pump chambers 5a, 5b, and pulsation is prevented. The coil spring 14 is compressed in order to absorb a change in dimensions between both ends of the bellows 3a, 3b at this time also.

When the first switch valve mechanism 80a attains the ON state whereby the extension step is switched to the compression step in the pump chamber 5a, the bellows 3a that has reached the extension limit position contracts so as to move in the pump head approach direction until its bottom section reaches the contraction limit position on an opposite side. Then, the shaft sections 12, 12 of the coupling shafts 11a, 11b again move in the pump head approach direction along an axial direction.

On the other hand, when, on a side of the pump chamber 5b that is still in the middle of the compression step at a time of time point t3, the bellows 3b has got to a final stage of its compression step to reach the vicinity of the contraction limit position in a state after time point t3 and before time point t4, the coupling plate 9b is abutted on by the tip section of the third valve body 25b of the third switching mechanism 20b disposed in the cylinder 2b. The coupling plate 9b continues to press the third valve body 25b causing it to retreat inside the third housing case 21b.

As a result, by the introduction port 22b and the discharge port 23b communicating via the flow diverting path 27b, the third switching mechanism 20b on the cylinder 2b side attains the ON state like that shown in FIG. 2 immediately before time point t4 at or after time point t3, while the first and second switch valve mechanisms 80a, 80b are in the ON state. This ON state of the third switching mechanism 20b is maintained by the flow diverting path 27b opening due to the third valve body 25b abutting continuously on the coupling plate 9b.

When the third switching mechanism 20b on the cylinder 2b side attains the ON state in this way, control air from the control air introduction path 91b passes along the third control air pipe 92b via the flow diverting path 27b and is introduced into the third control air inlet/outlet port 82b of the second switch valve mechanism 80b as shown by arrow J in FIG. 5. Due to pressure of this control air, the switch valve 86b moves to a right side in the second valve mechanism main body 85b as shown by arrow K in FIG. 5. Then, the actuation air inlet/outlet port 81b communicates with the actuation air discharge port 88b via the small-diameter section 98b and the distribution chamber 84b, and the second switch valve mechanism 80b attains the OFF state.

Note that the control air on a fourth control air inlet/outlet port 83b side in the second valve mechanism main body 85b is discharged from the fourth control air inlet/outlet port 83b by being pushed out by the switch valve 86b that has moved to the right side. This discharged control air passes along the fourth control air pipe 92d to be introduced into the fourth housing case 31b from the discharge port 33b of the fourth switching mechanism 30b on the cylinder 2b side, and passes through the escape hole 34b to be discharged to outside, as shown by arrow M in FIG. 5.

Such a structure results in the switch valve 86b moving smoothly to the right side along the inside of the second valve mechanism main body 85b. In this way, as shown by the arrow curve L4 in FIG. 2, the second switch valve mechanism 80b attains the OFF state at time point t4 immediately after the third switching mechanism 20b on the cylinder 2b side has attained the ON state. In this way, the overlap period OP is again provided between time point t3 and time point t4.

When the second switch valve mechanism 80b attains the OFF state, the actuation air inlet/outlet port 81b and the actuation air discharge port 88b communicate, hence actuation air in the actuation chamber 6b again passes through the distribution chamber 84b of the second switch valve mechanism 80b via the second main pipe 90b and is again discharged to outside from the actuation air discharge port 88b.

The shaft sections 13, 13 move in the pump head separation direction along an axial direction via the coil spring 14, and the coupling plate 9b cooperating with the shaft sections 13, 13 moves in the pump head separation direction, slightly later than the shaft sections 12, 12 of the coupling shafts 11a, 11b that are moving in the pump head approach direction along an axial direction on the side of the bellows 3a that is already in the compression step in a state after time point t4.

As a result, at time point t4, the compression step is switched to the extension step again in the pump chamber 5b. When the compression step is switched to the extension step in the pump chamber 5b, the bellows 3b that has reached the compression limit position extends so as to move in the pump head separation direction until its bottom section reaches the extension limit position on an opposite side. Then, the shaft sections 13, 13 of the coupling shafts 11a, 11b again move in the pump head separation direction along an axial direction.

In this way, in a state immediately after time point t4, the duplex reciprocating pump 1 becomes as shown in FIG. 6, for example. That is, the switch valves 86a, 86b of the first and second switch valve mechanisms 80a, 80b has moved to the right side in the first and second valve mechanism main bodies 85a, 85b. Actuation air from the first switch valve mechanism 80a is supplied to inside the actuation chamber 6a as shown by arrow N in FIG. 6, via the first main pipe 90a.

Control air from the control air introduction path 91c is introduced into the first valve mechanism main body 85a as shown by arrow O in FIG. 6, via the second control air pipe 92c and the second control air inlet/outlet port 83a. Control air in the first valve mechanism main body 85a is introduced into the first switching mechanism 20a and discharged from the escape hole 24a as shown by arrow P in FIG. 6, via the first control air inlet/outlet port 82a and the first control air pipe 92a.

In addition, actuation air in the actuation chamber 6b is introduced into the second valve mechanism main body 85b as shown by arrow Q in FIG. 6, via the second main pipe 90b and the actuation air inlet/outlet port 81b, and discharged via the distribution chamber 84b, the small-diameter section 98b, and the actuation air discharge port 88b. Control air from the control air introduction path 91b is introduced into the second valve mechanism main body 85b as shown by arrow J in FIG. 6, via the third control air pipe 92b and the third control air inlet/outlet port 82b. Control air in the second valve mechanism main body 85b is introduced into the fourth switching mechanism 30b and discharged from the escape hole 34b as shown by arrow S in FIG. 6, via the fourth control air inlet/outlet port 83b and the fourth control air pipe 92d.

The duplex reciprocating pump 1 according to the present embodiment repeats the above kind of operation from time t4 onwards. That is, the pair of pump chambers 5a, 5b are driven by switching supply of control air from the first through fourth switching mechanisms 20a, 30a, 20b, 30b to operate the first and second switch valve mechanisms 80a, 80b so as to have the overlap period OP.

In this way, the duplex reciprocating pump 1 according to the present embodiment makes it possible to drive the pump chambers 5a, 5b so as to have the overlap period OP by combining only mechanical configurations of the first and second switch valve mechanisms 80a, 80b or first through fourth switching mechanisms 20a, 30a, 20b, 30b, without adopting any electrical configuration such as a conventional controller or electromagnetic valve whatsoever.

Therefore, a lowering of cost of the duplex reciprocating pump 1 overall can be achieved while achieving a reduction of pulsation of the transfer fluid. Note that in the above-mentioned embodiment, for example, the first through fourth switching mechanisms 20a, 30a, 20b, 30b were configured by so-called mechanical valves and the first and second switch valve mechanisms 80a, 80b were configured by so-called spool valves. However, these mechanical configurations according to the present embodiment may take a variety of other forms.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments may be carried out in a variety of other forms: furthermore, various omissions, substitutions and changes may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

DESCRIPTION OF REFERENCE NUMERALS

• • 1 duplex reciprocating pump
  • 1 a pump head
  • 2 a, 2b cylinder
  • 3 a, 3b bellows
  • 4 a, 4b shaft fixing plate
  • 5 a, 5b pump chamber
  • 6 a, 6b actuation chamber
  • 7 a, 7b shaft
  • 9 a, 9b coupling plate
  • 11 a, 11b coupling shaft
  • 12, 13 shaft section
  • 14 coil spring
  • 20 a first switching mechanism
  • 20 b third switching mechanism
  • 30 a second switching mechanism
  • 30 b fourth switching mechanism
  • 80 a first switch valve mechanism
  • 80 b second switch valve mechanism

Claims

1. A duplex reciprocating pump, comprising: a case member forming a first space and a second space along an axial direction inside thereof;a movable partitioning member disposed deformably inside the first space and the second space, the movable partitioning member partitioning the first space into a first pump chamber and a first actuation chamber and partitioning the second space into a second pump chamber and a second actuation chamber;a first switch valve mechanism comprising a first valve mechanism that switches supply of an actuation fluid to the first actuation chamber;a second switch valve mechanism comprising a second valve mechanism that switches supply of an actuation fluid to the second actuation chamber;a first switching mechanism that switches supply to the first switch valve mechanism of a control fluid for operating the first valve mechanism; anda second switching mechanism that switches supply to the second switch valve mechanism of a control fluid for operating the second valve mechanism,whereinthe first and second switching mechanisms switch supply to the first and second switch valve mechanisms of the control fluid so as to have an overlap period in which a compression step of the first pump chamber and a compression step of the second pump chamber partially overlap.

2. The duplex reciprocating pump according to claim 1, wherein the first and second switch valve mechanisms each comprise a valve mechanism main body in which a distribution chamber of the actuation fluid is formed inside thereof and in which the first or second valve mechanism is disposed reciprocatingly inside the distribution chamber.

3. The duplex reciprocating pump according to claim 2, wherein each valve mechanism main body comprises:an actuation fluid introduction port through which the actuation fluid supplied from the actuation fluid source is introduced into the distribution chamber; andan actuation fluid inlet/outlet port through which the actuation fluid that has been introduced into the distribution chamber is discharged to the first or second actuation chamber.

4. The duplex reciprocating pump according to claim 3, wherein each valve mechanism main body further comprises a first control fluid inlet/outlet port and a second control fluid inlet/outlet port for introducing the control fluid into the valve mechanism main body.

5. The duplex reciprocating pump according to claim 3, wherein the first and second valve mechanisms each comprise a plurality of large-diameter sections formed with a predetermined interval therebetween in an axial direction and a small-diameter section formed between these large-diameter sections, andthe actuation fluid is discharged toward the first or second actuation chamber by the first or second valve mechanism moving whereby the actuation fluid introduction port and the actuation fluid inlet/outlet port communicate via the small-diameter section.

6. The duplex reciprocating pump according to claim 1, wherein the first and second switching mechanisms each comprise:a valve body housing case;a valve body that reciprocates inside the valve body housing case and is disposed such that a tip thereof projects from the valve body housing case to be capable of being abutted on by a cooperating member that cooperates with the movable partitioning member; andan elastic member that biases the valve body toward the cooperating member.