JP6850702B2 - Reciprocating piston pump - Google Patents

Description

The present invention relates to a reciprocating piston pump.

Conventionally, a forced valve type piston pump as a reciprocating piston pump is described in Patent Document 1 below. FIG. 4 shows an outline of a main part of the reciprocating piston pump described in Patent Document 1. As shown in FIG. 4, a piston rod 51 that reciprocates in the front-rear direction is housed in a cylindrical cylinder pipe 50, and a disk having a plurality of through holes 52a that communicate the front and rear is provided on the tip side of the piston rod 51. The shaped stopper 52 is fixed, and the disk-shaped water absorbing valve 53 is fixed to the rear side of the tip side of the piston rod 51. A substantially cylindrical packing 55 provided on the outer peripheral side of the substantially cylindrical water absorption valve seat 54 is in sliding contact with the inner peripheral surface of the cylinder pipe 50, and the water absorption valve seat 54 is formed between the stopper 52 and the water absorption valve 53. It is loosely fitted to the piston rod 51.

Here, the packing 55 that is in sliding contact with the inner peripheral surface of the cylinder pipe 50 is generally made of rubber, and the water absorption valve seat 54, the water absorption valve 53, the stopper 52, and the cylinder pipe 50 are generally made of metal. Further, the packing 55 is generally welded to the water absorption valve seat 54, and a component in which the packing 55 is integrally welded to the water absorption valve seat 54 is referred to as a piston packing 56 here.

Then, during the water absorption step shown in FIG. 4 in which the piston rod 51 moves rearward, the portion on the outer peripheral side of the through hole 52a of the stopper 52 comes into contact with the front portion of the water absorption valve seat 54, and the water absorption valve seat 54 and the water absorption valve seat 54. By separating from the water absorption valve 53, the flow path in the cylinder pipe 50 is opened so that the liquid used flows toward the pump chamber in front as shown by the arrow. On the other hand, in the discharge process in which the piston rod 51 moves forward, the stopper 52 is separated from the front portion of the water absorption valve seat 54 and the water absorption valve seat 54 comes into contact with the water absorption valve 53, referring to FIG. As a result, the flow path in the cylinder pipe 50 is closed, the working liquid in the pump chamber is pressurized, the discharge valve connected to the pump chamber is opened, and the working liquid is discharged. Here, the outer diameter of the metal water absorption valve seat 54 is smaller than the inner diameter of the cylinder pipe 50 in order to avoid contact with the inner peripheral surface of the metal cylinder pipe 50 during reciprocating movement. , Sufficient clearance is provided.

Japanese Unexamined Patent Publication No. 11-50970

By the way, when a working liquid containing fine sand or the like is used in the reciprocating piston pump, wear of the packing 55 sliding in the cylinder pipe 50 is promoted, the life of the packing 55 is shortened, and the cylinder It is pointed out that the degree of replacement of the packing 56 is high.

In particular, in recent years, exports to overseas have increased. For example, water used for control in Southeast Asia and China often absorbs water directly from irrigation canals and rivers, and the water contains various impurities. It is contained, and in particular, fine sand has a great influence on the life of the packing 55. Specifically, as shown in FIG. 5, the impurity A contained in the working liquid often precipitates and accumulates in the lower part of the cylinder pipe 50, and if the cleaning after use is insufficient, the next use Occasionally, the packing 55 reciprocates in a state where the impurity A is interposed (sandwiched) between the packing 55 and the cylinder pipe 50, so that the packing 55 wears significantly faster.

The wear of the packing 55 stops when the lower outer surface of the metal water absorption valve seat 54 comes into contact with the lower inner surface of the metal cylinder pipe 50. In that state, the packing 55 is worn. A space B is formed between the upper side shown in the drawing and the upper side shown in the cylinder pipe 50 to the extent that the sealing property cannot be ensured due to the wear of the packing 55, and the pump cannot act as a pump. In addition, since the water absorption valve seat 54 and the cylinder pipe 50 are made of metal, when the packing 55 is worn, the water absorption valve seat 54 and the cylinder pipe 50 come into contact with each other and are damaged, so that the inner peripheral surface of the cylinder pipe 50 becomes scratched. As a result of being damaged, the packing 55 sliding on the inner peripheral surface of the cylinder pipe 50 wears faster.

Further, since the water absorption valve seat 54, the water absorption valve 53, and the stopper 52 are made of metal, the impact noise of the water absorption valve seat 54 and the water absorption valve 53 contacting each other and the water absorption valve seat 54 and the stopper 52 contacting each other during operation. A striking sound was generated, which was a problem as noise of the pump itself.

The present invention has been made to solve such a problem, and it is possible to suppress the wear of the packing, improve the durability of the pump, reduce the striking noise during operation, and reduce the noise. It is an object of the present invention to provide a dynamic piston pump.

The reciprocating piston pump (100) according to the present invention includes a piston rod (7) that reciprocates in the cylinder pipe (3) and a water absorption valve seat (21b) that is loosely fitted in the piston rod (7) and can move in the axial direction. A piston packing (21) provided with a packing (21a) made of an elastic body that is housed and held in an annular recess (21f) on the outer peripheral side of the water absorption valve seat (21b) and is in sliding contact with the inner peripheral surface of the cylinder pipe (3). The water absorption valve (20) fixed to the piston rod (7) and positioned so as to be in contact with the rear side of the water absorption valve seat (21b) in the axial direction, and the piston packing (21) fixed to the piston rod (7). In the reciprocating piston pump (100) provided with a stopper (22) provided with a through hole (22a) communicating with the front and rear, which is positioned so as to be in contact with the front side in the axial direction of the water absorbing valve seat (21b). Predetermined only between the outer peripheral surface of the valve seat rear portion (21e) and the inner peripheral surface of the cylinder pipe (3), which are made of resin and are located on the rear side of the packing (21a) of the water absorption valve seat (21b). The minute gap (S) has a small gap (S), and the minute gap (S) is before the sealing property between the packing (21a) and the inner peripheral surface of the cylinder pipe (3) cannot be ensured due to the wear of the packing (21a). It is characterized in that the outer peripheral surface of the valve seat rear portion (21e) and the inner peripheral surface of the cylinder pipe (3) are in contact with each other.

According to such a reciprocating piston pump (100), when the operation is performed using the working liquid containing the impurity (A), the impurities (A) deposited on the inner surface of the cylinder pipe (3) cause the cylinder pipe (3) to be operated. The packing (21a) sliding on the inner peripheral surface is slightly worn, and a minute gap (S) is formed between the water absorption valve seat (21b) located behind the packing (21a) and the cylinder pipe (3). The rear portion (21e) of the valve seat to be held comes into contact with the inner surface of the cylinder pipe (3). Since the water absorption valve seat (21b) is made of resin, the cylinder pipe (3) is hardly damaged even if it comes into contact with the cylinder pipe (3), and the packing (21a) can be suppressed from being worn. The water absorption valve seat (21b) in contact with the cylinder pipe (3) prevents the packing (21a) from being worn more (more than a minute gap) and serves as a backup for the packing (21a). In this state, the packing (21a) can be expanded in a state where the sealing property is sufficiently secured with respect to the cylinder pipe (3) depending on the working pressure, and the operation in a state where the pressure is secured for a longer period of time becomes possible. .. That is, wear of the packing (21a) can be suppressed and the durability of the pump can be improved. Further, since the water absorption valve seat (21b) is made of resin and the water absorption valve (20) and the stopper (22) are generally made of metal, the water absorption valve seat (21b) and the water absorption valve (20) are used during operation. It is possible to reduce the hitting sound of the contact with the water absorption valve seat (21b) and the hitting sound of the contact between the water absorption valve seat (21b) and the stopper (22), and it is possible to reduce the noise.

Here, the outer peripheral edge of the rear end of the packing (21a) is recessed inward in the axial direction and faces the front surface of the valve seat rear (21e), and the liquid used flowing in the cylinder pipe (3) flows. If a recess (21 g) that can be entered is provided, the packing (21a) is assisted from the rear in terms of cooling and lubrication by the working liquid that has entered the recess (21 g), and the packing (21a) is provided. The life can be extended and the durability of the pump can be improved.

Further, a convex portion (21h) projecting rearward is provided in an annular shape on the rear end surface of the water absorption valve seat (21b), and the outer diameter of the convex portion (21h) is smaller than the outer diameter of the water absorption valve (20). Then, when the water absorption valve (20) pushes the piston packing (21) in a pressurized state during the discharge process, the outer peripheral edge portion (20a) of the water absorption valve (20) directly presses the water absorption valve seat (21b). Since it comes into contact with the convex portion (21h) without hitting the surface, deformation of the water absorption valve seat (21b) can be suppressed, the life of the resin water absorption valve seat (21b) can be maintained, and the durability of the pump can be improved.

Further, if the piston packing (21) is configured to incorporate the packing (21a) into the water absorption valve seat (21b), when the packing (21a) is worn, the water absorption valve seat (21b) remains as it is and only the packing (21a) is used. It is economical to replace the one.

As described above, according to the present invention, it is possible to provide a reciprocating piston pump capable of suppressing the wear of the packing, improving the durability of the pump, reducing the striking noise during operation, and reducing the noise.

It is a vertical sectional view which shows the reciprocating piston pump which concerns on embodiment of this invention. It is operation explanatory drawing of the main part at the time of the water absorption process of the reciprocating piston shown in FIG. It is operation explanatory drawing of the main part at the time of the discharge process of the reciprocating piston shown in FIG. It shows the structure of the main part of the reciprocating piston of the prior art, and is the operation explanatory drawing at the time of a water absorption process. It is explanatory drawing for pointing out the problem of the reciprocating piston of the prior art.

Hereinafter, a preferred embodiment of the reciprocating piston pump according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a vertical sectional view showing a reciprocating piston pump according to an embodiment of the present invention, FIG. 2 is an operation explanatory view of a main part during a water absorption process of the reciprocating piston pump, and FIG. 3 is a discharge of the reciprocating piston. It is operation explanatory drawing of the main part at the time of a process. The reciprocating piston pump of the present embodiment is used for equipment such as a power sprayer, and is also called a uniflow type piston pump or a forced valve type piston pump, for example. Further, as the working liquid used for the reciprocating piston pump, various liquids are used depending on the application.

As shown in FIG. 1, the reciprocating piston pump 100 is provided with a crankcase 1, a water absorption side manifold 2, a cylinder pipe 3, and a discharge side manifold 4 connected in this order from the right side to the left side of the drawing. A crankshaft 5 and a connecting rod 6 are arranged inside the crankcase 1, and a piston rod 7 is arranged inside the crankcase 1 to the cylinder pipe 3. The piston rod 7 is connected to the crankshaft 5 via a connecting rod 6. Then, the crankshaft 5 is rotationally driven by power input from an external engine, motor, or the like, and the piston rod 7 reciprocates in the cylinder pipe 3 via the connecting rod 6.

In FIG. 1, the portion above the center line C shows the state of being located at the top dead center in the discharge process in which the piston rod 7 advances due to the rotation of the crankshaft 5, and the portion below the center line C is the rotation of the crankshaft 5. Indicates a state in which the piston rod 7 is located at the bottom dead center in the water absorption process in which the piston rod 7 is retracted.

The crankcase 1 is filled with lubricating oil, and the position where the piston rod 7 passes is slidably contacted with the piston rod 7 to prevent the lubricating oil in the crankcase 1 from leaking to the water absorption side manifold 2 side. An oil seal 8 for the purpose is arranged. Further, a seal packing 9 is provided in the water absorption side manifold 2 for sliding contact with the piston rod 7 and preventing leakage of the working liquid on the water absorption side manifold 2 side to the oil seal 8 side. Further, the water absorption side manifold 2 is provided with a water absorption port 15 for sucking the working liquid into the inside.

In the cylinder pipe 3, it reciprocates in the axial direction together with the piston rod 7, closes and opens the flow path to the pump chamber 10 formed on the tip side of the cylinder pipe 3, and at the same time pressurizes / presses the pump chamber 10 by the pumping action. A water absorption valve mechanism 11 for reducing the pressure is provided (details will be described later).

Further, in the discharge side manifold 4, a flow path is opened and closed at the tip of the pump chamber 10 according to the pressurization / depressurization of the pump chamber 10 by the pumping action of the water absorption valve mechanism 11, and the liquid used in the pump chamber 10 is opened by opening. A discharge valve 12 for discharging to the outside is provided. The discharge side manifold 4 is provided with a pressure regulating valve 13 for adjusting the pressure of the working liquid discharged by the pumping action, and an air chamber 14 for buffering the pulsation of the working liquid discharged by the pumping action.

As shown in FIG. 2, the water absorption valve mechanism 11 mainly includes a water absorption valve 20, a piston packing 21 having a packing 21a sliding in contact with the inner peripheral surface of the cylinder pipe 3 and a water absorption valve seat 21b, and a stopper 22. , A collar 23, a washer 24, and a nut 25.

The water absorption valve 20 is a disk having a through hole for passing the piston rod 7 in the center, and the collar 23 is a cylinder having a through hole for passing the piston rod 7 in the center, and the water absorption valve seat 21b. It is long enough in the thickness direction.

The stopper 22 is a disk having a through hole for passing the piston rod 7 in the center, and the stopper 22 has a plurality of through holes 22a penetrating in the front-rear direction and communicating with each other in the front-rear direction. Is provided.

Then, from the base end side (right side in the drawing) of the piston rod 7, the water absorption valve 20, the collar 23, the stopper 22, and the washer 24 are fitted in this order, and the nut 25 is attached to the male screw 7a formed at the tip of the piston rod 7. The water absorption valve 20 is abutted against the large-diameter step portion 7b formed on the piston rod 7, and these members 20, 22, 23, 24 are combined with the step portion 7b and the nut. It is sandwiched and fixed between 25.

The piston packing 21 is formed in a substantially cylindrical shape, includes a packing 21a and a water absorption valve seat 21b for holding the packing 21a, and is externally inserted into a collar 23 between the water absorption valve 20 and the stopper 22.

The packing 21a is a ring-shaped elastic body having a substantially rectangular cross section, and is made of fluororubber, which is a chemical-resistant rubber-based material.

The water absorption valve seat 21b is made of resin, and here, for example, polyethylene. The water absorption valve seat 21b is provided at the tip of a substantially cylindrical main body portion 21c and the main body portion 21c, and has a brim-shaped front convex portion 21d that projects radially outward in a substantially annular shape and a rear end of the main body portion 21c. The concave groove 21f is provided with a collar-shaped rear convex portion 21e that protrudes outward in a radial direction in a substantially annular shape, and the concave groove 21f is formed by the front convex portion 21d, the main body portion 21c, and the rear convex portion 21e. Made. The outer diameter of the front convex portion 21d of the water absorption valve seat 21b is made smaller than the outer diameter of the rear convex portion 21e, and is substantially the same as the outer diameter of the stopper 22.

The packing 21a is pushed into the recessed groove 21f of the water absorption valve seat 21b to be accommodated and held. The outer peripheral surface of the packing 21a is in sliding contact with the inner peripheral surface of the cylinder pipe 3, and the front portion of the packing 21a is sandwiched between the inner peripheral surface of the cylinder pipe 3 and the front convex portion 21d of the water absorption valve seat 21b. It is arranged like this.

The rear portion of the valve seat located on the rear side of the packing 21a of the water absorption valve seat 21b is the rear convex portion 21e, and the space between the outer peripheral surface of the rear convex portion 21e and the inner peripheral surface of the cylinder pipe 3 is predetermined. A small gap S is provided. Here, the minute gap S is set to about 0.05 to 0.1 mm, as particularly preferable.

Further, in the outer peripheral edge portion of the rear end portion of the packing 21a, a recess 21g facing the front surface on the outer peripheral side of the rear convex portion 21e of the water absorption valve seat 21b is provided in an annular shape while being recessed in the front side and inward in the axial direction. .. The working liquid flowing in the cylinder pipe 3 can enter the recess 21g through the minute gap S.

Further, on the rear end surface of the rear convex portion 21e of the water absorption valve seat 21b, a convex portion 21h projecting rearward in an annular shape is provided at a position separated from the outer peripheral surface inward (axial side). The outer diameter of the convex portion 21h is smaller than the outer diameter of the water absorption valve 20.

Then, an annular gap C1 is formed between the inner peripheral surface of the water absorption valve seat 21b of the piston packing 21 and the outer peripheral surface of the collar 23, whereby the piston packing 21 is between the water absorption valve 20 and the stopper 22. It is loosely fitted to the outside of the collar 23 of the above, and is movable in the axial direction.

In the water absorption valve mechanism 11 having such a configuration, as shown in FIGS. 2 and 3, the packing 21a is in sliding contact with the inner peripheral surface of the cylinder pipe 3, and the outer peripheral surface of the stopper 22 is the cylinder pipe 3. It is located near the inner peripheral surface, and a minute gap S is provided between the outer peripheral surface of the rear convex portion 21e of the water absorption valve seat 21b and the inner peripheral surface of the cylinder pipe 3. Further, the rear end surface of the outer peripheral portion of the stopper 22 is in a positional relationship facing the front surface of the front convex portion 21d of the water absorption valve seat 21b. Then, as shown in FIG. 2, when the rear end surface of the outer peripheral portion of the stopper 22 comes into contact with the front surface of the front convex portion 21d of the water absorption valve seat 21b, a gap C2 is provided between the water absorption valve 20 and the convex portion 21h. Is formed in an annular shape.

In such a reciprocating piston pump 100, when the crankshaft 5 is rotationally driven, the piston rod 7 reciprocates in the cylinder pipe 3 and moves from the top dead center to the bottom dead center (see FIG. 2). The discharge process (see FIG. 3) of moving from the dead center to the top dead center is repeated.

Here, when the discharge process is switched to the water absorption process, the piston rod 7 moves rearward in the axial direction as shown in the portion below the center line C in FIG. 1, and the water absorption valve 20 is convex as shown in FIG. The seat is separated from the portion 21h (separated in the axial direction), and the stopper 22 and the front convex portion 21d of the water absorption valve seat 21b come into contact with each other.

Further, when the water absorption valve 20 is separated from the convex portion 21h, a gap C2 is generated between the water absorption valve 20 and the convex portion 21h to open the flow path, whereby the gap C2 and the gap C1 communicate with each other. Further, the working liquid that the through hole 22a communicates with and flows in from the water suction port 15 (see FIG. 1) of the water absorption side manifold 2 flows into the gap C1 through the gap C2.

Then, the convex portion 21h of the piston packing 21 maintains a gap C2 between the convex portion 21h and the water absorbing valve 20 that moves rearward in the axial direction together with the piston rod 7, and the packing 21a is in sliding contact with the inner peripheral surface of the cylinder pipe 3. In this state, the water absorption valve seat 21b is taken to the stopper 22 that moves rearward in the axial direction together with the piston rod 7, and the piston packing 21 moves rearward in the axial direction.

In the pump chamber 10, the volume increases due to the movement of the piston rod 7 rearward in the axial direction, and the pressure is reduced to a negative pressure. The working liquid flowing into the gap C1 is sucked into the pump chamber 10 through the through hole 22a. Inflow.

Further, when the water absorption process is shifted to the discharge process, the piston rod 7 moves forward in the axial direction as shown in the upper portion of the center line C in FIG. 1, and the stopper 22 and the water absorption valve seat 21b are shown in FIG. The front convex portion 21d of the water absorbing valve 20 is separated from the convex portion 21d, the water absorption valve 20 is seated on the convex portion 21h, the gap C2 is eliminated, and the flow path is closed.

Then, the piston packing 21 maintains contact with the water absorption valve 20 whose convex portion 21h moves forward in the axial direction together with the piston rod 7, and the packing 21a is in sliding contact with the inner peripheral surface of the cylinder pipe 3. The water absorption valve seat 21b is taken to the water absorption valve 20 that moves forward in the axial direction together with the piston rod 7, and the piston packing 21 moves forward in the axial direction.

In the pump chamber 10, as shown in FIG. 1, the piston rod 7 is pressurized by moving forward in the axial direction, the discharge valve 12 is opened, and the liquid used in the pump chamber 10 is supplied through the discharge valve 12. It is discharged to the outside from the discharge port 16 of the discharge side manifold 4. Then, the water absorption step and the discharge step described above are repeated.

Here, as shown in FIG. 3, if the liquid used contains impurities A, the impurities A are deposited on the lower part of the inner surface of the cylinder pipe 3 during operation. Due to this impurity A, the packing 21a sliding on the inner peripheral surface of the cylinder pipe 3 is slightly worn. Then, in the present embodiment, of the water absorption valve seat 21b, the rear convex portion 21e, which is the rear portion of the valve seat located on the rear side of the packing 21a and has a minute gap S with the cylinder pipe 3, is the cylinder pipe 3. Will come into contact with the inner surface of the. Here, since the water absorption valve seat 21b is made of resin, even if it comes into contact with the cylinder pipe 3, the cylinder pipe 3 is hardly damaged and the packing 21a can be suppressed from being worn, and the packing 21a is in contact with the cylinder pipe 3. The water absorption valve seat 21b prevents the packing 21a from being worn more (more than a minute gap) and serves as a backup for the packing 21a. In this state, the packing 21a can be expanded in a state where the sealing property with respect to the cylinder pipe 3 is sufficiently secured by the working pressure, and the packing 21a can be operated in a state where the pressure is sufficiently secured for a longer period of time. That is, wear of the packing 21a can be suppressed and the durability of the pump can be improved. Further, since the water absorption valve seat 21b is made of resin and the water absorption valve 20 and the stopper 22 are made of metal, the impact noise of the water absorption valve seat 21b and the water absorption valve 20 contacting each other during operation and the water absorption valve seat 21b and the stopper The striking sound that comes into contact with the 22 can be reduced, and the noise can be reduced.

Further, according to the present embodiment, the outer peripheral edge portion of the rear end portion of the packing 21a is recessed in the front side and inward in the axial direction, and faces the front surface of the rear side convex portion 21e which is the rear portion of the valve seat, and the cylinder pipe 3 Since the recess 21g is provided so that the working liquid flowing inside can enter, the packing 21a is assisted from the rear in terms of cooling and lubrication by the working liquid that has entered the recess 21g, and the packing 21a has a long life. The durability of the pump can be improved.

Further, the rear end surface of the water absorption valve seat 21b is provided with a convex portion 21h projecting rearward in an annular shape, and the outer diameter of the convex portion 21h is smaller than the outer diameter of the water absorption valve 20, and is therefore shown in FIG. During the discharge process, when the water absorption valve 20 pushes the piston packing 21 in a pressurized state, the outer peripheral edge portion 20a of the water absorption valve 20 does not directly hit the water absorption valve seat 21b but comes into contact with the convex portion 21h. .. As a result, the deformation of the water absorption valve seat 21b can be suppressed, the life of the resin water absorption valve seat 21b can be maintained, and the durability of the pump can be improved. In the prior art shown in FIG. 5, when the water absorption valve 53 pushes the piston packing 56 in a pressurized state during the discharge process, the outer peripheral edge portion 53a of the water absorption valve 53 directly contacts the water absorption valve seat 54. Therefore, if the water absorption valve seat 54 is made of resin, the water absorption valve seat is easily deformed and it is difficult to extend the service life.

Further, according to the present embodiment, since the piston packing 21 has a configuration in which the packing 21a is incorporated in the water absorption valve seat 21b, when the packing 21a is worn, it is sufficient to replace only the packing 21a while leaving the water absorption valve seat 21b as it is. It is economical.

When using fresh water, if the water absorption valve seat, water absorption valve, and stopper are made of metal and made of the same type of material, the same type of material may come into contact with each other during operation, causing a phenomenon of sticking to each other. In the present embodiment, since the water absorption valve seat 21b is made of resin, different materials come into contact with each other, and the sticking phenomenon can be suppressed.

Although the present invention has been specifically described above based on the embodiment, the present invention is not limited to the above embodiment. For example, in the above embodiment, the stopper 22 and the water absorption valve seat are used during the water absorption step. The type in which the front convex portion 21d, which is the front portion of the 21b, abuts is used. Can also be applied.

Further, the packing is made of rubber as being particularly preferable, but an elastic body may be used.

Further, in the above embodiment, an example in which the reciprocating piston pump is applied to the power sprayer is described as particularly preferable, but the fine mist cooling or mist is worried about the generation of cavitation by fresh water and the noise caused by the striking noise. The same can be applied to a reciprocating piston pump for.

3 ... Cylinder pipe, 7 ... Piston rod, 20 ... Water absorption valve, 21 ... Piston packing, 21a ... Packing, 21b ... Water absorption valve seat, 21e ... Rear convex part (rear part of valve seat), 21f ... Concave groove, 21g ... Recess , 21h ... Convex part, 22 ... Stopper, 22a ... Through hole, 100 ... Reciprocating piston pump, S ... Micro gap.

Claims (4)

A piston rod (7) that reciprocates in the cylinder pipe (3), a water absorption valve seat (21b) that is loosely fitted to the piston rod (7) and can move in the axial direction, and an outer peripheral side of the water absorption valve seat (21b). The piston packing (21) and the piston rod (7) have a packing (21a) made of an elastic body that is housed and held in the annular recess (21f) of the cylinder pipe (3) and is in sliding contact with the inner peripheral surface of the cylinder pipe (3). A water absorption valve (20) that is fixed and is located so as to be in contact with the axial rear side of the water absorption valve seat (21b), and is fixed to the piston rod (7) and is attached to the axial front side of the piston packing (21). In a reciprocating piston pump (100) provided with a stopper (22) which is positioned so as to be abuttable and has a through hole (22a) for communicating front and rear.
The water absorption valve seat (21b) is made of resin.
A predetermined minute amount is provided only between the outer peripheral surface of the valve seat rear portion (21e) located behind the packing (21a) of the water absorption valve seat (21b) and the inner peripheral surface of the cylinder pipe (3). Has a gap (S) and has a gap (S)
The minute gap (S) is formed in the rear portion (21e) of the valve seat before the sealing property between the packing (21a) and the inner peripheral surface of the cylinder pipe (3) cannot be ensured due to wear of the packing (21a). The reciprocating piston pump (100), characterized in that the outer peripheral surface of the cylinder pipe (3) and the inner peripheral surface of the cylinder pipe (3) are in contact with each other. The outer peripheral edge of the rear end of the packing (21a) is recessed in the front side and inward in the axial direction, and the working liquid that faces the front surface of the valve seat rear portion (21e) and flows in the cylinder pipe (3). The reciprocating piston pump (100) according to claim 1, wherein an enterable recess (21 g) is provided. A convex portion (21h) projecting rearward is provided in an annular shape on the rear end surface of the water absorption valve seat (21b).
The reciprocating piston pump (100) according to claim 1 or 2, wherein the outer diameter of the convex portion (21h) is smaller than the outer diameter of the water absorption valve (20). The reciprocating piston pump (100) according to any one of claims 1 to 3, wherein the piston packing (21) has a configuration in which the packing (21a) is incorporated in the water absorption valve seat (21b). ).

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