Oil well pump

Abstract

The invention provides an oil well pump which comprises a main body mechanism which comprises a first pump cylinder, a second pump cylinder concentrically arranged in the first pump cylinder and a driving channel which extends into the first pump cylinder and is in sealed connection with the lower end face of the second pump cylinder. The oil inlet valve is arranged in the first pump cylinder and located below the driving channel, the driving mechanism comprises a first plunger connected with the inner circumferential surface of the first pump cylinder in a sealed mode, an oil outlet valve arranged on the first plunger, and a second plunger connected with the second plunger in a sealed mode. And the second plunger is fixed on the lower end surface of the first plunger and extends and penetrates into the second pump cylinder. By changing the overall layout of the oil well pump, the device can meet the requirement for liquid extraction of a heavy oil well and can also meet the tripping-in requirement of a casing pipe.

Description

Technical Field

[0001] The invention relates to the field of oil and gas field drilling, and in particular to an oil well pump. Background Art

[0002] At present, the oil field is mainly dominated by heavy oil, among which mechanical pumping wells usually use heavy oil pumping pumps for lifting. The displacement of the Ф83 / 44mm heavy oil pump is the largest, and its displacement coefficient is 5.6. When the stroke is 5m and the stroke frequency is 5n / min, the liquid volume is 140 cubic meters / day.

[0003] As the water content of oil fields increases year by year, the geological demand for amplifying production pressure difference and extracting liquid is gradually increasing, and the daily liquid volume demand is more than 200 cubic meters. The current 83 / 44mm thickening pump cannot meet the geological needs. In addition, since the thickening pump adopts an offset valve structure design, the overall outer diameter is large, making it difficult to insert 7-inch and 7-inch 5 casings, and thus difficult to complete downhole tasks. At present, oil wells using 7-inch and 7-inch 5 casings account for 45% of the total number of oil wells.

[0004] Therefore, there is an urgent need to develop a thickening pump that can meet the demand for extracting liquid from heavy oil wells and can be lowered into a casing of this size to improve adaptability. Summary of the invention

[0005] The purpose of the present invention is to provide a well pump, which can change the overall layout of the well pump so that the oil inlet valve, the oil outlet valve and the second pump barrel are in a coaxial arrangement, thereby reducing the maximum outer diameter of the well pump. As a result, the present invention can meet the requirements of liquid extraction from heavy oil wells and the requirements of casing lowering, thereby improving the adaptability and flexibility of the well pump.

[0006] According to the present invention, there is provided an oil pump, comprising a main body mechanism, which comprises a first pump barrel, a second pump barrel arranged concentrically in the first pump barrel, and a drive channel extending into the first pump barrel and forming a sealed connection with the lower end surface of the second pump barrel,

[0007] an oil inlet valve disposed in the first pump barrel and below the drive channel, and

[0008] The driving mechanism includes a first plunger which forms a sealing connection with the inner peripheral surface of the first pump barrel, an oil outlet valve arranged on the first plunger, and a second plunger which is fixed on the lower end surface of the first plunger and extends into the second pump barrel.

[0009] In one embodiment, the second pump cylinder includes a main body portion and an extension portion disposed between the main body portion and the drive channel, wherein an inner peripheral surface of the main body portion is sealedly connected to an outer peripheral surface of the second plunger.

[0010] Among them, the second plunger is configured to be able to move upward after applying pressure through the drive channel and forming a pressure difference, thereby opening the oil inlet valve and closing the oil outlet valve to allow oil to enter the first pump barrel; and to move downward after relieving pressure through the drive channel, thereby opening the oil outlet valve and closing the oil inlet valve to allow the oil in the first pump barrel to flow out.

[0011] In one embodiment, the first plunger includes an oil discharge portion, an oil inlet portion disposed between the oil discharge portion and the second plunger, and a plurality of spaced-apart oil inlets disposed circumferentially along the oil inlet portion, wherein the oil outlet valve is disposed in the oil discharge portion.

[0012] In one embodiment, an oil inlet joint configured as a conical structure for guiding oil is formed at a junction of the oil inlet portion and the second plunger.

[0013] In one embodiment, a plurality of the oil outlet valves are arranged along the axial direction of the oil discharge portion; and a plurality of the oil inlet valves are arranged along the axial direction of the first pump barrel.

[0014] In one embodiment, the oil inlet valve, the oil outlet valve and the second pump cylinder are coaxially arranged.

[0015] In one embodiment, the main body mechanism further comprises a middle collar configured in an annular form and disposed between the main body portions of the first pump barrel and the second pump barrel, and a plurality of through holes allowing oil to pass therethrough are arranged at intervals along the circumference of the middle collar.

[0016] In one embodiment, the upper end surface of the middle coupling is configured as a conical surface.

[0017] In one embodiment, the main body structure further comprises a middle collar disposed between the main body portions of the first pump barrel and the second pump barrel, wherein the middle collar is composed of a plurality of collar segments arranged at intervals and configured in a trapezoidal structure.

[0018] In one embodiment, a filter ring for blocking foreign matter is provided at the junction of the main body portion and the first pump cylinder.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] First, the present invention changes the overall layout of the oil well pump so that the oil inlet valve, the oil outlet valve and the second pump barrel are in a coaxial arrangement, thereby reducing the maximum outer diameter of the oil well pump (from 178mm to 138mm). In this way, the device can meet the needs of heavy oil well extraction and the requirements of 7-inch and 7-inch 5-casing, thereby improving the adaptability and flexibility of the oil well pump.

[0021] Secondly, after lifting the plungers (the first plunger and the second plunger), the present invention can perform gas injection operation with a pump, so that the oil pump has the ability to pump and inject, thereby improving the flexibility of the device; it can also inject water into the first pump barrel, so that the oil pump has the ability to backwash; it can also cause the liquid in the oil pipe to smoothly enter the first pump barrel, so that the oil pump has the ability to drain oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be described in detail below with reference to the accompanying drawings, in which:

[0023] Figure 1 is a cross-sectional view of the oil well pump according to the present invention, which shows the upstroke process of the oil well pump;

[0024] Figure 2 is a cross-sectional view of the oil well pump according to the present invention, which shows the downstroke process of the oil well pump;

[0025] Figure 3 A partial schematic diagram of an oil well pump according to the present invention is schematically shown.

[0026] In the drawings, the same reference numerals are used for the same components. The drawings are not drawn to scale. DETAILED DESCRIPTION

[0027] In order to make the technical solutions and advantages of the present invention more clearly understood, the exemplary embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than an exhaustive list of all the embodiments. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0028] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0029] In the present invention, unless otherwise clearly stipulated and limited, terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal connection of two elements.

[0030] For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] The present invention will be further described below in conjunction with the accompanying drawings.

[0032] Figure 1 is a cross-sectional view of the oil well pump according to the present invention, which shows the upstroke process of the oil well pump;

[0033] Figure 2 is a cross-sectional view of the oil well pump according to the present invention, which shows the downstroke process of the oil well pump;

[0034] Figure 3 A partial schematic diagram of an oil well pump according to the present invention is schematically shown.

[0035] like Figure 1 As shown, the oil pump 100 according to the present invention includes a main body mechanism and a driving mechanism.

[0036] In one embodiment, Figure 1 As shown, the main mechanism includes a first pump barrel 11, a second pump barrel 12 concentrically arranged in the first pump barrel 11, and a drive channel 13 extending into the first pump barrel 11 and forming a sealed connection with the lower end surface of the second pump barrel 12.

[0037] In a preferred embodiment, the drive channel 13 is radially mounted on the inner wall of the first pump barrel 11, so as to provide effective support and a stable working environment for the second pump barrel 12. In addition, the pressure application and pressure relief measures of the drive channel 13 can also promote the formation of a stable pressure difference between the inside and outside of the first pump barrel 11, thereby promoting the second pump barrel 12 to move relative to the first pump barrel 11, so as to help achieve the purpose of downhole oil pumping in the subsequent process, which is described in detail below.

[0038] In one embodiment, Figure 1 As shown, the driving mechanism includes a first plunger 31. The outer peripheral surface of the first plunger 31 forms a sealed connection with the inner peripheral surface of the first pump barrel 11, so that under the action of the driving channel 13, a stable pressure difference can be formed between the inside and the outside of the first pump barrel 11, so as to ensure that the second pump barrel 12 can smoothly perform relative movement in the first pump barrel 11.

[0039] In one embodiment, Figure 1 As shown, the drive mechanism also includes a second plunger 33 fixed at the lower end surface of the first plunger 31. Preferably, the free end of the second plunger 33 can extend into the second pump barrel 12 and form a sealed connection with the main body 121 of the second pump barrel 12 (described below).

[0040] In one embodiment, Figure 1As shown, the oil pump 100 further includes an oil inlet valve 21 disposed in the first pump barrel 11. Preferably, the oil inlet valve 21 is located below the drive channel 13, so as to receive oil from downhole and cause the oil to be temporarily stored in the first pump barrel 11.

[0041] Preferably, a plurality of oil inlet valves 21 are arranged along the axial direction of the first pump barrel 11 , thereby effectively increasing the amount of oil pumped by the oil pump 100 each time.

[0042] Preferably, a baffle is provided above each oil inlet valve 21. Thus, the maximum movement stroke of the oil inlet valve 21 can be effectively limited under the action of the baffle, thereby ensuring that the oil inlet valve 21 can be flexibly opened and closed in the first pump barrel 11.

[0043] In one embodiment, Figure 1 As shown, the driving mechanism further includes an oil outlet valve 32 disposed on the first plunger 31. Preferably, the oil outlet valve 32 can allow the oil in the first pump barrel 11 to be output to the outside, and cooperates with the oil inlet valve 21 to achieve the purpose of pumping oil downhole.

[0044] In the present invention, the pressure application and pressure relief measures of the driving channel 13 can cause the second plunger 33 to perform axial reciprocating motion within the range of the second pump barrel 12, and cooperate with the oil inlet valve 21 and the oil outlet valve 32 to achieve the purpose of downhole oil pumping.

[0045] Preferably, pressure is applied through the drive channel 13 to cause a pressure difference to be formed between the inside and the outside of the first pump barrel 11, and the second plunger 33 moves upward (i.e., upstroke) under the action of the pressure difference. The oil inlet valve 21 opens under the action of the pressure difference, the volume of the pump chamber in the first pump barrel 11 increases, and the pressure in the pump chamber decreases. At the same time, the oil outlet valve 32 is closed under the action of the sinking pressure, and the oil can enter the first pump barrel 11 through the oil inlet valve 21 and can be temporarily stored in the first pump barrel 11.

[0046] Preferably, the pressure is released through the driving channel 13 to cause the second plunger 33 to move downward (i.e., down stroke), the volume of the pump chamber in the first pump barrel 11 becomes smaller, the pressure in the pump chamber increases, the oil inlet valve 21 is closed, and the oil outlet valve 32 is opened. At this time, the oil can be discharged from the first pump barrel 11 through the oil outlet valve 32 and enter the oil pipe (not shown) to complete the downhole oil pumping process.

[0047] It is worth noting that during the downstroke, since the oil inlet valve 21 is closed, the oil pressure in the pump chamber acts on the second plunger 33 (ie, feedback force), thereby helping the drive mechanism to overcome resistance and move downward.

[0048] According to the present invention, Figure 1As shown, the second pump barrel 12 includes a main body 121 and an extension portion 122 disposed between the main body 121 and the drive channel 13, wherein the inner peripheral surface of the main body 121 forms a sealed connection with the outer peripheral surface of the second plunger 33. In this way, the interior and exterior of the first pump barrel 11 have independent spaces, thereby facilitating the formation of a pressure difference between the interior and exterior of the first pump barrel 11 to achieve the purpose of pumping oil downhole.

[0049] According to a specific embodiment of the present invention, the second plunger 33 is configured to move upward after a pressure difference is formed by applying pressure through the drive channel 13, thereby opening the oil inlet valve 21 and closing the oil outlet valve 32, and the volume of the pump chamber in the first pump barrel 11 is increased to allow oil to enter the first pump barrel 11. At this time, the oil can be temporarily stored in the first pump barrel 11.

[0050] According to a specific embodiment of the present invention, the second plunger 33 is configured to move downward after the pressure is released through the drive channel 13, thereby opening the oil outlet valve 32 and closing the oil inlet valve 21, and the volume of the pump chamber in the first pump barrel 11 is reduced to allow the oil in the first pump barrel 11 to flow out, thereby completing the downhole oil pumping process.

[0051] According to the present invention, Figure 1 As shown, the first plunger 31 includes an oil discharge portion 311 that forms a sealing connection with the inner circumferential surface of the first pump barrel 11, an oil inlet portion 312 arranged between the oil discharge portion 311 and the second plunger 33, and a plurality of spaced-apart oil inlets 313 arranged circumferentially along the oil inlet portion 312.

[0052] Preferably, the oil inlet portion 312 is constructed in a roughly cylindrical form, and multiple oil inlets 313 are radially arranged on the oil inlet portion 312, so that it can more easily receive the oil from the first pump barrel 11 and smoothly transport this part of the oil to the upper oil pipe (not shown).

[0053] In one embodiment, the oil outlet valve 32 is disposed in the oil discharge portion 311 , and a plurality of oil outlet valves 32 are disposed along the axial direction of the oil discharge portion 311 , thereby being able to effectively limit the liquid level of the oil in the first pump barrel 11 .

[0054] Preferably, a baffle is provided above each oil outlet valve 32. Thus, under the action of the baffle, the maximum movement stroke of the oil outlet valve 32 can be effectively limited, thereby ensuring that the oil outlet valve 32 can be flexibly opened and closed in the first plunger 31.

[0055] In one embodiment, Figure 1As shown, an oil inlet joint 314 having a conical structure is formed at the junction of the oil inlet portion 312 and the second plunger 33. Therefore, during the downward movement of the first plunger 31, the oil inlet joint 314 can disperse and guide the oil in the first pump barrel 11, thereby ensuring that the oil smoothly passes through the oil outlet valve 32 and enters the oil discharge portion 311.

[0056] In the present invention, when the second plunger 33 moves downward, the first plunger 31 will follow the second plunger 33 downward, thereby reducing the volume of the pump chamber in the first pump barrel 11. In this process, the oil in the first pump barrel 11 will be diverted under the action of the oil inlet connector 314, and enter the first plunger 31 through the oil inlet 313 under the guidance of the oil inlet connector 314.

[0057] In this way, the first plunger 31 is subjected to the hydraulic feedback force brought by the oil during the downward movement, thereby helping the plungers (the first plunger 31 and the second plunger 33) to move downward, thereby preventing eccentric wear and further improving the service life of the oil pump 100.

[0058] In one embodiment, the oil inlet valve 21 , the oil outlet valve 32 and the second pump cylinder 12 are coaxially arranged.

[0059] In the present invention, the oil inlet valve 21 is disposed below the drive channel 13, and the oil inlet valve 21 and the oil outlet valve 32 are coaxially arranged, so that the maximum outer diameter of the oil well pump 100 is reduced, thereby being able to smoothly meet the requirement of running a 7-inch casing.

[0060] Preferably, the maximum outer diameter of the oil well pump 100 in the present invention is reduced from 178 mm to 138 mm, thereby being able to meet the requirement for running a 7-inch casing.

[0061] In one embodiment of the present invention, Figure 1 As shown, the main body mechanism also includes a middle hoop 16 disposed between the main body portion 121 of the first pump barrel 11 and the second pump barrel 12. Preferably, the middle hoop 16 is configured in an annular form and can firmly connect the first pump barrel 11 and the second pump barrel 12 together, thereby improving the working stability of the oil pump 100.

[0062] In a preferred embodiment, Figure 1 As shown, a plurality of through holes 142 for allowing oil to pass are arranged at intervals along the circumference of the middle coupling 16. In this way, the oil in the annular space between the first pump barrel 11 and the second pump barrel 12 can smoothly pass through the through holes 142 and continue to flow upward, so as to improve the patency of the inside of the oil well pump 100.

[0063] In one embodiment, the upper end surface of the middle collar 16 is configured as a conical surface. Preferably, the conical surface is an inner conical surface structure. The through holes 142 are arranged in an inclined manner in the middle collar 16, and the inclined directions are all toward the axial direction of the second plunger 33. In this way, the oil passing through the through holes 142 can be more easily gathered near the oil inlet connector 314, so that it can be more easily dispersed through the oil inlet connector 314.

[0064] Therefore, when the second plunger 33 moves downward in the first pump barrel 11, the first plunger 31 will be subjected to the hydraulic feedback force brought by the oil, thereby helping the plungers (the first plunger 31 and the second plunger 33) to move downward, so as to prevent eccentric wear and further improve the service life of the oil pump 100.

[0065] In another embodiment, the main body mechanism further comprises a middle coupling (not shown) disposed between the main body portion 121 of the first pump barrel 11 and the second pump barrel 12. Preferably, the middle coupling is composed of a plurality of coupling segments (not shown) arranged at intervals and configured in a trapezoidal structure.

[0066] In this way, the coupling segments can ensure the firmness of the first pump barrel 11 and the second pump barrel 12, thereby improving the service life of the oil pump 100; and a channel (not shown) can be formed between adjacent coupling segments to allow the oil to flow smoothly in the first pump barrel 11.

[0067] In one embodiment, Figure 1 As shown, a filter ring 15 for blocking foreign matter is provided at the junction of the main body 121 of the second pump barrel 12 and the first pump barrel 11. Preferably, the filter ring 15 in the present invention is preferably a sand retaining ring, which can prevent foreign matter from accumulating in the middle collar 16 next to the second plunger 33 when the oil pipe is positively injected to wash the well (described below), thereby affecting the subsequent operation of the liquid inlet and oil inlet valves 21.

[0068] In one embodiment, a first coupling 111 and a second coupling 112 for connecting to an oil pipe (not shown) are respectively provided on the upper end surface and the lower end surface of the first pump cylinder 11 .

[0069] In the present invention, if Figures 1 to 3 As shown, the oil well pump 100 can also perform pumping gas injection, backwashing wells and self-draining oil.

[0070] Gas injection with pump: The present invention can directly inject gas after the plungers (the first plunger 31 and the second plunger 33) are raised, and there is no need to remove the first pump barrel 11 during the gas injection process, thereby improving the flexibility of the oil pump 100 in pumping and injection conversion.

[0071] Backwash well: The present invention can inject water into the first pump barrel 11 after the plungers (the first plunger 31 and the second plunger 33) are raised, and the water can enter the oil pipe (not shown) through the first pump barrel 11, the second pump barrel 12 and the drive channel 13 in sequence, thereby achieving the purpose of backwashing.

[0072] Self-draining oil: After the plungers (the first plunger 31 and the second plunger 33) are raised in the first pump barrel 11, the liquid in the oil pipe can smoothly enter the first pump barrel 11, thereby achieving the purpose of oil drainage.

[0073] The application effect of the invention is: it has been applied to 2 wells in Tahe Oilfield, with an operation time of 150 days, a pump efficiency of 92%, a stroke of 5m, 5 strokes, a daily liquid volume of 208 cubic meters, and a cumulative increase in oil production of 2,810 tons. Among them, 3 wells replaced submersible electric pumps to lift liquid in 7-inch casing, and the large-displacement thickening pump operated normally.

[0074] The economic benefits of the present invention are as follows: investment cost: each large-displacement thickening pump costs 25,000 yuan, which is the same as the price of a conventional large-displacement offset thickening pump; output benefit: replacing electric pumps for 3 wells, saving 1.2 million yuan / well, cumulatively increasing oil production by 2,810 tons, the crude oil price is 1,700 yuan / ton, and the output benefit is 2810*1700 / 10000=4.78 million yuan; net benefit: it is estimated that after the comprehensive application and promotion of this process, the annual net benefit will be 4.78+3.60=8.38 million yuan.

[0075] Compared with the prior art, the present invention has the following advantages:

[0076] First, the present invention changes the overall layout of the oil well pump 100 so that the oil inlet valve 21, the oil outlet valve 32 and the second pump barrel 12 are coaxially arranged, thereby reducing the maximum outer diameter of the oil well pump 100 (from 178mm to 138mm). In this way, the device can meet the requirements of liquid extraction from heavy oil wells and the requirements of running 7-inch and 7-inch 5 casings, thereby improving the adaptability and flexibility of the oil well pump 100.

[0077] Secondly, after lifting the plunger (the first plunger 31 and the second plunger 33), the present invention can perform the pump-assisted gas injection operation so that the oil pump 100 has the ability to pump and inject, thereby improving the flexibility of the device; it can also inject water into the first pump barrel 11 so that the oil pump 100 has the ability to backwash; it can also cause the liquid in the oil pipe to smoothly enter the first pump barrel 11 so that the oil pump 100 has the ability to drain oil.

[0078] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art can easily make changes or modifications within the disclosure scope of the present invention, and such changes or modifications should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A well pump, comprising: A main body mechanism, comprising a first pump barrel (11), a second pump barrel (12) arranged concentrically in the first pump barrel (11), and a drive channel (13) extending into the first pump barrel (11) and forming a sealed connection with the lower end surface of the second pump barrel (12), an oil inlet valve (21) arranged in the first pump barrel (11) and below the drive channel (13), and A driving mechanism comprises a first plunger (31) which is sealedly connected to the inner circumferential surface of the first pump barrel (11), an oil outlet valve (32) arranged on the first plunger (31), and a second plunger (33) which is fixed to the lower end surface of the first plunger (31) and extends into the second pump barrel (12).

2. The oil well pump according to claim 1, characterized in that: The second pump cylinder (12) comprises a main body portion (121) and an extension portion (122) arranged between the main body portion (121) and the drive channel (13), wherein the inner peripheral surface of the main body portion (121) forms a sealed connection with the outer peripheral surface of the second plunger (33). The second plunger (33) is configured to move upward after applying pressure through the drive channel (13) and forming a pressure difference, thereby opening the oil inlet valve (21) and closing the oil outlet valve (32) to allow oil to enter the first pump barrel (11); and to move downward after relieving pressure through the drive channel (13), thereby opening the oil outlet valve (32) and closing the oil inlet valve (21) to allow oil in the first pump barrel (11) to flow out.

3. The oil well pump according to claim 2, characterized in that: The first plunger (31) comprises an oil discharge portion (311), an oil inlet portion (312) arranged between the oil discharge portion (311) and the second plunger (33), and a plurality of oil inlet ports (313) spaced apart from each other along the circumference of the oil inlet portion (312), wherein the oil outlet valve (32) is arranged in the oil discharge portion (311).

4. The oil well pump according to claim 3, characterized in that: An oil inlet joint (314) having a conical structure and used for guiding oil is formed at the junction of the oil inlet portion (312) and the second plunger (33).

5. The oil well pump according to claim 4, characterized in that: A plurality of oil outlet valves (32) are arranged along the axial direction of the oil discharge portion (311); and a plurality of oil inlet valves (21) are arranged along the axial direction of the first pump barrel (11).

6. The oil well pump according to claim 5, characterized in that: The oil inlet valve (21), the oil outlet valve (32) and the second pump barrel (12) are coaxially arranged.

7. The oil well pump according to claim 6, characterized in that: The main body mechanism also includes a middle collar configured in an annular form and arranged between the main body parts (121) of the first pump barrel (11) and the second pump barrel (12), and a plurality of through holes (142) allowing oil to pass therethrough are arranged at intervals along the circumference of the middle collar.

8. The oil well pump according to claim 7, characterized in that: The upper end surface of the middle coupling is configured as a conical surface.

9. The oil well pump according to claim 6, characterized in that: The main body structure further comprises a middle collar arranged between the main body parts (121) of the first pump barrel (11) and the second pump barrel (12), wherein the middle collar is composed of a plurality of collar segments arranged at intervals and configured in a trapezoidal structure.

10. The oil well pump according to claim 8 or 9, characterized in that: A filter ring (15) for blocking foreign matter is provided at the junction of the main body portion (121) and the first pump cylinder (11).

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