CN112923108A - Pilot pressurizing two-stage overflow valve - Google Patents
Pilot pressurizing two-stage overflow valve Download PDFInfo
- Publication number
- CN112923108A CN112923108A CN202110258929.4A CN202110258929A CN112923108A CN 112923108 A CN112923108 A CN 112923108A CN 202110258929 A CN202110258929 A CN 202110258929A CN 112923108 A CN112923108 A CN 112923108A
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- Prior art keywords
- pilot
- valve
- valve core
- outlet
- oil inlet
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 230000001105 regulatory effect Effects 0.000 claims abstract description 35
- 238000013016 damping Methods 0.000 claims abstract description 24
- 239000012530 fluid Substances 0.000 description 5
- 230000007306 turnover Effects 0.000 description 5
- 239000007788 liquid Substances 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K17/00—Safety valves; Equalising valves, e.g. pressure relief valves
- F16K17/02—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side
- F16K17/04—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side spring-loaded
- F16K17/044—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side spring-loaded with more than one spring
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/08—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
- F15B13/023—Excess flow valves, e.g. for locking cylinders in case of hose burst
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K17/00—Safety valves; Equalising valves, e.g. pressure relief valves
- F16K17/02—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side
- F16K17/04—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side spring-loaded
- F16K17/048—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side spring-loaded combined with other safety valves, or with pressure control devices
Abstract
The invention discloses a pilot pressurizing secondary overflow valve which comprises a valve body, wherein an A oil inlet and outlet is formed in one end of the valve body, a B oil inlet and outlet is formed in the side wall of the valve body, a main valve core is arranged in the valve body and positioned between the A oil inlet and outlet and the B oil inlet and outlet, a damping valve core connected with the A oil inlet and outlet is arranged in the main valve core, a pilot valve seat connected with the other end of the valve body is arranged on one side of the damping valve core, a damping spring is arranged between the pilot valve seat and the damping valve core, a main valve core spring is arranged between the pilot valve seat and the main valve core, a pilot valve core is arranged at one end of the pilot valve seat, a secondary pressure regulating screw sleeve is arranged at the other end of the pilot valve seat, a pilot spring seat is arranged at one end. The invention has the advantages of high boarding rotation starting speed and small boarding rotation stopping impact of the engineering machinery, and also has the advantages of low cost, low failure rate and wide application range.
Description
Technical Field
The invention belongs to the field of overflow valves of engineering machinery, and particularly relates to a pilot pressurizing two-stage overflow valve for the engineering machinery.
Background
In many construction machines (e.g., excavators), an upper vehicle turning function is provided. When in rotation, the rotation motor driven by the hydraulic system provides driving power. When the rotation is started, the rotation motor is required to provide large torque, and when the rotation is stopped, the rotation motor is required to provide small torque. This requires the swing motor to be able to provide the two torque functions. The common overflow valve is opened when the pressure of the motor reaches a set value, the torque provided by the motor during the rotation starting and the torque provided by the motor during the stopping are the same, namely if the starting large torque is met, the impact is large during the stopping, otherwise, if the impact is small during the stopping, the torque of the motor during the starting is small, and the starting speed is slow. Therefore, the existing engineering machinery has the defects of slow starting speed of getting-on rotation or large stopping impact.
Disclosure of Invention
The invention aims to provide a pilot pressurizing two-stage overflow valve. The invention has the advantages of high boarding rotation starting speed and small boarding rotation stopping impact of the engineering machinery, and also has the advantages of low cost, low failure rate and wide application range.
The technical scheme of the invention is as follows: the utility model provides a guide's pressure boost second grade overflow valve, one end including the valve body is equipped with A business turn over hydraulic fluid port, be equipped with B business turn over hydraulic fluid port on the lateral wall of valve body, be equipped with the main valve core that is located between A business turn over hydraulic fluid port and the B business turn over hydraulic fluid port in the valve body, be equipped with the damping valve core of being connected with A business turn over hydraulic fluid port in the main valve core, one side of damping valve core is equipped with the pilot valve seat of being connected with the valve body other end, be equipped with damping spring between pilot valve seat and the damping valve core, be equipped with main valve core spring between pilot valve seat and the main valve core, the one end of pilot valve seat is equipped with the pilot valve core, the other end of pilot valve seat is equipped with second grade pressure regulating swivel nut.
In the pilot pressurizing secondary overflow valve, two nuts are arranged on the outer side of the secondary pressure regulating threaded sleeve.
In the pilot booster two-stage overflow valve, a first flow channel is arranged in the damping valve core, and a first cavity connected with the first flow channel is formed between the pilot valve seat and the main valve core.
In the pilot booster two-stage overflow valve, the pilot valve seat is provided with a second flow passage connected with the first cavity, one end of the second flow passage is provided with a pilot valve core, and the other end of the second flow passage is connected with the oil inlet and outlet of the oil tank B.
In the pilot pressurizing secondary overflow valve, the primary pressure regulating threaded sleeve extends into the secondary pressure regulating threaded sleeve and is abutted against the pilot spring seat, the limiting ring is arranged on the outer side of the primary pressure regulating threaded sleeve, and the inner diameter of the limiting ring is larger than the outer diameter of the secondary pressure regulating threaded sleeve.
In the pilot pressurizing secondary overflow valve, one end of the pilot spring seat supports the pilot spring, the other end of the pilot spring seat is matched with an inner hole of the secondary pressure regulating threaded sleeve, and a D cavity communicated with the primary pressure regulating threaded sleeve is formed in the threaded sleeve when the pilot spring seat extrudes the pilot spring.
Compared with the prior art, the overflow valve of the engineering machinery is improved, and the overflow valve has a two-stage pressure opening state, wherein the first-stage opening pressure is lower, the second-stage opening pressure is higher, and the two-stage pressure opening state is controlled by the pilot external control of a hydraulic system. When the boarding rotation of the engineering machinery is started, the invention is in a second-stage pressure opening state, so that the rotation motor outputs the maximum torque, and the boarding rotation starting speed is ensured to be high; when the boarding rotation of the engineering machinery is stopped, the invention is in a first-stage pressure starting state, so that the rotation motor outputs smaller torque, the boarding rotation is stopped slowly, the impact is reduced, the service life of the engineering machinery is prolonged, and the comfort of operators can be improved. According to the invention, through the optimization of the structure, the part structure is simplified, the cost is reduced, and the failure rate is also reduced. In addition, the two-stage pressure parameter of the invention is adjustable, and the invention can be used on engineering machinery with different specifications, thereby having the advantage of wide application range. Therefore, the invention has the advantages of high boarding rotation starting speed and small boarding rotation stopping impact of the engineering machinery, and also has the advantages of low cost, low failure rate and wide application range.
Drawings
Fig. 1 is a schematic structural view of the present invention.
Fig. 2 is a hydraulic schematic of the present invention.
Fig. 3 is a schematic diagram of a D-chamber.
The labels in the figures are: 1-a valve body, 2-a main valve core, 3-a pilot valve seat, 4-a pilot spring seat, 5-a secondary pressure regulating threaded sleeve, 7-a nut, 8-a primary pressure regulating threaded sleeve, 9-a pilot spring, 10-a pilot valve core, 11-a main valve core spring, 12-a damping spring, 13-a damping valve core, 14-a first flow passage, 15-a first cavity, 16-a second flow passage and 17-a limiting ring.
Detailed Description
The invention is further illustrated by the following figures and examples, which are not to be construed as limiting the invention.
Examples are given. A pilot pressurizing secondary overflow valve is shown in figure 1, and comprises a valve body 1, wherein one end of the valve body 1 is provided with an oil inlet and outlet A, the side wall of the valve body 1 is provided with an oil inlet and outlet B, a main valve core 2 positioned between the oil inlet and outlet A and the oil inlet and outlet B is arranged in the valve body 1, a damping valve core 13 penetrating through one end of the main valve core 2 and connected with the oil inlet and outlet A is arranged in the main valve core 2, one side of the damping valve core 13 is provided with a pilot valve seat 3 in threaded connection with the other end of the valve body 1, a damping spring 12 is arranged between the pilot valve seat 3 and the damping valve core 13, a main valve core spring 11 is arranged between the pilot valve seat 3 and the main valve core 2, one end of the pilot valve seat 3 is provided with a pilot valve core 10, the other end of the pilot valve seat 3 is provided with a secondary pressure regulating screw sleeve 5, the other end of the secondary pressure regulating screw sleeve 5 is provided with a primary pressure regulating screw sleeve 8 which is in screw connection with the secondary pressure regulating screw sleeve.
The outside of second grade pressure regulating swivel nut 5 is equipped with two nuts 7, the nut is hexagonal thin nut, and two nuts 7 are used for the locking of second grade pressure regulating swivel nut 5 and one-level pressure regulating swivel nut 8 respectively
A first flow passage 14 is arranged in the damper valve element 13, and a first cavity 15 connected with the first flow passage 14 is formed between the pilot valve seat 3 and the main valve element 2.
And a second flow passage 16 connected with the first cavity 15 is arranged on the pilot valve seat 3, a pilot valve core 10 is arranged at one end of the second flow passage 16, and the other end of the second flow passage 16 is connected with an oil inlet and an oil outlet of the B.
The one-level pressure regulating swivel nut 8 stretches into in the second grade pressure regulating swivel nut 5 and with guide's spring holder 4 butt to and the outside of one-level pressure regulating swivel nut 8 is equipped with spacing ring 17, and the internal diameter of spacing ring 17 is greater than the external diameter of second grade pressure regulating swivel nut 5.
And one end of the pilot spring seat 4 supports a pilot spring 9, the other end of the pilot spring seat is matched with an inner hole of the second-stage pressure regulating threaded sleeve 5, and a D cavity communicated with the first-stage pressure regulating threaded sleeve 8 is formed in the threaded sleeve 5 when the pilot spring seat 4 extrudes the pilot spring 9. (shown as D in FIG. 1).
The working principle is as follows: as shown in fig. 2, two secondary relief valves (inside the dashed line) are connected to the rotary motor. One oil inlet and outlet (A in figure 2) of the rotary motor is connected with an oil inlet and outlet A of the upper secondary overflow valve, and the other oil inlet and outlet (B in figure 2) of the rotary motor is connected with an oil inlet and outlet A of the lower secondary overflow valve; the oil inlet and the oil outlet of the B of the two secondary overflow valves are communicated. An outer control port (shown as X in figure 2) of pilot oil of the engineering machinery is simultaneously connected with a primary pressure regulating screw sleeve 8 of the two secondary overflow valves. In fig. 2, T denotes an oil return port of the rotary motor, and S denotes an oil supply port of the rotary motor.
Assuming that an oil inlet and an oil outlet at the end A of the motor are oil inlets, and an oil inlet and an oil outlet at the end B of the motor are oil outlets, when the oil pressure at the end A reaches the set value of a secondary overflow valve, the secondary overflow valve (the upper side of a figure 2) overflows, oil enters the oil inlet and the oil outlet of the B from the oil inlet and the oil outlet of the A, and then enters the oil inlet and the oil outlet of the B of the other secondary overflow valve (the lower side of the figure 2), and oil is replenished at the.
When the motor is started in a rotary mode, the end A of the motor is assumed to be an oil inlet, the end B of the motor is assumed to be an oil outlet, the port X is connected with external control oil, a secondary overflow valve (the upper side of a figure 2) is in a secondary pressure overflow state, and the motor provides large torque; when the rotation stops, the X port does not lead oil, the secondary overflow valve (the lower side of the figure 2) is in a first-stage pressure overflow state, and the motor provides low torque.
Overflow valve principle: the main valve element 2 is pressed on the valve body 1 under the combined action of the pretightening force of the main valve element spring 11 and the damping spring 12 and the hydraulic pressure generated by the difference of the two end areas under the action of pressure oil, so that the oil liquid in the oil inlet and the oil outlet of the oil outlet A cannot flow to the oil inlet and the oil outlet of the oil outlet B. Along with the increase of the load, the pressure at the oil inlet and outlet end of the valve A continuously rises, the pressure of the first cavity 15 also continuously rises, when the force acting on the sealing area of the pilot valve core 10 and the pilot valve seat 3 in the first cavity 15 is larger than the sum of the pretightening force of the pilot spring 9 and the force acting on the sealing area of the pilot valve core 10 and the pilot valve seat 3 by the hydraulic pressure of the oil inlet and outlet of the valve B, the pilot valve core 10 moves downwards to separate from the pilot valve seat 3, the oil in the first cavity 15 flows to the oil inlet and outlet of the valve B through the second flow passage 16, at the moment, the hydraulic pressure at the oil inlet and outlet end of the valve A is larger than the hydraulic pressure in the first cavity 15 through the throttling action of the first flow passage 14 in the damping valve core 13, when the pressure difference is larger than the pretightening force of the main valve core spring 11 and the damping spring 12, the main valve core, the overflow pressure stabilizing function is realized. When the pressure of the oil inlet and outlet of the valve A is reduced and is lower than the set value of the valve, the pilot valve core 10 is tightly attached to the pilot valve seat 3 under the action of the pilot spring 9 to block the first cavity 15 and the second flow channel 16, and at the moment, the main valve core 2 is tightly pressed on the valve body 1 under the combined action of the pretightening force of the main valve core spring 11 and the damping spring 12 and the hydraulic pressure generated by the difference of the two end surfaces under the action of the pressure oil, so that the oil liquid of the oil inlet and outlet of the valve A cannot flow to the oil inlet and outlet of the valve B.
The two-stage supercharging principle of the invention is as follows: the pressure of the oil inlet and the oil outlet of the A is determined by the pretightening force of the pilot spring 9, namely the pressure of the oil inlet and the oil outlet of the A is set after the pretightening force of the pilot spring 9 is set. When the port X is not communicated with the pilot oil, the bottom of the pilot spring seat 4 is not stressed, and the pressure of the oil inlet and outlet of the port A is set by the first-stage pretightening force of the pilot spring 9. When the X port of the pilot oil port is connected with external control oil, the pilot spring seat 4 is pushed by the pilot oil to move upwards to form a D cavity (shown as D in figure 3), the oil enters the D cavity to push the pilot spring seat 4 to move upwards, the pilot spring seat 4 compresses the pilot spring 9, the pre-tightening force of the pilot spring 9 is increased to be a secondary pre-tightening force, the pressure of the A oil inlet and outlet port is increased at the moment, and the requirement of secondary pressure overflow pressure stabilization is met.
The one-way oil supplement principle: when the pressure of the oil inlet and outlet of the valve B is higher than that of the oil inlet and outlet of the valve A, the hydraulic pressure of the oil inlet and outlet of the valve B acting on the main valve element 2, the pressure of the oil inlet and outlet of the valve A acting on the main valve element 2 and the pressure of the oil inlet and outlet of the valve B acting on the main valve element 2 are higher than those of the oil inlet and outlet of the valve A acting on the main valve element 2, namely the acting force on the difference of the areas of the two ends of the main valve element 2 is higher than the pre-tightening force of the spring 11 and the damping.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.
The invention has the advantages of high boarding rotation starting speed and small boarding rotation stopping impact of the engineering machinery, and also has the advantages of low cost, low failure rate and wide application range.
Claims (6)
1. The utility model provides a guide's pressure boost two-stage overflow valve which characterized in that: the hydraulic control valve comprises a valve body (1), wherein an A oil inlet and outlet is formed in one end of the valve body (1), a B oil inlet and outlet is formed in the side wall of the valve body (1), a main valve core (2) positioned between the A oil inlet and outlet and the B oil inlet and outlet is arranged in the valve body (1), a damping valve core (13) connected with the A oil inlet and outlet is arranged in the main valve core (2), a pilot valve seat (3) connected with the other end of the valve body (1) is arranged on one side of the damping valve core (13), a damping spring (12) is arranged between the pilot valve seat (3) and the damping valve core (13), a main valve core spring (11) is arranged between the pilot valve seat (3) and the main valve core (2), a pilot valve core (10) is arranged at one end of the pilot valve seat (3), a secondary pressure regulating screw sleeve (5) is arranged at the other end of the pilot valve seat (3), a pilot spring seat (, the other end of the second-stage pressure regulating screw sleeve (5) is provided with a first-stage pressure regulating screw sleeve (8).
2. The pilot booster two-stage relief valve according to claim 1, characterized in that: two nuts (7) are arranged on the outer side of the secondary pressure regulating screw sleeve (5).
3. The pilot booster two-stage relief valve according to claim 1, characterized in that: a first flow channel (14) is arranged in the damper valve core (13), and a first cavity (15) connected with the first flow channel (14) is formed between the pilot valve seat (3) and the main valve core (2).
4. The pilot booster two-stage relief valve according to claim 3, characterized in that: and a second flow channel (16) connected with the first cavity (15) is arranged on the pilot valve seat (3), a pilot valve core (10) is arranged at one end of the second flow channel (16), and the other end of the second flow channel (16) is connected with the oil inlet and outlet of the oil tank B.
5. The pilot booster two-stage relief valve according to claim 1, characterized in that: one-level pressure regulating swivel nut (8) stretch into in second grade pressure regulating swivel nut (5) and with guide's spring holder (4) butt to and the outside of one-level pressure regulating swivel nut (8) is equipped with spacing ring (17), and the internal diameter of spacing ring (17) is greater than the external diameter of second grade pressure regulating swivel nut (5).
6. The pilot booster two-stage relief valve according to claim 1, characterized in that: and one end of the pilot spring seat (4) supports the pilot spring (9), the other end of the pilot spring seat is matched with an inner hole of the second-stage pressure regulating threaded sleeve (5), and a D cavity communicated with the first-stage pressure regulating threaded sleeve (8) is formed in the threaded sleeve (5) when the pilot spring seat (4) extrudes the pilot spring (9).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110258929.4A CN112923108A (en) | 2021-03-10 | 2021-03-10 | Pilot pressurizing two-stage overflow valve |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110258929.4A CN112923108A (en) | 2021-03-10 | 2021-03-10 | Pilot pressurizing two-stage overflow valve |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN112923108A true CN112923108A (en) | 2021-06-08 |
Family
ID=76172406
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110258929.4A Pending CN112923108A (en) | 2021-03-10 | 2021-03-10 | Pilot pressurizing two-stage overflow valve |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112923108A (en) |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN205278474U (en) * | 2015-12-28 | 2016-06-01 | 赛克思液压科技股份有限公司 | Pressurized construction of overflow valve |
| DE102018200951B3 (en) * | 2018-01-22 | 2019-02-21 | Hawe Hydraulik Se | Hydraulic seat valve with defined leakage, hydraulic pressure booster and hydraulic tool |
| CN110259751A (en) * | 2019-07-15 | 2019-09-20 | 宁波克泰液压有限公司 | Threaded insertion pilot is pressurized second level overflow valve |
| CN110259752A (en) * | 2019-07-15 | 2019-09-20 | 宁波克泰液压有限公司 | Threaded insertion pilot depressurizes second level overflow valve |
| CN209414290U (en) * | 2018-12-11 | 2019-09-20 | 烟台艾迪液压科技有限公司 | A kind of overflow valve with second level adjusting function |
| CN112283419A (en) * | 2020-11-27 | 2021-01-29 | 力源液压（苏州）有限公司 | Buffer valve for realizing overflow of two pressure levels |
-
2021
- 2021-03-10 CN CN202110258929.4A patent/CN112923108A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN205278474U (en) * | 2015-12-28 | 2016-06-01 | 赛克思液压科技股份有限公司 | Pressurized construction of overflow valve |
| DE102018200951B3 (en) * | 2018-01-22 | 2019-02-21 | Hawe Hydraulik Se | Hydraulic seat valve with defined leakage, hydraulic pressure booster and hydraulic tool |
| CN209414290U (en) * | 2018-12-11 | 2019-09-20 | 烟台艾迪液压科技有限公司 | A kind of overflow valve with second level adjusting function |
| CN110259751A (en) * | 2019-07-15 | 2019-09-20 | 宁波克泰液压有限公司 | Threaded insertion pilot is pressurized second level overflow valve |
| CN110259752A (en) * | 2019-07-15 | 2019-09-20 | 宁波克泰液压有限公司 | Threaded insertion pilot depressurizes second level overflow valve |
| CN112283419A (en) * | 2020-11-27 | 2021-01-29 | 力源液压（苏州）有限公司 | Buffer valve for realizing overflow of two pressure levels |
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Application publication date: 20210608 |