CN103015473A - Priority control method of excavator and movable arm to rotation and priority valve - Google Patents
Priority control method of excavator and movable arm to rotation and priority valve Download PDFInfo
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- CN103015473A CN103015473A CN2012105282607A CN201210528260A CN103015473A CN 103015473 A CN103015473 A CN 103015473A CN 2012105282607 A CN2012105282607 A CN 2012105282607A CN 201210528260 A CN201210528260 A CN 201210528260A CN 103015473 A CN103015473 A CN 103015473A
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Abstract
The invention provides a priority control method of an excavator and a movable arm to rotation and a priority valve. The priority control method of the movable arm to rotation comprises the following steps: connecting a fluid control two-way valve on a rotational main oil path in series; arranging a bypass oil path which is provided with a gradually changed throttle opening and is connected with the fluid control two-way valve in parallel; setting the size of the gradually changed throttle opening to be in inverse ratio with the pressure magnitude of the rotational main oil path; setting a control end of the fluid control two-way valve into the pressure magnitude of hydraulic oil controlled by a movable arm main oil path; and disconnecting the fluid control two-way valve when composition actions of lifting and rotation of the movable arm need to be executed, so that the hydraulic oil of the rotational main oil path flows into a rotational motor from the bypass oil path, thereby realizing dynamic adjustment of the throttle opening of the bypass oil path. With the adoption of the priority control method of the movable arm to rotation, not only is a priority function of the movable arm to rotation realized when the actions of lifting and rotation of the movable arm are realized, but also because the bypass oil path is provided with the gradually changed throttle opening, the priority control method of the excavator and the movable arm to rotation and the priority valve have better adaptability to different working conditions.
Description
Technical field
The present invention relates to hydraulic drive and control technology field, particularly a kind of excavator, swing arm are to revolution method for controlling priority and pressure-gradient control valve.
Background technology
At present, excavator sector adopts multiple channel to solve hydraulic system composite move problem of disharmony, mainly solve the uneven problem of main valve assignment of traffic by various means, wherein generally adopt pressure-gradient control valve, improve the valve core opening curve, the main valve valve gap increases and suppresses piston, adopts the modes such as interflow regeneration function to guarantee the flow reasonable distribution, promotes digging machine operation coordination performance.
At present, when coordinating swing arm with the revolution composite move, adopted following dual mode:
1, when making composite move one fixed throttle port is accessed rotation oil, restriction enters the flow of rotary motor, improves the ability of swing arm lifting thereby reach the restriction revolution;
2, the stroke of restriction revolution main valve plug when making composite move reaches the purpose that restriction enters the rotary motor flow.
What above two kinds of methods accessed all is fixed throttle port, can not adjust according to the difference of boom cylinder load, poor to different adaptability for working condition.
Summary of the invention
In view of this, the present invention is intended to propose a kind of excavator, swing arm to revolution method for controlling priority road and pressure-gradient control valve, to solve the non-adjustable excavator that is caused of the restriction problem poor to different adaptability for working condition of pressure-gradient control valve.
For achieving the above object, technical scheme of the present invention is achieved in that
On the one hand, the invention provides a kind of swing arm to the revolution method for controlling priority, at hydraulic control two-way valve of revolution working connection series connection, and a bleed off circuit with gradual change restriction in parallel with described hydraulic control two-way valve is set, the size of described gradual change restriction is set to be inverse ratio with the pressure size of described revolution working connection, the control end of described hydraulic control two-way valve is set to be controlled by the hydraulic fluid pressure size of swing arm working connection, when the lifting of needs execution swing arm adds rotating composite move, described hydraulic control two-way valve disconnects, make the hydraulic oil of revolution working connection flow into rotary motor by described bleed off circuit, and then realize that the restriction of bleed off circuit is dynamically adjustable.
Further, described bleed off circuit comprises adjustable throttling, and the control end of described adjustable throttling is communicated with the revolution working connection.
On the other hand, the invention provides a kind of pressure-gradient control valve, the first spool and the second spool that comprise valve body and coaxial setting, described the first spool and described valve body consist of guide's two-way cone valve, described the second spool is take described the first spool as valve body and its formation adjustable throttling, the oil-in of described guide's two-way cone valve and oil-out respectively with corresponding the communicating of oil-in, oil-out of described adjustable throttling, described valve body is provided with the first drain tap that is communicated with the second drain tap of described adjustable throttling.
Further, described valve body is provided with the first poroid valve body hole of ladder, the end that described the first valve body hole is less is the first oil-in, the other end is provided with guide's hydraulic fluid port, side at close described the first oil-in of described valve body hole is provided with the first undercut groove, also be provided with the first oil-out that is communicated with described the first undercut groove on described valve body, described the first oil-in and described the first oil-out are respectively oil-in and the oil-out of described guide's two-way cone valve.
Further, the column structure that the main body of described the first spool is slidingly matched for the large bore portion with described the first valve body hole, end at described column structure is provided with the frustum structure corresponding with the hole shoulder of described the first valve body hole, in described the first spool, be provided with the second valve body opening poroid with the coaxial ladder of described the first valve body hole, be provided with the second undercut groove and the 3rd undercut groove in the described second valve body opening, also be provided with the second oil-out that is communicated with the second undercut groove and the first undercut groove on described the first spool, described the second oil-out is the oil-out of described adjustable throttling.
Further, described the second spool is the multidiameter shape structure that is slidingly matched with described second valve body opening, the little shaft portion of described the second spool and the little bore portion of described the second spool are slidingly matched and stretch out in described the first spool, be provided with the restriction of the second oil-in and described the second undercut groove of connection and the 3rd undercut groove at described the second spool, described the second oil-in is made of axial blind hole and radial direction through hole, described axial blind hole is extended to macro-axis by the end face of the little axle of described the second spool, described radial direction through hole is communicated with described axial blind hole and described the 3rd undercut groove, and described the second oil-in is the oil-in of described adjustable throttling.
Further, the aperture area of described restriction diminishes gradually along the direction of the 3rd undercut groove to the second undercut groove.
Further, be provided with for the first valve gap of sealing the first valve body hole and the first back-moving spring that is used for driving described the first spool at the large nose end of described the first valve body hole, described guide's hydraulic fluid port is arranged on described the first valve gap.
Further, be provided with for the second valve gap of sealing second valve body opening and the second back-moving spring that is used for driving described the second spool at the large nose end of described second valve body opening, described the second drain tap is communicated with the cavity at described the second back-moving spring place.
Further, the stiffness factor of described the second back-moving spring is greater than the stiffness factor of described the first back-moving spring.
Further, described the second spool is provided with the cannelure that is communicated with described radial direction through hole, and described cannelure is the groove shape structure that circumferentially arranges along described the second spool.
On the one hand, the present invention also provides a kind of excavator again, and described excavator is provided with aforesaid pressure-gradient control valve.
With respect to prior art, the present invention has following advantage:
1) swing arm of the present invention is to the revolution method for controlling priority, not only can promote when adding back rotation and doing at actuating arm and realize swing arm to the revolution priority function, and be provided with the restriction of gradual change because of bleed off circuit, and is therefore better to different adaptability for working condition.
2) restriction of pressure-gradient control valve of the present invention is opened take swing arm working connection pressure as the reference stream on-off, and the pressure size of the size of restriction and revolution working connection is inverse ratio, is not changeless, and is therefore good to different adaptability for working condition; And pressure-gradient control valve of the present invention combines guide's two-way cone valve and adjustable throttling, compact conformation, is quick on the draw, and oil circuit arranges simply, has reduced cost of production.
Description of drawings
The accompanying drawing that consists of a part of the present invention is used to provide a further understanding of the present invention, and illustrative examples of the present invention and explanation thereof are used for explaining the present invention, do not consist of improper restriction of the present invention.In the accompanying drawings:
Fig. 1 is that the described swing arm of the embodiment of the invention is to the schematic diagram of the revolution mode of priority;
Fig. 2 is the structural representation of the described pressure-gradient control valve of the embodiment of the invention;
Fig. 3 is the structural representation of the valve body of the described pressure-gradient control valve of the embodiment of the invention;
Fig. 4 is the structural representation of the first spool of the described pressure-gradient control valve of the embodiment of the invention;
Fig. 5 is the structural representation of the second spool of the described pressure-gradient control valve of the embodiment of the invention.
Description of reference numerals:
The 1-valve body, 11-the first valve body hole, 12-the first oil-in, 13-the first oil-out, 14-the first undercut groove, 15-the first drain tap, 16-guide's hydraulic fluid port, 2-the first spool, 21-second valve body opening, 22-frustum structure, 23-the second oil-out, 24-the second undercut groove, 25-the 3rd undercut groove, 26-the second drain tap, 3-the second spool, 31-the second oil-in, 311-axial blind hole, 312-radial direction through hole, the 32-restriction, 33-cannelure, 4-the first valve gap, 5-the first back-moving spring, 6-the second valve gap, 7-the second back-moving spring, 8-hydraulic control two-way valve, the 9-adjustable throttling, 10-turns round main valve.
The specific embodiment
Need to prove, in the situation that do not conflict, embodiment and the feature among the embodiment among the present invention can make up mutually.Describe below with reference to the accompanying drawings and in conjunction with the embodiments the present invention in detail.
Fig. 1 is the described swing arm of the embodiment of the invention to the schematic diagram of the revolution mode of priority, as shown in FIG., the described swing arm of the present embodiment is to the revolution method for controlling priority, be on the revolution working connection with revolution main valve 10 hydraulic control two-way valve 8 of connecting, and a bleed off circuit with gradual change restriction in parallel with this hydraulic control two-way valve 8 is set, the pilot signal of this hydraulic control two-way valve 8 derives from the hydraulic oil pressure force signal of swing arm working connection, when the lifting of needs execution swing arm adds rotating composite move, this hydraulic control two-way valve 8 disconnects according to pilot signal, make the hydraulic oil of revolution working connection flow into rotary motor by this bleed off circuit, and then realize that swing arm is to turning round preferential function, this bleed off circuit mainly comprises an adjustable throttling 9, the size of the restriction of this adjustable throttling 9 is inverse ratio with the pressure of revolution working connection, and the control end of this adjustable throttling 9 is communicated with the revolution working connection.
Fig. 2 to Fig. 5 is the structural representation of the described pressure-gradient control valve of the embodiment of the invention, as shown in FIG., the described pressure-gradient control valve of the present embodiment comprises the first spool 2 and second spool 3 of valve body 1 and coaxial setting, this first spool 2 consists of guide's two-way cone valve with this valve body 1, the second spool 3 take the first spool 2 as valve body 1 with its formation adjustable throttling, the oil-in of this guide's two-way cone valve and oil-out respectively with corresponding the communicating of oil-in, oil-out of adjustable throttling, this valve body 1 is provided with the first drain tap 15 that is communicated with the second drain tap 26 of this adjustable throttling.
As shown in Figure 3, this valve body 1 is provided with the first poroid valve body hole 11 of ladder, these the first valve body hole 11 less ends are the first oil-in 12, the other end is provided with guide's hydraulic fluid port 16, side at close this first oil-in 12 of this valve body hole is provided with the first undercut groove 14, also be provided with the first oil-out 13 that is communicated with this first undercut groove 14 on this valve body 1, this first oil-in 12 and this first oil-out 13 are respectively oil-in and the oil-out of this guide's two-way cone valve.
As shown in Figure 4, the column structure that the main body of this first spool 2 is slidingly matched for the large bore portion with this first valve body hole 11, end at this column structure is provided with the frustum structure 22 corresponding with the hole shoulder of this first valve body hole 11, in this first spool 2, be provided with the second valve body opening 21 poroid with the coaxial ladder of this first valve body hole 11, be provided with the second undercut groove 24 and the 3rd undercut groove 25 in this second valve body opening 21, also be provided with the second oil-out 23 that is communicated with the second undercut groove 24 and the first undercut groove 14 on this first spool 2, this second oil-out 23 is the oil-out of this adjustable throttling.
As shown in Figure 5, this second spool 3 is the multidiameter shape structure that is slidingly matched with this second valve body opening 21, the little shaft portion of this second spool 3 and the little bore portion of this second spool 3 are slidingly matched and stretch out in this first spool 2, be provided with the restriction 32 of the second oil-in 31 and this second undercut groove 24 of connection and the 3rd undercut groove 25 at this second spool 3, the aperture area of this restriction 32 diminishes gradually along the direction of the 3rd undercut groove 25 to second undercut grooves 24, this second oil-in 31 is made of axial blind hole 311 and radial direction through hole 312, this axial blind hole 311 is extended to macro-axis by the end face of the little axle of this second spool 3, this radial direction through hole 312 is communicated with this axial blind hole 311 and the 3rd undercut groove 25, and this second oil-in 31 is the oil-in of this adjustable throttling.Be provided with the cannelure 33 that is communicated with this radial direction through hole 312 at this second spool 3, this cannelure 33 is the groove shape structure that circumferentially arranges along this second spool 3.
As shown in Figure 2, be provided with for the first valve gap 4 of sealing the first valve body hole 11 and the first back-moving spring 5 that is used for driving this first spool 2 at the large nose end of this first valve body hole 11, this guide's hydraulic fluid port 16 is arranged on this first valve gap 4.Large nose end at this second valve body opening 21 is provided with for the second valve gap 6 of sealing second valve body opening 21 and the second back-moving spring 7 that is used for driving this second spool 3, this second drain tap 26 is communicated with the cavity at these the second back-moving spring 7 places, and the stiffness factor of this second back-moving spring 7 is greater than the stiffness factor of this first back-moving spring 5.
When the described pressure-gradient control valve of the present embodiment was applied on the excavator, its operating principle was as follows:
The first oil-in 12 and first oil-out 13 of this pressure-gradient control valve are connected on the revolution working connection, guide's hydraulic fluid port 16 is communicated with the first oil-out 13, and formerly on the oil circuit of oil diverting port 16 and the first oil-out 13 pilot valve that is used for blocking this oil circuit is set, the oily connection of pilot pressure that the control end of this pilot valve and swing arm promote.
When excavator only turns round, there is not pressure on the control end of pilot valve, pilot valve does not disconnect, the hydraulic oil of revolution working connection acts on the first spool 2 right-hand members, push the first spool 2 to the left side, the first oil-in 12, the first undercut groove 14 and the first oil-out 13 are communicated with, and then the revolution working connection is opened, rotary motor normally turns round.
When excavator actuating arm lifting+rotating composite move, the pilot pressure oil that swing arm promotes is closed pilot valve, then the oil circuit of the first spool 2 left ends is closed, make the first spool 2 not remove to open the revolution working connection to left movement, the second oil-in 31 that the hydraulic oil of revolution working connection is forced through the second spool 3 flows into the 3rd undercut groove 25, flows into successively the second undercut groove 24, the second oil-out 23, the first undercut groove 14 and the first oil-out 13 to revolution working connection by restriction 32 again and goes to promote the rotary motor rotation.When the revolution working connection causes pressure rise owing to boom cylinder load rising, the power that pressure oil acts on the second spool 3 right-hand members increases, promote the second spool 3 motion compresses the second back-moving spring 7 left, the second spool 3 stop motions when the dynamic balance of hydraulic coupling and the second back-moving spring 7, this moment, the area of passage of restriction 32 reduced, limited the hydraulic fluid flow rate that enters rotary motor, made more hydraulic oil enter boom cylinder to improve the hoisting velocity of swing arm.
Except above-mentioned pressure-gradient control valve, the present invention also provides a kind of excavator that is provided with above-mentioned pressure-gradient control valve, and the structure of other each several part of this excavator is with reference to prior art, and this paper repeats no more.
The above only is preferred embodiment of the present invention, and is in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (12)
1. a swing arm is to the revolution method for controlling priority, it is characterized in that, at a revolution working connection series connection hydraulic control two-way valve (8), and a bleed off circuit with gradual change restriction in parallel with described hydraulic control two-way valve (8) is set, the size of described gradual change restriction is set to be inverse ratio with the pressure size of described revolution working connection, the control end of described hydraulic control two-way valve (8) is set to be controlled by the hydraulic fluid pressure size of swing arm working connection, when the lifting of needs execution swing arm adds rotating composite move, described hydraulic control two-way valve (8) disconnects, make the hydraulic oil of revolution working connection flow into rotary motor by described bleed off circuit, and then realize that the restriction of bleed off circuit is dynamically adjustable.
2. swing arm according to claim 1 is characterized in that the revolution method for controlling priority, and described bleed off circuit comprises adjustable throttling (9), and the control end of described adjustable throttling (9) is communicated with the revolution working connection.
3. pressure-gradient control valve, it is characterized in that, the first spool (2) and the second spool (3) that comprise valve body (1) and coaxial setting, described the first spool (2) consists of guide's two-way cone valve with described valve body (1), described the second spool (3) take described the first spool (2) as valve body (1) with its formation adjustable throttling, the oil-in of described guide's two-way cone valve and oil-out respectively with the oil-in of described adjustable throttling, the oil-out correspondence communicates, and described valve body (1) is provided with the first drain tap (15) that is communicated with second drain tap (26) of described adjustable throttling.
4. pressure-gradient control valve according to claim 3, it is characterized in that, described valve body (1) is provided with poroid the first valve body hole (11) of ladder, the end that described the first valve body hole (11) is less is the first oil-in (12), the other end is provided with guide's hydraulic fluid port (16), side at close described the first oil-in (12) of described valve body hole is provided with the first undercut groove (14), also be provided with the first oil-out (13) that is communicated with described the first undercut groove (14) on described valve body (1), described the first oil-in (12) and described the first oil-out (13) are respectively oil-in and the oil-out of described guide's two-way cone valve.
5. pressure-gradient control valve according to claim 4, it is characterized in that, the column structure that the main body of described the first spool (2) is slidingly matched for the large bore portion with described the first valve body hole (11), end at described column structure is provided with the frustum structure (22) corresponding with the hole shoulder of described the first valve body hole (11), in described the first spool (2), be provided with the second valve body opening (21) poroid with the coaxial ladder of described the first valve body hole (11), be provided with the second undercut groove (24) and the 3rd undercut groove (25) in the described second valve body opening (21), also be provided with the second oil-out (23) that is communicated with the second undercut groove (24) and the first undercut groove (14) on described the first spool (2), described the second oil-out (23) is the oil-out of described adjustable throttling.
6. pressure-gradient control valve according to claim 5, it is characterized in that, described the second spool (3) is the multidiameter shape structure that is slidingly matched with described second valve body opening (21), the little bore portion of the little shaft portion of described the second spool (3) and described the second spool (3) is slidingly matched and stretches out in described the first spool (2), be provided with the restriction (32) of the second oil-in (31) and described the second undercut groove of connection (24) and the 3rd undercut groove (25) at described the second spool (3), described the second oil-in (31) is made of axial blind hole (311) and radial direction through hole (312), described axial blind hole (311) is extended to macro-axis by the end face of the little axle of described the second spool (3), described radial direction through hole (312) is communicated with described axial blind hole (311) and described the 3rd undercut groove (25), and described the second oil-in (31) is the oil-in of described adjustable throttling.
7. pressure-gradient control valve according to claim 6 is characterized in that, the aperture area of described restriction (32) diminishes gradually along the direction of the 3rd undercut groove (25) to the second undercut groove (24).
8. according to claim 5,6 or 7 described pressure-gradient control valves, it is characterized in that, large nose end at described the first valve body hole (11) is provided with for first valve gap (4) of sealing the first valve body hole (11) and the first back-moving spring (5) that is used for driving described the first spool (2), and described guide's hydraulic fluid port (16) is arranged on described the first valve gap (4).
9. pressure-gradient control valve according to claim 8, it is characterized in that, large nose end at described second valve body opening (21) is provided with for second valve gap (6) of sealing second valve body opening (21) and the second back-moving spring (7) that is used for driving described the second spool (3), and described the second drain tap (26) is communicated with the cavity at described the second back-moving spring (7) place.
10. pressure-gradient control valve according to claim 9 is characterized in that, the stiffness factor of described the second back-moving spring (7) is greater than the stiffness factor of described the first back-moving spring (5).
11. pressure-gradient control valve according to claim 6, it is characterized in that, described the second spool (3) is provided with the cannelure (33) that is communicated with described radial direction through hole (312), and described cannelure (33) is the groove shape structure that circumferentially arranges along described the second spool (3).
12. an excavator is characterized in that, described excavator is provided with such as the described pressure-gradient control valve of claim 3 to 11 any one.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2012105282607A CN103015473A (en) | 2012-12-10 | 2012-12-10 | Priority control method of excavator and movable arm to rotation and priority valve |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2012105282607A CN103015473A (en) | 2012-12-10 | 2012-12-10 | Priority control method of excavator and movable arm to rotation and priority valve |
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| Publication Number | Publication Date |
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| CN103015473A true CN103015473A (en) | 2013-04-03 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2012105282607A Pending CN103015473A (en) | 2012-12-10 | 2012-12-10 | Priority control method of excavator and movable arm to rotation and priority valve |
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| Country | Link |
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| CN (1) | CN103015473A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103290869A (en) * | 2013-06-24 | 2013-09-11 | 山推工程机械股份有限公司 | Bulldozer and shovel blade inclination control system thereof |
| CN106593983A (en) * | 2017-02-22 | 2017-04-26 | 常熟华威履带有限公司 | Hydraulic control device of hydraulic excavator |
| CN111501893A (en) * | 2020-04-30 | 2020-08-07 | 徐州徐工挖掘机械有限公司 | Negative flow hydraulic system and excavator |
| CN112411647A (en) * | 2020-12-02 | 2021-02-26 | 龙工（上海）精工液压有限公司 | Swing arm pair rotation priority control system for hydraulic excavator and priority valve |
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| CN1165550A (en) * | 1995-09-18 | 1997-11-19 | 日立建机株式会社 | Hydraulic system |
| CN101892681A (en) * | 2009-05-22 | 2010-11-24 | 沃尔沃建造设备控股（瑞典）有限公司 | Hydraulic system with improved complex operation |
| JP4838555B2 (en) * | 2005-09-05 | 2011-12-14 | 株式会社渋彰建設 | Hydraulic circuit, electric control circuit and hydraulic motor cutting device |
| WO2012091187A1 (en) * | 2010-12-27 | 2012-07-05 | 볼보 컨스트럭션 이큅먼트 에이비 | Boom-swivel compound drive hydraulic control system of construction machine |
| CN102734244A (en) * | 2012-06-27 | 2012-10-17 | 上海三一重机有限公司 | Priority valve of hydraulic excavator, using method and excavator |
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2012
- 2012-12-10 CN CN2012105282607A patent/CN103015473A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1165550A (en) * | 1995-09-18 | 1997-11-19 | 日立建机株式会社 | Hydraulic system |
| JP4838555B2 (en) * | 2005-09-05 | 2011-12-14 | 株式会社渋彰建設 | Hydraulic circuit, electric control circuit and hydraulic motor cutting device |
| CN101892681A (en) * | 2009-05-22 | 2010-11-24 | 沃尔沃建造设备控股（瑞典）有限公司 | Hydraulic system with improved complex operation |
| WO2012091187A1 (en) * | 2010-12-27 | 2012-07-05 | 볼보 컨스트럭션 이큅먼트 에이비 | Boom-swivel compound drive hydraulic control system of construction machine |
| CN102734244A (en) * | 2012-06-27 | 2012-10-17 | 上海三一重机有限公司 | Priority valve of hydraulic excavator, using method and excavator |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103290869A (en) * | 2013-06-24 | 2013-09-11 | 山推工程机械股份有限公司 | Bulldozer and shovel blade inclination control system thereof |
| CN106593983A (en) * | 2017-02-22 | 2017-04-26 | 常熟华威履带有限公司 | Hydraulic control device of hydraulic excavator |
| CN111501893A (en) * | 2020-04-30 | 2020-08-07 | 徐州徐工挖掘机械有限公司 | Negative flow hydraulic system and excavator |
| CN112411647A (en) * | 2020-12-02 | 2021-02-26 | 龙工（上海）精工液压有限公司 | Swing arm pair rotation priority control system for hydraulic excavator and priority valve |
| CN112411647B (en) * | 2020-12-02 | 2024-03-12 | 龙工（上海）精工液压有限公司 | Swing arm-to-rotation priority control system and priority valve for hydraulic excavator |
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Application publication date: 20130403 |