CN215890629U - Hydraulic device - Google Patents

Abstract

The utility model relates to the field of hydraulic control, in particular to a hydraulic device. A hydraulic apparatus comprising: at least one hydraulic pump that ejects working oil; the backup link comprises a backup control valve and a backup actuator, a pressure oil port of the backup control valve is communicated with an outlet of the hydraulic pump, and the backup control valve controls the action of the backup actuator; at least one action train operating in communication with a supply of working oil from the at least one hydraulic pump. The hydraulic unit solves the technical problem that in the prior art, the working oil pumped by the hydraulic pump in the hydraulic unit flows to the standby unit to generate large pressure loss, so that the driving power is insufficient.

Description

Hydraulic device

Technical Field

The utility model relates to the field of hydraulic control, in particular to a hydraulic device.

Background

In the current engineering machinery, the excavator is greatly popularized and applied in use, and the oil consumption, the working efficiency and the operation convenience of the excavator are main attention objects of various host manufacturing companies, research and development mechanisms and customers. The excavator working device comprises a movable arm, an arm, a bucket and a working device hydraulic pipeline including a movable arm oil cylinder, an arm oil cylinder and a bucket oil cylinder, wherein the arm is used as an important component of the excavator working device, and the reasonable arrangement of a hydraulic system of the arm is of great significance to the working performance of the excavator.

In addition to the working device of the excavator, a spare joint is arranged in a hydraulic system of the excavator and used for driving a spare tool to be used. As in the actual use of excavators, crushing units are increasingly used, and the backup connection in the hydraulic system serves to drive the crushing units in operation. In the existing hydraulic system, the backup line is often disposed at the rear, and the working oil pumped by the hydraulic pump supplies oil to the backup line through the serial oil passage, for example, patent document CN201720180668.8 discloses a multi-way control valve for a hydraulic excavator, which includes a backup valve disposed in a right valve body and located between a rotary valve and a first bucket rod valve, and the backup valve is respectively communicated with a second serial oil passage and a second parallel oil passage. The standby valve is communicated with the first series oil path through a standby confluence oil path, one end of the standby confluence oil path is connected with the tail end of the first series oil path, and the other end of the standby confluence oil path is connected with a second parallel oil path communicated with the standby valve. The multi-way control valve in the application supplies oil to the standby valve through the series oil circuit and the parallel oil circuit, and the series oil circuit and the parallel oil circuit are generally narrow, so that large pressure loss can be generated.

As disclosed in patent document CN201921615606.0, a hydraulic control device for a working machine includes: a hydraulic control device for a working machine is used for controlling the walking and the action of the working machine. The hydraulic control apparatus includes a hydraulic pump for discharging working oil and a hydraulic unit that operates by supply of the working oil from the hydraulic pump. The hydraulic units are plural and include a traveling hydraulic unit that controls traveling of the working machine by working oil supplied from two hydraulic pumps and an boarding hydraulic unit. The getting-on hydraulic unit comprises a plurality of sub-units, specifically comprises a first getting-on hydraulic unit, a second getting-on hydraulic unit, a third getting-on hydraulic unit, a fourth getting-on hydraulic unit and a fifth getting-on hydraulic unit, and the first getting-on hydraulic unit is used for controlling the action of a movable arm; the second boarding hydraulic unit is used for controlling the action of the bucket rod; the third loading hydraulic unit is used for controlling the action of the excavator bucket; the fourth boarding hydraulic unit controls rotation; and the fifth boarding hydraulic unit is used for standby. The hydraulic control device in the above patent document can be used to control the traveling and operation of the working machine, but in the actual use of the existing excavator, the crushing unit is used more and more, the crushing unit can only be operated by the driving of the fifth boarding hydraulic unit, and since the fifth boarding hydraulic unit is disposed at a position away from the hydraulic pump, the working oil pumped by the hydraulic pump needs to pass through a long oil path to reach, and a large pressure loss is generated, which results in insufficient power for driving the crushing unit.

SUMMERY OF THE UTILITY MODEL

The utility model provides a hydraulic device, which solves the technical problem that the driving power is insufficient due to the fact that the working oil pumped by a hydraulic pump in the hydraulic device in the prior art flows to a standby unit to generate large pressure loss. The technical scheme of the utility model is as follows:

a hydraulic apparatus comprising:

at least one hydraulic pump that ejects working oil;

the backup link comprises a backup control valve and a backup actuator, a pressure oil port of the backup control valve is communicated with an outlet of the hydraulic pump, and the backup control valve controls the action of the backup actuator;

at least one action train operating in communication with a supply of working oil from the at least one hydraulic pump.

According to one embodiment of the utility model, the hydraulic pumps are two, respectively a first hydraulic pump and a second hydraulic pump, and the two hydraulic pumps can be combined or respectively supply oil for the standby combined supply.

According to one embodiment of the present invention, the pump outlet of the first hydraulic pump is communicated with the pressure port of the backup control valve through a first oil path, the pump outlet of the second hydraulic pump is communicated with the pressure port of the backup control valve through a second oil path, and the first oil path and the second oil path are both provided with an opening and closing valve for controlling the opening degree of the oil paths.

According to an embodiment of the present invention, the opening and closing valve is a logic valve.

According to one embodiment of the utility model, the backup control valve is a three-position, four-way valve having a pressure port, an oil return port, and two working ports in communication with the backup actuator.

According to one embodiment of the utility model, the hydraulic pump further comprises an oil discharge oil path, the oil discharge oil path is arranged for the hydraulic pump, an oil discharge valve is arranged on the oil discharge oil path, and the oil discharge valve controls the on-off and the oil flux of the oil discharge oil path.

According to one embodiment of the utility model, the oil discharge paths are two, the oil discharge paths are arranged in front, and at least one oil discharge path is communicated with the pump outlet of at least one hydraulic pump.

According to one embodiment of the utility model, the at least one action pair comprises a walking pair, the walking pair comprises a walking control valve group and a walking actuator group, the walking control valve group comprises a straight walking valve and two walking valves, the two walking valves are respectively a left walking valve and a right walking valve, two hydraulic pumps supply oil to the two walking valves under the control of the straight walking valve, a pressure oil port of the right walking valve is communicated with the second oil path, part of pressure oil pumped out by the second hydraulic pump can be directly supplied to the right walking valve, and pressure oil pumped out by the first hydraulic pump and/or the second hydraulic pump can flow to the first oil unloading path under the control of the straight walking valve.

According to an embodiment of the utility model, the at least one action link further comprises at least one boarding action link, and the hydraulic pump supplies oil to the boarding action link through a boarding oil supply passage.

According to one embodiment of the present invention, the two upper vehicle oil supply paths are a first upper vehicle oil supply path and a second upper vehicle oil supply path, the first upper vehicle oil supply path is communicated with the first oil path, a part of the working oil pumped out by the first hydraulic pump can be directly supplied to the first upper vehicle oil supply path, and the first hydraulic pump and/or the second hydraulic pump supplies oil to the second upper vehicle oil supply path through the straight traveling valve.

Based on the technical scheme, the utility model can realize the following technical effects:

1. according to the hydraulic device, the standby link is arranged in the front, working oil sprayed by the hydraulic pump can directly enter the standby link, and compared with the prior art, the working oil sprayed by the hydraulic pump can enter the standby link only through a longer oil duct;

2. according to the hydraulic device, the number of the hydraulic pumps is two, the two hydraulic pumps can be converged and can also respectively supply oil to the standby unit, and then the oil supply to the standby unit is realized according to the requirement; the first hydraulic pump supplies oil to the standby combined unit through a first oil path, the second hydraulic pump supplies oil to the standby combined unit through a second oil path, and the first oil path and the second oil path are both provided with an on-off valve; when the standby link is not needed, the two opening and closing valves can be closed, and the working oil of the two hydraulic pumps can be used for driving the action link to work;

3. according to the hydraulic device, the oil discharge oil path is arranged for the hydraulic pumps, the working oil pumped by each hydraulic pump can directly return to the oil return tank through the oil discharge oil path, the oil discharge oil path is provided with the oil discharge valve capable of controlling the on-off and oil flux of the oil discharge oil path, and the oil supply quantity of each hydraulic pump in a standby connection and an action connection can be adjusted by adjusting the oil flux on the oil discharge oil path. If oil supply is not needed, the working oil pumped out by each hydraulic pump can be directly returned through the oil discharge oil way, the speed regulation effect is realized, the oil way of the system is simplified, and the response of the system is fast;

4. the hydraulic device can realize independent control of the two hydraulic pumps and confluence control of the two hydraulic pumps by arranging the linear traveling valve, can improve the efficiency of overall operation, and cannot influence getting-on action during single traveling.

Drawings

FIG. 1 is a hydraulic schematic of the hydraulic apparatus of the present invention;

FIG. 2 is a partial hydraulic schematic of the hydraulic device;

in the figure: 1-spare union; 11-a backup control valve; 12-a first oil path; 121 — a first open-close valve; 13-a second oil path; 131-a second opening and closing valve; 21-a first oil discharge path; 211-a first oil drain valve; 22-a second oil discharge path; 221-a second oil drain valve; 31-a first boarding oil supply path; 32-a second boarding oil supply path; 4-a walking pair; 41-straight walking valve; 42-a walking valve; 421-left travel valve; 422-right travel valve; 43-a shunt oil way; 431-one-way throttle valve; 5, a first getting-on action link; 6-a second getting-on action link; 7-a third getting-on action link; and 8-a fourth getting-on action link.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the utility model, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

In the description of the present invention, it is to be understood that the orientation or positional relationship indicated by the orientation words such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc. are usually based on the orientation or positional relationship shown in the drawings, and are only for convenience of description and simplicity of description, and in the case of not making a reverse description, these orientation words do not indicate and imply that the device or element being referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore, should not be considered as limiting the scope of the present invention; the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of the present invention should not be construed as being limited.

As shown in fig. 1-2, the present embodiment provides a hydraulic apparatus including at least one hydraulic pump that pumps working oil and at least one actuator that operates in communication with a supply of working oil from the at least one hydraulic pump. In the present embodiment, there are two hydraulic pumps, i.e., a first hydraulic pump P1 and a second hydraulic pump P2.

The at least one action unit includes a walking unit 4 and at least one boarding action unit, the walking unit 4 controls the walking of the working machine by the working oil supplied from the two hydraulic pumps, and the boarding action unit controls the action of the working device by the working oil supplied from the two hydraulic pumps. The traveling unit 4 includes a traveling control valve group and a traveling actuator group, the traveling control valve group controls two hydraulic pumps to supply oil to the traveling actuator group, the traveling control valve group includes a linear traveling valve 41 and two traveling valves 42, the two traveling valves 42 are a left traveling valve 421 and a right traveling valve 422, the left traveling valve 421 controls left traveling of the working machine, and the right traveling valve 422 controls right traveling of the working machine. The travel actuator group includes a left travel motor and a right travel motor, and the left travel valve 421 and the right travel valve 422 control the left travel motor and the right travel motor, respectively. Part of the hydraulic oil pumped by the first hydraulic pump P1 is directly supplied to the upper traveling unit, part of the hydraulic oil pumped by the second hydraulic pump P2 is directly supplied to the right traveling valve 422, and the two hydraulic pumps supply the left traveling valve 421 and the right traveling valve 422 under the control of the straight traveling valve 41.

Specifically, two upper oil supply paths for supplying oil to the upper operation linkage are provided, the two upper oil supply paths are respectively a first upper oil supply path 31 and a second upper oil supply path 32, and hydraulic oil pumped out by the two hydraulic pumps is supplied to all the upper operation linkages through the first upper oil supply path 31 and the second upper oil supply path 32. The pump outlet of the first hydraulic pump P1 is communicated with the first boarding oil supply passage 31, and part of the working oil pumped out by the first hydraulic pump P1 can be directly delivered to the first boarding oil supply passage 31.

The straight traveling valve 41 is a three-position four-way valve and comprises a pressure oil port ip 1, a pressure oil port ii P2, two working oil ports a and b, the pressure oil port ip 1 is communicated with an outlet of the first hydraulic pump P1, the pressure oil port ii P2 is communicated with the second hydraulic pump P2, the working oil port a is communicated with the left traveling valve 421, and the working oil port b is communicated with the second boarding oil supply oil path 32. The straight traveling valve 41 has 3 working positions, when the straight traveling valve 41 is located at the first working position, the pressure oil port ip 1 is communicated with the working oil port a, the pressure oil port ii P2 is communicated with the working oil port b, namely, part of the working oil pumped out by the first hydraulic pump P1 is supplied to the left traveling valve 421 through the straight traveling valve 41, part of the working oil pumped out by the second hydraulic pump P2 is supplied to the second boarding oil supply oil passage 32 through the straight traveling valve 42, namely, the first hydraulic pump P1 simultaneously supplies oil to the left traveling valve 421 and the first boarding oil supply oil passage 21, and the second hydraulic pump ii P2 simultaneously supplies oil to the right traveling valve 422 and the second boarding oil supply oil passage 32, so that independent control of left-right traveling movement and boarding movement can be realized; when the straight traveling valve 41 is located at the second working position, part of the working oil pumped out by the first hydraulic pump P1 and part of the working oil pumped out by the second hydraulic pump P2 are converged by the straight traveling valve 41 and then are respectively supplied to the left traveling valve 421 and the second boarding oil supply oil path 32, so that the composite operation of traveling action and boarding action can be simultaneously performed, the operation efficiency can be obviously improved through the confluence of the first hydraulic pump P1 and the second hydraulic pump P2, and the stability of each action during the composite operation can be ensured; when the straight traveling valve 41 is located at the third operating position, part of the working oil pumped out by the first hydraulic pump P1 is supplied to the second boarding oil supply passage 22 through the straight traveling valve 41, and part of the working oil pumped out by the second hydraulic pump P2 is supplied to the left traveling valve 421 through the straight traveling valve 41, so that the first hydraulic pump P1 simultaneously supplies oil to the first boarding oil supply passage 21 and the second boarding oil supply passage 22, and the second hydraulic pump P2 simultaneously supplies oil to the left traveling valve 421 and the right traveling valve 422. Preferably, the straight travel valve 41, the left travel valve 421 and the right travel valve 422 may be electrically, hydraulically, electro-hydraulically or other servo motor controlled pilot operated valves.

As a preferable embodiment of the present embodiment, in order to realize the rapid evacuation, a branch oil path 43 is further provided for supplying a part of the working oil passing through the working oil port b of the straight traveling valve 41 to at least one traveling valve, that is, supplying more working oil to the traveling. Specifically, the branch oil path 43 communicates the working oil port b of the straight traveling valve 41 and the right traveling valve 422, and a part of the hydraulic oil flowing out through the working oil port b may enter the second boarding oil supply oil path 32 and a part of the hydraulic oil may reach the right traveling valve 422 through the branch oil path 43. Preferably, the branch oil path 43 is provided with a check throttle valve 431, and the check throttle valve 431 controls the working oil to flow only from the working port b to the right traveling valve 422 in a single direction and not to flow in a reverse direction. A part of the working oil supplied to the second boarding oil-supply passage 32 can be delivered to the right traveling valve 422 by providing the branch oil passage 43 and the one-way throttle valve 431 thereon.

As a preferable technical solution of the present embodiment, the at least one boarding movement pair includes a first boarding movement pair 5, a second boarding movement pair 6, a third boarding movement pair 7, and a fourth boarding movement pair 8, and the first boarding oil supply passage 31 and the second boarding oil supply passage 32 supply oil to the boarding movement pairs. Preferably, the first getting-on action linkage 5 can be used for driving a boom action, and the second getting-on action linkage 6 can be used for driving a bucket action; the third getting-on action linkage 7 can be used for driving rotation, and the fourth getting-on action linkage 8 can be used for driving the arm to act.

In order to use additional tools such as crushing, the hydraulic device also comprises a backup coupling 1, wherein the backup coupling 1 is arranged in front and is directly communicated with the hydraulic pump. Specifically, the backup unit 1 includes a backup control valve 11 and a backup actuator, the backup control valve 11 has a pressure port P, an oil return port t and two working ports c and d, a pump outlet of a first hydraulic pump P1 is communicated with the pressure port P of the backup control valve 11 through a first oil path 12, a pump outlet of a second hydraulic pump P2 is communicated with the pressure port P of the backup control valve 11 through a second oil path 13, and the two hydraulic pumps can be merged into oil supply for the backup control valve 11; the oil return port t is communicated with an oil return oil way, the working oil port c is communicated with a working oil port Bo of the standby actuator, and the working oil port d is communicated with a working oil port Ao of the standby actuator.

As a preferable mode of the present embodiment, the first oil passage 12 and the second oil passage 13 are each provided with an on-off valve for controlling opening and closing of the oil passage, specifically, the first on-off valve 121 is provided on the first oil passage 12, the second on-off valve 131 is provided on the second oil passage 13, and by providing the first on-off valve 121 and the second on-off valve 131, the first hydraulic pump P1 and the second hydraulic pump P2 can be controlled to merge or independently supply oil to the backup control valve 11. The first opening-closing valve 121 and the second opening-closing valve 131 are both optional but not limited to logic valves.

In order to facilitate speed regulation of the whole hydraulic device, two oil discharge oil ways are arranged in the hydraulic device, the two oil discharge oil ways are arranged for two hydraulic pumps and respectively comprise a first oil discharge oil way 21 and a second oil discharge oil way 22, the first oil discharge oil way 21 is communicated with a working oil port a of the linear traveling valve 41, the second oil discharge oil way 22 is communicated with an outlet of the second hydraulic pump P2, working oil pumped out by the first hydraulic pump P1 can be discharged through the first oil discharge oil way 21 under the control of the linear traveling valve 41, and working oil pumped out by the second hydraulic pump P2 can be discharged through the second oil discharge oil way 22 directly. In order to control the opening and on-off of the two oil discharge paths, a first oil discharge valve 211 is arranged on the first oil discharge path 21, and a second oil discharge valve 221 is arranged on the second oil discharge path 22.

With the above configuration, the hydraulic apparatus according to the present embodiment can control the traveling and boarding operations of the working machine. The spare joint 1 can be used for driving additional tools such as crushing and the like to work, the spare joint 1 is arranged in front, working oil pumped out by the first hydraulic pump P1 and the second hydraulic pump P2 can be converged or respectively supplied to the spare joint 1, the spare joint 1 can be reached without narrow oil passages such as a serial oil passage and a parallel oil passage, and the spare joint 1 can provide required driving force for the additional tools such as crushing and the like, so that the working effect of the spare joint is ensured; in addition, an oil discharge oil way is arranged and arranged in front, so that the working oil pumped by the two hydraulic pumps can be discharged through the oil discharge oil way, and the oil quantity supplied to the walking unit and the action unit can be controlled by adjusting the opening and closing and the on-off of the oil discharge oil way, so that the speed of the whole hydraulic device can be adjusted.

The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.

Claims (10)

1. A hydraulic device, comprising:

at least one hydraulic pump that ejects working oil;

the backup coupling (1), the backup coupling (1) is arranged in front, the backup coupling (1) comprises a backup control valve (11) and a backup actuator, a pressure oil port (p) of the backup control valve (11) is communicated with an outlet of the hydraulic pump, and the backup control valve (11) controls the action of the backup actuator;

at least one action train operating in communication with a supply of working oil from the at least one hydraulic pump.

2. A hydraulic device according to claim 1, characterized in that said hydraulic pumps are two, respectively a first hydraulic pump (P1) and a second hydraulic pump (P2), which can be combined or which can supply the backup (1) separately.

3. A hydraulic apparatus according to claim 2, wherein the pump outlet of the first hydraulic pump (P1) is communicated with the pressure port (P) of the backup control valve (11) through a first oil passage (12), the pump outlet of the second hydraulic pump (P2) is communicated with the pressure port (P) of the backup control valve (11) through a second oil passage (13), and an open-close valve (121, 131) for controlling the opening degree of the oil passage is provided on each of the first oil passage (12) and the second oil passage (13).

4. A hydraulic device according to claim 3, wherein said opening and closing valve (121, 131) is a logic valve.

5. A hydraulic device according to any one of claims 1-4, characterized in that the backup control valve (11) is a three-position four-way valve, the backup control valve (11) having a pressure port (p), a return port (t) and two working ports (c, d), both working ports (c, d) being in communication with the backup actuator.

6. A hydraulic device according to claim 3, further comprising an oil discharge path (21, 22), wherein the oil discharge path (21, 22) is provided for the hydraulic pump, an oil discharge valve (211, 221) is provided on the oil discharge path (21, 22), and the oil discharge valve (211, 221) controls the on/off and oil flux of the oil discharge path (21, 22).

7. A hydraulic device according to claim 6, characterized in that said oil discharge channels (21, 22) are two, said oil discharge channels being pre-positioned, at least one oil discharge channel being in communication with the pump outlet of at least one of said hydraulic pumps.

8. A hydraulic device according to claim 7, characterized in that said at least one kinematic coupling comprises a walking coupling (4), the walking unit (4) comprises a walking control valve group and a walking actuator group, the walking control valve group comprises a straight walking valve (41) and two walking valves (42), the two walking valves (42) are respectively a left walking valve (421) and a right walking valve (422), the two hydraulic pumps supply oil to the two walking valves (42) under the control of the straight walking valve (41), the pressure oil port of the right walking valve (422) is communicated with the second oil way (13), part of the pressure oil pumped by the second hydraulic pump (P2) can be directly supplied to a right walking valve (422), the pressure oil pumped by the first hydraulic pump (P1) and/or the second hydraulic pump (P2) may be flowed to the first oil discharge passage (21) under the control of the straight traveling valve (41).

9. The hydraulic apparatus of claim 8, wherein the at least one locomotion assembly further comprises at least one boarding locomotion assembly, the hydraulic pump supplying oil to the boarding locomotion assembly through a boarding oil supply passage.

10. A hydraulic apparatus according to claim 9, wherein there are two boarding oil supply paths, namely a first boarding oil supply path (31) and a second boarding oil supply path (32), the first boarding oil supply path (31) being in communication with the first oil path (12), a part of the working oil pumped out by the first hydraulic pump (P1) being directly supplied to the first boarding oil supply path (31), and the first hydraulic pump (P1) and/or the second hydraulic pump (P2) being supplied to the second boarding oil supply path (32) through the straight travel valve (41).

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