CN109707693B - Hydraulic oil cylinder and load balancing device - Google Patents
Hydraulic oil cylinder and load balancing device Download PDFInfo
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- CN109707693B CN109707693B CN201811593905.9A CN201811593905A CN109707693B CN 109707693 B CN109707693 B CN 109707693B CN 201811593905 A CN201811593905 A CN 201811593905A CN 109707693 B CN109707693 B CN 109707693B
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Abstract
The present invention provides a hydraulic cylinder, comprising: the balance piston and the working piston divide the interior of the shell into a balance cavity, a rodless cavity and a rod cavity, the piston rod is arranged in the rod cavity and is connected with the working piston, a limiting part for stopping is arranged between the balance piston and the working piston on the shell, oil ports which are communicated with the balance cavity, the rodless cavity and the rod cavity are respectively arranged on the shell, an oil hole which communicates the balance cavity with the rodless cavity is formed in the balance piston, and a check valve component which supplies hydraulic oil to flow from the rodless cavity to the balance cavity is arranged in the oil hole. The invention can realize the function of heavy load bearing of mutual balance among a plurality of hydraulic oil cylinders, adapts to the height difference on the structural connection of each hydraulic oil cylinder and ensures the self safety of the hydraulic oil cylinders and the safety of the self-elevating platform.
Description
Technical Field
The invention relates to the technical field of hydraulic oil cylinders, in particular to a hydraulic oil cylinder and an explosion load restraining balancing device.
Background
The bolt type lifting system used on the self-lifting platform has a plurality of arrangement forms, wherein some structural forms are directly connected with a hull column fixing chamber and a ring beam through a lifting oil cylinder, oil is fed into a rodless cavity, and a piston rod of the oil cylinder extends to lift the platform. And when the rodless cavity produces oil and the piston rod of the oil cylinder retracts, the platform descends.
As the number of the hydraulic oil cylinders used for lifting each pile leg is large, the number of the hydraulic oil cylinders on each pile leg is 4, 6 or 8, the maximum distribution distance between the hydraulic oil cylinders is about 4-8 meters, and the pile fixing chamber is also a large-scale welding structural part with square meters, the control precision is limited, so that the heights of the oil cylinder earrings fixed in the pile fixing chamber cannot be guaranteed to be consistent, and the difference is more than several millimeters under the general condition.
Under the condition that high-pressure oil exists in the rodless cavity, because the oil cylinders are input by the same oil source, the rodless cavity is communicated, the strokes of the piston rods naturally have difference, and the load of the oil cylinders can be balanced. When the oil source stops running and the main oil way of the oil cylinder is unloaded, the piston rod of the oil cylinder can be directly contacted with the rear end cover of the cylinder tail, the weight of the platform body is borne through the mechanical contact of the oil cylinder and the rear end cover, but not through the oil pressure, at the moment, the initial installation heights of the oil cylinders on the same ring beam are inconsistent, the uniform stress of all the oil cylinders cannot be guaranteed, and the bearing capacity of the oil cylinder which is firstly contacted with the rear end cover is overlarge, and even the oil cylinder parts are damaged. Because the single pile load of some platforms is large, even in a load balancing state, the stress of a single oil cylinder can reach thousands of tons, when the load is uneven, the bearing capacity of the single oil cylinder is even doubled due to the large rigidity of the mechanical structures of the pile fixing chamber and the oil cylinder, and the method is obviously unacceptable in engineering.
Therefore, a hydraulic oil cylinder capable of mutually balancing the heavy-load bearing function is needed.
Disclosure of Invention
In view of the above-mentioned disadvantages of the prior art, the present invention provides a hydraulic cylinder and a load balancing apparatus, which are used to solve the problem of insufficient manufacturing accuracy of the lifting system in the prior art.
To achieve the above and other related objects, the present invention provides a hydraulic cylinder, including: the balance piston and the working piston divide the interior of the shell into a balance cavity, a rodless cavity and a rod cavity, the piston rod is arranged in the rod cavity and is connected with the working piston, a limiting part for stopping is arranged between the balance piston and the working piston on the shell, oil ports which are communicated with the balance cavity, the rodless cavity and the rod cavity are respectively arranged on the shell, an oil hole which communicates the balance cavity with the rodless cavity is formed in the balance piston, and a check valve component which supplies hydraulic oil to flow from the rodless cavity to the balance cavity is arranged in the oil hole.
Preferably, a return spring for returning the balance piston is arranged in the balance cavity.
Preferably, the housing comprises a cylinder barrel, a rear end cover and a front end cover which are connected to two ends of the cylinder barrel, the piston rod extends out of the front end cover, and the balance cavity is formed by the rear end cover and the balance piston.
Preferably, a sleeve ring is arranged at the joint of the rear end cover and the cylinder barrel, a protruding part extending towards the balance cavity and the rodless cavity is arranged on the sleeve ring, and the protruding part forms the limiting part.
Preferably, the oil port communicated with the rod cavity is positioned on the front end cover, and the two oil ports respectively communicated with the balance cavity and the rodless cavity are positioned on the rear end cover.
Preferably, be equipped with the maintenance in the oilhole the pressurize subassembly of balanced chamber pressure, the pressurize subassembly includes pressurize valve barrel and pressurize case, pressurize valve barrel location is located in the oilhole, and at the oilhole orientation the tip in rodless chamber is equipped with the chock plug of location pressurize valve barrel, the pressurize case arrange in the pressurize valve barrel and with the pressurize valve inter-sleeve is equipped with the complex sealing portion, the pressurize case with be equipped with between the chock plug keep the pressurize case with the pressurize spring that the pressurize valve barrel is sealed mutually, be equipped with the oilhole on the pressurize case, check valve subassembly is located in the oilhole.
Preferably, a sealing table portion is arranged on the inner wall of the pressure maintaining valve sleeve, the pressure maintaining valve core is provided with a sealing cone portion, and the sealing table portion and the sealing cone portion are matched and sealed to form the sealing portion.
Preferably, the check valve assembly includes a check valve sleeve and a check valve core, the oil passing hole has a large hole portion with a large diameter, the check valve sleeve is fixed in one end of the large hole portion, the check valve core is located at the other end of the large hole portion, and the check valve core can seal the check valve sleeve.
Preferably, the one-way valve core is a round ball.
The invention provides a load balancing device which comprises at least two hydraulic oil cylinders, wherein oil ports in all the hydraulic oil cylinders, which are communicated with a balancing cavity, are connected through a balancing oil pipe.
As mentioned above, the hydraulic oil cylinder and the load balancing device have the following beneficial effects: its simple structure is compact, through setting up balanced chamber and balanced piston for hydraulic cylinder is under the condition of working oil circuit uninstallation, and the accessible links to each other with balanced oil pipe with the hydraulic fluid port that the balanced chamber links to each other, realizes the heavy load bearing function of mutual balance between a plurality of hydraulic cylinder, adapts to the difference in height on each hydraulic cylinder's the structural connection, has guaranteed hydraulic cylinder's self safety and self-elevating platform's security.
Drawings
FIG. 1 shows a cross-sectional view of a hydraulic ram of the present invention.
FIG. 2 is a block diagram of a balance chamber of a hydraulic ram of the present invention.
Fig. 3 is a block diagram of the check valve assembly of the present invention.
Figure 4 shows a state in which the piston rod of the hydraulic cylinder is retracted to the bottom.
Description of the element reference numerals
| 1 | |
| 11 | |
| 12 | |
| 13 | |
| 2 | |
| 21 | |
| 3 | One- |
| 31 | One- |
| 32 | One-way valve core |
| 4 | |
| 5 | Working piston |
| 6 | Reset spring |
| 7 | Piston |
| 8 | Lantern ring |
| 91 | Pressure maintaining |
| 911 | |
| 912 | |
| 92 | Pressure maintaining |
| 921 | |
| 922 | Sealed |
| 923 | Big hole part |
| 93 | |
| 94 | |
| 103、101、102 | |
| 100 | Cavity with |
| 200 | |
| 300 | Balancing chamber |
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
Please refer to fig. 1 to 4. It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions under which the present invention can be implemented, so that the present invention has no technical significance, and any structural modification, ratio relationship change, or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention. In addition, the terms "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for clarity of description, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not to be construed as a scope of the present invention.
As shown in fig. 1 and 2, the present invention provides a hydraulic cylinder, including: the balance piston type hydraulic pump comprises a shell 1 and a piston rod 7 arranged in the shell 1 in a penetrating mode, wherein a balance piston 2 and a working piston 5 are arranged in the shell 1, the balance piston 2 and the working piston 5 divide the interior of the shell 1 into a balance cavity 300, a rodless cavity 200 and a rod cavity 100, the piston rod 7 is arranged in the rod cavity 100 and is connected with the working piston 5, a limiting part for stopping is arranged between the balance piston 2 and the working piston 5 on the shell 1, oil ports 103, 101 and 102 which are communicated with the balance cavity 300, the rodless cavity 200 and the rod cavity 100 are further arranged on the shell 1, an oil hole 21 which communicates the balance cavity 300 with the rodless cavity 200 is formed in the balance piston 2, and a check valve assembly 3 for supplying hydraulic oil to flow to the balance cavity 300 from the rodless cavity 200 is arranged in the oil hole 21. According to the invention, the balance cavity 300 and the balance piston 2 are additionally arranged in the shell 1, when a plurality of hydraulic oil cylinders are used and each hydraulic oil cylinder is in a working oil way for unloading, the hydraulic oil cylinders still have a function of balancing heavy load and bearing pressure with other hydraulic oil cylinders, namely the hydraulic oil cylinders can adjust the pressure in the balance cavity 300 through the movement of the balance piston 2 to realize the balance of heavy load bearing pressure, and the balance cavity 300 can be specifically as follows: if the piston rod 7 retracts to abut against the balance piston 2 and move towards the balance cavity 300, so that the pressure in the balance cavity 300 is increased, the hydraulic oil in the balance cavity 300 can be discharged through the oil port 103 and then flows into the balance cavity 300 in the hydraulic oil cylinders of which the piston rod 7 retracts to not abut against the balance piston 2, and therefore the self-bearing pressure of each hydraulic oil cylinder is achieved.
In order to facilitate the return of the balance piston, as shown in fig. 2, a return spring 6 for returning the balance piston 2 is disposed in the balance chamber 300 in the present embodiment, and the return spring 6 can maintain the balance piston 2 at a position close to one side of the rodless chamber, i.e., at the right side of the balance chamber 300 in fig. 2, so as to facilitate the balance chamber 300 to be filled with oil.
Referring to fig. 1, in the present embodiment, the housing 1 includes a cylinder 11, and a rear end cap 12 and a front end cap 13 connected to two ends of the cylinder, the piston rod 7 extends from the front end cap 13, and the balance chamber 300 is formed by the rear end cap 12 and the balance piston 2. For convenient installation and fixation, the rear end cover 12 is connected with the cylinder barrel 11 through a plurality of screws in the embodiment, and the rear end cover 12 is provided with a cylinder tail ear ring. The front end cover 13 is also connected to the cylinder 11 by bolts, and an oil port 102 leading to the rod chamber 100 is provided in the front end cover 13. The left end of the piston rod 7 is connected with the working piston 5 and is pressed tightly by the locking nut 4. The working piston 5 divides the inner cavity of the cylinder 11 into two parts, the left side is a rodless cavity 200, the right side is a rod cavity 100, and when external pressure oil enters the rodless cavity 200 through the oil port 101, the piston rod 7 extends out; when the external pressure oil enters the rod chamber 100 through the oil port 102, the piston rod 7 is retracted. When the external oil source is unloaded, the rod chamber 100 and the rodless chamber 200 have no external pressure oil, and at this time, if the hydraulic oil cylinder bears pressure, the end face of the piston rod 7 contacts with the balance piston 2, as shown in fig. 4, and becomes a mechanical load-bearing state.
An oil port 102 communicated with the rod chamber 100 is positioned on the front end cover 13, and two oil ports 103 and 101 respectively communicated with the balance chamber 300 and the rodless chamber 200 are positioned on the rear end cover 12. The structure of the housing 1 is not limited to this, and it is sufficient if the piston rod 7 can be attached thereto, and functional structures such as the equilibrium chamber 300, the rodless chamber 200, and the rod chamber 100 can be formed.
In this embodiment, a collar 8 is disposed at a connection portion between the rear end cap 12 and the cylinder 11, and a protrusion (not labeled) extending to the balance cavity 300 and the rodless cavity 200 is disposed on the collar 8, and the protrusion constitutes the limiting portion. The lantern ring 8 extends out of the convex parts towards the rear end cover 12 and the cylinder barrel 11 respectively, so that on one hand, the concentricity of the rear end cover, the cylinder barrel and the convex parts is ensured; on the other hand, the maximum stroke of the balance piston 2 is limited by the boss extending inside the rear end cap 12, and the retraction stroke of the working piston 5 is limited by the boss extending inside the cylinder tube 11.
In this embodiment, to increase the safety, a pressure maintaining assembly for maintaining the pressure of the balance cavity 300 is further disposed in the oil hole 21 in the balance piston 2, as shown in fig. 3, the pressure maintaining assembly includes a pressure maintaining valve sleeve 91 and a pressure maintaining valve core 92, the pressure maintaining valve sleeve 91 is positioned in the oil hole 21, a plug 93 for positioning the pressure maintaining valve sleeve 32 is disposed at an end of the oil hole 21 facing the rodless cavity 200, the pressure maintaining valve core 92 is slidably disposed in an inner hole 912 of the pressure maintaining valve sleeve 91, a sealing portion is disposed between the pressure maintaining valve sleeve 91 and the plug 93, a pressure maintaining spring 94 for sealing the pressure maintaining valve core 92 and the pressure maintaining valve sleeve 91 is disposed between the pressure maintaining valve core 92 and the plug 93, an oil passing hole 921 is disposed on the pressure maintaining valve core 92, and the check valve assembly 3 is. In the embodiment, the pressure maintaining valve core 92 and the pressure maintaining valve sleeve 91 are ensured to be in sealing fit through the pressure maintaining spring 94, only when the pressure in the balance cavity 300 is greater than the elastic force of the pressure maintaining spring 94, the pressure maintaining valve core 92 is pushed to compress the pressure maintaining spring 94 to move, and then the sealing between the pressure maintaining valve core 92 and the pressure maintaining valve sleeve 91 is removed, so that the hydraulic oil in the balance cavity 300 enters the rodless cavity 200, the oil pressure in the balance cavity 300 is protected from being too large, and the pressure in the balance cavity 300 is ensured to be in a safe range.
By designing and calculating the area of the left end face of the pressure maintaining valve core 92 (i.e. the end face facing the balance chamber 300) and the pre-tightening force of the pressure maintaining spring 94, the pressure maintaining valve assembly can obtain a fixed opening pressure value, and since the wall thickness of the balance chamber 300 on the rear end cap 12 can be freely designed, which does not cause excessive cost variation, the pressure value can be designed to be higher. The pressure is multiplied by the area of the balance piston 2 to obtain a bearing capacity, and the bearing capacity is the balance bearing capacity of the hydraulic oil cylinder.
In the present embodiment, a seal land portion 911 is provided on an inner wall of the pressure maintaining valve sleeve 91, the pressure maintaining valve body 92 has a seal tapered portion 922, and the seal land portion 911 and the seal tapered portion 922 are fitted and sealed to form the seal portion. The pressure maintaining spring 94 of the present embodiment applies a leftward urging force to the pressure maintaining valve body 92, and ensures contact sealing between the tapered surface of the seal tapered portion 922 and the cylindrical surface of the seal land portion 911, thereby achieving pressure maintaining sealing of the oil hole 21.
Referring to fig. 3, the check valve assembly 3 includes a check valve sleeve 31 and a check valve core 32, the oil passing hole 921 has a large hole portion 923 with a large diameter, the check valve sleeve 31 is fixed in one end of the large hole portion 923, the check valve core 32 is located at the other end of the large hole portion 923, and the check valve core 32 can seal the check valve sleeve 31. The check valve element 32 in this embodiment is a ball. In this embodiment, the check valve sleeve 31 is fixedly arranged in the large hole portion 923, and the check valve element 32 is located in a space surrounded by the check valve sleeve 31 and the large hole portion 923, the hydraulic cylinder in this embodiment is generally used vertically, the check valve element 32 seals the check valve sleeve 31 due to gravity, so as to seal the whole oil passing hole 921, and therefore, hydraulic oil in the balance cavity 300 cannot enter the rodless cavity 200 through the oil passing hole 921; when the rodless chamber 200 contains hydraulic oil, it will push the check valve core 32 to move leftward, even if the check valve sleeve 31 is connected to the oil through hole 921, so that the hydraulic oil enters the balance chamber 300. The check valve assembly 3 is not limited thereto, and may be of other check valve structures as long as hydraulic oil can enter the balance chamber 300 only from the rodless chamber 200.
The invention provides a load balancing device which can be used for designing a lifting balance system of a self-elevating platform and comprises at least two hydraulic oil cylinders, wherein oil ports 103 in all the hydraulic oil cylinders, which are communicated with a balance cavity 300, are connected through balance oil pipes. When each hydraulic oil cylinder is in a working oil way for unloading, the hydraulic oil cylinder still has a function of balancing heavy load and bearing pressure with other hydraulic oil cylinders, namely the hydraulic oil cylinder can adjust the pressure in the balance cavity 300 by moving the balance piston 2, as shown in fig. 4, if the piston rod 7 retracts to abut against the balance piston 2 and move towards the balance cavity 300, and the pressure in the balance cavity 300 is increased, the hydraulic oil in the balance cavity 300 can be discharged through the oil port 103 and then flows into the balance cavity 300 in the hydraulic oil cylinder which does not abut against the balance piston 2 after retracting, so that the self-bearing pressure of each hydraulic oil cylinder is realized; the height difference of the structural connection of the hydraulic oil cylinders is adapted, and the safety of the hydraulic oil cylinders and the self-elevating platform is ensured.
In conclusion, the hydraulic oil cylinder and the load balancing device have simple and compact structures, and the balance cavity and the balance piston are arranged, so that the hydraulic oil cylinder can be connected with the balance oil pipe through the oil port connected with the balance cavity under the condition that the working oil way is unloaded, the heavy-load bearing function of mutual balance among a plurality of hydraulic oil cylinders is realized, the height difference on the structural connection of each hydraulic oil cylinder is adapted, and the self safety of the hydraulic oil cylinder and the safety of the self-elevating platform are ensured. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. A hydraulic cylinder, comprising: the balance piston and the working piston divide the interior of the shell into a balance cavity, a rodless cavity and a rod cavity, the piston rod is arranged in the rod cavity and is connected with the working piston, a limiting part for stopping is arranged between the balance piston and the working piston on the shell, oil ports which are respectively communicated with the balance cavity, the rodless cavity and the rod cavity are also arranged on the shell, an oil hole which is used for communicating the balance cavity with the rodless cavity is arranged on the balance piston, and a check valve component which is used for supplying hydraulic oil to flow from the rodless cavity to the balance cavity is arranged in the oil hole; when the piston rod retracts to abut against the balance piston, the balance piston moves towards the balance cavity, and hydraulic oil in the balance cavity is discharged through an oil port communicated with the balance cavity; when the piston rod retracts and does not abut against the balance piston, the oil port communicated with the balance cavity supplies hydraulic oil to flow into the balance cavity.
2. A hydraulic ram according to claim 1 wherein: and a return spring for returning the balance piston is arranged in the balance cavity.
3. A hydraulic ram according to claim 1 wherein: the shell comprises a cylinder barrel, a rear end cover and a front end cover, the rear end cover and the front end cover are connected to the two ends of the cylinder barrel, the piston rod extends out of the front end cover, and the balance cavity is formed by the rear end cover and the balance piston.
4. A hydraulic ram according to claim 3, wherein: the rear end cover is provided with a connecting portion with the cylinder barrel, the connecting portion is provided with a sleeve ring, the sleeve ring is provided with a protruding portion extending towards the balance cavity and the rodless cavity, and the protruding portion forms the limiting portion.
5. A hydraulic ram according to claim 3, wherein: the oil port communicated with the rod cavity is positioned on the front end cover, and the two oil ports respectively communicated with the balance cavity and the rodless cavity are positioned on the rear end cover.
6. The hydraulic oil cylinder according to claim 1, characterized in that a pressure maintaining component for maintaining the pressure of the balance cavity is arranged in the oil hole, the pressure maintaining component comprises a pressure maintaining valve sleeve and a pressure maintaining valve core, the pressure maintaining valve sleeve is positioned in the oil hole, a plug head of the pressure maintaining valve sleeve is arranged at the end part of the oil hole facing the rodless cavity, the pressure maintaining valve core is arranged in the pressure maintaining valve sleeve and provided with a matched sealing part between the pressure maintaining valve sleeve and the plug head, a pressure maintaining spring for maintaining the sealing between the pressure maintaining valve core and the pressure maintaining valve sleeve is arranged between the pressure maintaining valve core and the plug head, an oil passing hole is arranged on the pressure maintaining valve core, and the check valve component is arranged in.
7. The hydraulic oil cylinder as claimed in claim 6, wherein a sealing platform part is arranged on the inner wall of the pressure maintaining valve sleeve, the pressure maintaining valve core is provided with a sealing cone part, and the sealing platform part and the sealing cone part are matched and sealed to form the sealing part.
8. The hydraulic cylinder as claimed in claim 6, wherein said check valve assembly includes a check valve sleeve and a check valve core, said oil passing hole has a large hole portion with a large diameter, the check valve sleeve is fixed in one end of the large hole portion, the check valve core is located at the other end of the large hole portion, and the check valve core can seal the check valve sleeve.
9. The hydraulic ram of claim 8, wherein the check valve spool is a ball.
10. A load balancing device comprising at least two hydraulic rams as claimed in any one of claims 1 to 9, the ports of all the hydraulic rams communicating with the balance chamber being connected by balance oil lines.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811593905.9A CN109707693B (en) | 2018-12-25 | 2018-12-25 | Hydraulic oil cylinder and load balancing device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811593905.9A CN109707693B (en) | 2018-12-25 | 2018-12-25 | Hydraulic oil cylinder and load balancing device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109707693A CN109707693A (en) | 2019-05-03 |
| CN109707693B true CN109707693B (en) | 2020-09-18 |
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ID=66258080
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811593905.9A Active CN109707693B (en) | 2018-12-25 | 2018-12-25 | Hydraulic oil cylinder and load balancing device |
Country Status (1)
| Country | Link |
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| CN (1) | CN109707693B (en) |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2031790C3 (en) * | 1970-06-26 | 1975-12-04 | Alfred Dipl.-Ing. 4046 Buettgen Heitner | Double-acting, pneumatically operated working cylinder |
| US4397218A (en) * | 1980-12-23 | 1983-08-09 | Allis-Chalmers Corporation | Cushion stop for hydraulic cylinder |
| DE102010006117B3 (en) * | 2010-01-29 | 2011-06-16 | Stabilus Gmbh | Piston-cylinder assembly |
| CN103994117B (en) * | 2014-05-16 | 2016-07-06 | 中联重科股份有限公司 | Hydraulic jack and concrete pumping equipment |
| CN204113807U (en) * | 2014-09-29 | 2015-01-21 | 湖南协力液压有限公司 | A kind of concrete transfer pump main oil cylinder |
| CN104295557B (en) * | 2014-10-09 | 2016-08-17 | 徐州重型机械有限公司 | A kind of middle position locking oil cylinder and engineering truck |
| CN207634435U (en) * | 2017-11-22 | 2018-07-20 | 倪德忠 | Automatic reciprocating cylinder |
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2018
- 2018-12-25 CN CN201811593905.9A patent/CN109707693B/en active Active
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