CN111089550A - Ultrasonic synchronous detection method for film thickness and deformation distribution of plastic tile thrust bearing - Google Patents
Ultrasonic synchronous detection method for film thickness and deformation distribution of plastic tile thrust bearing Download PDFInfo
- Publication number
- CN111089550A CN111089550A CN202010056088.4A CN202010056088A CN111089550A CN 111089550 A CN111089550 A CN 111089550A CN 202010056088 A CN202010056088 A CN 202010056088A CN 111089550 A CN111089550 A CN 111089550A
- Authority
- CN
- China
- Prior art keywords
- thrust bearing
- plastic tile
- film thickness
- deformation
- tile thrust
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
- G01B17/02—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring thickness
- G01B17/025—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring thickness for measuring thickness of coating
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
- G01B17/04—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring the deformation in a solid, e.g. by vibrating string
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices Characterised By Use Of Acoustic Means (AREA)
Abstract
The invention discloses an ultrasonic synchronous detection method for the film thickness and deformation distribution of a plastic tile thrust bearing. The method has the advantages that the thickness information of the lubricating film layer and the deformation information of the plastic tile thrust bearing coating layer are reflected in different characteristics of ultrasonic waves in the interface reflection signals of the plastic tile thrust bearing and the lubricating layer, the film thickness and the deformation information of the plastic tile thrust bearing measuring point are obtained by respectively utilizing an ultrasonic phase film thickness measuring method and an ultrasonic flight time deformation measuring method, synchronous measurement of the film thickness and the deformation distribution of the plastic tile thrust bearing is achieved, an effective detection means can be provided for revealing the lubricating mechanism of the plastic tile thrust bearing, and meanwhile, an excellent online monitoring means is provided for monitoring the operating state of the large-sized plastic tile thrust bearing.
Description
Technical Field
The invention belongs to the technical field of lubrication state detection, and particularly relates to an ultrasonic synchronous detection method for the film thickness and deformation distribution of a plastic tile thrust bearing.
Background
The thrust bearing has the characteristics of high running precision, large impact load bearing capacity, long service life and the like, is particularly suitable for occasions of high speed, precision, heavy load and the like, has very wide application, and particularly becomes one of key core components in important equipment such as large thermal power, hydroelectric generating sets, nuclear power station main circulating pumps and the like. In order to improve the friction performance of the thrust bearing, a layer of wear-resistant material is generally poured on the surface of the bearing shell. The novel polymer composite material such as Polytetrafluoroethylene (PTFE) and polyether ether ketone (PEEK) has the characteristics of high allowable unit pressure, small friction coefficient and good wear resistance and corrosion resistance, so that the novel polymer composite material gradually replaces the traditional bus alloy as a thrust bearing surface coating material at present, and obtains good engineering application effect in a large-scale water turbine generator set.
The special elastic structure of the plastic tile and the high polymer tile surface material different from the metal material bring many advantages to the engineering application of the plastic tile bearing, but also bring many new problems to the lubrication theory and the application. For example, surface slip phenomenon due to poor surface adhesion of high molecular polymer material, complex elastic deformation due to low elastic modulus, and irregular thermal deformation due to poor thermal conductivity. These characteristics lead to the lubrication film mechanism of plastic shoe bearings being quite different from that of conventional metal bearings, and becoming quite complicated. Although the novel plastic tile bearing has the history of nearly fifty years since the first appearance of 1969, the lubrication mechanism of the novel plastic tile bearing is not really mastered, and the serious accidents caused by tile burning of the plastic tiles in engineering application still occur. The power station such as the Gezhou dam and the enlargement has a vicious accident of tile burning of plastic tiles in the starting process of the unit, and the hydraulic junction at the bottom of the small waves of the yellow river has a unit vibration accident caused by the plastic tiles when the unit is started.
The limitation of the theoretical research on the lubricating mechanism of the plastic tile thrust bearing calls for the supplement and verification of the experimental detection. At present, the lubrication mechanism research of the plastic tile thrust bearing is mainly based on theoretical simulation, more theoretical models are used for analyzing the lubrication performance of the novel thrust bearing under different structures and different working conditions at home and abroad, and some interesting results are obtained. For example: when the thrust bearing bears larger pressure, a key parameter for representing the lubricating performance of the thrust bearing, namely the phenomenon of necking when the thickness of a lubricating film is distributed at an oil outlet and is similar to that under the condition of classical elastohydrodynamic lubrication. However, these interesting phenomena have not been experimentally confirmed due to the lack of effective detection means. In addition, some assumed conditions usually exist in theoretical research and partial simplification is performed on the actual situation, so that deviation is undoubtedly introduced, and the accuracy of a theoretical model needs to be verified by experimental detection. Therefore, an online detection method is developed, can be used for experimental verification and supplement of lubrication theory research of the plastic tile bearing, and has very obvious significance.
The complexity of the lubrication mechanism requires experimental testing to provide multidimensional information. The traditional babbitt metal bush thrust bearing can be regarded as rigid or slightly elastically deformed in the actual operation process due to the fact that the traditional babbitt metal bush thrust bearing has a large elastic modulus, the plastic bush thrust bearing is a special elastic structure due to the fact that the plastic bush thrust bearing is provided with the bronze wire mesh layer and the plastic coating layer, obvious elastic deformation can occur in the maximum difference from the traditional babbitt metal bush thrust bearing in the actual operation, and the film thickness distribution in the operation is the result of the combined action of fluid dynamic pressure and elastic deformation of a bearing bush. In order to accurately reveal the lubrication mechanism of the plastic pad thrust bearing, the film thickness distribution and the elastic deformation distribution information need to be provided at the same time.
In order to make up the defects of the prior art, the invention aims to provide a detection technology capable of synchronously detecting the surface elastic deformation and the lubricating film thickness distribution in the operation process of the plastic tile thrust bearing in real time. The invention not only can provide an excellent detection means for the demonstration and correction of the theoretical research of the lubrication mechanism of the plastic tile thrust bearing, but also can be used for monitoring the lubrication state of large-scale rotating equipment in real time by developing the formed related detection technology, thereby ensuring the safe and reliable operation of the equipment.
Disclosure of Invention
The invention aims to provide an ultrasonic synchronous detection method for the thickness distribution and the elastic deformation distribution of a plastic tile thrust bearing lubricating film, provides an excellent detection means for the demonstration and correction of the theoretical research of the lubricating mechanism of the plastic tile thrust bearing, and can be used for monitoring the lubricating state of large-scale rotating equipment in real time and ensuring the safe and reliable operation of the equipment.
In order to achieve the purpose, the ultrasonic synchronous detection method for the thickness distribution and the elastic deformation distribution of the lubricating film of the plastic tile thrust bearing comprises the following steps of:
the method comprises the following steps: an ultrasonic sensor is embedded at each optimized measuring point of the back of the plastic tile thrust bearing tile;
step two: synchronously obtaining the film thickness and the deformation of the plastic tile thrust bearing by utilizing reflected signals of ultrasonic waves at each interface of the plastic tile thrust bearing;
step three: and (3) obtaining the film thickness and deformation distribution of the plastic tile thrust bearing by interpolation algorithm according to the film thickness and deformation information obtained at each measuring point.
The determination method of the plastic tile thrust bearing tile back optimized measuring point position in the first step comprises the following steps: and solving through a three-dimensional energy equation of the simultaneous plastic tile thrust bearing, a Reynolds equation for counting slippage, a heat conduction equation of the bearing bush and a thermoelastic deformation equation of the bearing bush to obtain theoretical pressure, film thickness, temperature and deformation distribution information of the plastic tile thrust bearing under different working conditions. And determining the number and the positions of the optimized measuring points according to the theoretical pressure, the film thickness, the temperature and the deformation distribution information.
And in the second step, the film thickness and the deformation of the plastic tile thrust bearing are synchronously obtained by utilizing the reflected signals of the ultrasonic waves at each interface of the plastic tile thrust bearing, and the method specifically comprises the following steps: obtaining the film thickness value of the plastic tile thrust bearing through the phase spectrum of the ultrasonic wave reflected signal at the interface of the plastic tile thrust bearing and the lubricating layer; and the deformation of the measuring point of the plastic tile thrust bearing is obtained through the variation of the flight time of the ultrasonic waves in the plastic tile coating layer under the loaded and unloaded working conditions.
In the second step, the method for obtaining the film thickness of the plastic tile thrust bearing by using the reflected signal of the ultrasonic wave at the interface of the plastic tile thrust bearing and the lubricating layer comprises the following steps: the complicated metal wire mesh structure of the plastic tile thrust bearing causes that the reflection signals of ultrasonic waves in the plastic tile thrust bearing are very complicated, the reflection signals can be overlapped, the overlapped ultrasonic wave reflection signals are equivalent to the superposition of a plurality of Gaussian echo signals, the overlapped ultrasonic wave signals are separated by using a matching tracking algorithm to obtain the reflection signals of the ultrasonic waves at the interface of the plastic tile thrust bearing and a lubricating layer, and the thickness value of the lubricating film of the measuring point is obtained by using the existing ultrasonic film thickness measuring method through the phase spectrum of the reflection signals at the interface of the plastic tile thrust bearing and the lubricating layer.
In the second step, the method for obtaining the deformation of the plastic tile by using the reflected signals of the ultrasonic waves at each interface of the plastic tile thrust bearing comprises the following steps: the method comprises the steps of conducting Hilbert change on reflected signals of ultrasonic waves under the working conditions of loading and unloading on the interface of a plastic tile thrust bearing and a lubricating film, constructing analytic signals, solving the mode of the analytic signals to obtain envelope signals of the reflected signals, removing flight time variation caused by phase change of the reflected signals on the lubricating film, conducting cross-correlation analysis on the envelope signals of the loaded and unloaded reflected signals, obtaining the variation of flight time of the ultrasonic waves in a coating under the working conditions of loading and unloading, and obtaining elastic deformation at a measuring point according to the relation between deformation and the flight time variation.
The measuring method for improving the measurement accuracy of the elastic deformation in the second step comprises the following steps: the obtained reflection signal is converted by Hilbert to obtain an envelope signal of the reflection signal, and 100 point linear interpolation is carried out on every two points of the envelope signal data to obtain a more high-precision envelope signal;
the method for obtaining the film thickness distribution of the plastic tile thrust bearing in the third step comprises the following steps: and the measured film thickness value of each measuring point obtains the film thickness and deformation distribution of the plastic tile thrust bearing through an interpolation fitting algorithm.
Compared with the prior art, the ultrasonic wave sensor is embedded on the back of the plastic tile thrust bearing tile, complex reflection signals of ultrasonic waves on each interface of the plastic tile thrust bearing are collected under the excitation of the ultrasonic wave pulse transmitting and receiving instrument, the obtained complex reflection signals are equivalent to superposition of a plurality of Gaussian echoes, the reflection signals of the ultrasonic waves on the interfaces of the plastic tile thrust bearing and a lubricating film are obtained by using a matching tracking algorithm, the film thickness value of a measuring point is obtained through phase information of the reflection signals, the deformation value of the measuring point is obtained through the flight time difference of the reflection signals under the loading and non-loading working conditions, and the ultrasonic synchronous detection of the film thickness and the deformation of the plastic tile thrust bearing is realized.
The invention skillfully utilizes the characteristic that the thickness information of the lubricating film layer and the deformation information of the plastic tile thrust bearing coating layer are reflected in different characteristics of ultrasonic waves in reflected signals of the plastic tile thrust bearing and the lubricating layer interface, the lubricating film thickness information is reflected in the phase change of the reflected signals, and the deformation information is reflected in the change quantity of the flight time of the reflected signals, and respectively utilizes an ultrasonic phase film thickness measuring method and an ultrasonic flight time deformation measuring method to obtain the film thickness and the deformation information at the measuring point of the plastic tile thrust bearing, thereby realizing the synchronous measurement of the film thickness and the deformation distribution of the plastic tile thrust bearing, providing an effective detection means for the disclosure of the lubricating mechanism of the plastic tile thrust bearing, and simultaneously providing an excellent on-line monitoring means for the monitoring of the carrying state of the large-scale plastic tile thrust bearing.
Description of the drawings:
FIG. 1 is a schematic diagram of ultrasonic synchronous detection principle of plastic tile thrust bearing film thickness and deformation distribution
FIG. 2 is a schematic view of the distribution of ultrasonic sensors used
FIG. 3 is a graph showing the superimposed reflected signals of ultrasonic waves on a plastic pad thrust bearing on a lubricating layer
Figure 4 plastic tile thrust bearing experiment table
Detailed Description
The invention will be further explained with reference to the drawings.
Referring to fig. 1, a specific embodiment of an ultrasonic synchronous detection method for the thickness and deformation distribution of a plastic pad thrust bearing lubricating film is as follows: an ultrasonic sensor (shown in figure 2) is embedded at an optimized measuring point position on the back of the plastic tile thrust bearing bush, and a complex reflected signal (shown in figure 3) of ultrasonic waves on the plastic tile thrust bearing is collected and transmitted to a PC (personal computer) for post-processing; the overlapped reflection signals are equivalent to superposition of a plurality of Gaussian echoes, reflection signals of ultrasonic waves at the interface of the plastic tile thrust bearing and the lubricating layer are obtained through a matching tracking algorithm, the phase information of the reflection signals of the ultrasonic waves at the interface of the plastic tile thrust bearing and the lubricating film is utilized, the film thickness value of the lubricating layer is obtained according to an ultrasonic phase film thickness measuring method, and deformation information of a measuring point is obtained according to the change of the flight time of the ultrasonic waves in the coating layer of the plastic tile thrust bearing when the plastic tile thrust bearing is loaded or unloaded; and obtaining the film thickness and deformation distribution of the plastic tile thrust bearing under different working conditions by utilizing the film thickness and deformation information of each optimized measuring point and by interpolation fitting.
Example (b):
taking a polymer thrust bearing with the inner diameter of 70mm and the outer diameter of 150mm as an example, an ultrasonic sensor is embedded at an optimized position of a measuring point on the back surface of a substrate, the bearing is used for a thrust bearing simulation experiment table (as shown in fig. 4), the film thickness and the deformation value of each measuring point are synchronously obtained through reflected signals of ultrasonic waves in the plastic tile thrust bearing, and the film thickness and deformation distribution information of the plastic tile thrust bearing under different working conditions is obtained through a three-dimensional imaging interpolation technology.
Claims (7)
1. An ultrasonic synchronous detection method for the thickness distribution and elastic deformation distribution of a plastic tile thrust bearing lubricating film is characterized by comprising the following steps:
the method comprises the following steps: an ultrasonic sensor is embedded at each optimized measuring point of the back of the plastic tile thrust bearing tile;
step two: and synchronously obtaining the film thickness and the deformation of the plastic tile thrust bearing by utilizing the reflected signals of the ultrasonic waves at each interface of the plastic tile thrust bearing.
Step three: and (3) obtaining the film thickness and deformation distribution of the plastic tile thrust bearing by interpolation algorithm according to the film thickness and deformation information obtained at each measuring point.
2. The ultrasonic synchronous detection method for the film thickness and the deformation distribution of the lubricating film of the plastic tile thrust bearing as recited in claim 1, wherein the determination manner of the optimized measuring point position of the plastic tile thrust bearing back in the first step is as follows: and solving through a three-dimensional energy equation of the simultaneous plastic tile thrust bearing, a Reynolds equation for counting slippage, a heat conduction equation of the bearing bush and a thermoelastic deformation equation of the bearing bush to obtain theoretical pressure, film thickness, temperature and deformation distribution information of the plastic tile thrust bearing under different working conditions. And determining the number and the positions of the optimized measuring points according to the theoretical pressure, the film thickness, the temperature and the deformation distribution information.
3. The ultrasonic synchronous detection method for the film thickness and deformation distribution of the lubricating film of the plastic tile thrust bearing as recited in claim 1, wherein in the second step, the film thickness and deformation of the plastic tile thrust bearing are synchronously obtained by utilizing the reflected signals of the ultrasonic waves at each interface of the plastic tile thrust bearing, specifically: the film thickness value of the plastic tile thrust bearing is obtained through phase information of signals reflected by ultrasonic waves at the interface of the plastic tile thrust bearing and the lubricating layer; and the deformation of the measuring point of the plastic tile thrust bearing is obtained through the variation of the flight time of the ultrasonic waves in the plastic tile coating layer under the loaded and unloaded working conditions.
4. The ultrasonic synchronous detection method for the film thickness and the deformation distribution of the lubricating film of the plastic tile thrust bearing as recited in claim 1, wherein the method for obtaining the film thickness of the plastic tile thrust bearing by using the reflected signal of the ultrasonic wave at the interface of the plastic tile thrust bearing and the lubricating layer in the second step comprises the following steps: the complicated metal wire mesh structure of the plastic tile thrust bearing causes that the reflection signals of ultrasonic waves in the plastic tile thrust bearing are very complicated, the reflection signals can be overlapped, the overlapped ultrasonic wave reflection signals are equivalent to the superposition of a plurality of Gaussian echo signals, the overlapped ultrasonic wave signals are separated by using a matching tracking algorithm to obtain the reflection signals of the ultrasonic waves at the interface of the plastic tile thrust bearing and a lubricating layer, and the thickness value of the lubricating film at the measuring point is obtained by using the conventional ultrasonic wave phase film thickness measuring method through the phase information of the reflection signals at the interface of the plastic tile thrust bearing and the lubricating layer.
5. The ultrasonic synchronous detection method for the film thickness and the deformation distribution of the lubricating film of the plastic tile thrust bearing as claimed in claim 1, wherein the method for obtaining the deformation of the plastic tile by using the reflected signals of the ultrasonic waves at each interface of the plastic tile thrust bearing in the second step comprises the following steps: the method comprises the steps of conducting Hilbert change on reflected signals of ultrasonic waves under the working conditions of loading and unloading on the interface of a plastic tile thrust bearing and a lubricating film, constructing analytic signals, solving the mode of the analytic signals to obtain envelope signals of the reflected signals, removing flight time variation caused by phase change of the reflected signals on the lubricating film, conducting cross-correlation analysis on the envelope signals of the loaded and unloaded reflected signals, obtaining the variation of flight time of the ultrasonic waves in a coating under the working conditions of loading and unloading, and obtaining elastic deformation at a measuring point according to the relation between deformation and the flight time variation.
6. The ultrasonic synchronous detection method for the film thickness and the deformation distribution of the lubricating film of the plastic tile thrust bearing as claimed in claim 1, wherein the measurement method for improving the measurement accuracy of the elastic deformation in the second step comprises the following steps: and (3) the obtained reflection signal is subjected to Hilbert transform to obtain an envelope signal of the reflection signal, and 100 point linear interpolation is carried out on every two points of the envelope signal data to obtain a more high-precision envelope signal.
7. The ultrasonic synchronous detection method for the film thickness and the deformation distribution of the lubricating film of the plastic tile thrust bearing as recited in claim 1, wherein the method for obtaining the film thickness distribution of the plastic tile thrust bearing in the third step comprises: and the actual measurement film thickness value and the deformation value of each measurement point are subjected to interpolation fitting to obtain the film thickness and deformation distribution of the plastic tile thrust bearing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010056088.4A CN111089550A (en) | 2020-01-18 | 2020-01-18 | Ultrasonic synchronous detection method for film thickness and deformation distribution of plastic tile thrust bearing |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010056088.4A CN111089550A (en) | 2020-01-18 | 2020-01-18 | Ultrasonic synchronous detection method for film thickness and deformation distribution of plastic tile thrust bearing |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN111089550A true CN111089550A (en) | 2020-05-01 |
Family
ID=70399598
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010056088.4A Pending CN111089550A (en) | 2020-01-18 | 2020-01-18 | Ultrasonic synchronous detection method for film thickness and deformation distribution of plastic tile thrust bearing |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111089550A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113848060A (en) * | 2021-09-27 | 2021-12-28 | 中国石油大学(华东) | Device and measurement system for dynamically measuring oil film cavitation area of sliding bearing |
-
2020
- 2020-01-18 CN CN202010056088.4A patent/CN111089550A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113848060A (en) * | 2021-09-27 | 2021-12-28 | 中国石油大学(华东) | Device and measurement system for dynamically measuring oil film cavitation area of sliding bearing |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Dazin et al. | Transient behavior of turbomachineries: applications to radial flow pump startups | |
| Wang et al. | Experimental research on film pressure distribution of water-lubricated rubber bearing with multiaxial grooves | |
| Wolfram et al. | On the estimation of Morison force coefficients and their predictive accuracy for very rough circular cylinders | |
| Cencîc et al. | Study of erosive cavitation detection in pump mode of pump–storage hydropower plant prototype | |
| Niknam et al. | Analysis of acoustic emission data for bearings subject to unbalance | |
| Bianchini et al. | A systematic approach to estimate the impact of the aerodynamic force induced by rotating stall in a vaneless diffuser on the rotordynamic behavior of centrifugal compressors | |
| Wei et al. | Online monitoring of oil film thickness of journal bearing in aviation fuel gear pump | |
| Arghir et al. | A new structural bump foil model with application from start-up to full operating conditions | |
| Howard et al. | A new analysis tool assessment for rotordynamic modeling of gas foil bearings | |
| Ouyang et al. | Experimental study on the distributed lubrication characteristics of full-size water-lubricated stern bearings under hull deformation | |
| Tallman et al. | Heat transfer measurements and predictions for a modern, high-pressure, transonic turbine, including endwalls | |
| CN111089550A (en) | Ultrasonic synchronous detection method for film thickness and deformation distribution of plastic tile thrust bearing | |
| Khan et al. | Numerical investigation of propeller-ice interaction effects | |
| Bajic | Multidimensional diagnostics of turbine cavitation | |
| Yang | Condition monitoring the drive train of a direct drive permanent magnet wind turbine using generator electrical signals | |
| Zeng et al. | Resonance risk assessment method on a storage pump’s centrifugal impeller by considering the hydrodynamic damping ratio | |
| Jang et al. | On the relationship between journal misalignment and web deflection in crankshafts | |
| Xu et al. | Modeling and simulation of aero-hydraulic pump wear failure | |
| Yan-chao et al. | Experimental investigation on friction and wear performance of C/C composite finger seal | |
| Abdel Fatah et al. | Health monitoring of centrifugal pumps using digital models | |
| Myrent et al. | Wind turbine blade shear web disbond detection using rotor blade operational sensing and data analysis | |
| Wang et al. | Research on wireless nondestructive monitoring method for film pressure of water-lubricated bearing | |
| Su et al. | Numerical and experimental investigations on the hydrodynamic performance of a tidal current turbine | |
| Meng et al. | Simulation analysis and experimental verification of tribodynamics of reciprocating friction pairs in low-speed marine engines | |
| Ma et al. | An in-situ measurement approach for the oil film characteristics of the spherical valve plate pair in axial piston pumps |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |