High-Pressure Valve Actuation Using a Planetary Roller Screw
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Solution Overview
Problem
High-pressure control valves in polyethylene production systems face challenges in achieving precise control and low maintenance due to the limitations of pneumatic drive systems, including low energetic density, compressibility, and synchronization issues between dual drives, which affect control accuracy and lead to increased wear and potential cold welding.
Innovation Solution
A high-pressure control valve with a pneumatic drive unit and a screw drive designed as a gearbox, featuring a planetary roller screw drive that translates driving force into high output force and reduces travel range, decoupling the drive and valve spindle, and using a primary transmission to enhance load capacity and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If pneumatic drive systems are used for high-pressure valve control, then the system can utilize available pneumatic auxiliary energy, but the control accuracy deteriorates due to air compressibility and large required actuating surfaces
Solution Approach 1:
The patent replaces the direct pneumatic actuation system with a mechanical screw drive system (ball screw or planetary roller screw) that is actuated by a smaller pneumatic motor. This substitution allows the use of pneumatic energy while eliminating the problems of air compressibility and large actuating surfaces, as the mechanical transmission provides precise positioning and the pneumatic motor only needs to overcome friction losses.
Solution Approach 2:
The patent introduces a mechanical transmission system (screw drive) as an intermediary between the pneumatic drive and the valve spindle. This intermediary mechanism converts the rotational motion of the pneumatic motor into precise linear motion of the valve spindle, while the mechanical advantage of the screw drive allows small pneumatic forces to generate large output forces with high precision.
2Force
If large pneumatic actuating surfaces are used to achieve necessary actuating forces, then sufficient force is available, but the stroke size increases which contradicts the requirement for small control stroke
Solution Approach 1:
The patent replaces direct pneumatic actuation with a mechanical screw drive system that provides mechanical advantage. The screw drive converts small rotational movements of the pneumatic motor into large linear forces with minimal stroke, enabling high actuating forces to be generated without requiring large pneumatic actuating surfaces or large strokes.
Solution Approach 2:
The patent changes the mechanical parameters of the transmission system by using high-lead screws or planetary roller screw mechanisms with favorable gear ratios. This allows the system to achieve high output forces with small input strokes by optimizing the mechanical advantage ratio, thereby decoupling the relationship between actuating force and stroke size.
3Measurement precision
If dual pneumatic actuators with lever linkages are used to achieve precise control, then control capability is improved, but synchronization issues arise that affect control accuracy
Solution Approach 1:
The patent merges the functions of multiple actuators into a single pneumatic motor that drives a common screw mechanism. This eliminates the synchronization problems between multiple actuators, as the single motor naturally ensures coordinated motion. The mechanical screw drive inherently couples the motion transmission, providing automatic synchronization without requiring complex control coordination between multiple independent actuators.
4Force
If threaded drive with large travel range is used, then actuating capability is sufficient, but control accuracy deteriorates due to excessive travel distance
Solution Approach 1:
The patent optimizes the mechanical parameters of the screw drive by selecting appropriate lead values, gear ratios, and transmission ratios. These parameter changes allow the system to achieve the required actuating capability while minimizing the travel distance of the valve spindle. The mechanical advantage of the screw drive enables large forces to be generated with small displacements, improving control accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design achieves precise control with reduced maintenance, increased load capacity, and improved mechanical safety, allowing for accurate operation in high-pressure environments while minimizing disturbances and wear, and eliminating the need for a ball screw, thus enhancing control accuracy and safety.
Implementation Method 1
a screw drive (11) designed as a gearbox (17), wherein the drive side (15) of the screw drive (11) is coupled to the drive unit (10) to initiate a rotary drive movement and the output side (16) of the screw drive (11) can be connected to the valve (200) to transmit a translational output movement
Implementation Method 2
featuring a planetary roller screw drive that translates driving force into high output force and reduces travel range
Data Source
Figure 1
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AI summary
The present invention relates to an apparatus for actuating a valve for a high-pressure system, in particular for a system for producing polyethylene, said apparatus including a pneumatic drive unit (10) and a threaded drive (11) which has a housing (12), a spindle (13) and a spindle nut (14). The drive side (15) of the threaded drive (11) is coupled to the drive unit (10) for introducing a rotational driving movement, the output side (16) of the threaded drive (11) is connectable to the valve for transmitting a translational output movement, the threaded drive (11) forming a transmission (17) which converts the drive force of the drive unit (10) into an output force of the threaded drive (11) for actuating the valve.