Hydraulic Cylinder Split Bushing for Pressure-Compensated Rod Sealing
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Solution Overview
Problem
Existing hydraulic cylinders face challenges in minimizing device technology outlay while maintaining a low-friction sealing system between the piston rod and guiding components, especially under increasing pressure, which requires dimensionally stable materials or large radial expansion to prevent split sleeve widening.
Innovation Solution
A hydraulic cylinder design featuring a split sleeve with radial play in the cylinder housing, forming a fluidically connected annular gap, and a seal positioned at an axial distance from the pressure chamber end face to generate inward counteracting forces, reducing radial forces on the split sleeve and allowing for pressure-force compensation, thus minimizing mechanical stress and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a split sleeve is used to seal the piston rod with precise fit, then sealing effectiveness is improved, but radial forces on the split sleeve increase with pressure causing widening and fit degradation
Solution Approach 1:
The cylinder housing is segmented into multiple sections: a first section with a smaller inner diameter that contacts the piston rod, and a second section with a larger inner diameter that receives the split sleeve with radial play. This segmentation allows the piston rod to be supported in a low-friction zone while the split sleeve operates in a pressure-compensated zone, separating the guiding function from the sealing function to reduce radial forces on the split sleeve.
Solution Approach 2:
A radial projection is introduced as an intermediary element between the piston rod and the split sleeve. This radial projection supports the piston rod and absorbs radial forces, preventing direct transmission of pressure-induced radial forces to the split sleeve. The intermediary structure allows the split sleeve to maintain sealing effectiveness without experiencing excessive radial loading.
2Stability of the object's composition
If dimensionally stable materials or large radial expansion are used for the split sleeve, then pressure resistance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The system uses the working pressure from the pressure chamber to generate counteracting forces on the split sleeve through the fluidically connected annular gap. The pressure differential created across the split sleeve automatically compensates for radial expansion tendencies, making the split sleeve self-regulating and pressure-force-compensated without requiring specialized dimensionally stable materials or complex pre-tensioning mechanisms.
Solution Approach 2:
The invention changes the operational parameters of the split sleeve by introducing radial play and positioning it in a second section with larger inner diameter. This parameter change allows the split sleeve to operate in a regime where pressure forces are balanced, reducing the requirement for high dimensional stability materials and simplifying manufacturing while maintaining sealing effectiveness under pressure.
3Adaptability or versatility
If the split sleeve is inserted with radial play in the cylinder housing, then accommodation of positional deviations is improved, but friction and pressure losses increase
Solution Approach 1:
The cylinder housing is divided into two functional sections: the first section provides precise guiding with minimal radial clearance to reduce friction, while the second section accommodates the split sleeve with radial play to tolerate positional deviations. This segmentation allows the system to benefit from both low friction (in the first section) and high adaptability (in the second section) simultaneously.
Solution Approach 2:
The radial projection acts as an intermediary that transfers the piston rod between the low-friction first section and the adaptive second section. This intermediary structure enables the piston rod to move smoothly through the first section with minimal friction while allowing the split sleeve in the second section to accommodate positional deviations without generating excessive friction or pressure losses.
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 a mechanically relieved split sleeve with reduced friction and pressure independence, enabling efficient sealing and guiding of the piston rod with minimal device complexity, accommodating positional deviations and maintaining sealing effectiveness under varying pressures.
Implementation Method 1
the working pressure of the pressure chamber can generate radially inward counteracting forces on the gap sleeve at a section of the outer circumference extending from the pressure chamber to the seal
Implementation Method 2
a seal is arranged on the outer circumference of the gap sleeve
Data Source
Figure 1~2
AI summary
A hydraulic cylinder having a piston rod is disclosed, said piston rod being surrounded by an annular pressure chamber and being guided in a through-aperture in the hydraulic cylinder. A split bushing forms a split seal with the piston rod over a particular axial length and in a precise fit with the piston rod. A first circular-cylindrical annular gap is formed on the outer circumference of the split bushing, with the result that the split bushing is inserted into the hydraulic cylinder with radial play. The annular gap is fluidically connected to the pressure chamber. A seal is arranged on the outer circumference of the split bushing and is at an axial distance from a first end side, facing the pressure chamber, of the split bushing. As a result, the working pressure of the pressure chamber can apply counter-pressures that are directed radially inwards to the split bushing, over a section of the outer circumference that extends from the pressure chamber to the seal, said counter-pressures counteracting the forces that are directed radially outwards and arise in the split seal. Thus, the split bushing is relieved of mechanical loads.