Spherical Joint Ending Rotational Surface for Hydrostatic Piston Machines
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Solution Overview
Problem
Existing hydrostatic piston machine joint couplings face high contact pressure and manufacturing costs due to strict tolerance requirements, and suffer from edge effects and increased stress at varying angles of inclination, leading to potential damage and inefficiency.
Innovation Solution
A spherical joint design featuring a ball pivot with a continuously connected ending rotational surface, formed by rotating a generating line around the symmetry axis, which reduces contact pressure and eliminates edge effects by allowing increased radial clearance and curvature, and an optional deformable end wall that adjusts the contact area under load, maintaining efficient force transmission across varying angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If strict tolerance requirements are applied to spherical surfaces of ball pivot and ball recess, then contact pressure is minimized, but manufacturing costs increase significantly
Solution Approach 1:
The patent applies a conical surface continuously connected to the spherical surface, creating a smooth curvature transition that distributes contact pressure across a larger area. This geometric modification reduces the need for strict spherical tolerance while maintaining low contact pressure, thereby reducing manufacturing costs.
Solution Approach 2:
The patent introduces a conical surface with a specific angle (α) between 10° and 30° to modify the contact geometry. This parameter change transforms the contact from a sharp edge to a distributed area, reducing contact pressure without requiring ultra-precise spherical tolerances.
2Adaptability or versatility
If ball pivot ends at a planar surface and ball recess ends at a rotational recess, then fluid circulation is permitted, but contact loads concentrate on edges causing high stress and potential damage
Solution Approach 1:
The continuous conical surface connects the spherical contact surface to the planar ending surface, eliminating the sharp edge where the spherical surface would otherwise terminate. This curvature transition distributes the contact load across the conical surface area, preventing stress concentration while maintaining fluid circulation capability.
Solution Approach 2:
The patent applies different surface geometries in different zones: a spherical surface for optimal contact, a conical transition zone for stress distribution, and a planar surface for fluid circulation. This localized quality variation resolves the contradiction between fluid circulation and load resistance.
3Stress or pressure
If conical surface is added to ball recess bottom, then contact pressure is partially decreased, but accuracy requirements and manufacturing costs remain as high as strict tolerance arrangements
Solution Approach 1:
The patent specifies a conical angle (α) between 10° and 30°, which optimizes the transition from spherical to planar surface. This parameter range ensures adequate contact pressure distribution while being manufacturable with standard precision, avoiding the need for ultra-precise spherical tolerances.
Solution Approach 2:
The continuous conical surface provides a smooth geometric transition that naturally distributes contact pressure. This curvature-based solution achieves pressure reduction through geometry rather than relying solely on tight dimensional tolerances, thereby reducing manufacturing precision requirements.
4Adaptability or versatility
If angle of inclination between slipper axis and piston axis increases, then adaptability is improved, but axial force becomes off-centred reducing contact area and increasing stresses
Solution Approach 1:
The continuous conical surface maintains contact across varying angles of inclination by providing a gradual transition zone. This curvature allows the contact area to adapt to different inclination angles without concentrating stresses, maintaining effective force transmission even at higher angles.
Solution Approach 2:
The conical surface geometry dynamically adapts the contact area as the inclination angle changes. The continuous curvature ensures that contact pressure remains distributed rather than concentrated, allowing the joint to maintain effectiveness across a range of operational angles.
Data Source
AI summary
A hydrostatic piston machine having a cylinder block with several cylinders, in which are slidably mounted pistons in load engagement with a reaction member via transmission members, each transmission member is connected to at least one of the piston or the reaction member via a spherical joint comprising a ball recess and a ball pivot comprising a convex spherical surface. The ball pivot has an ending rotational surface which is continuously connected to the convex spherical surface, created by rotating a continuous generating line around the axis of symmetry of the ball pivot, or at least one of the ball recess or the ball pivot has an end wall which is deformable under the loads acting on the spherical joint, so as to provide for an ending rotational surface having a curvature which is different from an initial curvature thereof.