Radial Piston Unit Bearing Arrangement

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Solution Overview

Problem

Radial piston units in the art have relatively high axial and radial dimensions, which complicates integration into vehicle frames, and there is a need for a design that reduces these dimensions while maintaining ease of assembly and cost efficiency.

Innovation Solution

A hydrostatic radial piston unit with a stationary shaft and a rotary casing supported by roller bearings, where the bearings are positioned outside the rotary distributor and axially overlapping with the stationary casing, reducing axial length and allowing for a robust, cost-effective design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If radial piston units are designed with conventional bearing arrangements, then the units provide sufficient structural support and reliability, but the axial length and radial diameter become relatively high, complicating integration into vehicle frames

Engineering Contradiction:
Improveaxial lengthVSAvoidintegration complexity
Core Design Contradiction:
Length of moving objectVSDevice complexity

Solution Approach 1:

The patent repositions the roller bearings from a conventional axial arrangement to a radial arrangement outside the rotary distributor. This dimensional change in bearing placement allows the bearings to support the rotary casing while occupying radial space rather than axial space, thereby reducing the overall axial length of the radial piston unit without compromising structural support or reliability

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Area of moving object

If radial piston units are designed with conventional bearing arrangements, then the units provide sufficient structural support and reliability, but the radial diameter becomes relatively high, complicating integration into vehicle frames

Engineering Contradiction:
Improveradial diameterVSAvoidintegration complexity
Core Design Contradiction:
Area of moving objectVSDevice complexity

Solution Approach 1:

The patent relocates the roller bearings to a radial position outside the rotary distributor, changing the spatial dimension in which the bearings are arranged. This allows the bearing support function to be achieved in the radial direction rather than increasing the radial diameter significantly, as the bearings are positioned to leverage existing structural elements and optimize space utilization

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Length of moving object

If roller bearings are positioned inside the rotary distributor, then the design may be more compact, but the assembly becomes more complex and costly

Engineering Contradiction:
Improveaxial lengthVSAvoidassembly ease
Core Design Contradiction:
Length of moving objectVSEase of manufacture

Solution Approach 1:

The patent extracts the roller bearings from the interior of the rotary distributor and positions them outside. This separation simplifies the assembly process by allowing the rotary distributor to be assembled independently without the complexity of integrating bearing mounting features, while the bearings can be installed on the stationary casing or support structure separately, reducing overall assembly complexity and manufacturing cost

Inventive Principle:
Principle #2Taking out (Extraction)

4Length of moving object

If roller bearings are positioned inside the rotary distributor, then the design may be more compact, but production costs increase

Engineering Contradiction:
Improveaxial lengthVSAvoidproduction cost
Core Design Contradiction:
Length of moving objectVSEase of manufacture

Solution Approach 1:

By extracting the roller bearings from the rotary distributor interior and positioning them externally, the patent eliminates the need for complex bearing housing features within the distributor, reduces machining requirements, and allows for the use of standard off-the-shelf bearings. This external positioning simplifies manufacturing processes and reduces production costs while maintaining the compact design goals

Inventive Principle:
Principle #2Taking out (Extraction)

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

The solution achieves a compact design with reduced axial length and diameter, facilitating easier integration into vehicle frames and lowering production costs through optimized bearing placement and simplified assembly.

Implementation Method 1

a rotary casing (40) which is capable of rotating relative to the stationary casing (20) around the rotational axis (10) of the radial piston unit (1)

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP4448953B1Bearing arrangement for radial piston units
Publication Date: 2025.06.25 DANFOSS AS
  • EP4448953B1 patent drawingFigure 1
  • EP4448953B1 patent drawingFigure 2
  • EP4448953B1 patent drawingFigure 3

AI summary

Hydrostatic radial piston unit of the cam-lobe type of construction comprising a non-rotary, stationary shaft defining a rotational axis of the hydrostatic radial piston unit. A non-rotary, stationary casing houses the shaft in a torque proof connection. A rotary casing is provided which is rotary around the rotational axis. A pair of roller bearings supports the rotary casing in a rotatable manner against the stationary casing, wherein the pair of roller bearings is arranged in an axial overlapping area in which the stationary casing and the rotary casing overlap.