Hydrostatic Drive Throttle for Cavitation Prevention

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Solution Overview

Problem

Existing hydrostatic drives face inefficiencies and high costs due to the need for large hydraulic components to handle maximum pressure medium volume flow, which occurs rarely, leading to cavitation risks and suboptimal operation.

Innovation Solution

A hydrostatic drive with a double-acting hydraulic cylinder and a pressure medium connection system that includes a third throttle device with an adjustable opening cross section, allowing partial volume flow regeneration and pressure control to prevent cavitation, enabling smaller hydraulic machine and pump designs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If large-capacity hydraulic components are used to handle maximum pressure medium volume flow, then the system can accommodate peak demand, but the components operate far below capacity most of the time, increasing costs and reducing efficiency

Engineering Contradiction:
Improveability to handle maximum pressure medium volume flowVSAvoidoperational efficiency
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent applies dynamics by making the throttle device adjustable, allowing the opening cross-section to be adapted to different operating conditions. This enables the hydraulic system to optimize flow rates dynamically, matching component operation to actual demand rather than operating at fixed maximum capacity.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of throttle opening cross-section to control pressure medium flow. By adjusting this parameter, the system can regulate flow rates to match actual operational needs, preventing oversized components from operating inefficiently while still handling peak demands when necessary.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If large-capacity hydraulic components are designed for maximum flow, then peak demand is met, but component size and cost increase

Engineering Contradiction:
Improveability to handle peak flow demandVSAvoidcost
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The adjustable throttle device allows the system to adapt to varying flow demands, enabling the use of smaller, more cost-effective hydraulic components that can be dynamically optimized rather than oversized for peak conditions only.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

By adjusting the throttle opening cross-section parameter, the system can maximize the utilization of smaller hydraulic components, allowing them to operate closer to their optimal capacity range and reducing the need for expensive oversized equipment.

Inventive Principle:
Principle #35Parameter changes

3Productivity

If pressure medium flows directly between piston chambers, then regeneration occurs and pump size is reduced, but cavitation risk increases in the expanding chamber

Engineering Contradiction:
Improveregeneration efficiencyVSAvoidcavitation risk
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The throttle device acts as an intermediary between the piston chambers, controlling the pressure medium flow during regeneration. It mediates the flow rate to ensure sufficient pressure medium supply to the expanding chamber, preventing cavitation while maintaining regeneration efficiency.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The throttle device changes the flow parameter by adjusting its opening cross-section, regulating the pressure medium flow during regeneration to prevent cavitation in the expanding piston chamber while maintaining efficient energy recovery.

Inventive Principle:
Principle #35Parameter changes

4Device complexity

If the throttle opening cross-section is fixed, then the system is simple, but it cannot adapt to varying pressure conditions and may cause cavitation

Engineering Contradiction:
Improvesystem simplicityVSAvoidprotection against cavitation
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The throttle device is made adjustable rather than fixed, allowing the opening cross-section to be adapted to different pressure conditions and flow demands, preventing cavitation while maintaining reasonable system simplicity.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The throttle opening cross-section parameter can be adjusted to adapt to varying operating conditions, providing cavitation protection and optimized performance without significantly increasing system complexity.

Inventive Principle:
Principle #35Parameter changes

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 solution reduces costs and improves efficiency by allowing the hydraulic pump to operate within its optimal range more frequently, while preventing cavitation and maintaining sufficient pressure for load handling.

Implementation Method 1

there is a constant need to prevent cavitation in the expanding piston chamber or at least to reduce the risk of cavitation

Methodology Applied
Scientific EffectCavitation: Cavitation

Implementation Method 2

a third pressure medium connection with a third throttle device with a third opening cross section which can be adjusted as a function of the pressure of the other piston chamber

Methodology Applied
Scientific EffectThrottling: Pressure Drop

Implementation Method 3

a second pressure medium connection, via which the other piston chamber can be supplied with a partial volume flow of an outflow volume flow flowing out of one piston chamber

Methodology Applied
Scientific EffectHydraulic regeneration: Hydraulic Press

Data Source

PatentEP2985469B1Hydrostatic drive and valve device for same
Publication Date: 2018.11.14 ROBERT BOSCH GMBH
  • EP2985469B1 patent drawingFigure 1~2
  • EP2985469B1 patent drawingFigure 3~4
  • EP2985469B1 patent drawingFigure 5~6

AI summary

Offenbart is a hydrostatic drive with a hydraulic cylinder for moving a load, one piston chamber of which can be fluidically connected to a hydraulic machine and/or a hydraulic accumulator for recuperating hydraulic energy from the hydraulic cylinder. Offenbart is also a valve device for this drive.