Hollow Piston Rod Forging for Lightweight High-Stress Cylinders
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Solution Overview
Problem
Current methods for manufacturing piston rod units in hydraulic cylinders, particularly for mining machines, face challenges in achieving lightweight construction while maintaining dynamic stress resistance due to the negative effects of screw- and weld connections on hollow piston rods.
Innovation Solution
A deep-hole drilling method followed by a forging process is used to create a hollow piston rod unit, where the material excess at the rod end is formed into a one-piece component, allowing for a screw connection without welds, and a mandrel is inserted to ensure precise closure and sealing of the bore opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If screw- or weld connections are used to attach hollow piston rod, then assembly is simplified, but dynamic stress resistance deteriorates
Solution Approach 1:
The piston rod head is integrated directly with the piston rod body through forging, creating a one-piece component that eliminates separate connection elements. This merging of the piston rod head and rod body removes the need for screw or weld connections, thereby preserving dynamic stress resistance while maintaining manufacturing feasibility.
Solution Approach 2:
The piston rod head is pre-formed as an integral part of the piston rod through the forging process before final assembly. This preliminary formation of the head ensures that no additional connection steps are required later, avoiding the stress concentration issues associated with post-assembly connections.
2Weight of moving object
If hollow piston rod construction is used, then weight is reduced, but connection reliability deteriorates
Solution Approach 1:
By forging the piston rod head and body as a single integrated component, the invention eliminates connection interfaces that would compromise reliability. The one-piece construction ensures continuous material flow and uniform stress distribution, maintaining high reliability while achieving weight reduction through the hollow rod design.
3Strength
If steel is tempered and quenched with refractory metals, then strength is increased, but weldability deteriorates
Solution Approach 1:
The invention removes the welding operation from the manufacturing process entirely by using a forging-based one-piece construction. This extraction of the welding step allows the use of high-strength tempered and quenched steel with refractory metals without compromising manufacturability, as the strength enhancement techniques no longer conflict with connection requirements.
Solution Approach 2:
The piston rod head and body are combined through forging rather than welding, allowing the use of high-strength heat-treated steels that would be difficult or impossible to weld. This merging process preserves the material's enhanced strength properties while avoiding the weldability issues.
4Weight of moving object
If deep-hole drilling is performed to create hollow piston rod, then weight saving is achieved, but manufacturing complexity increases
Solution Approach 1:
The hollow configuration is created during the initial forging process rather than requiring separate drilling operations. By pre-forming the hollow structure in the forging die, the manufacturing process achieves weight reduction without significantly increasing complexity, as the hollow shape is integral to the forming operation itself.
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 method enables weight savings in hydraulic cylinders, enhances dynamic stress resistance, and allows for the use of hollow piston rods in heavy mining machines by eliminating connection techniques that compromise stress resistance, achieving significant weight reduction without compromising performance.
Implementation Method 1
to first hollowly-drill a piston rod by means of deep-hole drilling in the rod shank
Implementation Method 2
This material excess, in a corresponding thermo-mechanical stress during the forging process, is ideally used to block the bore openings resulting from the deep bore. The material excess is consequently made to flow, due to the thermo-mechanical stress, in the radial direction of the cylinder.
Data Source
AI summary
A piston rod unit and a method for producing a piston rod unit, or a shaft, in light-weight construction, with a rod which is hollowly-drilled by means of a deep bore into the rod shank, and the resulting rod opening is closed subsequently by means of a forging process.