Piston Cylinder Unit Axial Securing Element Thread
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Solution Overview
Problem
Existing piston and cylinder units require high tightening moments for assembly and disassembly, necessitating special tools and additional components to prevent rotational movement, leading to increased complexity, cost, and difficulty in servicing.
Innovation Solution
A piston and cylinder unit design featuring a securing element with a thread that extends axially to prevent rotational movement, using opposite-handed threads to secure the piston to the piston rod, allowing for manual assembly and disassembly without high tightening moments, and reducing the structural length and material requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high tightening moments are used to secure the piston to the piston rod, then the connection strength is improved, but the ease of assembly and disassembly deteriorates requiring special tools
Solution Approach 1:
The connection system is segmented into two independent threaded connections: the primary connection between piston and piston rod, and the secondary securing connection between securing element and piston rod. This segmentation allows the primary connection to use low tightening moments for easy assembly, while the secondary connection provides the necessary anti-rotation security without requiring high tightening moments during assembly.
Solution Approach 2:
The securing element acts as an intermediary component that prevents rotational movement of the piston relative to the piston rod. It mediates between the low-tightening primary connection and the anti-rotation requirement, allowing the piston to be securely connected without requiring high tightening moments that would necessitate special tools.
2Reliability
If additional components are added to prevent rotational movement, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The securing element serves multiple functions: it prevents rotational movement of the piston, provides structural support, and maintains the axial positioning of the piston relative to the piston rod. By combining these functions into a single component, the design achieves reliable anti-rotation security without proportionally increasing device complexity.
Solution Approach 2:
Instead of preventing rotation through the primary piston-piston rod connection, the invention inverts the approach by allowing the primary connection to be simple and easy to assemble, while using the securing element to specifically address the anti-rotation requirement. This inversion separates the assembly simplicity function from the anti-rotation function.
3Strength
If engagement surfaces for rotational tools are arranged on the piston, then the connection strength is improved, but the ease of manufacture deteriorates
Solution Approach 1:
The requirement for high tightening moment capacity is extracted from the piston itself and transferred to the securing element. The piston can then be manufactured without complex engagement surfaces, while the securing element (which is accessed from the external end of the piston rod) provides the necessary tool engagement surfaces for applying tightening moments during assembly.
4Strength
If the piston and piston rod surfaces are hardened to withstand high tightening moments, then the strength is improved, but the ease of manufacture deteriorates
Solution Approach 1:
The invention uses a more economical approach by applying hardening only to the securing element, which is a smaller, more accessible component. The piston and piston rod surfaces remain softer and easier to manufacture, while the securing element (which承受s the high tightening moments) is hardened to withstand the assembly forces. This selective hardening reduces overall manufacturing complexity.
Data Source
AI summary
A piston and cylinder unit (1) includes a cylinder housing (2), a piston (7), a piston rod (18) and a securing element (20). The piston (7) includes an opening (13), at least one piston seal (11) and an inner thread (15) being located in the opening (13). The piston rod (18) has an axis (9) and includes a protrusion (21), an outer thread (23) and a second thread (27). The outer thread (23) is located on the protrusion (21). The second thread (27) is located at the piston rod (18). The piston (7) and the piston rod (18) are connected by the inner thread (15) and the outer thread (23). The securing element (20) is designed and arranged to substantially extend in the direction of the axis (9). The securing element (20) includes a thread (24), the securing element (20) and the piston rod (18) being connected by the thread (24) of the securing element (20) and the second thread (27) of the piston rod (18). The securing element (20) is designed and arranged to be active in an axial direction in a way to prevent rotational movement of the piston (7) in a loosening direction. The threads (15, 23) of the piston (7) and of the piston rod (18) are designed and arranged to be operated in a direction opposite to the threads (24, 27) of the securing element (20) and the piston rod (21).