Metering Pump Helical Spring End Geometry
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Solution Overview
Problem
Existing metering pump units with a displacement body driven by a connecting rod and a spring accumulator face challenges in assembly due to lateral forces caused by the compression spring, leading to membrane wear and increased complexity in design and adjustment.
Innovation Solution
A helical spring design where both axial ends are cut to length without applied ends in the relaxed state, with ground surfaces normal to the longitudinal axis, eliminating lateral forces and simplifying assembly by avoiding the need for adjustment screws.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the compression spring is designed with applied spring ends (conventional design), then the spring provides sufficient force, but lateral forces occur causing connecting rod misalignment and membrane wear
Solution Approach 1:
The spring end geometry is changed from applied/rounded ends to cut/flat ends perpendicular to the spring axis. This parameter change in the spring structure eliminates lateral forces while maintaining axial force, resolving the contradiction between providing sufficient force and preventing membrane wear.
Solution Approach 2:
The spring ends are given a specific local quality (flat, perpendicular cut) that differs from the conventional applied ends. This local modification at the spring ends eliminates lateral forces on the connecting rod, preventing misalignment and membrane wear while maintaining the overall spring function.
2Manufacturing precision
If adjustment screws are added to correct connecting rod alignment, then alignment accuracy improves, but device complexity increases
Solution Approach 1:
The adjustment screws and alignment correction mechanism are completely removed from the design. Instead of adding complexity to correct alignment issues, the invention eliminates the source of misalignment by using cut spring ends that prevent lateral forces, thereby simplifying the overall device structure.
Solution Approach 2:
The spring itself, through its cut end design, automatically prevents connecting rod misalignment by eliminating lateral forces. The system becomes self-aligning without requiring external adjustment mechanisms, reducing complexity while maintaining precision.
3Reliability
If the spring wire is cut to length with ground surfaces, then lateral forces are eliminated, but manufacturing complexity increases
Solution Approach 1:
The spring manufacturing process is modified to cut the spring wire to precise lengths and create flat perpendicular surfaces at the ends. While this adds a cutting step, it eliminates the need for complex adjustment mechanisms and ensures reliable operation, with the manufacturing complexity being offset by the elimination of lateral forces.
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 design reduces lateral forces on the displacement body, enhancing the service life of the membrane and simplifying the assembly process, resulting in a more reliable and long-term operational metering pump unit.
Implementation Method 1
a helical spring designed as a compression spring acts on the connecting rod and the displacement body. This forms a spring accumulator, which stores energy in one stroke direction and then releases it again in the other stroke direction.
Implementation Method 2
the spring wire is ground adjacent to the free end. The surface ground in this way extends normal to the longitudinal axis of the spring. A planar contact surface is thus created, which preferably extends over an angular or circumferential range of 200° to 300° around the longitudinal axis of the spring.
Data Source
Figure 1
Figure 2
AI summary
The unit has a dosing chamber (6) and a displacement body (8), where the displacement body is moved linearly by a connecting rod (10). A helical spring designed as a compression spring (20) pressurizes the connecting rod with force in movement direction. The helical spring is formed at an axial end such that an end of a spring wire is axially projected in relation to an adjoining winding in a relaxed state. The helical spring comprises a smoothed contact surface at the axial end, where the contact surface is defined at the axial end and extended toward a longitudinal axis of the spring.