Multichannel Pipette Threaded Connection Stability
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Solution Overview
Problem
Multichannel pipettes experience errors during autoclaving due to loosened threaded connections, leading to stroke and measuring issues, as the friction in plastic threads is reduced, causing unintended movement and potential misalignment of piston positions.
Innovation Solution
Incorporating form-fit blocking configurations in the threaded connection between the grip and displacement parts, which engage at the end position to prevent reverse rotation, supplemented by a manual release mechanism to allow rotation against high braking forces, ensuring the piston stroke and position remain unchanged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a threaded connection is used between grip part and displacement part, then the connection can be detached and reattached, but the friction in plastic threads is reduced during autoclaving, causing the connection to loosen and reverse rotation to occur
Solution Approach 1:
The connection system is divided into two independent parts: a threaded connection for detachable attachment and a form-fit blocking mechanism for rotational stabilization. The form-fit configurations are separate engagement elements that work independently of the threaded connection, providing additional rotational constraint without interfering with the detachable function.
Solution Approach 2:
The form-fit blocking configurations are designed to prevent reverse rotation before it can occur during autoclaving. By providing preliminary rotational constraint through geometric engagement, the system counteracts the loosening effect of thermal cycling on the threaded connection, preventing the harmful reverse rotation from happening in the first place.
2Stability of the object's composition
If friction braking is used to prevent reverse rotation, then the displacement part remains stable during operation, but the friction is insufficient after autoclaving when thread friction is reduced
Solution Approach 1:
The form-fit blocking configurations act as an intermediary mechanism between the threaded connection and the rotational stability requirement. Instead of relying solely on friction from the threaded elements, the form-fit configurations provide a direct geometric constraint that mediates the rotational stability, independent of frictional conditions.
Solution Approach 2:
The system transitions from relying on friction-based rotational constraint to geometric constraint-based stability. By changing the fundamental mechanism from friction-dependent to form-fit-dependent, the system maintains rotational stability across different thermal conditions, as geometric engagement is not affected by temperature-induced friction changes.
3Reliability
If the threaded elements are designed with high friction to maintain engagement, then the connection remains stable during normal operation, but the high friction prevents easy release during autoclaving when material properties change
Solution Approach 1:
The engagement mechanism is segmented into two functional components: threaded elements that provide detachable connection and form-fit configurations that provide rotational locking. This segmentation allows the threaded elements to be optimized for easy engagement/disengagement while the form-fit configurations handle the rotational stability, separating the functions to resolve the contradiction.
Solution Approach 2:
The form-fit blocking configurations serve as an intermediary that maintains rotational stability without requiring high friction from the threaded elements. This intermediary mechanism allows the threaded connection to remain easy to engage and disengage while still providing sufficient rotational constraint during autoclaving.
Data Source
AI summary
A multichannel pipette, including a grip part defining a longitudinal axis and including a piston-driving device movable axially thereon, a displacement part rotating about the axis and having cylinder and piston arrangements, and a connection device for detachably connecting the grip part to the displacement part and permitting a rotation of the displacement about the longitudinal axis. The connection device includes threaded connection elements engaged with one another. The pistons move axially to the cylinders via a piston-driving device. A connection part of the threaded elements is axially connected with the cylinders and includes a clearance for a rotary bearing provided therein. Form-fit configurations on the support and connection parts are engaged to prevent a reverse rotation of the connection part relative to the support part. By a manual release action, the form-fit configurations disengage, such that the connection part rotates in a reverse rotation relative to the support part.