Dual Spindle Helical Pump Shaft Segmentation for Assembly and Strength
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Solution Overview
Problem
The existing double-flow two-spindle screw pump design faces limitations due to a lower moment of resistance at the bearings, which restricts the permissible pressure difference and requires complex assembly and adjustment processes, especially when the root circle diameter of the delivery screw is larger than the seal and bearing diameters.
Innovation Solution
The design incorporates bushings with diameters matching the seal and bearing inner diameters, allowing for increased diameters and simplified assembly, along with a fastening element with adjustable backlash and a radial elongated hole for easy maintenance and adjustment, and a releasable cover for the gear section to reduce readjustment time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the root diameter of the feed screw is made larger than the seal diameter and bearing inner diameter for manufacturing reasons, then assembly is simplified, but the shaft section modulus in the bearing area decreases significantly
Solution Approach 1:
The shaft is divided into multiple sections with different diameters: a larger diameter section at the center for high strength, and a smaller diameter section in the bearing area to accommodate the seal and bearing. This segmentation allows each section to be optimized for its specific function while maintaining overall structural integrity.
Solution Approach 2:
The shaft exhibits local quality variations with different diameters at different locations. The central section has a larger diameter to handle high torsional loads, while the bearing area section has a smaller diameter to fit within the bearing inner diameter. This local differentiation resolves the contradiction between assembly requirements and structural strength.
2Ease of operation
If the shaft diameter in the bearing area is reduced to fit the bearing, then assembly is enabled, but the permissible pressure differential is limited due to increased shaft deflection
Solution Approach 1:
The shaft is segmented into a central high-strength section and bearing-area sections, allowing the bearing area to be optimized for assembly while the central section maintains high rigidity to withstand pressure differentials without excessive deflection.
Solution Approach 2:
The shaft diameter parameter is changed along its length, creating a stepped profile that optimizes both assembly feasibility and mechanical performance. The larger central diameter provides the necessary stiffness to maintain reliability under pressure while the smaller bearing-area diameter enables proper assembly.
3Ease of manufacture
If the shaft is stepped with a smaller diameter below the external bearings, then assembly of feed screws and mechanical seals is enabled, but the shaft exhibits significantly lower section modulus in the bearing area
Solution Approach 1:
The stepped shaft design segments the shaft into functional zones: a larger diameter section for high strength requirements and a smaller diameter section for assembly requirements. This segmentation allows the feed screws and mechanical seals to be slid over the smaller diameter section while the larger central section maintains the necessary structural strength.
Solution Approach 2:
Different diameter sections are assigned to different functional requirements: the smaller diameter at the bearing area localizes to accommodate assembly needs, while the larger central diameter locally provides the strength and stiffness required for operational reliability.
Data Source
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AI summary
A housing (11) has pump portion (12), bearing portion (13) and gear portion (14). The pump portion has conveyor housing in which screws (17,18) are arranged on shafts (15,16) mounted in bearing portion and extended into gear housing. The holes are formed in fastening element (27) for connecting shaft and gear so that gear and fastening element are rotated against each other and distance of flanges (29) and conveying screws is adjustable. A cover is detachably mounted in opening formed in gear portion so that backlash of screws is adjustable by using necessary tool.