Fuel Pump Cap External Thread Sealing Design
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Solution Overview
Problem
Existing pump units for feeding fuel to internal combustion engines face high manufacturing costs and wear issues due to complex precision-machining requirements for threaded surfaces and difficulties in achieving a reliable seal between components.
Innovation Solution
A pump unit design where the cap is fixed along the outer surface of the head, utilizing a ring nut with a threaded inner surface and a sealing element between the cap and the annular wall, simplifying the threaded connection and enhancing sealing efficiency, while reducing wear and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threaded surfaces are formed on the inner surface of the head wall through precision-machining, then the connection between cap and head is achieved, but the manufacturing cost increases and wear problems occur during operation
Solution Approach 1:
Instead of forming threaded surfaces on the inner surface of the head wall (conventional approach), the patent inverts the approach by forming threaded surfaces on the outer surface of the head wall. This allows the cap to be secured from the outside, eliminating the need for complex internal threading while maintaining connection reliability and reducing manufacturing complexity
Solution Approach 2:
The cap is divided into two functional parts: a cover-piece for closing the intake chamber and a ring nut for locking the cover-piece. This segmentation allows the sealing function and the fastening function to be separated, with the ring nut providing external threading that is easier to manufacture and less prone to wear than internal threading
2Reliability
If threaded surfaces are formed on the inner surface of the head wall, then the cap can be fixed to close the intake chamber, but wear and leak-tightness problems occur during working life due to high forces
Solution Approach 1:
The patent inverts the threading location from internal to external surfaces. The threaded connection on the outer surface of the head wall and inner surface of the ring nut is subjected to compressive forces during tightening, which strengthens the connection over time rather than causing wear and leakage as occurs with internal threading under high fuel forces
3Ease of manufacture
If the cover-piece is located outside the annular wall with external threading on the wall, then the threaded connection is simpler, but achieving a reliable seal between cover-piece and head becomes difficult
Solution Approach 1:
The patent introduces a sealing element as an intermediary component between the cover-piece and the head. This sealing element bridges the gap between the externally threaded connection and the sealing requirement, ensuring leak-tight closure while maintaining the manufacturing simplicity of external threading
Solution Approach 2:
The patent applies local quality by positioning contact surfaces and sealing elements at specific locations. The annular contact surface of the cover-piece contacts the head at a defined location between the inner surface of the annular wall, creating a localized sealing zone that ensures reliable closure without compromising the overall simple external threading design
Data Source
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AI summary
A pump unit for feeding fuel, preferably diesel fuel, to an internal combustion engine; the pump unit (1) comprising: a head (4) inside which a cylinder (12) extending along an axis (A1) is formed; a pumping piston (5) extending along the axis (A1) and slidingly coupled with the cylinder (12); a through-hole (13) which extends from the cylinder (12) towards the outside of the pump unit (1); an intake chamber (8) communicating with the cylinder (12) via the hole (13); an intake valve (7) which controls the flow of fuel from the intake chamber (8) to the hole (13); a cap (23; 123; 223) which is connected to the head (4), is arranged on the opposite side to the pumping piston (5) and can be selectively fixed along an outer surface (25) of the head (4) so as to close the intake chamber (8) on one side.