Coffee grinder
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Solution Overview
Problem
Existing coffee grinders with interlocking plugs experience significant 'play' or 'wiggle' between the plug and frustoconical burr due to manufacturing tolerances, leading to inconsistent grinding results, with some coffee beans being ground too fine while others remain under-grounded.
Innovation Solution
A coffee grinder design featuring an interlocking plug with tapered side surfaces and a cylindrical upper portion that securely engages a frustoconical burr, reducing lateral movement and ensuring proper alignment through a coaxial upper cylindrical surface, allowing for consistent grinding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flat side surfaces are used on the interlocking plug gears, then manufacturing is easier, but there is significant play or wiggle between the plug and frustoconical burr
Solution Approach 1:
The invention changes the geometric parameters of the interlocking plug by replacing flat side surfaces with tapered side surfaces that are angled relative to the shaft axis. This parameter change allows the tapered surfaces to self-align and engage properly with the frustoconical burr, eliminating play and wiggle while maintaining manufacturing feasibility through standardized taper angles.
Solution Approach 2:
The invention introduces asymmetry by using tapered side surfaces instead of symmetric flat surfaces. The tapered geometry creates a unique engagement orientation that prevents lateral movement and ensures consistent alignment between the interlocking plug and frustoconical burr, resolving the alignment precision issue while keeping the cylindrical center post for straightforward manufacturing.
2Manufacturing precision
If tapered side surfaces are used on the interlocking plug gears, then alignment precision improves, but the tapered center post may engage first and prevent proper seating of the side surfaces
Solution Approach 1:
The invention applies preliminary action by designing the cylindrical upper portion to engage first with the frustoconical burr during assembly. This preliminary engagement establishes proper alignment before the tapered side surfaces make contact, ensuring that the tapered surfaces seat correctly without interference from the center post engagement sequence.
Solution Approach 2:
The invention segments the interlocking plug into two distinct functional portions: an upper cylindrical portion for preliminary engagement and alignment, and a lower tapered portion for secure lateral engagement. This segmentation allows each portion to perform its specific function in the correct sequence, resolving the assembly difficulty caused by the tapered center post engaging first.
3Ease of manufacture
If significant tolerances are allowed for the interlocking plug and frustoconical burr, then manufacturing cost decreases, but there is a lot of movement between the parts during grinding
Solution Approach 1:
The invention changes the geometric parameters by introducing tapered side surfaces that convert lateral movement and play into axial engagement force. The taper angle is selected to transform tolerance-induced gaps into self-correcting engagement, allowing significant manufacturing tolerances while maintaining stable and consistent grinding performance throughout operation.
Data Source
AI summary
A coffee grinder has a housing that includes a ring burr, a shaft extending through the ring burr, a frustoconical burr, and an interlocking plug. An internal bore of the frustoconical burr has an upper cylindrical surface adjacent the top end, an interlocking portion adjacent the bottom edge, and a tapered side surface. The interlocking plug is shaped to extend through the internal bore of the frustoconical burr, and includes an upper cylindrical portion that fits through the upper cylindrical surface, and a lower portion that includes a sidewall surface which is also tapered such that the sidewall surface interlocks with the side surface of the frustoconical burr.