Weight Plate Stack Alignment Bushings for Friction Reduction
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Solution Overview
Problem
Existing user-manipulated exercise equipment with weight-plate stacks experiences friction and alignment issues due to manufacturing tolerances, leading to inefficient workouts and aesthetically unappealing misalignments, especially with reflective materials, as plates shift during use, causing friction loss and incorrect resistance adjustment during exercise phases.
Innovation Solution
The implementation of beveled alignment bushings within guide rod holes to ensure precise alignment between weight plates and guide rods, providing a tight clearance fit and plate-to-plate alignment, which minimizes contact with guide rods and maintains accurate plate positioning, thereby reducing friction and maintaining alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard manufacturing tolerances are used for weight plate openings and guide rod holes, then manufacturing cost and ease of manufacture are improved, but friction between plates and guide rods increases and alignment precision deteriorates
Solution Approach 1:
The patent introduces guide bushings as intermediary components between the weight plates and guide rods. These bushings have precise internal dimensions that mate with the guide rod outer diameter, providing accurate alignment without requiring tight tolerances on the weight plate holes themselves. The bushings act as mediators that transfer the alignment function from the plate-hole interface to the bushing-rod interface, where precision can be achieved more economically.
Solution Approach 2:
The patent changes the dimensional parameters of the guide rod and bushing interface to achieve better alignment. Specifically, the guide rod outer diameter and bushing inner diameter are designed with optimal clearance fits that minimize friction while maintaining alignment. This parameter optimization allows standard manufacturing tolerances on plates to be compensated by precisely controlled bushing dimensions.
2Loss of energy
If tight alignment between all weight plates and guide rods is achieved, then friction is reduced and workout effectiveness is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent segments the alignment function by introducing separate guide bushings for each weight plate. Instead of requiring all plates to have precisely fitted holes, each plate can use a standard bushing that provides the alignment function. This segmentation allows the complexity of precise alignment to be distributed across multiple simple, identical components rather than requiring complex precision machining on each plate.
Solution Approach 2:
The guide bushings serve as intermediary components that decouple the alignment requirement from the weight plates themselves. The bushings are the elements that directly contact and align with the guide rods, while the weight plates simply hold the bushings. This intermediary approach reduces friction effectively while keeping the weight plate manufacturing simple and the overall device complexity manageable.
3Shape
If reflective weight plate materials are used, then aesthetic appearance is improved, but sensitivity to misalignment increases and visual appeal deteriorates during movement
Solution Approach 1:
The guide bushings act as intermediaries that ensure consistent alignment of reflective weight plates during movement. By providing a precise, repeatable interface between the plates and guide rods, the bushings minimize lateral shifting and misalignment that would otherwise be visible as distracting reflections. This allows the use of aesthetically pleasing reflective materials without the penalty of exaggerated misalignment visibility.
4Manufacturing precision
If manufacturing tolerances in plate openings are reduced, then alignment precision is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The guide bushings serve as intermediary components that absorb the alignment precision requirement. Instead of demanding tight tolerances on the weight plate openings, the bushings provide the precise interface with the guide rods. The plate openings can therefore be manufactured with standard, more economical tolerances, while the bushings—being simpler, standardized components—achieve the necessary alignment precision through their design and fit with the guide rods.
Data Source
AI summary
User-manipulated exercise equipment of the type utilizing a weight-plate stack comprises a stack of weight plates, of which a user-selected portion moves as a unit along a pair of guide rods in response to an exercise movement by the user. The selected portion of the stack moves with virtually no cross-wise (i.e., lateral) shifting among the plates and virtually no friction between the moving portion of the stack and the guide rods because (1) a keystone bushing below the weight plate stack provides virtually error free alignment with the guide rods by setting the non-selected portion of the stack at a highly accurate “home” position that resets the moving stack if it has shifted laterally during movement, even if that shift is very slight, and (2) the guide rod holed in the weight plates carry bushings which align with the bushings of the adjacent weight plates to prevent the plates within the moving portion of the stack from shifting laterally with respect to each other and thereby contacting a guide rod. Preferably, the topmost weight plate in the moving portion of the stack carries bushings forming a smaller gap with the guide rods than the bushings of the remaining weight plates so that, at worst, only the topmost plate will contact a guide rod resulting in negligible friction.