US12142719B2 is a patent for a stacking apparatus that transports prismatic secondary-battery electrode sheets on a vacuum belt conveyor and aligns them with an XYθ module. The applicant is Innometry Co., Ltd.; the priority date is October 25, 2018, filing date October 25, 2019, and issue date November 12, 2024.
Problem Definition
Conventional zigzag-stacking apparatuses (citing Korean patents 10-1730469, 10-1662179, and others) moved electrode sheets from magazine to alignment table, then from alignment table to stack base, in two separate stages, resulting in long round-trip transport time. This patent proposes a structure that handles alignment and transport in a single step by moving the conveyor belt itself in XYθ, without a separate alignment table. The core of this patent’s claims is whether alignment precision can be maintained while shortening the transport path.
Kinematic Analysis
Per the claims, either the belt conveyor or the stack base is configured to be inclined relative to the horizontal plane, allowing a swing unit to load/unload electrode sheets at both ends of the trajectory. The stack base moves along a U-shaped or semicircular lower trajectory, intended to direct the acceleration direction upward so the stack gripper applies force to the separator’s broad face. The alignment unit consists of a module that adjusts the belt’s own XY position and rotation angle (θ), plus an electrode-sheet position-recognition module, instead of a separate alignment table.
Calculation / Formula Verification
As the belt’s incline angle increases, the risk of the electrode sheet slipping under its own weight alone increases. Applying a static friction coefficient of $\mu_s = 0.35$ (estimated; referencing the typical range between secondary-battery electrode foil and belt surface), the limiting incline angle below which the sheet does not slip under self-weight alone is $$\theta_{max} = \arctan(\mu_s) = \arctan(0.35) \approx 19.3°$$
Assuming the patent drawing’s example swing-unit load/unload approach angle of $\theta = 20°$ (drawing example, not a measured value, estimated), this exceeds 19.3°, meaning alignment could be lost from self-weight alone — which explains why this patent’s conveyor is named with “vacuum” attached. The self-weight slip-force component of the electrode sheet in this case is $$F_{slip} = mg\sin\theta = 0.0032 \times 9.81 \times \sin20° \approx 0.0107\text{ N}$$ (electrode-sheet mass $m=3.2\text{ g}$; the estimate reuses the assumption from the preceding zigzag-stacking article).
Applying the same vacuum-suction force as the preceding article ($F_{vac} \approx 3.02\text{ N}$), the primary safety factor is $SF_1 = F_{vac}/F_{slip} \approx 282$. Even under the secondary-verification condition of a 50% vacuum-pressure drop, $SF_2 \approx 141$ remains generous, meaning the inclined structure itself is better interpreted as contributing to shortening the transport path rather than as a drop-risk factor.
Shop-notes
An alternative of horizontal-only transport followed by a separate lift unit for loading/unloading could be considered, but the added lift round-trip time runs counter to this patent’s purpose of shortening transport time, making it a non-adoption candidate. Machining the belt frame’s incline poses no difficulty at an angular tolerance of ±0.1° via milling, but because the incline hinge’s bearing accompanies a bend in the vacuum piping, a separate note for piping fatigue-life review should be left on the machining drawing. Unconfirmed variables such as motor capacity should be confirmed after field measurement.
Design-Reflection Checklist
- Re-verify belt/stack-base incline angle and static friction coefficient with measured values
- Reflect the dual safety-factor condition for vacuum-pressure degradation in the line PM cycle
- Separately test the incline hinge’s vacuum-piping fatigue life
- Pre-review whether this patent’s claims conflict with in-house equipment design plans
One-line summary: The core of this patent is not alignment precision but a structure in which belt incline angle and vacuum pressure together shorten transport time.