Universal Motor Rotor Hook Friction Enamel Removal
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Solution Overview
Problem
The existing methods for connecting aluminum rotor winding wires with lower melting temperatures to copper commutator hooks result in excessive deformation and breakage due to heat-generated enamel melting, leading to unreliable electrical and mechanical connections and increased production waste.
Innovation Solution
The use of elastically deformable hooks with recessed cuttings on their internal surfaces to frictionally and abrasively remove the insulating enamel, allowing direct contact without excessive heat generation, combined with an automated process for forming these cuttings and closing the hooks around the wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat is generated to melt the insulating enamel for electrical contact, then electrical connection is achieved, but the aluminum wire undergoes excessive deformation and breakage due to its low melting temperature
Solution Approach 1:
The patent replaces the thermal process (heating to melt enamel) with a mechanical process (friction and abrasion through hook closing). The mechanical action of closing the hook against the wire creates friction that removes the insulating enamel, allowing electrical contact without generating excessive heat that would damage the aluminum wire
Solution Approach 2:
The insulating enamel acts as an intermediary layer that must be removed to enable electrical contact. The patent uses the friction and abrasion mechanism as an intermediary process to remove this layer, rather than directly applying heat that would affect the wire material
2Reliability
If diamond point knurling is used to create protruding areas on hook surfaces, then electrical contact is improved, but the wire resistant section is excessively deformed causing local breaks
Solution Approach 1:
The patent applies local quality by creating a recessed area with specific geometry on the hook surface rather than adding protrusions. This recessed area is locally configured to receive and properly position the wire, providing both mechanical support and friction-based enamel removal only where needed, without deforming the wire structure
3Ease of manufacture
If hooks with flat inner surfaces are used, then manufacturing is simpler, but wire positioning is incorrect allowing wire to slip below closing point and be damaged
Solution Approach 1:
The patent modifies the hook surface with a localized recessed area that has specific dimensional characteristics. This local modification provides proper wire positioning and protection during the closing operation, while the overall hook structure remains simple for manufacturing. The recessed area acts as a wire receiving zone that prevents wire slippage
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method establishes a stable and reliable electrical and mechanical connection between the wires and hooks, preserving the integrity of the aluminum wires and reducing production waste by avoiding excessive deformation and breakage.
Implementation Method 1
said hook (20) is approached to said bar (18), pressing down with a predetermined force so that edge portions (21C) of said first single cutting (21) locally remove by friction and abrasion the electrically insulating enamel
Implementation Method 2
said hook (20) is approached to said bar (18), pressing down with a predetermined force so that edge portions (21C) of said first single cutting (21) locally remove by friction and abrasion the electrically insulating enamel
Implementation Method 3
an electric current is passed through electrodes appropriately positioned on the hooks so as to cause the enamel to be melted locally by the heat that is generated
Implementation Method 4
each comprising a body element (19) having a longitudinal extension in a direction parallel to the axis (X-X) of said shaft (12), whose end facing said rotor lamination stack (16) is provided with a hook (20), essentially obtained as a flexible appendix
Data Source
Figure 1A~1B
Figure 2A~3A
Figure 2B~3B
AI summary
The present invention regards a rotor (10) of a universal electric motor comprising a commutator (14) and a rotor lamination stack (16) arranged coaxially with each other along a first axis (X-X), and at least a winding wire (22) obtained with a first conductive material and coated with an electrically insulating enamel. Said commutator (14) comprises a plurality of bars (18), obtained from a second conductive material, having ends facing said rotor lamination stack (16) each having a hook (20) for said wire (22) adapted to be moved between an initial open position and a final closed position. In particular, on the internal surface (20A) of each of said hooks (20) is obtained at least a first cutting (21) that is recessed with respect to the surface of the corresponding bar (18) and has a top opening (23) having a width (A) that is smaller than the diameter (D) of the wire (22) so that, when said hook (20) is displaced from the open position to the closed position, the edge portions (21C) of said opening (23) remove locally by friction and abrasion the electrically insulating enamel that coats said portion (24) of the wire (22) to allow the electrical connection between the wire (22) and the bar (18). The present invention also concerns a process for associating at least one hook (20) of a bar (18) of a commutator (14) to at least one portion (24) of wire (22) of a rotor winding, an apparatus (60) for obtaining a commutator of a rotor (10), and a process for obtaining a commutator of a rotor (10).