Metal working – Method of mechanical manufacture – Electrical device making
Patent
1996-05-13
1998-03-17
Hall, Carl E.
Metal working
Method of mechanical manufacture
Electrical device making
29598, 2642722, 310 43, 310235, H02K 1510
Patent
active
057273073
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for manufacturing an armature for an electric motor with a shaft, a stack of laminations arranged on the shaft, a commutator likewise arranged on the shaft and comprising several commutator segments and a plastic filling, and a wire winding wound around the stack of laminations and welded to the commutator.
2. The Prior Art
In the methods hitherto generally performed for manufacturing such armatures, prefabricated components are used, in particular, a prefabricated commutator, and the commutator comprises the usual ring consisting of copper segments insulated from one another and a plastic filling introduced into the interior of the ring and usually consisting of thermosetting plastic, with a central bore. The stack of laminations and the commutator are pushed with a tight fit onto the shaft, and the stack of laminations can be additionally supported at the end faces thereof. The wire winding consisting of insulated copper wire is then placed around the stack of laminations so as to extend in the grooves thereof and is connected by welding to the individual segments of the commutator so that all of the commutator segments are provided with wires and the wire winding comprises a previously determined number of windings. During the joining of the copper wire to the commutator segments, such heat is generated that the enamel insulation of the copper wire burns off, and the wire may start to glow. Finally, a casting lacquer is introduced in drops into and cured in the area of the wire winding between commutator and stack of laminations so that the individual wires of the wire winding are fixed in relation to one another.
The armatures for electric motors manufactured in accordance with the hitherto method have two main disadvantages: The prefabricated commutator is fixed on the armature shaft by being pushed with its inner plastic filling with a press fit onto the shaft. Since the shaft diameter for achieving the press fit is somewhat larger than the bore in the plastic filling of the commutator, the commutator is necessarily widened somewhat, in all, which can cause loosening of the firm seating of the commutator segments in the plastic filling and impairment of the running characteristics of the electric motor. As long as the plastic filling of the commutators consisted of thermosetting plastics filled with asbestos, the filling had an excellent elasticity and a very strong adhesion to the copper metal of the commutator and so the aforementioned disadvantage virtually did not occur. However, such thermosetting plastics filled with asbestos are now no longer allowed to be used in view of their detrimental effect on health.
The further main disadvantage of the armatures manufactured in accordance with the above method originates from the welding of the wires to the commutator segments, which is carried out under the action of strong heat. The welding temperatures must be so high that the insulating enamel of the copper wire burns. This results in temperatures occurring at least for a short time at the commutator, which are higher than those tolerated by the thermosetting plastics forming the plastic filling. The welding thus results in a certain damage in advance to the commutator. As long as the commutators comprised thermosetting plastics containing asbestos, the high welding temperature was unproblematic because these thermosetting plastics were insensitive to heat to that extent. However, damage to the asbestos-free plastic filling of the commutator owing to the high welding temperatures now likewise results in a considerable reduction in the service life of the electric motor armature.
SUMMARY OF THE INVENTION
Therefore, the object of the invention is primarily to propose a new method for manufacturing armatures for electric motors with a stack of laminations which is free from the deficiencies explained hereinabove and results in a firm seating of the commutator on the armature shaft, but not in damage to the comm
REFERENCES:
patent: 1857175 (1932-05-01), Apple
patent: 3212170 (1965-10-01), Marshall
patent: 4263711 (1981-04-01), Sakamo et al.
Patent Abstract of Japan, vol. 14, No. 108 (E-0896), Feb. 1990.
Gstohl Eugen
Hoeptner Hans-Gerd
Hall Carl E.
Vacontec
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