Metal working – Method of mechanical manufacture – Electrical device making
Patent
1990-06-19
1992-05-19
Hall, Carl E.
Metal working
Method of mechanical manufacture
Electrical device making
21598, 310 42, 310 71, 310234, H01R 4304
Patent
active
051135744
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for the production of an electrically-conducting and mechanically solid connection of armature coil wires with the lamellas of a commutator in which the wires are laid around the hooks of the lamellas of the commutator during the winding process without prior stripping of the insulation and the free ends of the hooks are connected with the corresponding lamellas of the commutator by ultrasonic welding. The invention also includes devices which are specifically suited for the execution of the process, in combination with a sonotrode which is movable relative to the commutator for bending back the hooks and the ultrasonic welding of the ends of the hooks with the lamellas of the commutator.
THE PRIOR ART
It has been previously proposed to connect the wires of an armature coil with the lamellas of a commutator, which connection is both electrically conductive as well as mechanically solid, by means of ultrasonic welding (DE-OS 27 39 730; DE-OS 30 17 426). Because of the careful thermal treatment of the commutator which can thereby be attained, this process is particularly advantageous; but this process does not provide reproducible electrical connections between the armature coil wires and the lamellas of the commutator. It has been shown, rather, that an electrical connection which is consistently good from one lamella to the other is not possible, because the wire insulation or the remnants of the insulation produce unsatisfactory transition resistances and, in the worst cases, completely prevent an electrical connection.
DE-OS 30 17 426 discloses a process in which the lamellas of the commutator are supposed to be rolled and/or reversed on the contact surface of a sonotrode, by means of which, during the welding process, the varnish insulation of the armature coil wires is flaked away and, at the same time, a mechanical connection between the hooks and the lamellas is supposed to be created by means of ultrasonic welding. The desired flaking away of the varnish insulating layer does not, however, take place uniformly and/or completely so that this process does not lead to reproducible electrical connections of the individual lamellas of a commutator. A high rate of rejects results, so the process is not suitable for the mass production of commutators.
Another process has been proposed (DE-OS 24 16 411) in which the insulation is removed from the armature wire loops before they are laid around the hooks. The hooks are subsequently bent back and pressure-welded with the ends of the lamellas. The partial removal of the varnish insulation from the wire loops before their application to the hooks is, however, an expensive operation, one which has to be carried out separately for every wire loop. In order to avoid short circuits between adjacent wire loops stripped of insulation, the ends of the lamellas are in this case, positioned alternately in different planes, which makes the production of such types of commutators more expensive.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a process which produces good electrically-conductive connections between the armature coil wires and all lamellas of a commutator, without the ends of the lamellas having to be positioned in different planes in order to prevent short circuits.
In accordance with the invention, the layer of varnish insulation on the armature wire is at least partially destroyed before bending the hooks by thermal and/or mechanical means. The partial destruction occurs only at the points or curves of the hooks. The residue or remnant of the layer of varnish insulation during the bending back of the hooks is at least partially removed by the ultrasonic oscillations before welding the ends of the hooks to the lamellas of the commutator.
By means of the thermal and/or mechanical destruction of the varnish insulating layer on the wires already placed around the hooks of the lamellas of the commutator, the steps involving a prior stripping of the insulation are
REFERENCES:
patent: 3781981 (1974-01-01), Miura et al.
patent: 4835430 (1989-05-01), Sin
Hall Carl E.
STAPLA Ultraschall-Technik GmbH
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