Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-10-25
2001-06-26
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S261100, C029S609000
Reexamination Certificate
active
06252329
ABSTRACT:
DESCRIPTION
The present invention refers to a new kind of mutual connection of the laminations of a rotor stack to be used in electric motors.
The manufacturing technology for these rotors, and in particular for such mutual connections of the laminations thereof, is generally known in the art and is used in a most identical manner by the various manufacturers, except for a few obvious differences that are prevailingly due to manufacturing optimization steps taken by the individual manufacturers or design constraints.
Said rotor stacks are essentially manufactured under utilization of such an expedient for locking the laminations in relation with each other as this is shortly described below in view of facilitating a comparison with the method according to the present invention which is described further on. In the production of so-called squirrel-cage rotors for motors to be in particular, but not solely used in such applications as refrigeration compressors, the rotor stack is required to be manufactured under compliance, as far as possible, with following requirements:
in the first place, the laminations should maintain a maximum extent of integrity when undergoing processing for connection or “buttoning” to each other, since any processing that is likely to remove iron content from them is going to impair the ferromagnetic properties thereof;
the perimetrical slots that are provided within the rotor stack receive the die-cast material that definitively links and locks together said rotor stack as shown in the cross-sectional view appearing in
FIG. 8
;
said slots shall furthermore be slightly inclined (skew) with respect to the rotor axis in view of enabling these slots to more softly move past the slots of the stator, thereby opposing an effect that is generally well-known to those skilled in the art, so that it does not need to be illustrated any further.
To the purpose of accelerating and rationalizing the formation of the rotor stack, the latter is usually assembled directly in the punching die, where also the elements used to bring about said mutual fastening or buttoning of the laminations are formed.
The term “buttoning” is used here in a rather symbolic way, since said laminations are processed in such a manner as to be provided with protrusions and recesses or cavities so that said protrusions of a lamination are then able to be press-fitted into the corresponding cavities of a contiguous lamination, in such a manner that eventually all said laminations are fastened up to each other almost as if they were actually “buttoned” together.
With reference to
FIGS. 1
,
2
a
,
2
b
,
2
c
and
2
d
it can be noticed that said mutual buttoning of the laminations is obtained, according to the state-of-art technlogy, by processing the laminations in the following manner:
the laminations are made according to two distinct topologies, ie. a first topology as illustrated in
FIG. 2
b
and a second topology as shown in
FIGS. 2
a
and
2
c
;
a plurality of punchings
2
are provided in the lamination according to the illustration in
FIG. 2
b
, and are arranged in the same lamination according to the pattern shown therein, so that the related punched portions or tabs
25
are caused to protrude from the respective laminations, whereas respective cavities are provided in correspondence with said tabs.
Furthermore, a small zone of said laminations is further processed by punching a perforation
4
on the side of said tabs
25
, as this is shown in the enlarged view appearing in
FIG. 1
referring to said first lamination topology and illustrating, further to said perforation, also a respective adjacent protruding tab
25
.
The laminations according to the second topology, which are illustrated in
FIGS. 2
a
and
2
c
, are made in a much identical manner, except for the fact that punchings are provided in the laminations to likewise form respective tabs
5
, which however have a length that is shorter than the overall length L of the tab and the therewith associated perforation of the laminations of the above described first type (see FIG.
1
); moreover, these punchings are not associated with any perforation
Such laminations are then associated with each other alternately, as this is best shown in the central portion G of
FIG. 2
d
, so that the tabs of the laminations of the second type are able to press-fit into the corresponding cavities that are provided, along with the above mentioned perforations, in the laminations of the first type, so as to thereby ensure a firm mutual fastening of adjacent laminations.
The afore mentioned “skew effect” is brought about by the fact that, owing to the tabs of the laminations of the first type being shorter than their respective receiving recesses in the contiguous laminations including the therewith associated perforation, it is possible for a lamination to be rotated by a small, but anyway sufficient extent with respect to the adjacent lamination so as to obtain the desired rotational misalignment, or skew, of the laminations with respect to each other.
The foregoing is well-known and clearly shown in U.S. Pat. No. 3,590,208, European Patent No. EP 0,160,147, and U.S. Pat. No. 5,163,217.
However, such a solution has a twofold drawback in that ferromagnetic material, ie. the one relating to said perforations made in the laminations of the first type, is anyway removed, while the possibility furthermore arises for overlapping perforations in contiguous laminations to practically form continuous channels into which die-cast alloy may then be poured so as to form further alloy bars
20
, as this is symbolically shown in
FIG. 7
, that unavoidably affect the electrical behaviour of the same rotor, as anyone skilled in the art is well aware of.
It thereforewould be desirable, and actually is a purpose of the present invention, to provide a rotor stack that enables both such a perforation of the laminations and the resulting removal of ferromagnetic material to be avoided, and such additional bars of die-cast alloy to be prevented from forming during the die-casting process.
REFERENCES:
patent: 3590208 (1971-06-01), Martini et al.
patent: 4110895 (1978-09-01), Mitsui
patent: 4619028 (1986-10-01), Neuenschwander
patent: 4979285 (1990-12-01), Martin
patent: 5142178 (1992-08-01), Kloster et al.
patent: 5163217 (1992-11-01), Sakanishi
patent: 5338996 (1994-08-01), Yamamoto
patent: 5649349 (1997-07-01), Greenway
patent: 5767607 (1998-06-01), Kieffer
patent: 5894182 (1999-04-01), Saban et al.
patent: 0160147A2 (1985-11-01), None
Pearne & Gordon LLP
Waks Joseph
Zanussi Elettromeccanica S.p.A.
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