Electrical generator or motor structure – Dynamoelectric – Reciprocating
Reexamination Certificate
2000-06-19
2001-06-19
Enad, Elvin (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Reciprocating
C310S012060
Reexamination Certificate
active
06249065
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of electromagnetic actuators which produce alternating movement.
2. Discussion of the Background
Such actuators are provided in known manner with a central pole and two lateral poles. The central pole supports an exciting coil as well as a mobile portion equipped with thin permanent magnets magnetized along the direction of the air gap. German Patent DE 2603681 describes such an actuator. This actuator is provided with a fixed coil which generates an alternating flux and with two mobile magnets which are displaced in opposite senses. The electromagnetic phenomena involved obey Laplace's law (flux passing through the coil due to magnets). The magnets are not pairs of thin magnets attached to one another in opposite senses, but are two magnetic bars, each interacting with the magnetic flux created by the coil.
Such a prior art actuator suffers from major disadvantages: the structure obeying Laplace's law does not guarantee linearity of the relationship between force and the current supplying the coil. Furthermore, the efficiency of such actuators, or in other words the force per applied watt, is low. The lack of linearity leads to operating irregularity, and makes it necessary to provide complex automatic control electronics to remedy such linearity defects.
A solution to this general problem was provided by the Applicant in the form of European Patent EP 93910083.0, which describes an actuator exhibiting three stator poles and a single coil surrounding the central pole. This solution comprises using a fundamentally different electromagnetic structure, which does not obey LAPLACE's law. The proposed structure is provided with two pairs of thin magnets, which are attached to one another in alternating senses and which are displaced in an air gap.
It has become apparent with prior art devices that the vibration frequency of the mobile member is limited. As soon as the frequency is increased, the force delivered per unit of electrical power dissipated decreases, thus limiting the performances of the actuator constructed by application of European Patent EP 93910083.0. The objective of the invention is to extend the limits of vibrational frequencies by proposing a structure capable of increasing the electromagnetic efficiency.
SUMMARY OF THE INVENTION
For this purpose, the invention relates in its most general sense to an electromagnetic actuator provided with a fixed stator having two poles, the said stator being provided with at least one exciting coil supplying the two poles, the actuator additionally being provided with a mobile portion comprising at least two independent elements, each mobile in opposite senses along directions parallel to the intersection of the plane of the air gap and the central plane of the fixed stator, each of the mobile elements being equipped with thin permanent magnets magnetized transversely along the direction of the air gap, characterized in that each of the mobile elements has three thin magnets magnetized in alternating senses, which magnets may or may not be integral with a yoke of soft material, the said thin magnets of one of the said mobile elements being magnetized along the sense opposite to that of the corresponding thin magnets of the second mobile element, the yoke and fixed stator part defining therebetween the air gap E.
Advantageously, the mobile member comprises two parts which are mobile in opposition, each of the said mobile parts being joined to the fixed stator by elastically deformable means in order to allow clearance along the mobility direction while maintaining a substantially constant air gap E.
According to a preferred embodiment, the joint between each of the mobile parts and the fixed stator is ensured by leaf springs extending substantially perpendicular to the plane of the air gap.
According to another alternative embodiment, the length Xc of the stator poles is greater than or equal to the travel X of the mobile member plus a length substantially equal to E.
Preferably the distance e separating the central pole and each of the lateral poles is greater than or equal to 0.5 E, where E denotes the width of the air gap.
According to an advantageous embodiment, the actuator has a latching force which tends to restore the mobile part to central position.
According to a preferred embodiment, each of the mobile elements comprises a mobile yoke integral with the three permanent magnets magnetized transversely in alternating senses.
REFERENCES:
patent: 5175457 (1992-12-01), Vincent
patent: 5208498 (1993-05-01), Hamajima
patent: 0 228 055 (1987-07-01), None
patent: WO 97/29534 (1997-08-01), None
Frachon Didier
Oudet Claude
Enad Elvin
Jones Judson H.
MMT SA
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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