Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – With magneto-mechanical motive device
Patent
1988-02-01
1990-03-13
Harris, George
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
With magneto-mechanical motive device
335230, H01F 708
Patent
active
049085921
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic actuating device comprising a movable member and a stator structure. The movable member comprises at least one portion magnetized perpendicularly to the direction of its movement and having a small thickness with respect to its other while, the stator structure comprises at least one magnetic circuit made of a material of very high magnetic permeability, an air-gap in which at least one portion of the magnetized part is arranged, and at least one electric energizing coil coupled with the magnetic circuit.
2. Description of the Prior Art
Devices of this general type are used in rotatory motors with rapid speed variations in which it is generally desired to accomplish a great number of elementary movements or steps per revolution of the rotor. These devices, however, do not provide a constant force over a relatively long distance and they are not entirely free of residual torque, i.e., torque in the absence of current. Furthermore, they are generally relatively complex, be it in single phase or two-phase design.
SUMMARY OF THE INVENTION
The invention aims in particular at providing a simple and economic actuating device for effecting movement of the movable member over a limited distance with a substantially constant force and having practically no residual torque. Such a device can be used, for example, for actuating the supporting arm of the reading and writing head of a rotatory disc memory, such as a hard or floppy disc, of a magnetic or optical disc. For such applications, one often uses devices with a movable coil in a stator structure with a permanent magnet, called "voice coil" devices. These devices require a relatively large magnet which leads to a relatively high cost. It further has, in particular, a volume and an inertia which are not of a minimum value with respect to the force produced.
The invention has also for its object to remedy the inconvenience of these known devices. To this effect, the device according to the invention is arranged so that the magnetized part can effect a limited movement inside the air-gap under the action of a constant force which is proportional to the current flowing in the energizing coil or coils and is practically free from residual torque in the absence of energizing current. Preferred embodiments of the invention for providing such benefits are described in claims 1 to 8.
BRIEF DESCRIPTION OF THE DRAWING
The features, the advantages and the possibilities of application of the invention will become more clearly apparent from the description given hereunder of various non-limiting examples of embodiments thereof which are illustrated in the attached drawing in which:
FIG. 1 is a view of a linear actuating device according to the invention,
FIG. 2 is a view in section along line II--II of FIG. 1,
FIG. 3 is a view of an alternative embodiment of the linear actuation device of FIG. 1,
FIG. 4 is a section along line IV--IV of FIG. 3,
FIG. 5 is a view of an actuating device with a rotating arm according to the invention,
FIG. 6 is a section along line VI--VI of FIG. 5,
FIG. 7 is an axial section of a linear actuating device with a cylindrical magnet,
FIG. 8 is an axial view, partially in section, of the device of FIG. 7, and
FIG. 9 is a schematic view in perspective of a rectangular assembly of magnetized parts which can be used in a device similar to that of FIG. 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The linear actuating device shown in FIGS. 1 and 2 comprises a longitudinal stator structure 1 having an air-gap 19 between two stator parts 2,3, each formed by a stack of sheets of a material of very high magnetic permeability, for example, of iron-nickel 50/50. The sheets such as a sheet 4 referenced in FIG. 2 extend in the longitudinal direction and are assembled by fixing members (not shown), extending, for example, through assembling holes 5,6,7,8. The lamellar configuration of the parts thus formed allows the losses by eddy currents in
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patent: 4527139 (1985-07-01), Bohg et al.
patent: 4703297 (1987-10-01), Nagasaka
Harris George
Portescap
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