Pumps – Motor driven – Electric or magnetic motor
Reexamination Certificate
2002-03-29
2003-11-25
Freay, Charles G. (Department: 3746)
Pumps
Motor driven
Electric or magnetic motor
C417S415000, C310S012060, C310S013000
Reexamination Certificate
active
06652252
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to electromagnetic devices. The invention is particularly useful as an electromagnetic vibrator for a fluid pump, and is therefore described below with respect to this application.
Electromagnetic devices include cores containing electrical coils which generate a circulating loop of magnetic flux producing an attractive force with respect to a movable armature, to convert the electrical current passed through the coil to mechanical movements of the armature. The strength of the circulating loop of magnetic flux, and therefore the strength of the force supplied to the armature, is determined by the coil size, current flow through the coil, magnetic permeability of the core, and the magnetic reluctance across the various air gaps.
Electromagnetic devices in general, and electromagnetic vibrators in particular, include two types of air gaps: a fixed air gap, namely one in which the distance between the relatively moving surfaces of the armature and core remains substantially the same; and a variable air gap, in which the distance changes during such movements. The force developed by an electromagnetic device is a function of the rate of change of the magnetic reluctance (or permeance) of the air gap. Accordingly, a fixed air gap does not contribute to the attractive force produced by the electromagnetic device; rather it reduces the strength of the circulating loop of magnetic flux through the core produced by a given current through the coil. Fixed air gaps are generally provided merely for manufacturing tolerances; they should therefore be as small as possible in order to minimize the power consumed by the device and the heat generated by the device.
Variable air gaps, on the other hand, which produce the attractive force between the fixed core and movable armature, should be designed to produce maximum force with respect to the armature during the movement of the armature for a given power consumption. Electromagnetic solenoids have been previously developed providing two variable air gaps in order to provide an increased operating force in the operating direction of the solenoid, for example as described in U.S. Pat. No. 4,812,884.
OBJECTS AND BRIEF SUMMARY OF THE PRESENT INVENTION
One object of the present invention is to provide a new and efficient electromagnetic device particularly useful as a vibrator, e.g., for operating a fluid pump, but also having features useful in other electromagnetic devices, such as solenoids. Another object of the invention is to provide a new and efficient electromagnetic vibrator particularly useful for driving a fluid pump.
According one aspect of the present invention, there is provided an electromagnetic device, comprising: a core of magnetically permeable material having a longitudinal axis, a central section coaxial with the longitudinal axis, an outer section spaced outwardly from the central section, and a bridging side section bridging the outer and central sections at one side of the core, the opposite side of the core being open; a coil in the space between the central and outer sections of the core and spaced inwardly of the open side of the core such that the coil is completely recessed within the core, and the outer and central sections of the core define an extension extending laterally past the recessed coil; a movable armature of magnetically permeable material facing and aligned with the extension in the core, the armature being movable towards and away from the coil and being formed with a central recess; and a pair of springs on the opposite ends of the core and coaxial with the longitudinal axis of the core, the pair of spring mounting the armature for straight-line reciprocatory movements parallel to the longitudinal axis of the core; the armature and its recess being configured and located such that during the movement of the armature towards and away from the coil: (a) the recess receives the central section of the core; (b) the outer surface of the armature defines a first working gap with the inner surface of the core outer section at the extension; (c) and the inner surface of the armature at the recess defines a second working gap with the outer surface of the core central section at the extension.
The first and second gaps referred above are referred to as “working gaps” since the distance between the respective surfaces defining each gap (and thereby the gap permeance or reluctance) changes during the operation of the device to produce the attractive force, or the work performed by the electromagnetic device. As described above, this is to be distinguished from fixed air gaps, which do not produce an attractive force and therefore are not “working gaps”.
Several preferred embodiments of the invention are described below for purposes of example. According to further features in the described preferred embodiments, the armature is movable from an initial position with respect to the outer face of the core central section at the extension, to an inner position within the extension but outwardly of the respective end of the coil, and to an outer position outwardly of the outer face of the core central section at the extension.
In addition, in some described embodiments, the armature is mounted for the straight-line reciprocatory movements by a shaft coupled to the armature and extending through the core coaxially with the longitudinal axis of the core; whereas in another described embodiment, the armature is mounted for the straight-line reciprocatory movements by a shuttle member coupled to the springs on opposite sides of the core for reciprocatory movement parallel to the longitudinal axis of the core.
In a further described embodiment the electromagnetic device includes a plurality of cores, coils and armatures arranged in tandem with all the armatures coupled together to produce a powerful, compact electromagnetic vibrator (or other electromagnetic devices such as a solenoid).
In all the described embodiments, the coil is energized by an alternating current source having a half-wave rectifier effective to energize the coil in half-cycles to drive the armature in one direction, and to de-energize the coil in the remaining half-cycles to permit the pair of springs to drive the armature in the opposite direction.
As will be described more particularly below, electromagnetic devices incorporating the foregoing features may be constructed as compact units producing large mechanical forces for the electrical power consumed, and generating small amounts of heat for the mechanical force generated.
Further features and advantages of the invention will be apparent from the description below.
REFERENCES:
patent: 4172229 (1979-10-01), Guimbal
patent: 4812884 (1989-03-01), Mohler
patent: 5233140 (1993-08-01), Asano et al.
patent: 5280775 (1994-01-01), Tanamura et al.
patent: 5503364 (1996-04-01), Enomoto et al.
patent: 6127750 (2000-10-01), Dadd
patent: 6323568 (2001-11-01), Zabar
patent: 6540485 (2003-04-01), Nara et al.
patent: 62-112369 (1987-07-01), None
Freay Charles G.
G. E. Ehrlich (1995) Ltd.
Gray Michael K.
MNDE Technologies L.L.C.
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