Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – With magneto-mechanical motive device
Reexamination Certificate
1999-12-22
2001-07-24
Barrera, Ramon M. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
With magneto-mechanical motive device
C335S278000, C335S281000
Reexamination Certificate
active
06265956
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to solenoids, especially to permanent magnet latching-type solenoids.
BACKGROUND OF THE INVENTION
There are numerous uses for solenoids that have a plunger which may be held in either of two end positions while being selectively movable between those positions by pulsed energization of an electromagnetic coil. Uses of such devices include holding, locking, or latching another device in a predetermined position, subject to release upon appropriate energization of a coil in the solenoid. All such uses are sometimes referred to hereinafter as “latching.” One particular example is the use of a latching solenoid to lock the cover of a computer device in a closed position.
A typical magnetic latching solenoid basically comprises a conventional electrical coil operated solenoid with a permanent magnet in the structure. The permanent magnet provides a permanent magnetic attraction force for retaining a solenoid armature, sometimes referred to as a “plunger,” in either of two end positions. The electric coil is used to generate a momentary pulse of a magnetic field to momentarily overcome the magnetic attraction field of the permanent magnet and to drive the plunger to change its position. The resulting movement of the plunger will drive a push rod that may be used to perform a locking operation. The same coil or another coil then may be energized momentarily in an opposite sense to release and move the plunger in the opposite direction for unlocking purposes, such as by using an electrical pulse generating device that is activated only upon entry of an appropriate code on a related keyboard. Latching solenoids are used in great numbers for such operations. It is desirable to provide solenoids which will operate reliably for such uses and which can be produced in a facile manner at low costs.
OBJECTS AND SUMMARY OF THE INVENTION
The general aim of the present invention is to provide improved latching solenoids, and, particularly, improved double acting permanent magnet latching solenoids.
It is another object of this invention to provide solenoids of designs which can be manufactured and assembled in a facile, economic manner.
A further object of this invention is to provide an improved method to facilitate economic assembly of such solenoids.
These and other objects and advantages of the invention will become more apparent from the following description and the accompanying drawings.
A permanent magnet latching solenoid is provided which comprises a bobbin of non-magnetic material that carries the actuating electrical winding. The bobbin has a central passage for receiving a reciprocative plunger, often referred to herein as the armature. A hollow cylindrical magnetically permeable bushing is mounted in each end of the bobbin, with the internal opening of each of those bushings providing an extension of the central bobbin passage, to define a bore in which the armature has free sliding reciprocative movement. The outer ends of the bushings, sometimes referred to herein as the “distal” ends, define the ends of that bore. A separate magnetically permeable frame surrounds the bobbin and includes end wall portions that extend close to and preferably abut the distal ends of the bushings. Each bushing thus is closely coupled magnetically with a respective end wall of the frame. At least one permanent magnet is mounted between the bobbin and the frame. In the preferred embodiment two permanent magnets of equal magnetic power are disposed on opposite sides of the bore in which the armature moves. Openings in the end wall portions of the frame accommodate free passage of an operator rod element which is affixed to the armature. This rod element serves as the operator element for carrying out one or more desired functions, such as locking another component in a predetermined position. One example of such use is in locking a computer cover, as noted above.
The armature is of an axial length that is substantially less than the length of the bore and is freely movable there along between two end positions by the permanent magnets and the electric coil. More specifically, the armature is of a length such that when one end portion of the armature is within the bushing at one end of the bore, with the respective end of the armature abutting or in close-coupled magnetic relation to the respective end wall of the frame, the opposite end of the armature is near the inward end of the bushing at the opposite end of the bore. With the armature in such a first end position, the magnetic field of the permanent magnets is concentrated through the respective mutually adjacent end portions of the frame, the respective bushing and the armature, for example the right end portions in
FIG. 1
, to hold the armature in that first end position. However, an appropriate brief pulsing of the coil, such as for about 50 milliseconds, temporarily will create an opposing magnetic field, i.e., opposing the field of the permanent magnet, to release the armature from that first end position and create an attractive field therefor through the bushing and end wall at the opposite end and thereby impel the armature from the first end position toward the opposite end position.
The bushing around the seated end of the armature shunts a portion of the magnetic field of the permanent magnets radially from the armature to the respective bushing and thence to the adjacent end wall of the frame. This reduces the axial magnetic seating force on the armature and accordingly facilitates release of the armature upon pulsing of the respective coil for movement of the armature toward the opposite end of the frame. Further, the axial adjacency of the other bushing to the opposite end of the armature enhances the axial magnetic attraction force that is briefly applied to the armature by the respective coil for impelling the armature toward that opposite end.
The electrical pulse through the coil should impel the armature significantly past a longitudinally centered position in the bore, whereafter the attractive force of the permanent magnet circuit through the opposite end of the frame and the related adjacent bushing will predominate and complete the movement of the armature to the opposite end position in abutment or close coupled relationship with that opposite end of the frame. The magnetic field generated by the permanent magnet will thereafter retain the armature in that opposite end position until such time as an opposite electrical pulsing of the coil will similarly impel the armature back toward the first end position.
The permanent magnet(s) provides holding force in each end position, without any continuing current being necessary through the coil. Dual coil windings may be provided for converting electrical pulses to the appropriate magnetic flux patterns, or a single coil may be used with appropriate power pulsing techniques, as is known in this art.
Several features relate to the numerous benefits available with this invention. For example, the magnetic frame preferably is preformed of a single piece of conductive material, i.e., magnetically permeable metal, with opposite ends joined to form a unitary hollow box-like structure which is open on at least one side to allow lateral sliding insertion of the bobbin assembly. The magnetically permeable end bushings are press-fit into appropriate end portions of the bobbin, with their opposite end surfaces being spaced a distance which is essentially equal to the internal length dimension of the magnetic frame. The armature is inserted in the bore of the bobbin. This forms an assembly of the wound bobbin, bushings and armature which may be slid laterally into the described frame. A non-magnetic operating rod is then inserted through at least one opening in an end wall of the frame and secured to the armature. This rod provides an external operating element to make appropriate use of the movement and positioning of the armature, as well as to hold the described bobbin assembly within the frame. In one alternative construction, one or both en
Cascolan Anthony J.
Mishler Ralph E.
Barrera Ramon M.
Leydig , Voit & Mayer, Ltd.
Magnet-Schultz of America, Inc.
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