U.S. patent number 3,828,288 [Application Number 05/365,025] was granted by the patent office on 1974-08-06 for magnetic actuator device.
This patent grant is currently assigned to Allis-Chalmers Corporation. Invention is credited to Donald R. Boyd.
United States Patent |
3,828,288 |
Boyd |
August 6, 1974 |
MAGNETIC ACTUATOR DEVICE
Abstract
There is provided in accordance with an embodiment of the
invention a magnetic actuator device comprising an annular-shaped
permanent magnet having magnetic pole pieces in contact with the
opposite axial ends of the permanent magnet. A bobbin member of a
nonmagnetic electrically insulating material such as nylon is
coaxially and concentrically positioned within the central opening
of the annular permanent magnet. A trip coil connected to an
electrical signal source is positioned on the hollow cylindrical
hub of the bobbin. A cylindrical plunger or armature of magnetic
material is positioned for axial linear sliding movement in the
hollow hub of the bobbin. The forward end of the plunger carries a
colored stud member which projects forwardly of the front pole
piece and serves by its position as an indicator of whether the
magnetic actuator device is in tripped or untripped condition. The
rearwardly facing end of the magnetic plunger carries a nonmagnetic
spindle which projects rearwardly through the rear pole piece and
bears against a spiral spring mounted on the rear or outer surface
of the rear pole piece. Normally, the magnetic actuator device is
in a magnetically latched condition in which the rearwardly facing
end of the plunger bears against the inner face of the rear pole
piece, with the armature being held in this magnetically latched
position against the force of the spring by the magnetic flux from
the permanent magnet passing through the magnetic plunger. Upon the
receipt of a momentary electrical signal pulse on the coil, a
magnetomotive force with resulting magnetic flux is set up by the
coil which opposes the magnetic flux of the permanent magnet to a
sufficient extent to permit the spring to rapidly move the plunger
to its forward or tripped position, thereby causing the signal
indicator carried by the plunger to be projected forwardly to a
position in which it indicates that the magnetic actuator device
has been tripped. The linear movement of the plunger to tripped
position upon the receipt of a trip signal on the coil may also be
used to actuate a suitable switch, such as a microswitch,
positioned contiguous the magnetic actuator device. The magnetic
actuator device may be reset after tripping by manually pushing the
plunger rearwardly against the spring force until it magnetically
latches against the inner surface of the rear pole piece.
Inventors: |
Boyd; Donald R. (Waukesha,
WI) |
Assignee: |
Allis-Chalmers Corporation
(Milwaukee, WI)
|
Family
ID: |
23437168 |
Appl.
No.: |
05/365,025 |
Filed: |
May 29, 1973 |
Current U.S.
Class: |
335/234;
340/815.91; 335/274 |
Current CPC
Class: |
H01F
7/1615 (20130101); G08B 5/22 (20130101); H01F
7/122 (20130101); H01F 2007/163 (20130101); H01H
71/322 (20130101) |
Current International
Class: |
H01F
7/08 (20060101); H01F 7/16 (20060101); G08B
5/22 (20060101); H01H 71/32 (20060101); H01H
71/12 (20060101); H01t 007/08 () |
Field of
Search: |
;340/373,378
;335/229,230,234,274 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Harris; George
Attorney, Agent or Firm: Sullivan; Robert C.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A magnetic actuator device comprising a permanent magnet, said
magnet having a central opening therein, a bobbin of nonmagnetic
material positioned within said central opening in concentric
coaxial relation to said permanent magnet, an electrical winding
positioned on said bobbin, said winding being adapted to be
connected to an electric signal source, a first magnetic pole piece
in contact with one axial end of said permanent magnet, a second
magnetic pole piece in contact with the opposite axial end of said
permanent magnet, said bobbin having a hollow hub lying
substantially along the central longitudinal axis of said actuator
device, a magnetic armature positioned in said hollow hub of said
bobbin and being axially movable along said hub, means carried by
said armature at one end of said armature contiguous said first
magnetic pole piece, said means being movable by movement of said
armature to an extended position forwardly of said first magnetic
pole piece, a spindle member carried by the opposite end of said
armature and movable with said armature, said spindle member
extending through a passage in said second magnetic pole piece, a
spring mounted on the outer surface of said second magnetic pole
piece, said spindle member engaging said spring, said armature
being movable against the force of said spring to a position in
which it is magnetically latched by magnetic flux from said
permanent magnet against the inner surface of said second magnetic
pole piece, a signal on said electrical winding being effective to
counteract the magnetic effect of said permanent magnet of said
armature sufficiently to permit said spring to move said armature
axially away from said second pole piece, whereby to cause said
means carried by said armature to be projected to an extended
position forwardly of said first pole piece.
2. A magnetic actuator device as defined in claim 1 in which said
means carried by said armature at said one end of said armature is
an indicating device to indicate whether said actuator device has
been moved to tripped position.
3. A magnetic actuator device as defined in claim 1 in which said
means carried by said armature comprises a sleeve-like stud member
mounted on an integral extension of said armature.
4. A magnetic actuator device as defined in claim 1 comprising a
sheet of spring-like metal secured to said outer surface of said
second pole piece, and a spiral spring etched from said sheet of
metal but remaining connected to said sheet of metal, said spindle
engaging and being engaged by said spiral spring.
5. A magnetic actuator device as defined in claim 4 in which said
first pole piece has a circular outer periphery having a diameter
substantially the same as the outer diameter of said annular
permanent magnet, said second pole piece having a semicircular
outer periphery having substantially the same radius as the outer
radius of said annular permanent magnet, the remaining portion of
the periphery of said second pole piece being of generally
rectangular-shape and formed of straight edges, the outer
peripheral contour of said sheet of spring-like metal being
substantially the same as the peripheral contour of the outer face
of said second pole piece.
6. A magnetic actuator device as defined in claim 1 in which said
permanent magnet is of annular shape, and said central opening is
defined by said annular shape.
7. A magnetic actuator device as defined in claim 1 in which the
axial end of said armature which magnetically latches against the
inner surface of said second magnetic pole piece lies substantially
entirely radially inwardly of said permanent magnet and has a
substantially smaller area than the area of said inner surface of
said second magnetic pole piece.
8. A magnetic actuator device as defined in claim 1 in which said
spindle is made of nonmagnetic material.
9. A magnetic actuator device as defined in claim 1 in which said
means carried by said armature remains projected in said extended
position until said armature is reset by a force external of said
device against the force of said spring to a position in which said
armature is again magnetically latched against the inner surface of
said second magnetic pole piece.
10. A magnetic actuator device as defined in claim 1 in which said
spindle includes an enlarged head portion engaging said spring,
said head portion serving as a stop which engages the outer surface
of said second pole piece to limit the tripping movement of said
armature, the distance of the axial tripping movement of said
armature as determined by the position of said head portion being
such that upon completion of said tripping movement said armature
has moved a sufficient axial distance away from the inner surface
of said magnetic pole piece that said armature must be reset by a
force external of said magnetic actuator device against the force
of said spring to a position in which said armature is again
magnetically latched against the inner surface of said second
magnetic pole piece.
11. A magnetic actuator device comprising a permanent magnet, said
magnet having a central opening therein, a bobbin of nonmagnetic
material positioned within said central opening in coaxial relation
to said permanent magnet, an electrical winding positioned on said
bobbin, said winding being adapted to be connected to an electric
signal source, a first magnetic pole piece in contact with one
axial end of said permanent magnet, a second magnetic pole piece in
contact with the opposite axial end of said permanent magnet, said
bobbin having a hollow hub lying substantially along the central
longitudinal axis of said actuator device, a magnetic armature
positioned in said hollow hub of said bobbin and being axially
movable along said hub, an indicator device carried by said
armature at one end of said armature contiguous said first magnetic
pole piece, said indicator device being movable by movement of said
armature to an extended position forwardly of said first magnetic
pole piece, a spindle member carried by the opposite end of said
armature and movable with said armature, said spindle member
extending through a passage in said second magnetic pole piece, a
spring mounted on the outer surface of said second magnetic pole
piece, said spindle member engaging said spring, said armature
being movable against the force of said spring to a position in
which it is magnetically latched by magnetic flux from said
permanent magnet against the inner surface of said second magnetic
pole piece, a signal on said electrical winding being effective to
counteract the magnetic effect of said permanent magnet on said
armature sufficiently to permit said spring to move said armature
axially away from said second pole piece, whereby to cause said
indicator device carried by said armature to be projected to said
extended position forwardly of said first pole piece, said
indicator device remaining projected in said extended position
until said armature is reset by a force external of said magnetic
actuator device against the force of said spring to a position in
which said armature is again magnetically latched against the inner
surface of said second magnetic pole piece.
12. A magnetic actuator device as defined in claim 11 in which said
permanent magnet is of annular shape, and said central opening is
defined by said annular shape.
13. A magnetic actuator device as defined in claim 11 in which said
spindle is made of nonmagnetic material.
14. A magnetic actuator device as defined in claim 11 in which said
spindle includes an enlarged head portion engaging said spring,
said head portion serving as a stop which engages the outer surface
of said second pole piece to limit the tripping movement of said
armature, the distance of the axial tripping movement of said
armature as determined by the position of said head portion being
such that upon completion of said tripping movement said armature
has moved a sufficient axial distance away from the inner surface
of said magnetic pole piece that said armature must be reset by a
force external of said magnetic actuator device against the force
of said spring to a position in which said armature is again
magnetically latched against the inner surface of said second
magnetic pole piece.
15. A magnetic actuator device as defined in claim 11 comprising a
sheet of spring-like metal secured to said outer surface of said
second pole piece, and a spiral spring etched from said sheet of
metal but remaining connected to said sheet of metal, said spindle
engaging and being engaged by said spiral spring.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to magnetically operated actuator devices
such as a magnetic flux cancelling device which may be used, for
example, as an indicating device to indicate the occurrence of a
fault current such as a ground fault or a phase-to-phase fault, for
example. However, the linear mechanical movement produced during
the operation of the device of the present invention may be
utilized in other ways although it will be described as embodied as
used in an indicating device.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a magnetically
operated actuator device such as a flux cancelling device which can
be manufactured and sold at relatively low cost.
It is a further object of the invention to provide a magnetically
operated actuator device which is useful in indicating that a fault
has occurred (i.e., a ground fault or phase-to-phase fault) which
has caused a circuit breaker to trip.
BRIEF DESCRIPTION OF THE DRAWING
Further objects and advantages of the invention will become
apparent from the following description taken in conjunction with
the accompanying drawing in which:
FIG. 1 is a front elevation view of the magnetic actuator device of
the invention;
FIG. 2 is a view partially in section along line II--II of FIG. 1,
and also partially in elevation, showing the plunger or armature of
device 10 in magnetically latched position; and
FIG. 3 is a rear elevation view of the device of FIGS. 1 and 2.
In achievement of these objectives, there is provided in accordance
with an embodiment of the invention a magnetic actuator device
comprising an annular shaped permanent magnet having magnetic pole
pieces in contact with the opposite axial ends of the permanent
magnet. A bobbin member of a nonmagnetic electrically insulating
material such as nylon is coaxially and concentrically positioned
within the central opening of the annular permanent magnet. A trip
coil connected to an electrical signal source is positioned on the
hollow cylindrical hub of the bobbin. A cylindrical plunger or
armature of magnetic material is positioned for axial linear
sliding movement in the hollow hub of the bobbin. The forward end
of the plunger carries a colored stud member which projects
forwardly of the front pole piece and serves by its position as the
indication of whether the magnetic actuator device is in tripped or
untripped condition. The rearwardly facing end of the magnetic
plunger carries a nonmagnetic spindle which projects rearwardly
through the rear pole piece and bears against a spiral spring
mounted on the rear or outer surface of the rear pole piece.
Normally, the magnetic actuator device is in a magnetically latched
condition in which the rearwardly facing end of the plunger bears
against the inner face of the rear pole piece, with the plunger or
armature being held in this magnetically latched position against
the force of the spring by the magnetic flux from the permanent
magnet passing through the magnetic plunger. Upon the receipt of a
momentary electrical signal pulse on the coil, a magnetomotive
force with resulting magnetic flux is set up by the coil which
opposes the magnetic flux of the permanent magnet to a sufficient
extent to permit the spring to rapidly move the plunger to its
forward or tripped position, thereby causing the signal indicator
carried by the plunger to be projected forwardly to a position in
which it indicates that the magnetic actuator device has been
tripped. The linear movement of the plunger to tripped position
upon the receipt of a trip signal on the coil may also be used to
actuate a suitable switch, such as a microswitch, positioned
contiguous the magnetic actuator device. The magnetic actuator
device may be reset after tripping by manually pushing the plunger
rearwardly against the spring force until it magnetically latches
against the inner surface of the rear pole piece.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawing, the magnetic actuator device of the
invention is generally indicated at 10 and comprises an
annular-shaped permanent magnet 12 which may, for example, be a
ceramic compound of barium ferrite mixed with ferric oxide. Such
ceramic permanent magnet materials are well known in the art under
the general name "ferrite" and are manufactured under the trade
name "Arnox" by Arnold Engineering Company and under the trade name
"Indox" by Indiana General Corporation. The annular shape of
permanent magnet 12 defines a central opening 14.
A bobbin of a nonmagnetic, electrically insulating material such as
nylon generally indicated at 15, is positioned within the central
opening 14 of the annular-shaped permanent magnet 12 in coaxial and
concentric relation to permanent magnet 12. Bobbin 15 includes an
axially extending hollow cylindrical hub portion 16 and radially
extending front and rear flanges 17 and 18. The outer diameter of
the radially extending flanges 17 and 18 is just slightly less than
the inner diameter of the annular permanent magnet 12. Hollow hub
portion 16 of bobbin 15 also includes a hollow axial extension 20
which projects axially beyond the front flange 17 of the bobbin
relative to the view of FIG. 2 and through a passage 24 in the
generally disc-shaped front pole piece 22 of the device 10. Axial
extension 20 of bobbin hub 16 is threaded as indicated at 21 to
permit mounting of device 10 on a panel or the like.
Front pole piece 22 has the same outer diameter as annular
permanent magnet 12 and is suitably adhesively attached to the
axially front end annular surface of annular permanent magnet 12.
The disc-shaped pole piece 22 is made of a suitable magnetic
material such as soft iron or soft steel.
An electrical winding or coil 26 is mounted on hub 16 of bobbin 15
and a wrapping of a suitable insulating material 28 is positioned
on the outer periphery of the winding 26. Electrical leads or
conductors 30 connected to winding 26 extend through a suitable
opening or slot 32 in front pole piece 22 to permit connection of
winding 26 to the electrical signal source.
A back magnetic pole piece generally indicated at 25 formed of the
same magnetic material such as soft iron or soft steel as the front
magnetic pole piece 22 is adhesively secured to the back annular
surface (or lower surface relative to FIG. 2) of permanent magnet
12.
As viewed in FIG. 1, back pole piece 25 has a semicircular
peripheral edge 33 having the same radius as front pole piece 22
for 180 degrees of its periphery (the upper 180 degrees as viewed
in FIG. 1). For the lower half of its periphery, back pole piece 25
is of generally rectangular shape, as bounded by the straight or
flat edges 34, 36, 38. Straight or flat edge 38 might be considered
the "base edge" of device 10.
The internal periphery of hollow cylindrical hub member 16 of
bobbin 15 serves as a bearing for a linearly movable cylindrical
plunger or armature member 40 of a suitable magnetic material such
as soft iron or soft steel.
The outer diameter of the cylindrical plunger member 40 is just
sufficiently less than the inner diameter of the hollow cylindrical
bobbin hub 16 (and of the hollow cylindrical axial extension 20 of
hub 16) to permit easy linear sliding movement of the plunger as
will be described. The axial length of plunger or armature 40 is
such that in the magnetically latched position of armature 40, as
seen in FIG. 2 the axially innermost or rear end surface of
armature 40 abuts against the inner surface of rear pole piece 25
while the opposite axial end or forward end of the armature 40
projects slightly beyond the forward surface or axially outer
surface of front pole piece 22.
The forward end of magnetic plunger 40 has a sleevelike stud member
42 of a colored (such as red), preferably nonmagnetic and
preferably electrically insulating plastic material or the like
suitably pressed onto an integral reduced diameter extension 41
which forms part of and is carried by plunger or armature 40. A
spindle member 44 of a suitable nonmagnetic preferably electrically
insulating material such as a suitable plastic material such as
nylon has a threaded end 46 which is in threaded engagement with a
threaded bore 48 in the rearwardly facing surface of plunger 40.
Spindle 44 extends through a passage 50 in back pole piece 25 and
projects, in the magnetically latched position shown in FIG. 2, for
a distance, for example, approximately one-half inch rearwardly of
back pole piece 25, in the illustrated embodiment. Spindle 44 is
provided with an enlarged head portion 52 at the axially rearmost
end thereof which cooperates with the spring generally indicated at
54 to be hereinafter described.
A thin sheet of a spring-like material such as beryllium cooper or
the like, generally indicated at 56 (FIG. 3) is mounted on back
pole piece 25. Sheet 56 has substantially the same contour as back
pole piece 25 as previously described, including a semicircular
edge portion 33' which substantially coincides with semicircular
edge portion 33 of back pole piece 25, and straight or flat edge
portions 34', 36', 38' which respectively coincide with edge
portions 34, 36, 38 of back pole piece 25. Edge 38' of beryllium
copper sheet 56 is secured to corresponding edge 38 of back pole
piece 25 by rivets 58 or other suitable fasteners. With the
exception of the rivets 58 which secure bottom edge 38' of
beryllium copper sheet 56 to the corresponding edge 38 of pole
piece 25, the beryllium copper sheet 56 is otherwise free or
unsecured to the rear surface of the rear pole piece 25.
Prior to being secured to the surface of the pole piece 25, the
beryllium cooper sheet 56 is subjected to a photographic etching
process whereby to cut from the sheet 56 the spiral spring member
generally indicated at 54 which is extendable in spring-like
fashion from the remaining portions of sheet 56, while still
remaining attached to sheet 56, as best seen in the magnetically
latched position of FIG. 2 in which spring 54 is in its extreme
tensioned position. During the outer axial movement of spiral
spring 54 to its tensioned position as seen in FIG. 2, when
armature 40 is moved to its magnetically latched position, the
peripheral edges 33', 34', 36', 38' of the beryllium copper sheet
56 remain in substantially a common plane substantially parallel to
the flat rear surface of rear pole piece 25. Spring 54 includes a
central nub 60 having a point 62 which lies substantially in
alignment with the central longitudinal axis of spindle 44. The
enlarged head portion 52 at the outer or rearmost end of spindle 44
is adapted to engage and be engaged by the nub portion 60 of spring
54.
DESCRIPTION OF OPERATION
The device 10 is placed into magnetically latched position as seen
in FIG. 2 of the drawing by manually pushing inwardly on stud
portion 42 at the forward or front end of the magnetic plunger or
armature 40, causing the rearward end of the plunger 40 to move
against the force of spring 54 until the axially rearmost end of
plunger 40 moves into engagement with the inner surface of rear
pole piece 25. In this position of the armature, the armature is
held in magnetically latched position by the magnetic flux which
passes from the annular permanent magnet 12 into the rear pole
piece 25 and thence forwardly through the magnetic armature 40 in
its magnetically latched position, the magnetic flux returning from
forward end of armature 40 to the forward or front pole piece 22.
It should also be noted that the magnetic circuit of the magnetic
flux from the forward end of the plunger 40 to the front pole piece
22 includes a annular nonmagnetic gap defined by the radial
thickness of the hub portion 16 of bobbin 15. In the magnetically
latched position of the device 10 as seen in FIG. 2, the head
portion 52 on the rearmost end of the plastic spindle 44 engages
the central nub 60 of spring 54 and holds the spiral spring 54 in
the extended position shown in the magnetic latched position of
FIG. 2 in which the spring 54 is tensioned and exerts a force on
armature or plunger 40 through spindle 44 trying to return plunger
40 to its unlatched position.
The coil 26 on the bobbin 15 is wound in such direction that when a
signal, such as a fault signal, for example, is received through
the conductors 30 which connect the signal source to coil 26, a
magnetomotive force (MMF) is set up by the coil during the brief
moment of a pulse signal which might last, for example, for 12
milliseconds, that will oppose the magnetic field of the permanent
magnet 12 in such manner as to reduce the magnetic force holding
the armature 40 in it magnetically latched position against the
inner surface of rear pole piece 25 to such an extent as to permit
the force of the tensioned spring 54 to return the plunger to its
unlatched position. When the inner end 53 of the head portion 52 of
spindle 44 abuts against the rear surface of rear pole piece 25,
the plunger 40 will have reached the limit of its forward travel in
the unlatching direction. The unlatching movement of plunger 40
under the influence of the spring 54 upon the receipt of a signal
pulse on the coil 26 will, of course, advance the colored plastic
stud 42 to a position forwardly of that shown in the view of FIG. 2
by distance equal to the stroke of the plunger 40 during the
unlatching motion just described. This advanced position of the
colored stud portion 42 attached to plunger 40 will serve as
indication to an observer that the device 10 has been moved to its
tripped position by the receipt of a signal pulse on coil 26,
thereby advising the observer that a predetermined condition has
occurred such as a ground fault or a phase-to-phase fault which may
have caused an associated circuit breaker to trip. Of course, the
particular signal which is used to energize the coil 26 may be
derived from any suitable source and may indicate any desired
condition. It should also be noted that during the tripping
operation of device 10 the linear movement of the stud portion 42
at the forward end of the device 10 or the corresponding linear
movement of the nub portion 60 of spring 54 at the rear of device
10 may be utilized to actuate a suitable switch device such as a
microswitch, for example, to thereby perform some desired switching
operation such as the actuation of an alarm signal or the like.
When plunger 40 moves to its advanced forward position upon the
receipt of a trip signal on coil 26 as previously described,
plunger 40 will remain in the tripped position until it is manually
reset by manually pushing on stub 42 at the forward end of the
device 10 to axially push the plunger toward the rear pole piece 25
to the position in which the plunger is held in its magnetically
latched position as previously explained.
From the foregoing detailed description of the invention, it has
been shown how the objects of the invention have been obtained in a
preferred manner. However, modifications and equivalents of the
disclosed concepts, such as readily occur to those skilled in the
art are intended to be included within the scope of this
invention.
* * * * *