U.S. patent number 3,792,390 [Application Number 05/365,024] was granted by the patent office on 1974-02-12 for magnetic actuator device.
This patent grant is currently assigned to Allis-Chalmers Corporation. Invention is credited to Donald R. Boyd.
United States Patent |
3,792,390 |
Boyd |
February 12, 1974 |
MAGNETIC ACTUATOR DEVICE
Abstract
There is provided in accordance with an embodiment of the
invention a magnetic actuator device, such a flux cancelling,
transferring or shifting type trip device comprising an annular
permanent magnet, and a first main pole piece of magnetic material
engaging one axial end of the permanent magnet and a threaded
magnetic hollow stud member integral with the first main pole piece
and extending axially upwardly through the central opening of the
annular-shaped permanent magnet. One end of an annular magnetic
shunting pole piece engages the opposite axial end of the permanent
magnet. An annular magnetic sleeve engages the opposite axial end
of the annular shunting pole piece. A plastic bobbin on which is
wound an electrical trip coil is positioned radially inwardly of
the annular magnetic sleeve. A second magnetic main pole piece of
annular-shape engages the axially outer end of the magnetic sleeve.
The second main pole piece has an integral hollow threaded magnetic
stud member extending axially inwardly of the assembly. A hollow
cylindrical magnetic armature is axially movable against a spring
force through the opening of the annular second main pole piece and
in the communicating hollow interior of the stud member carried by
the second main pole piece. The armature is normally held in
magnetically latched position by the magnetic field of the
permanent magnet against the spring force and in contact with the
axially inner end of the stud member carried by the first main pole
piece. When a signal pulse is applied to the coil, a substantial
amount of the permanent magnet flux is diverted through the
shunting pole piece, permitting the biasing spring force to move
the armature to a tripped position. An important feature of the
construction is the fact that the plastic bobbin on which the trip
coil is wound is threadedly engaged with the threaded studs carried
by the oppositely disposed first and second main pole pieces
whereby to hold the assembly securely together without the use of
bolts or other fastening means. A further feature of the
construction is the provision of a "built-in" non-magnetic gap on
the movable armature member in the form of a plated coating of a
non-magnetic material on the surface of the armature which engages
the stud member of the first pole piece in the latched position of
the armature. This "built-in" gap, insures that the movable
armature and cooperating stationary magnetic structure operate at
an optimum point or region on the curve of magnetic force exerted
on the armature vs. gap between the armature and the axially inner
end of the stud member carried by the first main pole piece.
Inventors: |
Boyd; Donald R. (Waukesha,
WI) |
Assignee: |
Allis-Chalmers Corporation
(Milwaukee, WI)
|
Family
ID: |
23437165 |
Appl.
No.: |
05/365,024 |
Filed: |
May 29, 1973 |
Current U.S.
Class: |
335/229; 335/234;
335/174 |
Current CPC
Class: |
H01H
71/322 (20130101) |
Current International
Class: |
H01H
71/32 (20060101); H01H 71/12 (20060101); H01f
007/08 () |
Field of
Search: |
;335/174,229,230,234,279 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign 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 assembly comprising a permanent
magnet having a central opening therethrough which extends in a
direction axially of said assembly, a magnetic first pole piece
positioned axially on one side of said permanent magnet and located
at one axial end of said assembly, a magnetic first stud member
carried by said first pole piece and extending axially inwardly of
said assembly, said first stud member being threaded, a second
magnetic pole piece positioned axially on an opposite side of said
permanent magnet and located at an opposite axial end of said
assembly, a magnetic second stud member carried by said second pole
piece and extending axially inwardly of said assembly and toward
said first stud member, said second stud member being threaded, at
least one of said stud members being hollow, a magnetic armature
member slidably movable in the hollow interior of said one stud
member, a nonmagnetic bobbin axially interposed between said first
magnetic pole piece and said second magnetic pole piece, and
coaxially positioned about said first stud member and said second
stud member, an electrical winding carried by said bobbin, said
armature normally being held in magnetically latched position by
magnetic flux from said permanent magnet flowing through said
armature, spring means normally biasing said armature away from its
magnetically latched position, an electrical signal on said winding
being effective to counteract the magnetic effect of said permanent
magnet whereby to permit said spring to move said armature to
released position, said bobbin being threaded and being in threaded
engagement with said threaded first and second stud members whereby
to hold said assembly in assembled relation.
2. A magnetic acutator device as defined in claim 1 in which each
of said stud members is externally threaded and said bobbin has a
hub member which is internally threaded, said threaded stud members
being in threaded engagement with said threaded hub member.
3. A magnetic actuator device assembly comprising a permanent
magnet having a central opening therethrough which extends in a
direction axially of the assembly, a magnetic first pole piece
located at one axial end of said assembly and engaging one axial
end of said permanent magnet, a magnetic first stud member carried
by said first pole piece and extending axially inwardly through
said central opening of said permanent magnet, said first stud
member being threaded, a second magnetic pole piece positioned at
an opposite axial end of said assembly from said first pole piece
and adapted to receive magnetic flux from said permanent magnet,
said second magnetic pole piece having a central opening extending
axially of said assembly, a hollow axially inwardly extending
second stud member carried by said second magnetic pole piece in
coaxial relation to said central opening of said second magnetic
pole piece, said second stud member being threaded, a magnetic
armature member slidably movable through said central opening of
said second pole piece and in the hollow interior of said second
stud member and towards the facing axial end of said first stud
member, spring means biasing said armature away from said first
stud member, a nonmagnetic bobbin axially interposed between said
first magnetic pole piece and said second magnetic pole piece, an
electrical winding carried by said bobbin, said armature normally
being held in magnetically latched position against said facing
axial end of said first stud member by magnetic flux from said
permanent magnet flowing through said armature and through said
first stud member, an electrical signal on said winding being
effective to counteract the magnetic effect of said permanent
magnet on said armature whereby to permit said spring to move said
armature to tripped position, said bobbin having threaded means
thereon in threaded engagement with said first and second stud
members whereby to hole said assembly in assembled relation.
4. A magnetic actuator device assembly as defined in claim 3 in
which each of said stud members is externally threaded and said
bobbin has a hub member which is internally threaded, said threaded
stud members being in threaded engagement with said threaded hub
member.
5. A magnetic actuator assembly as defined in claim 3 in which the
end of said second stud member is positioned at a predetermined
axial distance from said facing axial end of said first stud member
whereby to define a predetermined air gap between said facing ends
of said first and second stud members, said predetermined air gap
being less than the axial distance between the end of said armature
and said first stud member during most of the tripping travel of
said armature, whereby to provide a lower reluctance shunt path for
magnetic flux through said second stud member to said first stud
member than through said armature to said first stud member during
most of the tripping travel of said armature, thus reducing
magnetic force acting on said armature during its tripping
travel.
6. A magnetic actuator device assembly comprising a permanent
magnet having a central opening therethrough which extends in a
direction axially of the assembly, a magnetic first pole piece
located at one axial end of said assembly and engaging one axial
end of said permanent magnet, a magnetic first stud member carried
by said first pole piece and extending axially inwardly through
said central opening of said permanent magnet, said first stud
member being threaded, one axial end of a shunting magnetic pole
piece engaging an axial end of said permanent magnet opposite said
one end of said permanent magnet, said shunting pole piece being
radially spaced outwardly of said first stud member to define an
air gap between said shunting pole piece and said first stud
member, a second magnetic pole piece positioned at an opposite
axial end of said assembly from said first pole piece, means
defining a magnetic path from said shunting pole piece to said
second magnetic pole piece, said second magnetic pole piece having
a central opening extending in a direction axially of said
assembly, a hollow axially inwardly extending second stud member
carried by said second magnetic pole piece in coaxial relation to
said central opening of said second magnetic pole piece, said
second stud member being threaded, a magnetic armature member
slidably movable through said central opening of said second pole
piece and in the hollow interior of said second stud member and
toward the axial end of said first stud member, spring means
biasing said armature away from said first stud member, a
nonmagnetic bobbin axially interposed between said shunting pole
piece and said second magnetic pole piece, said bobbin being
bounded radially outwardly thereof by said means defining a
magnetic path from said shunting pole piece to said second magnetic
pole piece, an electrical winding carried by said bobbin, said
armature normally being held in magnetically latched position by
magnetic flux from said permanent magnet flowing through said
armature, an electrical signal on said coil being effective to
cause mangetic flux from said permanent magnet to bypass said
armature through said shunting pole piece and said air gap to
permit said spring to move said armature to released position, said
bobbin having threaded means thereon in threaded engagement with
said first and second stud members whereby to hold said assembly in
assembled relation.
7. A magnetic acutator device assembly as defined in claim 6 in
which each of said stud members is externally threaded and said
bobbin has a hub member which is internally threaded said stud
member being in threaded engagement with said hub member.
8. A magnetic actuator device assembly as defined in claim 6 in
which at least the axial end of said armature which faces the axial
end of said first stud member has a nonmagnetic plating thereon to
define a shim which spaces the magnetic material of said armature a
predetermined optinum axial distance from said axial end of said
first stud member when said armature is in magnetically latched
position.
9. A magnetic actuator device assembly comprising a permanent
magnet having a central opening therethrough which extends in a
direction axially of the assembly, a magnetic first pole piece
located at one axial end of said assembly and engaging one axial
end of said permanent magnet, a magnetic first stud member carried
by said first pole piece and extending axially inwardly through
said central opening of said permanent magnet, said first stud
member being threaded, one axial end of a shunting magnetic pole
piece engaging an axial end of said permanent magnet opposite said
one end of said permanent magnet, said shunting pole piece being
radially spaced outwardly of said first stud member to define an
air gap between said shunting pole piece and said first stud
member, one axial end of a magnetic sleeve engaging an axial end of
said shunting pole piece opposite said one end of said shunting
pole piece, a second magnetic pole piece positioned at an opposite
axial end of said assembly from said first pole piece, said second
magnetic pole piece engaging the axial end of said magnetic sleeve
opposite said one end of said magnetic sleeve, said second magnetic
pole piece having a central opening, a hollow axially inwardly
extending second stud member carried by said second magnetic pole
piece in coaxial relation to the central opening of said second
magnetic pole piece, said second stud member being threaded, a
magnetic armature member slidably movable through said central
opening of said second pole piece and in the hollow interior of
said second stud member and toward the axial end of said first stud
member, spring means biasing said armature away from said first
stud member, a nonmagnetic bobbin bounded radially outwardly
thereof by said magnetic sleeve, said bobbin being coaxial with
said first and second stud members, an electrical winding carried
by said bobbin, said armature normally being held in magnetically
latched position by magnetic flux from said permanent magnet
flowing through said armature, an electrical signal on said coil
causing magnetic flux from said permanent magnet to by-pass said
armature through said shunting pole and said air gap to permit said
spring to move said armature to released position, said bobbin
having threaded means thereon in threaded engagement with said
threaded first and second stud members whereby to hold said
assembly in assembled relation.
10. A magnetic actuator device assembly as defined in claim 9 in
which each of said stud members is externally threaded and said
bobbin has a hub member which is internally threaded, said stud
members being in threaded engagement with said hub member.
11. A magnetic actuator device assembly as defined in claim 9 in
which at least the axial end of said armature which faces the axial
end of aid first stud member has a nonmagnetic plating thereon to
define a shim which spaces the magnetic material of said armature a
predetermined optimum axial distance from said axial end of said
first stud member when said armature is in magnetically latched
position.
12. A magnetic actuator device assembly comprising an annular
permanent magnet having a central opening therethrough which
extends in a direction axially of said assembly, a cylindrical
magnetic first pole piece engaging one axial end of said permanent
magnet, a cylindrical magnetic first stud member carried by said
first pole piece and extending axially inwardly through said
central opening of said permanent magnet, said first stud member
being threaded on the external surface thereof, one axial end of a
shunting magnetic pole piece of annular shape engaging an axial end
of said permanent magnet opposite said one end of said permanent
magnet, said shunting pole piece being radially spaced outwardly of
said first stud member to define an annular air gap between said
shunting pole piece and said first stud member, one axial end of an
annular magnetic sleeve engaging an axial end of said shunting pole
piece opposite said one end of said shunting pole piece, an annular
second magnetic pole piece engaging the axial end of said annular
sleeve opposite said one end of said magnetic sleeve, said annular
second magnetic pole piece having a central opening extending in a
direction axially of said assembly, a hollow cylindrical axially
inwardly extending second magnetic stud member carried by said
second magnetic pole piece in coaxial relation to the central
opening of said second magnetic pole piece, said cylindrical second
stud member being externally threaded, a magnetic armature member
slidably movable through said central opening of said second pole
piece and in the hollow interior of said second cyindrical stud
member and toward the axial end of said first stud member, spring
means biasing said armature away from said first stud member, a
nonmagnetic bobbin bounded radially outwardly thereof by said
magnetic sleeve, said bobbin being coaxially positioned about said
first and second stud members, an electrical winding carried by
said bobbin, said armature normally being held in magnetically
latched position by magnetic flux from said permanent magnet
flowing through said armature, an electrical signal on said coil
causing magnetic flux from said permanent magnet to by-pass said
armature through said shunting pole and said air gap to permit said
spring to move said armature to released position, said bobbin
having a hollow internally threaded hub member, said threaded hub
member being in threaded engagement with said externally threaded
first and second stud members whereby to hold said assembly in
assembled relation.
13. A magnetic actuator device assembly as defined in claim 12 in
which at least the axial end of said armature which faces the axial
end of said first stud member has a nonmagnetic plating thereon to
define a shim which spaces the magnetic material of said armature a
predetermined optimum axial distance from said axial end of said
first stud member when said armature is in magnetically latched
position.
14. A magnetic actuator device assembly comprising a permanent
magnet having a central opening therethrough which extends in a
direction axially of the assembly, a magnetic first pole piece
located at one axial end of said assembly and engaging one axial
end of said permanent magnet, a magnetic first stud member carried
by said first pole piece and extending axially inwardly through
said central opening of said permanent magnet, a second magnetic
pole piece positioned at an opposite axial end of said assembly
from said first pole piece and adapted to receive magnetic flux
from said permanent magnet, said second magnetic pole piece having
a central opening extending in a direction axially of said
assembly, a hollow axially inwardly extending second stud member
carried by said second magnetic pole piece in coaxial relation to
said central opening of said second magnetic pole piece, a magnetic
armature member slidably movable through said central opening of
said second pole piece and in the hollow interior of said second
stud member and toward the axial end of said first stud member,
spring means biasing said armature away from said first stud
member, a nonmagnetic bobbin axially interposed between said first
magnetic pole piece and said second magnetic pole piece, an
electrical winding carried by said bobbin, said armature normally
being held in mangetically latched position by magnetic flux from
said permanent magnet flowing through said armature, an electrical
signal on said winding being effective to counteract the magnetic
effect of said permanent magnet on said armature whereby to permit
said spring to move said armature to released position, at least
the axial end of said armature which faces the axial end of said
first stud member having a nonmagnetic plating thereon to define a
shim which spaces the magnetic material of said armature a
predetermined optimum axial distance from said axial end of said
first stud member when said armature is in magnetically latched
position.
15. A magnetic actuator device assembly comprising a permanent
magnet having a central opening therethrough which extends in a
direction axially of the assembly, a magnetic first pole piece
located at one axial end of said assembly and engaging one axial
end of said permanent magnet, a magnetic first stud member carried
by said first pole piece and extending axially inwardly through
said central opening of said permanent magnet, one axial end of a
shunting magnetic pole piece engaging an axial end of said
permanent magnet opposite said one end of said permanent magnet,
said shunting pole piece being radially spaced outwardly of said
first stud member to define an air gap between said shunting pole
piece and said first stud member, one axial end of a magnetic
sleeve engaging an axial end of said shunting pole piece opposite
said one end of said shunting pole piece, a second magnetic pole
piece positioned at an opposite axial end of said assembly from
said first pole piece, said second magnetic pole piece engaging the
axial end of said magnetic sleeve opposite said one end of said
magnetic sleeve, said second magnetic pole piece having a central
opening which extends in a direction axially of the assembly, a
hollow axially inwardly extending second stud member carried by
said second magnetic pole piece in coaxial relation to the central
opening of said second magnetic pole piece, a magnetic armature
member slidably movable through said central opening of said second
pole piece and in the hollow interior of said second stud member
and toward the axial end of said first stud member, spring means
biasing said armature away from said first stud member, a
nonmagnetic bobbin bounded radially outwardly thereof by said
magnetic sleeve, said bobbin being coaxial with said first and
second stud members, an electrical winding carried by said bobbin,
said armature normally being held in magnetically latched position
by magnetic flux from said permanent magnet flowing through said
armature, an electrical signal on said coil causing magnetic flux
from said permanent magnet to by-pass said armature through said
shunting pole and said air gap to permit said spring to move said
armature to released position, at least the axial end of said
armature which faces the axial end of said first stud member having
a nonmagnetic plating thereon to define a shim which spaces the
magnetic material of said armature a predetermined optimum axial
distance from said axial end of said first stud member when said
armature is in magnetically latched position.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to magnetically operated actuator devices
such as a magnetic flux cancelling, transferring or shifting trip
device which may be used as a tripping device for electrical
breakers or the like. However, the linear mechanical movement
produced during the operation of the device of the present
invention may be utilized in other environments than in the
tripping of electrical circuit breakers, although it will be
described as embodied in such an environment.
2. Description of the Prior Art
Devices of the general type to which the present invention relates
are well known per se in the art and are shown, for example, in the
U.S. Pat. No. 3,693,122 issued to Henry G. Willard on Sept. 19,
1972, and in the patents referred to in the specification of the
foregoing patent.
These devices in general operate upon the principle that an
armature formed of magnetic material is retained in a magnitically
latched position by a permanent magnet which forms part of the
structure, but that upon transmission of an electrical pulse to an
electrical winding forming part of the device, the magnetic effect
of the permanent magnet upon the armature is counteracted in such
manner as to permit a biasing spring to linearly move the armature
to a tripped position. The movement of the armature to the tripped
position upon the receipt of the electrical pulse applied to the
electrical winding may be utilized to trip a circuit breaker or to
perform other switching operations or the like.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a magnetically
operated actuator device such as a flux cancelling, transferring or
shifting trip device, which has an improved assembly arrangement as
compared to prior art devices of this type.
It is a further object of the invention to provide a magnetically
operated actuator device of the flux cancelling, transferring or
shifting type, such as a magnetic trip device of this type, which
may be assembled without the use of bolts or other fasteners.
It is an object of a further feature of the invention to provide a
magnetically operated actuator device such as a flux cancelling,
transferring or shifting trip device, in which the movable armature
member is provided with a "built-in" non-magnetic gap between the
armature and the stationary part of the magnetic circuit, whereby
to permit operation of the device on an optimum portion of the
curve of magnetic force exerted on the armature by the permanent
magnet field of the device vs. dimension of gap between the movable
armature and the stationary part of the magnetic circuit toward
which the armature moves.
In achievement of these objectives, there is provided in accordance
with an embodiment of the invention a magnetic actuator device,
such as a flux cancelling, transferring or shifting type trip
device comprising an annular permanent magnet and a first main pole
piece of magnetic material engaging one axial end of the permanent
magnet and a threaded hollow magnetic stud member integral with the
first main pole piece and extending axially upwardly through the
central opening of the annular-shaped permanent magnet. One end of
an annular magnetic shunting pole piece engages the opposite axial
end of the permanent magnet. An annular magnetic sleeve engages the
opposite axial end of the annular shunting pole piece. A plastic
bobbin on which is wound an electrical trip coil is positioned
radially inwardly of the annular magnetic sleeve. A second magnetic
main pole piece of annular-shape engages the axially outer end of
the magnetic sleeve. The second main pole piece has an integral
hollow threaded magnetic stud member extending axially inwardly of
the assembly. A hollow cylindrical magnetic armature is axially
movable against a spring force through the opening of the annular
second main pole piece and in the communicating hollow interior of
the stud member carried by the second main pole piece. The armature
is normally held in magnetically latched position by the magnetic
field of the permanent magnet against the spring force and in
contact with the axially inner end of the stud member carried by
the first main pole piece. When a signal pulse is applied to the
coil, a substantial amount of the permanent magnet flux is diverted
through the shunting pole piece, permitting the biasing spring
force to move the armature to a tripped position. An important
feature of the construction is the fact that the plastic bobbin on
which the trip coil is wound is threadedly engaged with the
threaded studs carried by the oppositely disposed first and second
main pole pieces, whereby to hold the assembly securely together
without the use of bolts or other fastening means. A further
feature of the construction is the provision of a "built-in"
non-magnetic gap on the movable armature member in the form of a
plated coating of a non-magnetic material on the surface of the
armature which engages the stud member of the first pole piece in
the latched position of the armature. This "built-in" gap insures
that the movable armature and cooperating stationary magnetic
structure operate at an optimum point or region on the curve of
magnetic force exerted on the armature vs. gap between the armature
and the axially inner end of the stud member carried by the first
main pole piece.
Further objects and advantages of the invention will become
apparent from the following description taken in conjunction with
the accompanying drawing in which:
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a view partially in elevation and partially in vertical
section of a device in accordance with the invention, the device
being shown in magnetically latched position;
FIG. 2 is an exploded perspective or isometric view of the device
of FIG. 1; and
FIG. 3 is a curve showing the typical relation between the magnetic
force exerted on the movable armature by the magnetic field of the
permanent magnet as a function of the gap between the movable
armature and the stationary stud 16 to which the armature is
magnetically attracted by the field of the permanent magnet.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawing, the actuator device of the invention
is generally indicated at 10 and includes what might be termed a
base member generally indicated at 12 including a cylindrical base
portion or main pole piece 14 from the opposite surface of which
projects an upstanding centrally located hollow cylindrical stud or
leg 16. The member 12 including pole piece 14 and stud 16 is formed
of a magnetic material such as soft iron or soft steel. The stud 16
has a hollow interior 18. The upper end of stud 16 is open and the
lower end of the hollow interior 18 of stud 16 is defined by
surface 20 which is flush with the upper surface 22 of the
cylindrical pole piece 14 of member 12 which lies radially
outwardly of stud 16. Stud 16 is externally threaded for
approximately the upper half of the height thereof as indicated at
24.
A permanently magnetized annular-shaped permanent magnet 26 which
has the same outer diameter as the outer diameter of the
cylindrical pole piece 14 is seated on upper surface 22 of member
12. THe inner diameter of permanent magnet 26 is substantially
greater than the outer diameter of stud 16, whereby to define a
core window 28 between the inner diameter of permanent magnet 26
and the outer diameter of stud 16.
The annular permanent magnet 26 may be made of any suitable
permanent magnet material, but is preferably made of Alnico V,
which is well known in the art.
A second or shunting pole piece or member 30 of annular shape and
having the same outer diameter as pole piece 14 of base number 12
and as permanent magnet 26 is seated on the upper surface (relative
to FIG. 1) of permanent magnet 26. In the illustrated embodiment,
the upper surface of shunting pole piece 30, when seated in
position, is flush with the upper surface of stud 16. Pole piece
30, like member 12, is formed of a magnetic material such as soft
iron or soft steel. The inner diameter of shunting pole piece 30 is
approximately one-eighth inch greater, for example, than the outer
diameter of the upper threaded end of stud 16, thereby defining an
annular air gap 31 between the upper end of stud 16 and pole piece
30.
A bobbin generally indicated at 32 of a suitable non-magnetic
material which is also an electrical insulator, such as nylon, for
example, is adapted to be mounted above shunting pole piece 30 in a
manner which will now be described. Bobbin 32 includes a axially
extending hollow cylindrical hub portion 34 and oppositely disposed
radially extending annular flanges 36 and 38. Bobbin 32 is also
provided with a short hollow cylindrical flange-like extension 40
which extends in an axial direction beyond the lower radial flange
36 and which, in substance, is an axial extension of hub portion 34
of the bobbin. It will be noted that the flange-like extension 40
of bobbin 32 serves as a guide means interposed between the upper
end of stud 16 and the inner periphery of shunting pole piece 30
which insures concentric coaxial relation of pole piece 30 relative
to the rest of the assembly.
An electrical winding or coil 42 which may have, for example, 1,000
turns, is positioned on the outer surface of hub portion 34 of
bobbin 32 between radial flanges 36 and 38 of the bobbin. A
suitable insulating covering or wrapping 44 covers the radially
outer periphery of coil 42. The internal periphery of hollow hub 34
of bobbin 32 including the internal periphery of the axially
extending flange-like extension 40 of the bobbin is threaded. The
internal thread of bobbin hub 34 including extension 40 is adapted
to threadedly engage the threaded upper portion of stud 16 of base
member 12, and also to threadedly engage stud 54 of the upper main
pole piece 50, as will be described.
An annular sleeve 46 of magnetic material such as soft iron or soft
steel and having the same outer diameter as pole piece 14 and also
the same outer diameter as permanent magnet 26 and shunting pole
piece 30 is adapted to seat on the upper surface (relative to FIG.
1) of pole piece 30 in concentric coaxial relation with respect to
bobbin 32. The outer diameter of radial flanges 36 and 38 of the
bobbin is just slightly less than the inner diameter of the annular
magnetic sleeve member 46 whereby the bobbin 32 serves to properly
locate the magnetic sleeve 46 in concentric coaxial relation to the
rest of the assembly 10.
It will be noted that magnetic sleeve member 46 is provided with a
passage 47 through which connection leads 49 of coil 42 may be
brought out for connection to the source of the electrical control
signal applied to coil 42.
What will be referred to as end member generally indicated at 48 is
provided and includes an annular main pole piece 50 having the same
outer diameter as the member 14, 26, 30 and 46 and an inner
diameter somewhat greater than the outer diameter of the slidable
armature 60 to be hereinafter described, and adapted to receive
non-magnetic bushing 56 (to be described) in which armature 60 is
slidably movable. The inner diameter of the annular pole piece 50
bounds a central opening indicated at 52. A hollow cylindrical stud
member generally indicated at 54 is integral with and projects
downwardly from the undersurface (relative to FIG. 1) of annular
portion 50 of member 48. The passage through stud 54 has the same
diameter as and is in axial registry with the central opening 52 of
annular pole piece 50. Stud member 54 is of such outer diameter
that it may be received within the upper end of threaded hollow hub
34 of bobbin 32. The outer surface of stud 54 is threaded and
adapted to threadedly engage the thread on the inner periphery of
hollow hub member 34 of bobbin 32.
The member generally indicated at 48, including the annular main
pole piece 50 thereof and also the integral stud 54 thereof, is
made of the same magnetic material, such as soft iron or soft
steel, of which the members 12, 30 and 46 are made.
An armature member of a magnetic material such as soft iron or soft
steel generally indicated at 60 is adapted to be received in axial
sliding engagement iwth the inner periphery of a bushing 56 of a
suitable non-magnetic material such as brass which lines the inner
periphery of the axial passage through main pole piece 50 and
through stud 54 which extends axially inwardly from member 50. The
use of non-magnetic bushing 56 maintains armature 60 in coaxial
relation to the passage through the pole piece 50 and through stud
member 54, whereas in the absence of such a non-magnetic bushing
56, the armature, under the influence of magnetic forces acting
thereon, would be pulled into an eccentric relation to the passage
in which it is received. Armature 60 is of cylindrical outer
periphery, has a hollow interior or recess indicated at 61, and is
open at the lower end thereof relative to the view in FIG. 1.
In accordance with a further feature of the construction, the
armature 60 is plated on the entire outer surface thereof with a
plating of a suitable non-magnetic material such as nickel
phosphate to a coating thickness of, for example, 4 mils (0.004
inch). The purpose of this is to provide the bottom surface 63 of
armature 60 with a "built-in" non-magnetic shim which will space
the magnetic material of armature 60 contiguous the bottom surface
of the armature in its magnetically latched position as seen in
FIG. 1 at a distance from the facing upper surface 17 of magnetic
stud 16 which will cause the armature 60 to operate at an optimum
point or region on the curve of magnetic force on the armature vs.
gap between the armature and the facing surface of stud 16.
Refer to the curve of FIG. 3, which is a graphical example of a
typical relationship between force exerted on the armature by the
field of the permanent magnet vs. gap in mils between the facing
surfaces 63 and 17 of the armature and stud 16. It can be seen that
this curve is very steep in the portion of the curve lying between
0 and 3 mils, for example. Thus, for example, at 0 mils spacing,
the force on the armature might be 75 pounds, while at 3 mils
spacing, the force on the armature might be 35 pounds, a difference
of 40 pounds between 0 mils spacing and 3 mils spacing. However,
after about 3 mils spacing, the curve of FIG. 3 "flattens out"
considerably (or is less steep) so that the difference in force
exerted on the armature between 3 mils and say 5 mils is much less
than between 0 mils and 2 mils. Since it is inevitable that
particles or a layer of dust having an axial thickness of, for
example, 1 mil, will get between the surfaces 63 and 17 of the
armature 60 and stud 16, it can be seen that if no intentional
non-magnetic gap were provided, such as the plated non-magnetic
coating of the present construction, then the assumed 1 mil thick
or greater layer of dust just mentioned would be a variable unknown
which would have a pronounced effect on what part of the steep
portion of the curve of FIG. 3 the armature 60 would be operating.
In fact, if no nonmagnetic gap were provided and the device were
operating on the steep portion of the curve between 0 and 3 mils, a
deposit of dust of say 1 mil thickness could simulate the effect of
a trip signal received on coil 42 in causing a lessened magnetic
attraction exerted on armature 60, and cause a false tripping of
the armature 60. However, by providing a "built-in" gap of
non-magnetic material in the form of a plated coating of
non-magnetic material of, for example, 4 mils thickness, on the
external surface of armature 60, as in the construction of the
present invention, it can be insured that the armature operates on
the flatter portion of the curve of FIG. 3 which starts, for
example, at approximately 3 mils gap. Thus, in accordance with the
construction of the present invention, any additional thickness of
gap caused by a layer of dust between armature 60 and stud 16 will
not cause a significant change in the force exerted on armature 60
by the field of the permanent magnet in the latched position of the
armature. This permits a spring 84 to be selected which will be
capable of operating in the relatively narrow range of force
exerted in the flat portion of the curve of FIG. 3 in which
armature 60 will operate. In other words, the magnetic force shown
in the curve of FIG. 2 which the spring 84, aided by the opposing
or negative magnetic force set up by the electric signal on coil
42, must overcome, varies over a narrower range when the "built-in"
nonmagnetic shim of the type just described is used. Consequently,
the magnetic actuator device 10 is more sensitive because of the
use of the plated nonmagnetic coating just described.
It will be understood, of course, that the gap value of 3 mils as
the point at which the curve begins to flatten out is given only by
way of example, and this gap thickness might vary in different
constructions. It might be pointed out that it is not broadly new
to use non-magnetic shims for the purpose just described. However,
it is believed that the use of a plated non-magnetic coating on the
armature to achieve this result is new.
A rod or stem member generally indicated at 66 which is formed of a
nonmagnetic material such as aluminum extends through a passage 68
in the upper end wall 70 of armature 60. Stem or rod 66 is suitably
rigidly secured as by pinning or the like to end wall 70 of the
armature so that the stem or rod 66 and the armature 60 move
linearly as a unit. Rod 66 projects through end wall 70 of armature
60 and through the hollow interior 61 of the armature, thence
through the hollow interior 18 to stud 16 of base 12, and thence
through a passage 74 in the pole piece 14 of member 12, stem or rod
66 being of sufficient length to project several inches or more
beneath pole piece 14 as seen in FIG. 1. A portion of stem or rod
66 indicated at 76 projects above upper end wall 70 of armature 60.
The lower portion of stem or rod 66 is externally threaded as
indicated at 78 and a nut member 80 is threadedly engaged with
threaded stem 66 at a predetermined adjusted position to serve as a
stop member which limits the upward motion of the armature 60 and
of the connected stem or rod 66 under the influence of the spring
biasing means as will be described.
a nut member 83 is threadedly engaged with rod 66 contiguous the
lower end of rod 66. Nut member 83 is adjusted to engage a
mechanical latch on a circuit breaker when armature 60 and stem 66
move upwardly relative to FIG. 1 upon the receipt of the trip
signal by control coil 42, to thereby trip to open position the
associated circuit breaker, as will be explained in more detail
hereinafter.
A spring generally indicated at 84 is positioned coaxially about
rod or stem 66 in such manner that the upper end of the spring
relative to FIG. 1 bears against the under surface of the wall 70
of armature 60, while the opposite end of spring 84 bears against
the surface 20 which defines the bottom of the hollow interior 18
of stud 16 which forms a part of base 12. In the latched position
to armature 60 as shown in FIG. 1, the spring is under its maximum
compression.
In assembling the device of FIG. 1, and with the parts in the
relative relation shown in FIG. 2, base portion 12 is rotated
relative to bobbin 32, and the opposite end 48 is rotated relative
to bobbin 32 in such manner as to threadedly engage the thread on
stud 16 of member 12 with the internal thread at one end (or lower
end relative to FIG. 1) of the bobbin and to threadedly engage the
thread on stud 54 with the thread at the opposite end (or upper end
relative to FIG. 1) of the bobbin whereby to tighten the assembly
of parts into tightly assembled relation with respect to each other
without use of bolts or other fasteners.
Throughout the specification, any use of the terms "upper" or
"lower" etc., is with reference to the view shown in FIG. 1, and
these terms are only used for convenience in description.
DESCRIPTION OF OPERATION
Assume that the device of FIGS. 1 and 2 is intended for use in
tripping and associated electrical circuit breaker. During the
tripping operation of the associated circuit breaker, which was
initiated by the upward movement (relative to FIG. 1) of armature
60 and nut 83, as will be explained, a suitable mechanism on the
circuit breaker will engage end wall 70 of armature 60 and will
push the armature 60 axially downwardly relative to FIG. 1 against
the force of spring 84 to approach the position shown in FIG. 1 in
which the lower or open end of the armature bbuts against the upper
surface of stud 16, to thereby reset the device of FIG. 1 for the
next tripping operation. The mechanical pushing movement of the
mechanism on the circuit breaker need not push armature 60 the
complete distance just described since the magnetic attraction of
the magnetic field of the permanent magnet 26 will draw the
magnetic armature 60 during the final portion of the closing
movement of the armature to the position shown in FIG. 1 in which
the bottom surface 63 of the armature is in contact with the facing
top surface 17 of stud 16. Armature 60 is magnetically held in the
latched position shown in FIG. 1 by the magnetic field of permanent
magnet 26. In the closed or latched position of the armature shown
in FIG. 1, most of the magnetic flux of permanent magnet 26 will
pass from permanent magnet 26 upwardly (relative to FIG. 1) axially
through pole piece 30, through magnetic sleeve 46, thence radially
inwardly across pole piece 50 and into the armature 60, thence
axially downwardly through armature 60 into stud 16, thence
radially outwardly across the lower pole piece 14 and back to
permanent magnet 26. The magnetic force of the magnetic flux just
described will hold armature 60 in the latched position of FIG. 1
against the force of the compressed spring 84.
Assume now that a control signal, which typically might have a
duration of 10 milliseconds, is received through the conductors 49
and transmitted to coil 42. This control signal calls for tripping
of the associated circuit breaker. The winding of coil 42 will set
up a magnetomotive force (MMF) with associated magnetic flux which
will oppose the magnetic field of permanent magnet 26 in such
manner that a substantial amount of the magnetic flux of the
permanent magnet instead of passing upwardly from pole piece 30
into magnetic sleeve 46, pole piece 50 and armature 60 as
previously described will instead pass from pole piece 30 across
the air gap 31 into the stud 16, thence downwardly relative to FIG.
1 through the stud 16 into the pole piece 14 and thence back to
permanent magnet 26, thereby diverting (or short circuiting) the
path of a substantial amount of the magnetic flux from permanent
magnet 26 which had previously flowed through armature 60. The
diversion of the magnetic flux path away from armature 60 due to
the signal pulse applied to coil 42 will cause armature 60 under
the influence of spring 84 to practically instantly release from
contact with stud 16 and the armature will move very rapidly
upwardly until stop member 80 on stem 66 abuts against the lower
surface, relative to FIG. 1, of pole piece 14. During the travel of
stem 66, which travel typically might be about seven-sixteenths,
the nut or abutment 83 on stem 66 will engage tripping mechanism on
the associated circuit breaker to cause tripping of the circuit
breaker. As previously mentioned, the armature 60 is rest to its
magnetically latched position as seen in FIG. 1 by mechanism on the
breaker during the tripping operation of the breaker.
It will be noted that in the assembled position of FIG. 1, the
lower end of magnetic stud 54 is spaced from the upper end or
surface 17 of stud 16 by a distance which typically might be about
one-eighth inch, thereby defining an air gap 19 between the lower
end of upper stud 54 and the upper end 17 of lower stud 16. Thus,
when armature 60 is in magnetically latched position as seen in
FIG. 1, practically all of the magnetic flux passing from pole
piece 50 will pass through armature 60 to lower stud 16, and
practically no magnetic flux will pass through upper stud 54 to
lower stud 16.
However, when the device of FIG. 1 is actuated to tripped position
by the action of trip coil 42, as previously described, armature 60
moves upwardly through a travel of typically about seven-sixteenths
inch until nut 80 abuts against the under surface of lower pole
piece 14. Thus, in the tripped position of armature 60, the lower
end (i.e., the open end) of armature 60 will be spaced about 7/16
inch (i.e., the travel of armature 60) from the upper end 17 of
lower stud 16. During most of the tripping movement of armature 16
just described, practically all magnetic flux flowing from upper
pole piece 50 to lower stud 16 (this will normally now be a
relatively minor portion of the total magnetic flux) will flow
through upper stud 54 to lower stud 16, rather than through
armature 60 to stud 16. This is because during most of the tripping
stroke of the armature 60, the air gap between armature 60 and the
upper end 17 of stud 16 is considerably greater than the air gap
between the lower end of upper stud 54 and the upper end 17 of
lower stud 16, thus causing the shunting path from upper stud 54 to
lower stud 16 to have a lower reluctance then the path from the
upwardly moving armature 60 (during the tripping movement of the
armature) to stud 16. Shunting the magnetic flux away from armature
60 and through stud 54 during the upward tripping movement of
armature 60 as just described reduces the magnetic force pulling
armature 60 toward stud 16, thus making more efficient use of the
stored energy of spring 84 during the tripping operation. Under the
tripping or tripped condition just described, a substantial part of
the magnetic flux will flow through shunting pole piece 30, and
across air gap 31 to lower stud 16, and thence through lower pole
piece 14 back to the permanent magnet 26.
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 with the scope of this
invention.
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