U.S. patent number 3,732,512 [Application Number 05/200,877] was granted by the patent office on 1973-05-08 for trip mechanism.
Invention is credited to Donald W. Puttick.
United States Patent |
3,732,512 |
Puttick |
May 8, 1973 |
TRIP MECHANISM
Abstract
A trip mechanism which can be actuated by a magnet, by inertia,
by a mechanical movement or by an electrical current, has powerful
magnets in mutual repulsion constrained close together by the
attraction of a short length of ferromagnetic material; this
attraction balances the repulsion and allows energy to be stored in
the magnetic field. When the balance is upset -- which can be done
in a number of ways -- the magnet previously held by the short
length of ferromagnetic material is driven away by the stored
energy and may be used to close a pair of circuit contacts.
Inventors: |
Puttick; Donald W. (Ottawa,
Ontario, CA) |
Family
ID: |
10483264 |
Appl.
No.: |
05/200,877 |
Filed: |
November 22, 1971 |
Foreign Application Priority Data
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Dec 12, 1970 [GB] |
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59,192/70 |
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Current U.S.
Class: |
335/302;
335/207 |
Current CPC
Class: |
H01H
71/322 (20130101) |
Current International
Class: |
H01H
71/32 (20060101); H01H 71/12 (20060101); H01h
007/04 () |
Field of
Search: |
;335/302,306,207 ;308/10
;310/15 ;272/8 ;46/236,240,242 ;74/5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Broome; Harold
Claims
I claim:
1. A trip mechanism comprising,
at least two permanent magnet means, arranged coaxially with like
poles facing one another,
a non-magnetic axial constraint means to keep the magnetic axes
aligned, thereby maintaining like poles facing while allowing
movement of at least one permanent magnet means therealong,
a means for providing a datum plane for another of said permanent
magnet means,
a catch means comprising a piece of magnetic material for applying
a force to said one moveable permanent magnet means, and
means for locating said catch means adjacent to said datum plane at
a position to urge said moveable permanent magnet means towards
said datum plane, said position being a predetermined distance from
said datum plane,
the predetermined distance between said catch means position and
said datum plane being determined so that the force exerted by the
catch on the moveable permanent magnet means urging it towards the
datum plane is balanced by the mutual repulsion between the two
permanent magnet means,
whereby the force on the catch stores energy in the repulsion field
for sudden release.
2. A trip mechanism as claimed in claim 1, wherein
said means for locating said catch means is at a position closer to
said other permanent magnet means than the position normally
occupied by said moveable permanent magnet means in the absence of
said catch means.
3. A trip mechanism as claimed in claim 1, wherein
said catch means is of ferromagnetic material having an axial
length of about the same dimension as the magnetic length of said
moveable permanent magnet means.
4. A trip mechanism as claimed in claim 1, wherein the
said means for locating said catch means comprises means for moving
said catch means towards said predetermined distance from said
datum plane.
5. A trip mechanism as claimed in claim 1, wherein
said means for locating said catch means comprises means for
fixedly securing said catch means at said predetermined distance
from said datum plane.
6. A trip mechanism as claimed in claim 1, wherein
said moveable permanent magnet means is annular, said axial
constraint is a thin walled tube, and said catch means is a
cylindrical core within said thin walled tube.
7. A trip mechanism as claimed in claim 6, wherein
said means for locating said cylindrical core catch means comprises
means for moving said catch means towards said predetermined
distance position from said datum plane.
8. A trip mechanism as claimed in claim 1, wherein there
are at least three permanent magnet means, and wherein at least two
of said permanent magnet means are free to move along said axial
constraint.
9. A trip mechanism as claimed in claim 1, wherein said
datum plane providing means is a flange secured to said axial
constraint means, to provide a retaining means for the other
permanent magnet means.
10. A trip mechanism as claimed in claim 1, wherein
two similar trip mechanisms are arranged symmetrically upon a
single axial constraint means, and
said datum plane is provided by the interaction of said two similar
trip mechanisms, one with the the other, at a plane midway between
the two catch means.
11. A relay comprising a trip mechanism as claimed in claim 1, and
further comprising
a pair of contacts, and
wherein a moveable permanent magnet means has a conductive surface,
whereby the pair of contacts are connected together when the
mechanism trips.
Description
This invention relates to a trip mechanism, which can be operated
by mechanical, electrical or magnetic actuation.
Usually, such devices comprise a spring loaded latch, and a catch
which releases the latch when the catch is moved. This mechanical
loading decreases the sensitivity of the trip mechanism, and the
wear which occurs will affect operation.
Accordingly, it is an object of this invention to provide a trip
mechanism in which the latch and catch are not in physical contact;
it is another object of this invention to achieve this with a few
inexpensive magnets in mutual repulsion and a magnetic catch.
It is a further object of this invention to provide a preset catch
and electrical contacts so that the assembly will function as an
inertia switch. It is yet another object of this invention to
provide a trigger that can be directly operated by electrical,
mechanical or magnetic forces .
The invention will best be understood by reference to the drawing
which illustrates, by way of example, two embodiments. In this
drawing:
FIG. 1 illustrates one embodiment with a preset catch the mechanism
being in a cocked position, that is ready to be tripped;
FIG. 2 illustrates the same mechanism after tripping;
FIG. 3 shows a simpler embodiment.
In these figures, items 2, 4 and 6 are magnets which have north and
south poles as indicated on FIG. 1; that is to say, they are
magnetized through their thickness. These magnets are such that if
they are placed with like poles facing one another (and their
magnetic axes constrained from turning through 180.degree., so that
unlike poles can never attract one another) they will float one
above another by mutual repulsion; such magnets are commercially
available.
The drawing illustrates constraint of the magnetic axes by using
magnets of annular form and using a tube 8 of a non-magnetic
material, such as brass, passing through the central hole. The
magnet 6 is located by a flange 7 on the brass tube, the upper face
of flange 7 giving a datum plane for magnet 6. Both the flange and
this magnet are surrounded by a plastic structure, 9, 10 and 11
which forms a supporting base. The upper face of the magnet 6 is
thus fixed relative to the datum plane, of flange retaining means,
7.
A short ferromagnetic core, 12, is located within the brass tube 8
at such a distance from the datum face, that, in FIG. 1, it can
retain annular magnet 2 closer to magnets 4 and 6 than would be
possible without the core 12 (in the absence of any external
force). That is, the attraction of core 12 for magnet 2 overcomes
the repulsion forces between magnets 2, 4 and 6 if the magnets are
squeezed together and then released gently.
To give dimensions by way of example, and not by way of
limitations, I have used annular magnets 0.750 inches outside
diameter, with a 0.271 inch diameter hole and a thickness of 0.250
inch. I find that the best length for the core 12 is about
three-sixteenths inch although there is not much difference if the
length is one-fourth inch. However, cores 1/8 inch long or 3/8 inch
long will operate satisfactorily as a catch, but the energy stored
in the latch system is less. If the core is made either more than
1/2 inch or less than 1/16 inch long the trip mechanism is only
marginally operable because it would seem that the attraction
between the core 12 (the catch) and the magnet 2 (the latch) is
either insufficiently localized or insufficient to overcome the
repulsion of the adjacent magnet; this results in so little release
of energy from the system that there is very little movement of the
latch, magnet 2, when the catch, core 12 releases it.
In the absence of core 12, there is a 1/2 inch gap when one magnet
floats above another freely, and the gap between the second magnet
and the next beneath it is about 3/8 inch. Thus the overall height
of the stack of three magnets, 2, 4, and 6 without the core present
is about 15/8 inch.
If now the core 12 is moveable and introduced at the top of tube 8,
and moved downwardly as by rod 5, towards the locating flange 7, it
will drag magnet 2 with it against the repulsion of the magnetic
field until the position shown in FIG. 1 is reached; a 3/16 inch
long core will provide enough attraction so that the overall stack
height is reduced to about 1 inch (one inch). At this point, if
downward movement of core 12 is stopped, the position is stable,
but with stored spring-like energy.
However this stable position may be upset by mechanical or even
magnetic forces. A light mechanical impulse, such as a shock, a
small acceleration, a tilt, or a change in magnetic environment
trips the mechanism by upsetting the balance of forces, and magnet
2 is impelled upwardly by the energy, previously stored in the
magnetic field, being suddenly released. This upset, or tripping,
may also be carried out electromagnetically by passing a current
through a coil around latch magnet 2 (this coil is not shown) to
upset the balance of magnetic forces. Of course, if movement of the
core 12 is continued downwardly this too will trip the mechanism,
as will the approach of a permanent magnet of correct polarity. The
result of any of these tripping forces, which can be very light, is
that the system reverts to the uncocked position shown in FIG.
2.
The effect is increased in some cases (depending on magnetic
materials, dimensions, the nature of the tripping impulse and the
like) because as magnet 4 is repelled upwardly by magnet 6 it is
caught by core 12 and so comes to rest at a point higher than it
would naturally assume.
The endpiece, 14, represents the height to which the uppermost
magnet 2 will rebound and it is fitted with relay contacts 16 which
will actuate a circuit when closed. A coat of conducting silver
paint 18 is provided because these magnets are usually
non-conducting. I prefer to make contacts 16 close a self holding
relay (not shown) but if desired another core (not shown) can be
fixed at the top of tube 8 to hold magnet 2 with its conducting
coat 18 against contacts 16.
The trip mechanism will work with only two magnets as shown in FIG.
3. Here, core 12 is much closer to the datum face of the retaining
flange 7, and the mutual repulsion of magnets 4 and and 6 is
balanced by the attraction of core 12 for magnet 4. Although less
energy is stored in the "spring" system, the assembly is more
convenient if it is desired to have a moveable core.
Although I have used the terms "upwardly" and "downwards", it will
be understood that these refer to the illustrated embodiments and
that the device is not dependent upon the force of gravity; a
slight adjustment may be necessary to the position of the core 12
to achieve maximum energy storage, if the embodiment of FIG. 3 were
inverted, but basically the operation is unimpaired. It will also
be obvious to those skilled in the art that various other changes
and modifications may be made without departing from the invention
as defined by the appended claims. For example, in an inertia
switch with a horizontal axis, it is possible to omit flange 7, and
its physical face; the relay is made double ended by providing two
cores 12, each attracting a permanent magnet against the mutual
repulsion of a stack. The "datum plane" is halfway between the two
cores, and acceleration is sensed, not only in magnitude but also
in direction by the magnet which escapes from its core.
* * * * *