U.S. patent number 3,863,182 [Application Number 05/453,722] was granted by the patent office on 1975-01-28 for magnetically operated electrical switch.
This patent grant is currently assigned to Magsat Corporation. Invention is credited to Lloyd J. Lapointe.
United States Patent |
3,863,182 |
Lapointe |
January 28, 1975 |
MAGNETICALLY OPERATED ELECTRICAL SWITCH
Abstract
An electrical switch has a freely movable magnetic ball contact
maintained in a first position out of engagement with at least one
of a plurality of stationary electrical contacts by a permanent
magnet. The ball contact is movable to a second position wherein it
engages all of the contacts in response to magnetic influence
exerted thereon by an iron rod carried by a reciprocally movable
push button and disposed within a flux path of the magnet. The rod
exerts greater magnetic influence on the ball contact than magnet
during only an initial portion of push button travel toward a fully
depressed position whereby to cause the ball contact to return to
its first position in response to magnetic influence of the magnet
before the push button reaches its fully depressed position.
Inventors: |
Lapointe; Lloyd J. (West
Hartford, CT) |
Assignee: |
Magsat Corporation (West
Hartford, CT)
|
Family
ID: |
23801790 |
Appl.
No.: |
05/453,722 |
Filed: |
March 22, 1974 |
Current U.S.
Class: |
335/207;
335/280 |
Current CPC
Class: |
H01H
41/04 (20130101); H01H 36/00 (20130101); H01H
13/50 (20130101) |
Current International
Class: |
H01H
36/00 (20060101); H01H 41/00 (20060101); H01H
41/04 (20060101); H01H 13/50 (20060101); H01h
013/00 () |
Field of
Search: |
;335/205,206,207,280,306
;200/67F,153J,160 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Broome; Harold
Attorney, Agent or Firm: McCormick, Paulding & Huber
Claims
1. An electrical switch comprising a plurality of electrical
contacts spaced from each other, a permanent magnet mounted in
fixed position relative to said electrical contacts, a magnetic
switching part disposed within the magnetic influence of said
magnet and maintained in one switching position by the magnetic
attraction of said magnet, said switching part in said one position
being out of electrical contact with at least one of said
electrical contacts and being movable to another position wherein
it is in electrical contact with each of said electrical contacts,
an operating part supported for movement relative to said
electrical contacts and said magnet between first and second
positions, a ferromagnetic element carried by said operating part
and disposed within the magnetic influence of said magnet and in
close proximity to said switching part when said operating part is
in its first position and said switching part is in said one
position, said ferromagnetic element exerting a greater magnetic
attraction for said switching part than said magnet when said
operating part is in its first position and during at least a
portion of the travel of said operating part from its first toward
its second position, said switching part being movable from its one
to its other position with said operating part when the latter part
is moved from
2. An electrical switch as set forth in claim 1 wherein said
ferromagnetic element exerts greater magnetic attraction for said
switching part than said magnet during only the initial portion of
the travel of said operating part from its first toward its second
position, said switching part attains its other position in
response to movement of said operating part from its first toward
its second position before said operating part attains its second
position, said magnet exerts greater attraction for said switching
part than said ferromagnetic element after said switching part
attains its other position and said switching part moves from its
other position to its one position in response to magnetic
attraction of said magnet during the final portion of the travel of
said operating part
3. An electrical switch as set forth in claim 1 wherein said
electrical contacts comprise three stationary contacts, said
switching part passes through an intermediate position wherein it
is in electrical contact with two of said contacts in traveling
from its one to its other position, and said switching part remains
in electrical contact with said two contacts during its movement
from said intermediate position to its other position in response
to movement of said operating part from its first toward its
4. An electrical switch as set forth in claim 3 wherein said
switching part
5. An electrical switch as set forth in claim 4 wherein said
ferromagnetic
6. An electrical switch as set forth in claim 2 wherein said switch
includes a hollow housing which has a bore, said electrical
contacts comprise stationary contacts fixedly mounted in said
housing, said operating part comprises a push button which has a
hollow shank slidably received in said bore, and said switching
part is disposed generally
7. An electrical switch has set forth in claim 6 wherein said
switching
8. An electrical switch as set forth in claim 7 wherein one of said
stationary contacts partially defines said bore, said shank has a
slot therein adjacent said one stationary contact, and said ball
engages said
9. An electrical switch as set forth in claim 8 wherein said one
stationary contact comprises means for supporting said magnet in
fixed position in
10. An electrical switch as set forth in claim 7 wherein said
ferromagnetic
11. An electrical switch as set forth in claim 1 wherein said
switch includes means for biasing said operating part in one
direction toward its first position and said ferromagnetic element
comprises means for limiting
12. An electrical switch as set forth in claim 11 wherein said
switch includes a housing which has a slot therein, said operating
member is supported by said housing for movement relative thereto,
and said ferromagnetic element comprises a rod received in said
slot.
Description
BACKGROUND OF THE INVENTION
This invention relates in general to electrical switches and deals
more particularly with an improved magnetically operated electrical
switch suitable for use as a keyboard switch or the like.
The switch of the present invention is particularly adapted for use
as a keyboard switch on an electric typewriter, business machine,
computer or like apparatus which requires single pulse switch
output during each switching cycle. In a keyboard switch of the
aforedescribed type, it is generally required that the electrical
output of the switch be isolated from and wholly independent of the
mechanical output of the operator. Thus, the operator controls the
occurrence of switch pulse output but not the duration thereof. It
is further desirable that such a switch have a tactile feedback
characteristic to indicate to the keyboard operator, as by sharp
reduction of key stroke pressure, that a character has been
transmitted.
Accordingly, the general aim of the present invention is to provide
an improved magnetically operated switch which possesses the
aforedescribed desired operational characteristics and which is of
simple durable construction for low cost manufacture.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved electrical
switch is provided which comprises a plurality of stationary
electrical contacts, a permanent magnet mounted in fixed position
relative to the contacts, a movable switching part maintained by
the magnet in one switching position out of engagement with at
least one of the contacts, an operating part supported for movement
relative to the contacts and magnet between first andd second
positions, and a ferromagnetic element carried by the operating
part and disposed within the magnetic influence of the magnet and
in close proximity to the switching part when the operating part is
in its first position and the switching part is in its one
position. The ferromagnetic element exerts a greater magnetic
attraction for the switching part than the magnet when the
operating part is in its first position and during at least a
portion of its travel toward its second position whereby the
switching part moves with the operating part to another position
wherein it engages each of the stationary contacts when the
operating part is moved from its first position toward its second
position.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an axial sectional view through an electrical switch
embodying the present invention.
FIG. 2 is a sectional view taken along the line 2--2 of FIG. 1.
FIG. 3 is a sectional view taken generally along the line 3--3 of
FIG. 2.
FIG. 4 is a fragmentary sectional view taken along the line 4--4 of
FIG. 1.
FIG. 5 is a sectional view similar to FIG. 1 but shows the
operating button in a partially depressed position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now to the drawing, an electrical switch embodying the
present invention and indicated generally at 10, comprises a switch
housing designated generally by the numeral 12 supporting a
plurality of spaced stationary contacts 14, 16 and 18 and a
permanent magnet 20 associated with the contact 14. The illustrated
switch 10 is particularly adapted for use as a keyboard switch and
further includes an operating part or push button indicated
generally at 22 which carries a ferromagnetic element 24. The push
button is supported by the housing 12 for movement relative thereto
and controls movement of a switching part or movable spherical
contact 26 preferably made from steel and contained in the housing
and within magnetic influence of the magnet 20. The movable
magnetic ball contact 26 is maintained in one position out of
electrical contact with at least one of the stationary contacts by
the magnetic attraction of the magnet and is movable to another
position wherein it is in electrical contact with each of the
stationary contacts to establish electrical connection therebetween
in response to movement of the operating part.
Considering now the housing 12 in further detail, it includes a
hollow generally rectangular base 28 and a terminal board 30
secured to the base by threaded fasteners 32, 32 as best shown in
FIG. 3. The base 28 has a reduced neck portion at its upper end
which partially defines a generally rectangular bore 34 which
extends through the base. A downwardly opening recess 36 in one
side of the base communicates with the bore 34 as best shown in
FIG. 2.
The stationary contacts 14, 16 and 18 are supported on the terminal
board 30 and have terminal portions which extend downwardly
therethrough for connection in an external circuit or, if desired,
to a printed circuit associated with the terminal board. The
contact 14 comprises a generally rectangular plate which is
disposed within the base and has its marginal side edges received
and supported in opposing slots 38, 38 formed in the base as best
shown in FIG. 2. The contact 14 forms a partition or dividing wall
between the recess 36 and the bore 34 and defines a continuation of
one wall of the rectangular bore 34, as best shown in FIG. 1. A
pair of bent mounting clips 40, 40 struck from the contact 14
support the magnet 20 within the recess 36. The contacts 16 and 18
are generally cylindrical and project upwardly from the terminal
board generally within a plane through the bore axis. Each of the
contacts 16 and 18 has a generally conical upper end portion to
provide a contact surface for electrical contact engagement with
the ball contact 26. The contacts 16 and 18 are spaced from each
other and from the contact 14. It should be noted that the contact
16 is of somewhat greater length than the contact 18 and extends
for a slightly greater distance above the terminal board 30 than
the contact 18.
The push button or key is preferably molded from plastic or like
material and has a button portion 42 and an integral hollow shank
44 which depends from the button portion. The shank has a generally
rectangular cross sectional configuration which complements the
cross-sectional configuration of the bore 34 in which it is
slidably received. At its lower end, the shank 44 has a downwardly
opening slot 46 formed in the wall thereof adjacent the contact 14.
The ferromagnetic element 24 comprises an iron rod which extends
transversely through the lower end of the shank portion 44 between
the contact 14 and the contacts 16 and 18. The end portions of the
rod 24 project from opposite sides of the shank 44 and into a
downwardly opening slot 48 formed in the base 28. The end portions
of the rod cooperate with the upper wall of the slot 48 to retain
the push button 22 in assembly with the housing 12 and function as
a stop to limit its upward travel relative to the housing. The push
button 22 is biased to a projected or first position, indicated by
full lines in FIG. 1, by a compression spring 50 which surrounds
the neck portion of the base 28 and acts between the base and the
button portion 42. The push button 22 is manually movable against
bias of the spring 30 to a fully depressed or second position
indicated by broken lines in FIG. 1.
The spherical or ball contact 26 is disposed in the housing 12
within the magnetic influence of the magnet 20 and more
specifically within the hollow shank 44 and above the iron rod 24.
The magnet is preferably of the type which includes a plurality of
poles arranged in alternate series. The illustrated magnet 20 has
three alternate poles arranged substantially as indicated in FIG.
1. It should be further noted that when the push button 22 is in
its projected position, the ferromagnetic rod 24 is disposed in
close proximity to and preferably in contact with the ball contact
26, substantially as shown in FIG. 1.
When the push button 22 is in its projected position, the ball
contact 26 is maintained in a generally central position relative
to the magnet 20 and in electrical contact with the contact 14 by
the magnetic attraction of the magnet. However, when the ball
contact 26 is in the latter position, as it appears in FIG. 1, it
is out of electrical contact with the stationary contact 16 and 18,
as best shown in FIG. 3. When the push button 22 is in its
projected position, the rod 24 is generally adjacent the ball
contact 26 and within the magnetic influence of the magnet 20 and
acts as a temporary magnet to exert further magnetic influence upon
the ball 26. During initial movement of the push button 22 from its
projected toward its depressed position, the rod 24 exerts a
substantially greater influence upon the ball contact 26 than the
magnet 20. Thus, the ball contact 26 moves downward with the push
button and toward the stationary contacts 16 and 18 in rolling or
sliding engagement with the contact 14. Due to the height
differential between the contacts 14 and 16 relative to the base
30, the ball contact 26 establishes electrical contact with the
stationary contact 16 before it engages the contact 18. However,
the ball contact 26 ultimately attains another position, in
response to continued downward movement of the push button 22,
wherein it is in simultaneous engagement and electrical contact
with all of the stationary contacts, as indicated in full lines in
FIG. 5 and in broken lines in FIG. 3. The ball contact 26 attains
the latter "make" position before the push button 22 is fully
depressed and is restrained against further downward movement by
the stationary contacts. When the ball contact 26 makes contact
with all of the stationary contacts, the rod 24 is still within the
magnetic influence of the magnet 20 and continues to be attracted
to the ball contact. As the rod 24 continues to move downward and
away from the ball contact 26, its influence on the ball contact
sharply decreases. In the illustrated switch 10 an almost immediate
reversal of magnetic influence occurs when the rod separates from
the ball contact. More specifically, as the rod 24 moves out of
engagement with and away from the ball contact 26, the latter
contact comes under the greater influence of the magnet 20 which
causes it to break contact and return to its initial or full line
position in FIG. 1 before the push button 22 attains its fully
depressed or broken line position in FIG. 1.
An increase resistance to the downward movement of the push button
or key 22 is felt at the instant the ball contact 26 establishes
simultaneous electrical contact with the stationary contacts 14, 16
and 18 and separates from the rod 24. Further, a sharp reduction in
key stroke pressure is felt at the instant that the ball leaves the
magnetic influence of the rod 24 and returns to its initial
position under the magnetic influence of the magnet 20. This
tactile feedback is highly desirable in a keyboard switch, since it
enables a keyboard operator to sense when a character has been
transmitted by a key.
The switch 10 provides a single pulse output during each complete
switching cycle. It will be apparent that after the push button 22
has been depressed a sufficient distance to cause the ball contact
26 to make and then break and return to its centralized position on
the magnet 20, the switch cannot again be operated until the push
button 22 has returned to its projected position to bring the rod
24 into adjacent relation with the ball contact 26 and within the
magnetic influence of the magnet 20.
It will be further noted that the switch 10 may be connected in
circuit so that it is first conditioned to establish two circuit
paths through the terminals associated with the stationary contacts
14 and 16 and then establish a common path to ground through the
terminals 18. Thus, the switch may be employed to provide
simultaneous output at the two terminals 14 and 16.
* * * * *