U.S. patent number 3,689,859 [Application Number 05/126,491] was granted by the patent office on 1972-09-05 for reed switch.
Invention is credited to E. R. Carl Straub, 1611 LINCOLN Ave..
United States Patent |
3,689,859 |
|
September 5, 1972 |
**Please see images for:
( Certificate of Correction ) ** |
REED SWITCH
Abstract
A reed switch includes a housing with a pair of
magnetically-responsive contacts mounted therein, which contacts
are closed when an axially-movable magnetic actuator reaches a
specified distance with respect to the contacts. A plunger is
carried by the housing and moves the actuator toward and away from
the contacts. Adjusting means are provided which operatively engage
the magnet and the plunger for varying the initial distance of the
magnet from the contacts. A cap is removably attached to the
plunger and is constructed to conceal and protect the adjusting
means.
Inventors: |
E. R. Carl Straub, 1611 LINCOLN
Ave. (Cozad, NB 69130) |
Family
ID: |
22425117 |
Appl.
No.: |
05/126,491 |
Filed: |
March 22, 1971 |
Current U.S.
Class: |
335/206 |
Current CPC
Class: |
H01H
36/004 (20130101) |
Current International
Class: |
H01H
36/00 (20060101); H01h 003/12 (); H01h
036/00 () |
Field of
Search: |
;335/206,205,207 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Roy N. Envall, Jr.
Attorney, Agent or Firm: Prangley, Clayton, Mullin, Dithmar
& Vogel
Claims
1. A reed switch comprising a housing having a wall, an outwardly
protruding neck on said wall and having an opening extending
therethrough, a pair of magnetically responsive contacts in said
housing and having open and closed conditions, a plunger including
first and second mating plunger portions, said first plunger
portion including a sleeve and a flange on the outer end of said
sleeve, said sleeve being disposed in said neck and slidably
movable therein along a predetermined path, said second plunger
portion including a peg frictionally engaging in said sleeve and a
shoulder on said sleeve, said shoulder being adapted to engage the
inside of said wall of said housing to limit outward movement of
said plunger, a magnet operatively engaged by said second plunger
portion to be movable therewith along said predetermined path to
vary the magnetic field presented to said contacts, a spring
engaging said housing and said magnet resiliently to urge said
shoulder against said wall, adjusting means operatively engaging
said magnet and said second plunger portion for varying the initial
distance of said magnet from said contacts, and a cap removably
attached to said flange and constructed to conceal and protect
2. The reed switch set forth in claim 1, wherein said second
plunger portion has an axially threaded opening extending
therethrough, said adjusting means including a screw in said
opening and engaging with said magnet for varying the initial
distance of said magnet from said contacts.
3. The reed switch set forth in claim 1, wherein said first plunger
portion includes a laterally extending wall having an access
opening therethrough in axial alignment with the threaded opening
in said second plunger portion, said access opening accommodating
the shank of a tool to be
4. The reed switch set forth in claim 1, wherein said second
plunger portion includes a pair of depending legs defining a guide
for said
5. The reed switch set forth in claim 1, wherein said cap includes
a top wall, four depending side walls, and two ramps respectively
on opposite ones of the side walls, each of said ramps having
adjacent the top wall thereof a notch, said ramps serving to guide
said flange to said notches to be snap-fit thereinto.
Description
This invention is directed to a switch utilizing
magnetically-responsive contacts which are actuated by a magnetic
field.
It is an important object of the present invention to provide a
reed switch which is actuated by depressing a button and which
includes improved means for adjusting the amount by which the
button must be depressed to cause actuation.
Another object of the invention is to provide a reed switch in
which the adjusting means are concealed and protected so as to
prevent inadvertent alteration of the setting during use.
Still another object is to provide a reed switch usable in
conjunction with a number of other similar reed switches in a
keyboard, which reed switches include concealed adjusting means to
enable each switch to be actuated in response to the same amount of
depression.
Yet another object is to provide a reed switch which includes
concealed adjusting means to enable compensation for variations in
the characteristics from one reed to another reed.
A further object is to provide a reed switch in which access to the
adjusting means is gained by removing a push-button cap.
In summary, there is provided a reed switch comprising a housing
having a wall with an opening therein, a pair of
magnetically-responsive contacts in the housing and having opened
and closed position conditions, the contacts being arranged to
switch from one condition to the other condition when a magnetic
field presented thereto reaches a predetermined value, a plunger
disposed partly in the opening and slidably movable therein along a
predetermined path adjacent to the contacts, a magnetic actuator
including a movable portion operatively engaged by the plunger to
be moved therewith along the predetermined path to vary the
magnetic field presented to the contacts, an adjustment device
operatively engaging the movable portion and the plunger for
varying the initial distance of the movable portion from the
contacts, and a cap removably attached to the plunger and
constructed to conceal and protect the adjustment device.
The magnetic actuator may be a magnet which is movable along the
predetermined path to close and open the contacts. Also, the
plunger may consist of two separate sections, one section being
provided with means to receive a snap-fitted cap and the other
section being provided with means to limit outward movement of the
plunger.
Further features of the invention pertain to the particular
arrangement of the elements of the reed switch, whereby the
above-outlined and additional operating features thereof are
attained.
The invention, both as to its organization and method of operation,
together with further objects and advantages thereof, will best be
understood by reference to the following specification taken in
connection with the accompanying drawings, in which:
FIG. 1 is a view in longitudinal cross section of a reed switch
incorporating the features of the present invention;
FIG. 2 is a view in longitudinal cross section taken along line
2--2 of FIG. 1;
FIG. 3 is a view in horizontal cross section of the reed switch of
FIG. 1 taken along the line 3--3 thereof;
FIG. 4 is a view similar to the view in FIG. 2, but with the
push-button cap depressed so as to close the switch contacts;
FIG. 5 is a view of the reed switch also similar to FIG. 2, with
the cap removed and with a hex driver inserted to adjust the
initial position of the magnet; and
FIG. 6 is a view in horizontal cross section taken along the line
6--6 of FIG. 5.
Referring now to the drawings, there is shown a reed switch 10
incorporating therein the features of the present invention. The
reed switch finds particular use on a keyboard such as that
employed in a computer input device or in a calculator. The reed
switch 10 is of the push-button variety, that is, the switch
includes an outwardly-biased button which is operative to close an
electrical circuit as long as the button is depressed. The reed
switch 10 is shown as being mounted on such a keyboard 11, the
keyboard 11 having a hole 12 (FIG. 1) to accommodate a projection
on the reed switch 10 as will be described. A threaded bolt is
provided which passes through a suitably-formed hole in the reed
switch 10 and passes through an opening in the keyboard 11 for
engagement with a nut 14, thereby securely to retain the reed
switch 10 in the selected location.
The reed switch 10 comprises a rectangular housing, which, in the
form shown, is constructed of plastic. The housing 20 is
rectangular in transverse cross section and has a wall 23 adjacent
to one end thereof, a neck 21 being provided on the wall 23 and
protruding outwardly therefrom. An opening 22 (FIG. 1) extends
through the neck 21 and the wall 23, with the opposite end of the
housing 20 being open. There is also provided a base 25 having a
rectangular bottom wall 26 and four depending side walls 27, which
side walls fit into and frictionally engage respectively the inside
of the side walls of the housing 20. Formed on the bottom wall 26
and protruding outwardly therefrom is a projection 28 (FIG. 1)
which fits into the hole 12 formed in the keyboard 11, thereby to
prevent turning of the reed switch 10 as it is secured to the board
11 by means of the bolt 13 and the nut 14. Protruding inwardly in
the same direction as the side walls 27 is a cylindrical post 29.
After the parts are properly located within the housing 20, the
base 25 is force fitted into the open end of the housing 20. In
addition to the frictional engagement, it is preferable to use
cement to insure a long lasting connection.
Mounted on the base 25 and extending upwardly therefrom is a pair
of dry reeds, respectively consisting of elongated glass envelopes
30 and 30a, each being hermetically sealed and containing an inert
gas. Encased in the envelope 30 is a pair of beams 31 which are in
the form of very thin, narrow, metal strips that are directed
toward one another and extend in a direction substantially parallel
to the longitudinal axis of the housing 20. Respectively at the
ends of the beams 31 are contacts 32 which are spaced from each
other, that is, open, as shown in FIG. 2 or closed as shown in FIG.
4. The beams 31 respectively penetrate the ends of the envelope 30
and are connected to terminals 33 which protrude outwardly of the
base 25. When the contacts 32 are oppositely magnetically poled so
as to be attracted to each other, they will close. This occurs when
they are exposed to a magnetic field of sufficient magnitude to
overcome the rigidity of the beams 31. The beams 31 are constructed
to possess the characteristic of a leaf spring so that, when their
mechanical stiffness is overcome by the strength of magnetic
attraction, the contacts 32 close.
The other envelope 30a similarly includes a pair of beams 31a which
are in the form of very thin narrow metal strips that are directed
toward one another and extend in a direction substantially parallel
to the longitudinal axis of the housing 20. Respectively at the
ends of the beams 31a are contacts 32a which are spaced from each
other, that is, open, as shown in FIG. 2 or closed as shown in FIG.
4. The beams 31a respectively penetrate the ends of the envelope
30a and are connected to the terminals 33a which protrude outwardly
of the base 25. When the contacts 32a are oppositely magnetically
poled so as to be attracted to each other, they will close. This
will occur when they are exposed to a magnetic field of sufficient
magnitude to overcome the rigidity of the beams 31a. The beams 31a
are constructed to possess the characteristics of a leaf spring so
that, when their mechanical stiffness is overcome by the strength
of the magnetic attraction, the contacts 32a close.
The reed switch 10 further comprises a plunger 40 including a first
plunger portion 41 and a mating second plunger portion 50. The
first plunger portion 41 includes a sleeve 42 also made of plastic
in the preferred form and having a lateral wall 43 therein. The
interior of the sleeve above the lateral wall 43 defines a recess
44. There is provided a depending tongue 46 on the lateral wall 43,
which tongue extends along the diameter of the lateral wall 43 and
is generally rectangular in transverse cross section. An access
opening 45 extends through the lateral wall 43 and the tongue 46,
which opening extends along the axis of the sleeve 42. On one end
of the sleeve 42, the upper end as viewed in the FIGS. 1-6, there
is a square flange 47 having a notch 48 (FIG. 3) in each of its
four sides. The diameter of the sleeve 42 is slightly less than the
inside diameter of the neck 21 to enable the sleeve freely to slide
in the neck 21 along a predetermined path defined by the axis of
the housing 20. The flange 47 is adapted to engage the outer end of
the neck 21 so as to limit inward movement of the sleeve 42.
A second plunger portion 50 includes a dowel or peg 51 that has a
diameter approximately equal to the inside diameter of the sleeve
42. The peg 51 carries a pair of depending arcuate legs 52 each
having an angular extent of on the order of 90.degree. in the
embodiment shown. The inside of each leg is round and is about
90.degree. in extent, so as to define between the legs 52 a channel
53 for a cylindrical magnet. The peg 51 has a
diametrically-extending notch in the outer end thereof with a shape
to receive the tongue 46 on the first plunger portion 41. There is
provided a threaded opening 54 (FIG. 4) extending axially through
the peg 51, with a screw 55 being provided therein. The screw 55
has a hex-shaped socket 56 in the outer end thereof in the
embodiment shown. Finally, the laterally-disposed surfaces at the
juncture of the peg 51 and the legs 52 define shoulders 57.
The second plunger portion 50 is disposed in the housing 20 with
the peg being force fitted into the sleeve 42 so as frictionally to
engage the same, with the tongue 46 being disposed or partly
disposed in the complementary-shaped groove in the second plunger
portion 50. With the plunger portions 41 and 50 thus
interconnected, the shoulders 57 limit outward movement of the
plunger 40 by engaging the wall 23.
The reed switch 10 further comprises a magnet 60 which, in the form
shown, is a solid cylinder, the magnet being axially magnetized so
as to have the north and south poles at opposite ends. The diameter
of the magnet 60 is slightly less than the distance between the
legs 52 which define the channel 53. The magnet 60 is disposed in
said channel 53 so as to be axially movable therein as will be
described presently. In one form of the invention, there is
sufficient frictional engagement between the legs 52 and the magnet
60 to retain the magnet 60 against the action of gravity. There is
also provided a spacer 61 which is disposed against the lower end
of the magnet 60 and a compression spring 62 between the lower end
of the spacer 61 and the bottom wall 26 of the base 25, the post 29
being disposed within the spring 62. The spring urges the magnet 60
against the second plunger portion 50 so that the shoulders 57
thereon are resiliently urged against the wall 23 of the housing
20. It may be seen that, as the magnet is moved axially toward and
away from the axial position of the contacts 32 and 32a, the
magnetic field presented thereto varies. When the magnet reaches a
certain position such that the magnetic field reaches a
predetermined value, the contacts 32 and 32a close.
Lastly, the reed switch 10 comprises a cap 70 which has a top wall
72 with four depending, slightly inclined side walls 71. Formed in
the top wall 72 is a depression 73 to accommodate the tip of a
finger. On the interior of the top wall 72 is a set of four
depending posts 74 adjacent to the corners thereof. On each of the
side walls 71 is a ramp 75 having an inclined cam surface 76 and a
laterally-disposed notch 77 near the upper end of each ramp 75. The
four ramps 75 and the four notches 77 are respectively laterally
aligned with the four notches 48 in the flange 47 of the first
plunger portion 40.
In assembling the cap 70 on the first plunger portion 41, the ramps
75 on the cap 70 are respectively aligned with the notches 48 in
the flange 47. The cap 70 is pushed downwardly to carry the plunger
40 down until further movement is prevented, which, in the
embodiment shown, occurs when the spacer 61 strikes the post 29.
Further force on the cap 70 will cause the ramps 75 thereon to ride
down on the flange 47, with the cam surfaces 76 guiding the flange
47 until the sides thereof respectively snap into the notches 77.
The notches 77 have therein the adjacent portion of the flange 47
so as to retain securely the cap 70 in position. Removal of the cap
70 is accomplished by forceably tilting the same until one side of
the flange 47 is unseated from the associated notch 77, after which
the other sides of the flange 47 naturally become unseated from
their respective notches 77. The cap 70 may then be lifted to
expose the recess 44 in the first plunger portion 41.
In use, the reed switch 10 is mounted on a keyboard 11 as
previously explained with the sets of terminals 33 and 33a being
electrically connected to their respective circuits. When it is
desired to complete these electrical circuits, the user depresses
the cap 70 which moves the plunger 40, consisting of the first and
second plunger portions 41 and 50, downwardly, that is, toward the
base 25, which, in turn, carries the magnet 60 downwardly against
the action of the spring 62. When the magnet 60 reaches a
predetermined axial position, that is, presents to the contacts 32
and 32a a magnetic field of a predetermined value, the contacts 32
and 32a close.
It has been found that one magnet may be stronger than another.
Whereas a given displacement of the cap 70 would be required to
close the contacts 32 and 32a with a stronger magnet, a greater
displacement of the cap 70 would be required to close the contacts
with a weaker magnet. Also, the reeds themselves vary in that it
takes differing magnetic field strengths to effect closure of the
contacts. For example, one reed may require a magnet intensity of
27 ampere turns to effect closure, whereas another reed may require
42 ampere turns to effect closure. Although a certain displacement
of the cap 70 will close the contacts requiring the weaker magnetic
strength, the contacts requiring a greater magnetic intensity would
require a greater displacement of the cap 70. Particularly when a
number of such reed switches 10 are mounted on a keyboard 11, such
as in the case of a computer input or a calculator, it is desirable
that the same displacement of each cap 70 will actuate the
associated reed switch 10. The invention includes improved
adjustment means to insure that this does occur. In the form shown,
the adjustment means is the screw 55 in the threaded opening 54.
When the lower end of the screw 55 is within the opening 54 or at
least flush with the bottom surface of the peg 51 as shown in FIGS.
1 and 2, the magnet 60 will be resiliently urged by the spring 62
against that surface. In this position, as is most clearly shown in
FIGS. 1 and 2, the initial distance of the magnet 60 from the
contacts 32 and 32a would be a maximum. To reduce this initial
distance, the screw 55 may be adjusted to its position shown in
FIG. 5. To this end, there is provided a tool 80 having a handle 81
and a hexagonal shank 82. The shank 82 is inserted through the
access opening 45 in the first plunger portion 41 and into the
socket 56 of the screw 55. The tool 80 may be rotated to turn the
screw 55 and adjust its axial height. If screwed downwardly, the
magnet 60 is moved downwardly, that is, away from the plunger 40
and against the action of the spring 62. As the magnet 60 is moved
downwardly, its initial distance from the contacts 32 and 32a is
reduced.
Either before or after the cap 70 is placed in position, the reed
switch 10 is tested to determine the amount of displacement of the
plunger 40 required to close the contacts 32 and 32a. As an
example, assume that the test indicates that a particular reed
switch 10 requires a displacement of .25 inches before the contacts
32 and 32a are closed, whereas predetermined specifications require
that the contacts should close with a displacement of .225 inches.
In that case, the cap 70 would be removed as previously explained,
and the tool 80 inserted in the hex socket 56. The screw 55 would
be rotated to move the magnet 60 downwardly, that is, reduce the
initial axial distance between the magnet 60 and the contacts 32
and 32a. With the proper adjustment, the contacts 32 and 32a will
close when the plunger 40 is displaced .225 inches. If the test, on
the other hand, established that the plunger 40 had to be displaced
.275 inches to close the contacts 32 and 32a, the screw 55 would be
withdrawn partially to increase the initial distance between the
magnet 60 and the contacts 32 and 32a and by an amount to cause
closure at the selected .250 inch displacement. After the proper
adjustment has been made, the cap 70 is replaced as previously
described. The same procedure is effected in respect to each reed
switch 10 in a multiple-switch system, so that all of the reed
switches 10 mounted on a given keyboard or in a particular unit
will be actuated by the same displacement of the cap 70. This
procedure may be performed either at the manufacturing facility of
the reed switches and/or at the user's plant. For example, after
extended usage, it may be determined that the switch 10 should be
readjusted to meet original specifications. Alternatively, after a
certain amount of usage, it may be determined that a different
displacement of the reed switch 10 would be desirable. Also, it may
be found that the particular environment in which the reed switch
10 is used differs substantially from that in which the reed switch
was adjusted such as, for example, humidity which would require a
readjustment at the user's location. The user can perform the
adjustment merely by removing the cap 70 as previously explained
and utilizing the tool 80.
One very important advantage of the instant invention is that the
adjusting means, consisting of the screw 55 in its threaded opening
54, is concealed and protected by the cap 70. Thus, inadvertent
variation of the adjusting means during day-to-day operation is
prevented. The user can make necessary adjustments easily and
simply, yet at the same time have assurance that inadvertent
variations will not occur.
Although the drawings illustrate the reed switch 10 as having two
pairs of contacts 32 and 32a, it should be appreciated that any
number of pairs of contacts may be utilized, limited by the
available space within the housing 20. Of course, one pair of
contacts with its attendant elements is also contemplated. Also,
although the particular form illustrates a magnet 60 as being the
actuating element, it can be appreciated that the magnet 60 may be
fixed in position and a shield be provided around the magnet 60,
which shield is axially movable so as to vary the magnetic field
presented to the contacts 32 and 32a.
While there has been what is at present considered to be the
preferred embodiment of the invention, it will be understood that
various modifications may be made therein, and it is intended to
cover in the appended claims all such modifications as fall within
the true spirit and scope of the invention.
* * * * *