U.S. patent application number 10/252075 was filed with the patent office on 2003-12-11 for limit switch.
Invention is credited to Asa, Yukihiro.
Application Number | 20030226749 10/252075 |
Document ID | / |
Family ID | 29706847 |
Filed Date | 2003-12-11 |
United States Patent
Application |
20030226749 |
Kind Code |
A1 |
Asa, Yukihiro |
December 11, 2003 |
LIMIT SWITCH
Abstract
A limit switch sealing anon-contact type microswitch has a
stainless steel actuator lever subjected to nitriding processing
which is cantilever supported on a housing upper portion by a plate
spring made of polyimide. A non-contact type microswitch stored
inside a housing cavity is slightly adjusted for upward and
downward positions by a screw mechanism, and after that, is sealed
inside the cavity by the filler such as silicon rubber and the
like. A piston which transmits the movement of the actuator lever
to the microswitch is supported air tight by the housing at the
center of a flat conical bellows, and the limit switch including a
return coil spring is highly sensitive, and is excellent in water
resistance, oil resistance, abrasion resistance and durability.
Inventors: |
Asa, Yukihiro; (Tokyo,
JP) |
Correspondence
Address: |
FLYNN THIEL BOUTELL & TANIS, P.C.
2026 RAMBLING ROAD
KALAMAZOO
MI
49008-1699
US
|
Family ID: |
29706847 |
Appl. No.: |
10/252075 |
Filed: |
September 20, 2002 |
Current U.S.
Class: |
200/573 |
Current CPC
Class: |
H01H 13/063 20130101;
H01H 9/0207 20130101; H01H 13/186 20130101 |
Class at
Publication: |
200/573 |
International
Class: |
H01H 003/42 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2002 |
JP |
2002-170001 |
Claims
What is claimed is:
1. A limit switch, comprising: a box type housing: a non-contact
type microswitch provided inside a cavity of the housing; an
actuator lever supported on an upper surface of the housing by a
cantilever plate spring; a piston provided between the actuator and
microswitch connecting both of them; and an elastic membrane to
seal and combine the piston.
2. The limit switch according to claim 1, wherein, on two surfaces
functioning as mounting surfaces of the housing, low small
protrusions are convexly provided at least on two places of one
surface, and hole portions to fit to the small protrusions are
concavely provided on corresponding positions of the other
surface.
3. The limit switch according to claim 1, wherein the plate spring
is formed by polyimide.
4. The limit switch according to claim 1, wherein the elastic
membrane is a disc bellows having an inclination along a flat
conical surface and is formed by polyimide as a raw material.
5. The limit switch according to claim 1, wherein the actuator is
formed by stainless steel and the surface thereof is subjected to
nitriding processing.
6. The limit switch according to claim 1, wherein a top end of the
actuator lever is extended to the housing side, and a square hole
which controls a moving range is piercingly provided at a position
facing the housing side so as to idly fit to a protrusion of the
housing side.
7. The limit switch according to claim 1, wherein a compression
coil spring is insertably mounted between the piston and a mounting
board of the microswitch and supports a weight of the piston and an
urging force by the elastic membrane.
8. The limit switch according to clam 7, wherein the mounting board
of the microswitch is provided with an external thread on an outer
periphery thereof and screwed into an internal thread provided on a
piercing hole of the housing.
9. The limit switch according to claim 8, wherein the mounting
board of the microswitch is rotated so as to move a position
relative to the actuator lever by a screw mechanism and a distance
of an operating position by the actuator lever for a free position
of the microswitch is made adjustable.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a limit switch which limits
or controls a movement, and, in particular, to a constitution of a
non-contact type microswitch extensively used for industrial
purpose which comprises water resistance, corrosion resistance and
abrasion resistance. It is to be noted that the limit switch is a
switch to detect a position, a displacement, a movement, a passage
and the like, and the microswitch is defined as a compact type
switch designed and produced so that a switching operation to open
and close an electrical current can be promptly and reliably
performed with a small force.
[0003] 2. Description of the Related Art
[0004] A conventional limit switch generally has an actuator of a
lever type rotatably supported by a hinge, and when a free end of
the actuator is pushed and moved by a cam and a dog of an
operational mechanism, the movement thereof is transmitted to a
slide pin, and by a snap action of a toggle mechanism and the like,
a contact thereof is switched to OFF from ON or ON from OFF, so
that a signal is outputted and an operation of a moving mechanism
is detected.
[0005] However, since an urging force which actuates the limit
switch receives resistance due to a reaction accompanied with a
snap action of the contact by moving the actuator lever, an urging
force large enough to overcome the resistance is required.
Therefore, in order to avoid an influence, which exerts a
counteraction on the function, it is better that an operating force
of the limit switch is as weak as possible. Further, in bad
surroundings where the limit switch is used not only for industrial
machines, but also for field equipment of civil engineering,
building construction and the like, abrasion due to accumulation of
dust and repeated operations is unavoidable for a spindle of the
hinge which supports the lever to function as the actuator. A
sealed microswitch of JIS C 4508 is a large type, and is difficult
to use conveniently for the places, which require a compact
construction.
SUMMARY OF THE INVENTION
[0006] Therefore, the object of the present invention is to provide
a general type limit switch, which has abrasive resistance,
corrosion resistance and water resistance, and is excellent in
durability and, moreover, can function with a weak operating
force.
[0007] In order to achieve the above-described object, the limit
switch according to the present invention is a flat box type
housing as a basic model with a cavity concavely provided, and an
outer surface of the housing comprises: two surfaces backward and
forward in a thickness direction where mounting holes are
piercingly provided at standard positions (a center distance
between two places of mounting holes according to JIS C 4505 is:
25.4 mm) and which function as mounting surfaces; an upper surface
which defines upper edges of these two surfaces and supports an
actuator lever; and an under surface which defines under edges of
these two surfaces and where the cavity is open, wherein a
non-contact type microswitch is provided inside the cavity with
upper and lower positions adjustable; and the actuator lever is
supported on the upper surface by a cantilever plate spring; and a
piston connecting the actuator lever and the microswitch is
insertably mounted between both of them; and an annular concave
portion circumference on the upper surface, where a piercing hole
to fittingly mount the piston by being connected with the cavity is
open, is sealed at the outer edge of the elastic membrane which
supports the piston by seal-connecting the piston with the center
potion; and, moreover, the cavity which stores the microswitch is
filled with a sealing agent.
[0008] In two surfaces which function as the mounting surfaces, low
small protrusions are convexly provided on at least two places of
one side, and in the corresponding position of the other side, hole
portions to fit the small protrusions are concavely provided.
Further, the plate spring is formed by polyimide, and the elastic
membrane is formed by a disc bellows having an inclination along a
flat conical surface with polyimide as a raw material. Further, the
actuator lever is formed by stainless steel (SUS304) and the
surface thereof is subjected to nitriding processing. In addition,
a top end of the actuator lever is extended to the housing side,
and a square hole which controls a moving range is piercingly
provided at a position facing the housing side so as to idly fit to
a protrusion of the housing side. On the other hand, a compression
coil is insertably mounted between the piston and a mounting board
of the microswitch and supports a weight of the piston and an
urging force by the elastic membrane. Further, the mounting board
of the microswitch is provided with an external thread on an outer
periphery thereof and screwed into an internal thread provided on a
piercing hole of the housing, and the mounting board of the
microswitch is rotated so as to move a position relative to the
actuator lever by a screw mechanism and a distance of an operating
position by the actuator lever for a free position of the
microswitch is made adjustable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows one embodiment of a limit switch according to
the present invention. FIG. 1A is a plane view, and FIG. 1B is a
cross sectional view cut along the line BB in FIG. 1A;
[0010] FIG. 2 is a bottom view cut along the line II-II in FIG. 1B;
and
[0011] FIG. 3 is a side view of a part by a cross-sectional view
cut along the line III-III in FIG. 1B.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0012] Hereinafter, an embodiment of a limit switch according to
the present invention will be described based on the drawings. FIG.
1 shows one embodiment of a limit switch 10 according to the
invention, and FIG. 1A is a plane view and FIG. 1B is a sectional
view cut along the line B-B in FIG. 1A. Further, FIG. 2 is a bottom
view cut along the line II-II in FIG. 1B, and further FIG. 3 is a
side view of a partial sectional view cut along the line III-III in
FIG. 1B.
[0013] A housing 12 of the limit switch 10 is an aluminum die cast
molded article piercingly provided with mounting holes 16, 17 which
pass through two surfaces (surface parallel to the paper surface of
FIG. 1B) 14, 15 frontward and backward in a thickness direction at
two places. A center distance between the mounting holes 16, 17 is
preferably set to 25.4 mm based on JIS C 4505 standard. Front
surface 14 side opening of the mounting holes 16, 17 is concavely
provided with counter sinking holes 18, 19 which sink heads of
mounting bolts (not shown), and low small protrusions 20, 21
loosely fittable to the counter sinking holes 18, 19 are convexly
provided on the periphery of the rear surface 15 of the mounting
holes 16, 17.
[0014] Hence, for example, by providing a concave portion, to which
the small protrusions 20, 21 are fittable, on a mounting member
(not shown), the position of the limit switch can be easily and
precisely decided.
[0015] In FIG. 1B, screw holes 23a are carved at two places of a
seat 23 provided at right side in the drawing of the upper surface
22 which defines the upper edges of the frontward and backward two
surfaces 14, 15, and bolt holes 24b are piercingly provided at two
places at positions aligned with the holes 23a in the plate spring
25 of polyimide and a clamp 24, respectively. A plate spring 25 is
piercingly provided between the seat 23 and the clamp 24, and s
bolt 26 inserted into the bolt hole 24b is screwed into the screw
hole 23a and clamped, and the plate spring 25 is compressed and
fixed to the seat 23 by the clamp 24. In the clamp 24 is concavely
provided a counter sinking hole 24a which sinks a head 26a of the
bold 26. The plate spring 25 is detachable by this bolt connection
so that, when dust is accumulated in a gap 22a between the upper
surface 22 and the plate spring 25, it is possible to remove and
clean the plate spring 25. In the case where the plate spring 25
suffers an accidental damage from an external force, the plate
spring 25 has advantages of being exchanged.
[0016] Reference numeral 28 denotes an actuator lever, which is
connected with a free end of the plate spring 25 by a rivet 29. The
actuator lever 28 is formed by a plate of stainless steel (SUS304)
and is subjected to nitriding processing, and therefore, is
excellent in corrosion resistance and abrasion resistance, and has
little friction. Hence, there is a considerable degree of freedom
in an operating direction by an operating member such as a dog, a
cam and the like, and an exact vertical degree for an edge line of
a sliding portion 28b is not necessarily required. Since the
actuator lever 28 is supported by the plate spring 25 having a
cantilever constitution, an axis or a bearing that wears by
receiving rotation does not exist. Accordingly, the actuator lever
28 does not require lubrication, and abrasion is not expedited by
insertion of dust and rust.
[0017] A free end 28a of the actuator lever 28 is provided with a
sliding portion 28b with the dog and the cam not shown which
receives operation and which is greatly bent upward in the drawing
from an extension of the plate spring 25 at an angle of 45.degree.
and is further bent at the sliding portion 28b at about 90.degree..
Further, a top end portion 28c is bent along the side 30 of the
housing 21 and hangs down almost in parallel. On upper portion of
the housing side 30 is concavely provided a notched portion 30a,
which movably stores the top end portion 28c.
[0018] On the other hand, in the actuator lever top end portion 28c
is piercingly provided a square hole 32 (see FIG. 3), and the
notched portion 30a notches a position corresponding to almost a
center of the square hole 32 and forms a control portion 30b, which
is idly fitted to the square hole 32. Accordingly, the movement of
the actuator lever 28 by a compelling force from the outside is
controlled within a range where an inner edge of the square hole 32
abuts against the control portion 30b. Further, the left and right
peripheral walls 30c remained on the outer periphery of the notched
portion 30a and a counter surface 30d at the lower end of the top
end portion 28c control excessive movement and function as a safety
stopper.
[0019] Against the vicinity of the connecting portion with the
plate spring 25 of the actuator lever 28, a spherically formed apex
face of a head 36a of a piston 36, which transmits the movement of
the actuator lever 28 to a non-contact type microswitch 34, abuts.
A base 36b of the piston 36 is cylindrical, and on the upper end
thereof, a seat 36d having a diameter slightly larger than the base
36b extends from an upper portion of a flange 36c expanded in
diameter, and a center hole of the head 36a fits to a small
diameter boss 36e protruding from a center of the seat 36d. A
central portion of the disc bellows 38 of the elastic membrane
formed by polyimide is insertingly mounted between the under
surface of the head 36a and the upper surface of the boss 36d, and
the joined surface thereof is completely sealed by polyimide. The
disc bellows 38 has a coaxial wavelike convex-concave formed along
a flat conical surface, and the same size diameter see-through hole
as the boss 36a passes through the center.
[0020] As shown in FIG. 1B, in the housing 12 is formed a cavity 42
opened to an under surface 40 in the drawing at the side opposing
to the upper surface 22, and is shown in FIG. 2 as a bottom view.
From the upper surface 22 to the cavity 42 is passed a piercing
hole 44 having steps. On the upper surface 22 to which the piercing
hole 44 is opened is formed an inclined plane annular concave
portion 46 expanded upward in diameter, where a peripheral wall 46a
expands upward, and a circumference where a peripheral wall 46a
contacts a under surface 46b is allowed to abut against an outer
periphery of the disc bellows 38 so as to be sealed by s bonding
agent. In the under surface 46 is concavely provided a step portion
46c having a diameter slightly larger than an outer shape of the
flange 36b which overhangs from the piston 36, and the step portion
46c controls a downward moving area of the flange 36b and functions
as a safety stopper for an excessive external force in a vertical
direction.
[0021] In the under portion of a reduced diameter cylindrical hole
46d communicating with the cavity 42 from the step portion 46c is
carved an internal thread 48, and in the cavity 42, an opening
expanded in diameter functions as a linear line guide portion 52 of
a microswitch mounting board 50. The microswitch mounting board 50
is cylindrical, and in the top end portion thereof is provided an
external thread 54 which is screwed into an internal thread 48 of a
lower portion of the cylindrical hole 46d, and a base 56 is
slidably fits to the linear line guide portion 52. The under
portion in the drawing of the base 56 is expanded in diameter and
forms a microswitch mounting seat 58, and is carved with a counter
sinking hole 62 adapted to the outer shape of the ready-made
non-contact type microswitch 34, and the ready-made non-contact
type microswitch is fixed inside the hole 62 by adequate means.
Note that a hole IC is utilized for the non-contact type
microswitch 64.
[0022] In the center of the microswitch mounting board 50 is
provided a through hole 50a so that a base 36b of the piston 36 is
slidably fittingly mounted. The lower end portion of the through
hole 50a is a sliding portion 50b which has little gap with the
piston base 36b, and in the upper portion other than this is
provided an escape way expanded in diameter. Between the under
surface of the flange 36c of the piston and the upper surface of
the external thread 54 of the microswitch mounting board is
insertably mounted a compression coil 64, which energizes the
piston 36 upward so that the apex surface of the piston head 36a is
allowed to always abut against the under surface of the actuator
lever 28. On the other hand, the lower end in the drawing of the
piston 36 abuts against a top end of an operating pin (actuator)
34a, which is located at a free position of the ready-made
microswitch 34. Since the microswitch 34 is a non-contact type, a
return spring is weak, and in contrast to a contact which operates
by a snap action of the conventional general industry limit switch,
the microswitch 34 can be sufficiently functioned by an extremely
slight operating force.
[0023] In order that the operating position of the contact is not
largely affected by tares of the actuator lever 28 and the piston
36 depending on a mounting direction of the limit switch 10,
elasticity of the plate spring 25, the disc bellows 38 and the
compression coil spring 64 is comprehensively set. By rotation of
the microswitch mounting board 50, the piston 36 and the
compression coil spring 64 moves together upward and downward, and
can adjust a distance of an operating position (shown by two-dot
chain line) relative to the free position of the actuator lever 28
shown in FIG. 1A by a solid line. After performing a prescribed
operating position adjustment in a plant and drawing out a cable
(not shown) wired in the non-contact type microswitch 34 from a
distribution port 66 of the housing 12, the cavity 42 is sealed by
silicon rubber or an epoxy filler.
[0024] As described above, while one embodiment of the limit switch
according to the present invention is described based on the
drawings, the invention is not limited to the illustrated
embodiment, and it is expected that a variety of changes and
modifications with respect to the details and alternation such as
reconstitution of parts and the like can be performed in a range
not deviating from the constituent features of the present
invention. For example, as an operating indicator light, a light
emitting diode 68 may be mounted.
[0025] As evidenced by the above-described explanation, according
to the limit switch according to the present invention, since a
micro-shaped non-contact type microswitch requiring a delicate
attention in handling is sealed into a basic model limit switch,
the microswitch can be handled as a sensor also for an extremely
sensitive positioning, a displacement, a movement or a passage with
a sense for usual machine parts, and moreover, the same operating
sensitivity as the microswitch is guaranteed. By the convex portion
and the concave portion which are provided on the mounting surface
and fit to each other, mutual precise positioning can be easily
performed in using the lamination layers of a plurality of
microswitches.
[0026] Further, since the non-contact type microswitch is installed
with the upper and lower positions adjustable, an appropriate
operating position can be set. Furthermore, the actuator lever is
supported by a cantilever plate spring, and the piston, which
transmits the movement of the actuator lever to the non-contact
type microswitch, is supported by a bellows-shaped elastic
membrane. Since there exist no frictional portions, lubrication is
not required, and since there exist no frictional components,
durability is improved. Further, since the connecting portion
between the bellows-shaped piston and the housing is sealed air
tight and the non-contact type microswitch is sealed inside the
cavity of the housing by the filler, the electrical contact is
completely isolated from the external world, and the limit switch
becomes completely a waterproof and dustproof type, so that use in
water and oil and in bad surroundings where a lot of dusts abound
is possible.
[0027] Further, since the actuator lever is formed by stainless
steel (SUS304), and the surface thereof is subjected to nitriding
processing, and the plate spring and the bellows-shaped elastic
membrane are formed by polyimide, the actuator lever is excellent
in erosion resistance and abrasion resistance. In addition, a
moving range of the actuator lever is controlled by the protrusion
of the housing side which idly fits inside the square hole of the
top end, and moreover, the notched portion of the housing which
stores the top end of the actuator lever can be allowed to function
as a safety stopper. Further, for the downward movement in an
excessive vertical direction, which acts on the actuator lever,
since the lower step of the disc bellows elastic membrane prevents
the downward movement of the piston flange, the non-contact type
microswitch can be prevented from being affected by unreasonable
external force.
[0028] On the other hand, since the compression coil spring
insertably mounted between the piston and the microswitch mounting
board supports the urging force by the tare of the piston and the
wavelike elastic membrane, regardless of a mounting posture of the
limit switch, a stable constant operating position can be secured,
and the microswitch mounting board can precisely set the operating
position for the free position of the microswitch by the actuator
by a slight adjustment by a screw mechanism.
* * * * *