Electricity: electrothermally or thermally actuated switches – Electrothermally actuated switches – With bimetallic elements
Reexamination Certificate
1999-07-26
2001-05-22
Picard, Leo P. (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Electrothermally actuated switches
With bimetallic elements
C337S085000, C337S333000, C337S334000, C337S362000, C337S351000, C200S043110, C200S013000, C200S179000, C200S273000
Reexamination Certificate
active
06236299
ABSTRACT:
FIELD OF INVENTION
This invention is related to an auto tripping key switch, in particular to a key switch that can be automatically tripped to form a closed circuit while encountering current overload so as to ensure electrical safety.
BACKGROUND OF INVENTION
FIG. 1
illustrates an exploded view of a conventional key switch
1
, comprising an upper housing
10
, a lower housing
11
, a hollow cylindrical housing
12
that substantially extends upwards from a center of the upper housing
10
, the cylindrical housing
12
being formed at an inner face thereof with four linear guide grooves
13
that are spaced from each other in 90 degrees apart, the guiding grooves
13
being formed with a beveled step face
14
therebetween, the step faces
14
each having a top of a relatively greater thickness and projecting towards an inner side of the hollow cylindrical housing
12
. The switch
1
further comprises a cylindrical key
15
being formed at a bottom thereof with four pentagonal protrusions
16
engaging and moving along the linear guide grooves
13
, the pentagonal protrusions
16
each having a tip
22
facing downwards and a bottom edge
17
located between the protrusions
16
and extending upwards along the tips
22
to form inverse-V configurations such that the entire bottom edge
17
of the key
15
forms a serrate periphery. The key
15
may engage an engaging unit
18
therein; the engaging unit
18
is formed with a square aperture
19
therein and includes four triangular protrusions
20
at the bottom thereof. The triangular protrusions
20
form an outer diameter that is in-between the inner diameters formed by opposing ends of the step faces
14
in the hollow cylindrical housing
12
. The triangular protrusions
20
each has a beveled face
21
that adapts to the tips
22
of the pentagonal protrusions
16
located at the bottom of the key
15
.
The engaging unit
18
is further provided therebeneath with a follower rotary body
23
having a square column
24
at an upper portion that adapts
5
to be inserted into the square aperture
19
of the engaging unit
18
such that the follower rotary body
23
may be driven to rotate by the engaging unit
18
. The follower rotary body
23
has a bottom being formed by a disc
25
, above that a spring
26
is provided engaging around the square column
24
. The spring
26
has an upper end that engages a lower edge of the engaging unit
18
. The disc
25
is provided with two opposing raised faces
27
at the outer bottom edge of the disc
25
, the raised faces
27
each having a thickness that gradually increases while approaching towards a periphery of the disc
25
. The disc
25
is further provided with two separate semi-circular supports
28
at the center thereof. The semi-circular supports
28
each have an arcuate inner edge and are provided with a Z-like metallic strip
29
therebetween, as shown in FIG.
1
. The lower housing
11
of the conventional switch
1
is formed with a circular recess
2
for receiving the disc
25
located at the bottom of the follower rotary body
23
. The recess
2
is formed with an emboss
3
at the center thereof for engaging the two semi-circular supports
28
located at the bottom of the disc
25
. The lower housing
11
is further provided with two metallic conductive contacts
4
each having an end
5
that forms a leaf extending towards the circular recess
2
and elevating slightly upwards. The two conductive contacts
4
are each provided with a screw
6
thereon for connecting electrical leads (not shown.)
FIGS. 2A
to
2
C are cross-sectional views of the conventional key switch
1
illustrating internal structure of the key switch
1
and the switch transition from open to closed circuits.
FIG. 2A
illustrates the switch
1
in its state of closed circuit. Under the state of closed circuit, the ends
5
of the two contacts
4
are in contact with the raised faces
27
located at the bottom of the disc
25
. The follower rotary body
23
made of insulative material subjects the switch
1
to be in the state of closed circuit. A user may push the key
15
to switch the switch
1
from the state of closed circuit to the state of open circuit. At this time, the pentagonal protrusions
15
located at the bottom of the key
15
still overlay the triangular protrusions
20
located at the bottom of the engaging unit
18
as that shown in
FIG. 2A
, and engage the linear guide grooves
13
such that both the key
15
and engaging unit
18
are movable along a perpendicular direction. When the engaging unit
18
moves downward to outside of the step faces
14
of the triangular protrusions
20
located at the bottom of the engaging unit
18
, the engaging unit
18
is no longer retrained by the linear grooves
13
because the outer diameter of the triangular protrusions
20
located at the bottom of the engaging unit
18
is smaller than the inner diameter of the hollow cylindrical housing
12
beneath the step faces
14
, and the engaging unit
18
is thus now rotatable. Because the spring
26
will exert an upward force on the engaging unit
18
after being compressed by the engaging unit
18
, the spring
26
will subject the triangular protrusions
20
located at the bottom of the engaging unit
18
to follow the pentagonal protrusions
16
and serrate edges
17
for upward and rotary motions. While viewing from top, the engaging unit
18
rotates a minute angle in a counterclockwise direction subjecting the triangular protrusions
20
to engage the inverse-V serrate edges
17
of the key
15
, such as that shown in
FIG. 2B
, and driving the follower rotary body
23
to rotate simultaneously.
When the user releases the key
15
, the thrust of the spring
26
subjects upward movement of the engaging unit
18
such that the triangular protrusions
20
of the engaging unit
18
urge against the lower edges of the beveled step faces
14
and the engaging unit
18
continues to trace along the lower edges of the beveled step faces
14
in upward and counterclockwise rotary motions. The engaging unit
18
further drives simultaneous rotation of the follower rotary body
23
until the triangular protrusions
18
of the engaging unit
18
re-enter the linear grooves
13
. At this time, the pentagonal protrusions
16
located at the bottom of the key
15
again overlay the triangular protrusions
20
located at the bottom of the engaging unit
18
; the key
15
and the engaging
18
are further pushed upwards by the spring
26
until the pentagonal protrusions
16
of the key
15
urge against a lip
7
of the hollow cylindrical housing
12
, as shown in FIG.
2
C. At this time, the follower rotary body
23
is exactly 90 degrees away from the upper and lower housings
10
,
11
of the switch
1
, and opposing sides of the Z-like metallic strip
29
on the bottom of the disc
25
are in contact with the two ends
5
of the conductive contacts
4
, respectively, such that the two contacts
4
are electrically connected by means of the ends
5
and the Z-like metallic strip
29
to enable open circuit of the switch
1
.
The user may push and release the key
15
again such that the is engaging unit
18
and the follower rotary body
23
may rotate for 90 degrees in a similar manner to cause the ends
5
of the two conductive contacts
4
to be in contact with the raised faces
27
located at the bottom of the disc
25
, so as to switch the switch
1
from the state of open circuit to the state of closed circuit, such as that shown in FIG.
2
A.
However, such a conventional construction is of a passive switch type, which relies on pushing motions of the user to switch between the open circuit and the closed circuit and thus fails to provide auto switch features. Therefore, when the switch encounters current overload under the state of open circuit, it is liable to cause electrical sparks and result in safety hazards.
SUMMARY OF INVENTION
It is a primary object of this invention to overcome defects of conventional art and to provide an auto tripping key switch, the switch comprisi
Picard Leo P.
Senniger Powers Leavitt & Roedel
Vortman Anatoly
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