Electricity: circuit makers and breakers – Fluid pressure – Diaphragm
Reexamination Certificate
2000-01-13
2001-12-11
Luebke, Renee (Department: 2832)
Electricity: circuit makers and breakers
Fluid pressure
Diaphragm
C200S0830SA
Reexamination Certificate
active
06329619
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a structure of a pressure switch mainly used in a refrigeration cycle of a cooling device mounted on a vehicle, which is set to stop a compressor and protect the system when a refrigerant pressure in the refrigeration cycle becomes either more than or equal to a predetermined pressure or less than or equal to a predetermined pressure.
DESCRIPTION OF THE RELATED ART
A conventional pressure switch of this kind is shown in
FIGS. 2 and 3
.
FIG. 2
is a vertical cross-sectional view showing the structure of a pressure switch.
FIG. 3
is an enlarged cross-sectional view showing a portion of
FIG. 2
encircled by a broken line A. In both drawings, the pressure switch is shown in an inverted position from the actual position of use.
In the drawing, the pressure switch
100
comprises a housing
1
including an inner space, a switch case
2
, a diaphragm
3
, a first snap disk
41
, a second snap disk
42
, a receive member
5
, a working shaft
6
, a first switch lever
7
and a second switch lever
8
.
The housing
1
comprises a passage
11
equipped to one end for introducing fluid, an inner space
12
opening to the other end, a stopper
15
for fixing a seal member
29
, and a seal support member
16
.
The seal member
29
is formed as an annular elastic body formed for example of nitrile butadiene rubber, and the member is supported by the seal support member
16
.
The switch case
2
, made of an electric insulating material such as a polybutyl terephthalate resin reinforced by glass fiber, has an opening portion formed to one end thereof which is mechanically press-fixed to the other end of the housing
1
with the seal member
29
placed therebetween.
The switch case
2
comprises an inner space
21
with one end being opened and to which a pressure switch mechanism is placed, and an opening
22
formed on the other end for electrical connection. The inner space
21
and the opening
22
are separated by a partition wall.
A guide wall
24
for guiding a receive member
5
is formed around the inner space
21
. On the guide wall
24
in the partition wall-side is formed a limiting step
25
which protrudes inwardly so as to limit the movement of the receive member
5
toward the partition wall.
Moreover, a supporting step
26
with a smaller diameter for supporting the rim portion of a second snap disk
42
is formed inwardly on the partition wall-side of the limiting step
25
.
The pressure switch mechanism stored inside the inner space
21
of the switch case
2
comprises a diaphragm
3
made for example of polyimide resin film, a first snap disk
41
made of steel, a receive member
5
made for example of polybuthylene terephthalate (PBT) resin, a second snap disk
42
made of steel, a working shaft
6
made for example of ceramic, a first switch lever
7
, a second switch lever
8
, and a pair of terminals
9
.
The peripheral of the diaphragm
3
in the pressure switch mechanism is mounted to an end
27
of the surrounding wall of the inner space
21
in the switch case
2
, which is airtightly fixed through a seal member
29
to the seal support member
16
equipped to the housing
1
.
The receive member
5
is disk-shaped, and on the rim portion of the surface of the disk is formed an outer wall
51
protruding upwards. A penetrating hole
52
is formed to penetrate through the front surface and the back surface of the receive member at the center area, and a central protrusion
53
is formed to protrude around the penetrating hole
52
on the back surface.
The receive member
5
is stored in the inner space so that it slides in the central axis direction of the switch case, guided by the guide wall
24
of the switch case
2
.
The first snap disk
41
is placed so as to contact the diaphragm
3
, being supported by the surface of the receive member
5
, and further being positioned by the outer wall
51
. The working shaft
6
is stored inside the penetrating hole
52
of the receive member
5
and is contacted to the back surface of the first snap disk
41
, and it is further extended toward the second switch lever
8
.
To the exterior of the central protrusion
53
of the receive member
5
is assembled a central opening
43
formed to the center of the convex-shaped second snap disk
42
. The end of the central protrusion
53
is placed opposite to the center surface of the first switch lever
7
.
The working shaft
6
is made for example of ceramic, and the peripheral area of the end surface thereof may be chamfered. The chamfering may either be linear, as is shown in the drawing, or may be arc-like.
The first switch lever
7
is formed of an elastic body having conductivity, such as phosphorus bronze, and one end portion of the lever
7
is fixed to the surrounding wall of the inner space
21
. A contact
71
is equipped to the other end of the first switch lever
7
, and an opening
72
is formed to the intermediate area of said one end and the other end, through which the working shaft
6
penetrates.
The second switch lever
8
is formed of an elastic body having conductivity, such as phosphorus bronze, and one end portion of the lever
8
is fixed to the surrounding wall of the inner space
21
. A contact
81
is equipped to the other end of the second switch lever
8
, and a contact portion
82
is formed to the intermediate area between said one end and the other end, to which the end surface of the working shaft
6
touches.
One pair of terminals
9
are connected to the first switch lever
7
and the second switch lever
8
respectively, which penetrate through the partition wall
23
and are taken out from the opening
22
.
The first switch lever
7
and the second switch lever
8
constitute the switch mechanism.
As shown in
FIG. 3
, the contact portion
82
equipped to the second switch lever
8
is formed for example through press-working, and the surface of the contact portion
82
is formed as a flat surface
89
.
The operation of the pressure switch of the prior art will now be explained.
The fluid pressure loaded to the diaphragm
3
through the fluid passage
11
pushes the diaphragm
3
downward, and the receive member
5
supporting the first snap disk
41
is pushed down. When this pressure reaches 0.25 MPa for example, the second snap disk
42
, which is originally in its first position in which the disk protrudes toward the diaphragm (as shown in the drawing), is shifted to a second position in which the center portion of the disk is displaced toward the partition wall. When the snap disk
42
is displaced, the receive member
5
is pushed by the fluid pressure and moves toward the partition wall, and the central protrusion
53
presses the first switch lever
7
, thereby making the switch.
The receive member
5
being moved toward the partition wall will bump against the limiting step
25
formed to the inner wall of the switch case
2
, which limits further movement of the receiver member toward the partition wall even when fluid pressure rises. Therefore, the second snap disk
42
will not receive further force, and the disk
42
will be free from any unnecessary deformation which may damage its function.
When pressure is reduced and the fluid pressure lowers to 0.21 MPa, the second snap disk
42
shifts from the second position to the first position (shown in the drawing), the receive member
5
moves toward the passage
11
, and the central protrusion
53
will no longer be pressed against the first switch lever
7
. Thus, the switch is opened.
When fluid pressure rises to 2.7 MPa during the state the receive member
5
is bumped against the limiting step
25
and the switch is made, the first snap disk
41
shifts from the first position in which the disk is protruded toward the diaphragm (as shown in the drawing) to the second position in which the center portion protrudes toward the partition wall. The displacement is transmitted through the working shaft
6
to the second switch lever
8
, which is pushed down, thus opening the switch.
As explained, the prior art pressure swi
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujikoki Corporation
Luebke Renee
Nguyen Nhung
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