Electricity: circuit makers and breakers – Fluid pressure – Diaphragm
Reexamination Certificate
2002-03-14
2003-10-14
Enad, Elvin (Department: 2832)
Electricity: circuit makers and breakers
Fluid pressure
Diaphragm
C200S08100R, C200S0830SA, C200S0830SA, C200S0830SA, C200S0830SA, C200S0830SA
Reexamination Certificate
active
06633010
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of pressure switches which may be used in the transmission of an automobile by way of example.
BACKGROUND OF THE INVENTION
It has been known to use pressure switches in the prior art which work with a controller to control various systems of an automobile such as the transmission mechanism. For example, a controller receives information from pressure switches as to whether the fluid pressure is of a prescribed level and with this information controls certain functions related to the operation of the automobile.
As is shown in
FIG. 6
, a prior art pressure switch
100
is provided with a switch chamber
103
that has been partitioned by a diaphragm
102
inside of a switch housing
101
. A snap action disc member
104
is provided in switch chamber
103
which is connected to plus terminal
105
and which is movable in and out of engagement with a contact member
106
depending upon the pressure of the fluid exerted upon it. When the disc member
104
is in engagement with contact member
106
, an electrical signal is transmitted to a controller through connection of negative electrical terminal
107
.
In said pressure switch
100
moreover, an oil cavity
100
is provided in housing
101
to receive oil from oil passage
109
to exert pressure on diaphragm
102
. An oil pan
108
surrounds switch
100
as reservoir for the transmission use. It is desirable to try to prevent contaminants in the oil such as dust, chips, etc., from entering switch chamber
103
. One method is to make the entrance route of the oil from the oil passage
109
to chamber inside of housing
101
a complicated path, for example, a tortuous path flowing around resin cover
111
and gasket
112
.
In regard to switch
100
, however, there is a need to put switch chamber
103
in communication with oil pan
108
for the purpose of stabilizing the pressure between the two. As a consequence of this, there have been cases where oil enters the switch chamber
103
. In such a case, an oil film is produced between snap acting disc
104
and contact terminal
106
with the result that operational characteristics of the switch can change with changes in the viscosity of the oil. That is, the snap action of disc
104
in making contact with terminal
106
will vary with changes in viscosity of the oil.
Accordingly, there are instances where pressure switch
100
cannot transmit a proper pressure signal based upon the oil pressure instantaneously to the controller, especially in low temperature conditions. In the case where pressure switch
100
is mounted on a plate
113
to be apart from oil pan
108
, on the other hand, there are design considerations related to strength, dimensional accuracy etc., with a resultant rise in manufacturing costs, in connection with the installation of each switch
100
on plate
113
so as to prevent a possible leak of oil inside of the oil pan
108
onto plate
113
through switch chamber
103
.
In short, there is a strong need to prevent the possible encroachment of oil into switch chamber
103
and to minimize the affect of temperature on switch signal accuracy. Further, there is a need for a compact switch that can be manufactured economically and reliably which has superior operational stability.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a fluid pressure responsive switch with a sealed switching chamber to prevent fluid and other debris from entering the switching chamber thereby providing for a highly reliable switch.
It is another object of the present invention to minimize the effects of temperature variation on the operational performance of the switch.
It is yet another object of the present invention to provide for a compact switch with a simple design which can be manufactured economically and reliably.
More specifically, a pressure switch according to the present invention comprises a base electrode which has a central through hole running therethrough, having a top opening and a bottom opening, a terminal member at least a part of which is containing in said through hole which is electrically insulated from the base electrode by a seal member completely sealing the top opening, a curved shaped fluid pressure responsive disc located in said central through hole adapted to snap over center between a first position in which said disc is not in engagement with the terminal member and a second position in which said disc is in engagement with the terminal member in response to being exposed to a fluid pressure of predetermined value, said disc being electrically connected to said base electrode, and a diaphragm member positioned adjacent said disc for transmitting said fluid pressure from an external source to said disc, said diaphragm being in sealing engagement with said base electrode to completely seal closed the bottom opening of said base electrode thereby providing for a sealed chamber in said base electrode.
In accordance with an embodiment of this invention, the switch chamber is sealed in a vacuum state.
Additional objects and features of the invention will be set forth in part in the description which follows and in part will be obvious from the description. The objects and advantages of the invention may be realized and attained by means of the instrumentalities, combinations and articles particularly pointed out in the appended claims.
REFERENCES:
patent: 4939321 (1990-07-01), Tanaka et al.
patent: 5004876 (1991-04-01), Sogge et al.
patent: 5101549 (1992-04-01), Sogge et al.
patent: 5278367 (1994-01-01), Homol
patent: 5308940 (1994-05-01), O'Brien et al.
patent: 5338908 (1994-08-01), Rahman et al.
patent: 5508483 (1996-04-01), Czarn et al.
patent: 5619022 (1997-04-01), Long
Mikawa Yoshihiko
Tanaka Shuji
Baumann Russell E.
Enad Elvin
Poker Jennifer A.
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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