Surgery – Diagnostic testing – Cardiovascular
Utility Patent
1998-10-14
2001-01-02
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S561000, C073S700000, C073S715000
Utility Patent
active
06168566
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of pressure sensing devices, and in particular to a pressure sensing device, such as a blood pressure gauge, utilizing a member for supporting an expandable diaphragm and the gauge movement mechanism.
BACKGROUND OF THE INVENTION
Pressure sensing devices are widely known, such as sphygmomanometers which include a pneumatic bulb used to inflate a pressure chamber of an attached sleeve or cuff that is fitted over the arm or leg of a patient. A bellows assembly, responsive to fluid changes of the pneumatic bulb and the sleeve pressure chamber is positioned in a dial indicator housing. The pointer of the dial indicator is interconnected to the bellows assembly by a movement mechanism of the gauge, whereby expansion of the bellows assembly causes a corresponding circumferential movement of the pointer.
Known designs of these devices require separate support plates for independently supporting the movement mechanism and the diaphragm, respectively, and defining an expansion chamber for the diaphragm therebetween. These designs require a maintained height dimension of the housing, making the development of a compact design difficult, at best.
Numerous changes have been effected concerning the movement mechanism of pressure sensing devices. In the past, these mechanisms were intricate and precise and were akin in their manufacture and precision to Swiss watches. For example, in one such mechanism, a pair of diaphragm springs are attached adjacent opposite ends of a spindle. A bottom end of the spindle is placed in contact with the inflatable bellows assembly and a twisted bronze band perpendicularly disposed at the top end of the spindle is connected thereto by a horizontally disposed spring bent part. As the spindle axially deflects due to the inflation of the bellows assembly, the bent spring part is caused to deflect and the band twists. The twisting of the bronze band causes corresponding rotation of a pointer relative to an adjacent dial indicating face.
Movement mechanisms, such as the preceding, involve a plurality of moving components, each having multiple bearing surfaces. As a consequence, significant tolerancing is required in their assembly.
A more simplified movement mechanism design is described, for example, in copending and commonly assigned U.S. Ser. No. 08/972,573, filed Nov. 18, 1997, which utilizes a vertically disposed linear cartridge including a spirally wrapped ribbon spring having one end mounted to an axially movable elongate pin and a remaining end attached to a cap member fixed to the cartridge. A bottom portion of the pin is positioned relative to the expandable diaphragm, wherein subsequent axial translation of the pin elongates the spirally wound ribbon member and produces repeatable circumferential movement of a needle or pointer element supported at the top end of the pin relative to the dial indicator face.
Though the manufacture of a pressure sensing device is considerably simplified utilizing the above movement mechanism design, there have been to date no efforts made to simplify the manufacture of the device relative to the support of the diaphragm and/or the interaction between the deflection of the diaphragm and the movement mechanism of the gauge.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to improve the state of the art of pressure sensing devices.
It is a further primary object of the present invention to provide a pressure sensing device, such as a blood pressure gauge, which can be lighter in weight than previously known sensing devices.
It is yet a further primary object of the present invention to provide a pressure sensing device having improved features with regard to the assembly and support of the bellows assembly and the movement mechanism.
Therefore and according to a preferred aspect of the present invention, a pressure sensing device is provided comprising:
a housing having a hollow interior and including at least one inlet disposed in a lower portion thereof;
a source of fluid in communication with said at least one inlet;
a flexible diaphragm adjacently disposed relative to said at least one inlet, said diaphragm having a surface which is responsive to the flow of fluid entering and leaving said housing through said at least one inlet;
a movement mechanism having an input member disposed adjacently to the flexible expanding surface of said diaphragm and an outlet member attached to indicating means in an upper portion of said housing; and
means for supporting said flexible diaphragm and said movement mechanism within the interior of said housing, said supporting means including a common support plate having a bottom side and a top side, wherein said diaphragm is disposed adjacent the bottom side of said support plate, and wherein the lower part of said housing and said support plate define a pressure chamber sized for allowing deflection of said diaphragm.
Preferably, the common support plate includes a center opening sized for retaining one end of the movement mechanism and includes means for positioning the input element relative to the deflecting surface of the diaphragm.
A feature of the present invention is that the support plate is substantially circular in shape and includes a plurality of ears which engage tabs provided in the circumferential inner wall of the housing using a bayonet type of connection.
Another feature of the invention is that a flexible gasket, such as an O-ring, is provided between the support plate and the outer edge of the diaphragm. The flexible gasket seals the outer edge of the diaphragm relative to the bottom of the housing and also provides increased linearity and repeatability, as opposed to conventional pressure sensing device gauge designs requiring two or more support plates.
Yet another feature of the present invention is that positioning the diaphragm on the interior side of a common support plate allows the pressure chamber to be established between the housing interior and the support plate. Moreover, a common support plate also fixedly supports the movement mechanism, in the manner of prior bridge plate assemblies, and suitably positions an input member of the mechanism relative to the deflecting diaphragm. By inverting the diaphragm against the bottom of the single support plate, all required functions previously requiring at least two support plates are accomplished. Preferably, the walls of the housing are made from a flexible plastic material to allow minor flexing thereof due to the presence of entering air.
Alternatively, and depending on the design of the gauge housing, a separate intermediate structure or adapter can be interposed between the support plate and the lower part of the housing. This intermediate fixture includes means for retaining the support plate and a flexible gasket and is used to define a pressure chamber for the flexible diaphragm. The adapter can be fixedly but removably attached from the housing, as needed.
According to another preferred aspect of the invention, there is provided a blood pressure measuring device comprising:
a housing having a hollow interior;
a flexible diaphragm disposed in a lower portion of said housing interior, said diaphragm including a surface which deflects in response to pressure changes within the housing interior;
a movement mechanism having an input member and an output member, said output member being attached to indicating means;
a support plate having means for supporting said movement mechanism, wherein said diaphragm is positioned against a bottom surface of said support plate, said plate having a center opening sized for receiving said movement mechanism and means for aligning said input member relative to said diaphragm and wherein said diaphragm and said housing form a pressure chamber.
A perceived advantage of the present design is that the use of an O-ring or other flexible gasket forms the pressure chamber, along with the diaphragm and the housing. The use of the flexible gasket is an improvement over previous designs req
Baxter James M.
Lia Raymond A.
Vivenzio Robert L.
Nasser Robert L.
Wall Marjama & Bilinski
Welch Allyn Inc.
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