Rolling seal spirometer

Claim 2

A spirometer for receiving and measuring the exhaled breath of a human, said spirometer comprising a cylinder having a front closure, a rear closure and an internal cylindrical surface, a piston mounted within said cylinder intermediate said front and rear closures, said piston having a shaft extending axially through said rear closure, bearing means centrally disposed in said rear closure adapted to receive said shaft whereby said piston is supported within said cylinder for substantially unrestrained axial movement therein, inlet means in said front closure adapted to admit the exhalation breath to the cylinder to exert a force against said piston, venting means in said rear closure adapted to vent said cylinder to atmosphere whereby said piston is caused to be displaced toward said rear closure, calibration means associated with said piston shaft to measure the axial displacement of said piston, seal means positioned between said piston and said internal cylindrical surface, said seal means having been constructed from a frusto-conical cone of uniformly thin, homogeneous silicone rubber sheet stock, said seal having the interior edge surface of the smaller end sealed to said piston and having the interior edge surface of the larger end sealed to said internal cylindrical surface, said seal further defining a U-shaped configuration having the concavity thereof facing said front closure of said cylinder whereby said seal is adapted to roll during the displacement of said piston and thereby create negligible friction to the displacing of said piston.

Claim 3

A spirometer comprising a cylinder having an internal cylindrical surface, a cylindrically shaped piston mounted in the cylinder for substantially free and unrestrained axial movement in the cylinder, means for admitting air preSsure such as would be generated by human breathing into one end of said cylinder to exert a force on one side of the substantially unrestrained piston, means venting the other side of the substantially unrestrained piston to the atmosphere whereby a differential pressure across said piston may be readily created upon the admission of air pressure created by human breathing into the said one end of said cylinder, means connected to the piston and extending from said other side to give an external indication of the displacement of the piston, means mounting said piston for substantially free and unrestrained axial movement in said cylinder comprising bearing means supporting the piston in a central disposition with regard to said cylinder, said bearing means disposed on the said other side of said piston and arranged to support the movement of the piston in a substantially horizontal plane whereby the movement of the piston will be substantially unaffected by gravity forces, said mounting means further including a rolling seal positioned between said piston and said cylinder, said rolling seal having been constructed from a frusto-conical cone of uniformly thin homogeneous silicone rubber sheet stock, said seal having the interior edge surface of the smaller end hermetically joined to the piston and having the former interior edge surface of the larger end hermetically joined to the cylinder at a location closely adjacent the piston surface, said seal further defining a fold having a concavity facing the said one end of the cylinder which accommodates said differential pressure but permits substantially free axial movement of said piston in response to said differential pressure.

Claim 4

A spirometer comprising a cylinder having an internal cylindrical surface, a cylindrically shaped piston mounted in the cylinder for substantially free and unrestrained axial movement in the cylinder, means for admitting air preSsure such as would be generated by human breathing into one end of said cylinder to exert a force on one side of the substantially unrestrained piston, means venting the other side of the substantially unrestrained piston to the atmosphere whereby a differential pressure across said piston may be readily created upon the admission of air pressure created by human breathing into the said one end of said cylinder, means connected to the piston and extending from said other side to give an external indication of the displacement of the piston, means mounting said piston for substantially free and unrestrained axial movement in said cylinder comprising bearing means supporting the piston in a central disposition with regard to said cylinder, said bearing means disposed on the said other side of said piston and arranged to support the movement of the piston in a substantially horizontal plane whereby the movement of the piston will be substantially unaffected by gravity forces, said mounting means further including a rolling seal positioned between said piston and said cylinder, said rolling seal having been constructed from a frusto-conical cone of uniformly thin homogeneous silicone rubber sheet stock, said seal having the interior edge surface of the smaller end hermetically joined to the piston and having the former interior edge surface of the larger end hermetically joined to the cylinder at a location closely adjacent the piston surface, said seal further defining a fold having a concavity facing the said one end of the cylinder which accommodates said differential pressure but permits substantially free axial movement of said piston in response to said differential pressure.