Incentive spirometer

An incentive spirometer for measuring the volume of inspired air or the volume of exhaled air capable of relatively easy assembly comprising an upper cylindrical housing having an internal cylindrical surface, said upper cylindrical housing having an enclosing top, said top having at least one port means providing communication internally of said upper housing and externally thereof and adapted and constructed to receive a tubular means when said incentive spirometer is used for measuring the volume of inspired air, a lower cylindrical housing having an internal cylindrical surface of the same diameter as the cylindrical suface of the upper housing, said lower cylindrical housing having an enclosing bottom said upper housing being open at its bottom, said lower housing being open at its top, said upper housing at its bottom having a first outwardly radially extending annular flange, said lower housing at its top having a second outwardly radially extending annular flange, said first flange and said second flange being in confronting relating relationship mating said upper and lower housings together, means associated with said first and said second flange to secure the upper housing and the lower housing together, a cylindrical hollow free floating piston being positioned in said secured complementary mating upper and lower housings, saidn piston having outwardly radially extending means at the top portion thereof and at the bottom portion thereof, said radially extending means having a diameter slightly less than the diameters of the internal cylindrical surfaces of the upper and lower housings whereby the said extending means act as guide means against the internal cylindrical surface of the upper housing and the internal cylindrical surface of the lower housing to permit virtually frictionless vertical movement when said spirometer is utilized, said piston having an external diameter less than the diameters of the internal cylindrical surfaces of the upper and lower housings whereby an annular space is defined between said piston and said internal cylindrical surfaces of said housings, a flexible imperforate sleeve being positioned in said space, one end portion thereof being annularly secured to approximately the midportion of said piston, the other end portion being affixed between said first and said second flanges of said housings, said sleeve having a length between its attachment on said piston and its attachment between said flanges of approximately one half of the length of said free floating piston, said upper housing having at least a portion that is transparent whereby any vertical movement of the piston in the upper housing may be viewed, said lower housing having at least one port means providing communication internally of said lower housing and externally thereof.