Butterfly valve assembly and method of manufacture

In a butterfly valve assembly having a body of plastic material, a disc for closing a passageway therethrough, a round stem affixed to the valve body for supporting the disc, a keyed stem supported in the valve body for rotating the disc throughout 360.degree., the improvement comprising:

• the cylindrical valve body having an internal shoulder at one end, and a pair of internal peripheral grooves;
• a valve seat within said valve body having core of hard plastic with a sealing surface of resilient material bonded thereto for engagement with the disc, said valve seat sealed to said valve body by o-rings in said peripheral grooves, said valve seat having radial bores surrounding the round stem and the keyed stem therein, said bores having counterbores with o-rings therein for sealing the round stem and the keyed stem to the valve seat;
• and
• a retainer ring for biasing said valve seat between the shoulder and the retainer ring.

A method of manufacturing a valve assembly comprising:

• forming a valve body of thermoplastic material having an internal shoulder at one end and two spaced apart internal circumferential grooves, and a pair of diametrically opposed apertures intermediate said internal circumferential grooves;
• forming a composite valve seat having a rigid plastic core and a resilient cover, and having a pair of diametrically opposed bores therethrough that are counterbored in the rigid plastic to accommodate o-rings therein;
• positioning o-rings in the circumferential grooves of the valve body and in the counterbores of the valve seat;
• placing said valve seat against the shoulder in said valve body;
• affixing a retainer ring of thermoplastic material within said valve body against said valve seat compressing the resilient cover of said valve seat between the shoulder and the retainer ring;
• installing a closure disc having a keyed stem hole and a round stem hole in said valve body by affixing a round stem within one aperture and bore and extending into the round stem hole of the closure disc, and supporting a keyed stem seated in the keyed stem hole through the other bore and aperture with the keyed stem extending from the valve body;
• securing a handle to said keyed stem for rotating the stem throughout 360.degree..