Bubble cap and riser construction

A synthetic plastic bubble cap and riser apparatus, comprising:

• (a) a synthetic plastic cup-shaped bubble cap having at least three equally spaced, integral, axially depending legs secured to the internal top of the cap, each leg having a radially outwardly extending projection on a lower end thereof;
• (b) a synthetic plastic tubular riser having an external flange on a first end of the riser adapted to be seated on a bore in a rectifier tray and having a second end telescoped around the legs and into the bubble cap, the riser having an internal groove extending around the internal surface of the riser for receiving and releasably seating the projections on the legs to releasably secure the bubble cap on the riser in a spaced relationship above the upper surface of the rectifier tray thereby permitting the passage of fluids through the riser and out the lower edge of the bubble cap;
• and
• (c) means including threads on the riser adjacent the flange for releasably securing the tubular riser in a bore in a rectifier tray.