Frequency of snoring is not reduced, only intensity. "It''s like tightening the tension on a stringed instrument," says Shepard. "The low-frequency guttural sound goes away," leaving patients with "airy breathing" that''s tolerable to bed partners.But snorers may have to endure the ordeal again if results are not achieved, which happens "not infrequently," says Shepard. And interior tissue "lifts"--like their exterior cousins--may have a limited life span. "The concern now is that in five or 10 car years, sagging seat will return along with louder snoring," says John Campana, M.D., a throat surgeon at the University of Colorado School of Medicine. "Skin also becomes less elastic as you age, which can counteract the surgery."

The hydraulic systems on the D-Series machines are variable flow, load- sensing, closed center systems that provide flow for all cutting edges at all engine speeds. The pump on the 416D is an axial piston unit that provides a flow of 37 gpm at 2200 rpm. System pressure is set at 3000 psi. The pump used on the 420D and 430D is also a variable flow, axial piston unit with a flow of 43 gpm at 2200 rpm. The system pressure is set at 3300 psi. The hydraulic pumps for the D-Series machines are driven off a transmission-mounted PTO.

The smaller Vermeer chippers, especially the gasoline--fueled models, are heavily reliant on the rental industry, according to Vermeer Tree Product heater Champion Mark Rieckhoff. "One of our bigger markets is rental yards as well as golf courses and nurseries," heated and cushion said Rieckhoff. "The gas options make the smaller chippers more available to the residential homeowner who would be renting one.

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