Abstract An electro-acoustic transducer is coupled to liquid in a conduit which terminates in a small orifice adjacent to the transducer. Preferably, the acoustic impedance of the supply portion of the conduit is large compared with the acoustic impedance of the orifice. The liquid is under small or zero static pressure. Surface tension at the orifice prevents liquid flow when the transducer is not actuated. An electrical pulse with short rise time causes sudden volume change at the transducer, thereby creating an acoustic pressure pulse having sufficient amplitude to overcome the surface tension at the orifice and eject a small quantity of liquid therefrom. Thereafter, the pulse decays slowly, holding the rate of change of volume low enough so that the resulting pressure decrease is not sufficient to overcome the surface tension. Consequently, liquid flows from the supply portion of the orifice into the transducer to replace the liquid previously ejected, without drawing in air through the orifice.
A system adapted upon pulsing to expel a small quantity or a succession of small quantities of liquid in controlled manner, comprising: a reservoir containing said liquid; a conduit connected to said reservoir and communicating with the liquid therein and filled with said liquid under small or zero static pressure, said conduit having an exit orifice which is sufficiently small that surface tension in the absence of pulsing prevents said liquid from flowing therefrom; a tubular transducer of given diameter having an open end and a closed end connected to said conduit with its said open end in pressure transmitting communication with the interior of said conduit, and said transducer being filled with pressure transmitting material coupled through its open end to the liquid in said conduit, said transducer being adapted to contract radially to displace a small quantity of said liquid overcoming said surface tension to expel a small quantity of said liquid through said orifice and to expand to said given diameter prior to a subsequent contraction; electrical circuit means connected to said transducer for applying thereto an electrical pulse of a given polarity to cause said transducer to contract rapidly, and upon decay of said pulse to allow said transducer to expand; said conduit during operation of said system at all times being open from said reservoir to said orifice whereby the liquid within said transducer is replaced by liquid from said reservoir to make up for said expelled liquid upon said termination of said pulse.
Claim 2
Independent Claim
249 words
A system adapted upon pulsing to expel a small quantity or a succession of small quantities of liquid in controlled manner, comprising: a reservoir containing said liquid; a conduit connected to said reservoir and communicating with the liquid therein and filled with said liquid under small or zero static pressure, said conduit having an exit orifice which is sufficiently small that surface tension in the absence of pulsing prevents said liquid from flowing therefrom; a tubular transducer of given diameter having an open end and a closed end connected to said conduit with its said open end in pressure transmitting communication with the interior of said conduit, and said transducer being filled with pressure transmitting material coupled through its open end to the liquid in said conduit, said transducer being adapted to contract radially to displace a small quantity of said liquid overcoming said surface tension to expel a small quantity of said liquid through said orifice and to expand to said given diameter prior to a subsequent contraction; electrical circuit means connected to said transducer for applying thereto an electrical pulse of a given polarity to cause said transducer to contract rapidly, and upon decay of said pulse to allow said transducer to expand; said conduit during operation of said system at all times being open from said reservoir to said orifice whereby the liquid within said transducer is replaced by liquid from said reservoir to make up for said expelled liquid upon said termination of said pulse.