1. Technical Field
The present invention relates to a technology of injecting liquid from an injection nozzle.
2. Related Art
A liquid injection device developed in recent years injects pressurized liquid such as water and physiological salt water through an injection nozzle toward living tissue to incise or excise the living tissue. When used in surgery, this type of liquid injection device can selectively incise or excise only the target tissue such as internal organs without damaging vascular structures such as blood vessels, and thus can reduce injuries of the surrounding tissue. Accordingly, this device is expected to decrease the burden imposed on a patient receiving the surgery.
According to the liquid injection device having this structure, however, the visibility of the surgery target area deteriorates due to accumulation of liquid injected from the injection nozzle or blood flowing from the living tissue as liquids remaining on the surgery target area. For overcoming this problem, such a liquid injection device which has a suction port disposed in the vicinity of the injection nozzle and connected with a suction pump has been proposed (JP-A-1-313047). According to this device, the liquid or blood remaining on the surgery target area is sucked and discharged through the suction port brought near the surgery target area, so that sufficient visibility of the surgery target area can be secured.
In addition, such a liquid injection device which injects liquid from an injection nozzle not continuously but in pulses produced by periodically varying the flow of injection has been proposed (JP-A-2008-82202). This liquid injection device has a supply pump which pressurizes and supplies liquid toward a liquid chamber connected with the injection nozzle, and an actuator which varies the volume of the liquid chamber. The liquid injection device thus constructed pressurizes liquid within the liquid chamber and injects the liquid in pulses from the injection nozzle by rapidly decreasing the volume of the liquid chamber filled with liquid. According to the device which injects liquid in pulses, injection of only a small amount of liquid is required for incising or excising living tissue. Thus, reduction of the quantity of the liquid remaining on the surgery target area can be achieved.
According to this type of liquid injection device, however, liquid continuously flows from the injection nozzle and accumulates on the surgery target area even during suspension of incision or excision of living tissue. More specifically, in the case of the liquid injection device capable of injecting liquid in pulses, the supply pump keeps operating to maintain a sufficient pressure of liquid to be supplied to the liquid chamber even while the operation of the actuator is stopping (injection of pulsed liquid is stopping). In this case, liquid pressurized and supplied from the supply pump continuously flows from the injection nozzle. Even when the operation of the supply pump is stopped, the liquid keeps flowing from the injection nozzle until the time when the pressure of the liquid pressurized and supplied toward the liquid chamber sufficiently drops, which pressure drop cannot be produced immediately after the stop of the supply pump. Thus, the liquid remaining on the surgery target area as liquid not used for incision or excision of the living tissue (that is, unnecessary liquid) is required to be sucked and removed, which increases labor for the user.