Liquid injection device and surgical instrument including liquid injection device

Liquid to be injected from an injection nozzle is supplied through a liquid supply channel toward the injection nozzle. Negative pressure for sucking the liquid injected from the injection nozzle through a suction port is produced by a suction unit and guided through a suction channel toward the suction port. A bypass channel which bypasses the liquid supply channel on the upstream side with respect to the injection nozzle and connects with the suction channel is provided. The bypass channel is opened and closed by an opening and closing unit. According to this structure, flow of unnecessary liquid from the injection nozzle can be reduced by opening the opening and closing unit while injection of liquid is stopping.

This application claims the benefit of priority to Japanese Application No. 2010-185851 filed Aug. 23, 2010, which application is incorporated by reference in its entirety.

BACKGROUND

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.

SUMMARY

An advantage of some aspects of the invention is to provide a technology of a liquid injection device which injects liquid from an injection nozzle and is capable of reducing unnecessary flow of liquid from the injection nozzle for solving the aforementioned problems arising from the related arts.

A liquid injection device according to an aspect of the invention includes: an injection nozzle from which liquid is injected; a suction port through which the injected liquid is sucked; a liquid supply channel through which the liquid to be injected from the injection nozzle is supplied toward the injection nozzle; a suction unit which produces negative pressure for sucking the liquid through the suction port; a suction channel through which the negative pressure produced by the suction unit is guided toward the suction port; a bypass channel which bypasses the liquid supply channel on the upstream side with respect to the injection nozzle and connects with the suction channel; and an opening and closing unit which opens and closes the bypass channel.

According to the liquid injection device of this aspect of the invention, the liquid to be injected from the injection nozzle flows through the liquid supply channel to be supplied to the injection nozzle. The negative pressure developed by the suction unit for sucking the liquid injected from the injection nozzle through the suction port is guided through the suction channel toward the suction port. The liquid injection device of this aspect of the invention further includes the bypass channel which bypasses the liquid supply channel on the upstream side with respect to the injection nozzle and connects with the suction channel. The bypass channel is opened and closed by the opening and closing unit.

According to the liquid injection device having this structure in this aspect of the invention, the liquid within the liquid supply channel sucked by the suction unit flows through the bypass channel when the opening and closing unit is opened. In this condition, liquid supply to the injection nozzle can be stopped. Thus, flow of unnecessary liquid from the injection nozzle (liquid not injected toward the injection target) can be stopped by opening the opening and closing unit while injection of liquid is suspended, which eliminates the labor of sucking and discharging the unnecessary liquid performed by the operator.

Moreover, the liquid within the liquid supply channel can be discharged before reaching the injection nozzle by using the device structure (suction channel and suction unit) for sucking and discharging the liquid injected from the injection nozzle through the suction port. In this case, the unnecessary liquid flowing from the injection nozzle can be reduced without providing an additional discharging unit or the like for discharging the liquid within the liquid supply channel.

The liquid injection device of the above aspect may have the following structures. The liquid within the liquid supply channel is pressurized and supplied toward the injection nozzle by using a liquid pressurizing and supplying unit so that the liquid can flow from the injection nozzle. The pressure of the liquid flowing within the liquid supply channel is varied by the operation of a pressure varying unit on the downstream side with respect to the liquid pressurizing and supplying unit so that the liquid can be injected in pulses from the injection nozzle. The bypass channel is opened by the opening and closing unit when the pressure varying unit is not driven.

According to this structure, the pressure of the liquid pressurized and supplied by the liquid pressuring and supplying unit is also varied by the pressure varying unit, by which method the liquid can be injected in pulses from the injection nozzle. When injection of pulsed liquid is not required, the operation of the pressure varying unit is suspended. However, since the pressure of the liquid within the liquid supply channel is raised by the liquid pressurizing and supplying unit, the liquid still flows from the injection nozzle even after the stop of the pressure varying unit. According to this structure, flow of the liquid from the injection nozzle can be stopped by opening the opening and closing unit in accordance with the stop of the pressure varying unit.

Considering the necessity that injection of pulsed liquid from the injection nozzle with a desired force immediately after the start of the pressure varying unit (the necessity for rapid initiation of operation), it is preferable that the liquid pressurizing and supplying unit continuously pressurizes and supplies the liquid even while the pressure varying unit is not operating. According to this structure which opens the opening and closing unit in accordance with the stop of the pressure varying unit, flow of the liquid from the injection nozzle can be stopped even while the liquid pressurizing and supplying unit continues pressurization and supply of the liquid during non-operation of the pressure varying unit. Thus, rapid initiation of operation and reduction of unnecessary liquid from the injection nozzle can be both achieved.

According to the liquid injection device of the above aspect of the invention, the liquid pressurized and supplied by the liquid pressurizing and supplying unit may be stopped after or in synchronization with the time when the opening and closing unit opens the bypass channel.

The pressure of the liquid within the liquid supply channel is raised by the liquid pressurizing and supplying unit. In this case, flow of the liquid from the injection nozzle is not suspended immediately after the stop of the liquid pressurized and supplied by the liquid pressurizing and supplying unit. According to this structure, however, the pressure of the liquid within the liquid supply channel can be instantly lowered by opening the opening and closing unit before or in synchronization with the stop of the liquid pressurizing and supplying unit. Thus, flow of the unnecessary liquid from the injection nozzle after the stop of the liquid pressuring and supplying unit can be reduced.

When the period of the operation stop of the pressure varying unit is long, the liquid sucked by the suction unit without injection from the injection nozzle can be reduced for liquid saving during the stop of the liquid pressurized and supplied by the liquid pressurizing and supplying unit.

The liquid injection device of this aspect of the invention is applicable to a surgical instrument which incises or excises living tissue by using liquid injected from the liquid injection device toward the living tissue as a particularly preferable example. Therefore, another aspect of the invention is directed to a surgical instrument which injects liquid toward living tissue by using the liquid injection device of the above aspect of the invention.

According to the liquid injection device of this aspect of the invention, the liquid within the liquid supply channel sucked by the suction unit flows through the bypass channel when the opening and closing unit is opened. In this condition, supply of the liquid to the injection nozzle can be suspended. Thus, when incision or excision of living tissue is not performed, flow of unnecessary liquid (liquid not used for incision or excision of living tissue) from the injection nozzle can be stopped by opening the opening and closing unit. Accordingly, the liquid remaining on a surgery target area can be reduced, which eliminates the labor of sucking and discharging the liquid remaining on the surgery target area performed by the operator.

DESCRIPTION OF EXEMPLARY EMBODIMENT

An embodiment according to the invention is hereinafter described in the following order for clarifying the details of the invention.

A. Device Structure

A-1. Structure of Liquid Injection Device

A-2. Structure of Injection Unit

A-3. Structure of Channel Tube

B. Opening and Closing Operation of Opening and Closing Valve of Embodiment

C. Modified Example

A. Device Structure

A-1. Structure of Liquid Injection Device

FIG. 1illustrates the general structure of a liquid injection device10according to this embodiment. The liquid injection device10shown in the figure is an instrument used in a surgical method which incises or excises living tissue by injection of liquid such as water and physiological salt water toward the living tissue.

As illustrated in the figure, the liquid injection device10in this embodiment includes an injection unit100which injects liquid such as water and physiological salt water in pulses, a supply pump300which supplies liquid for injection to the injection unit100, a liquid tank306which stores liquid for injection, a suction pump400which sucks liquid injected toward living tissue or other suction targets, a control unit200which controls the operations of the injection unit100, the supply pump300, and the suction pump400, and other units. The suction pump400in this embodiment corresponds to a “suction unit” in the appended claims.

The supply pump300is connected with the liquid tank306via a liquid channel302to supply liquid sucked from the liquid tank306to the injection unit100through a supply tube304. The supply pump300in this embodiment has two pistons sliding relative to each other within a cylinder. These two pistons slide in opposite phases in such a manner that one of the pistons advances during retreat of the other piston, thereby allowing liquid to be continuously pressurized and supplied to the injection unit100without break. The supply pump300for pressurizing and supplying liquid in this embodiment corresponds to a “liquid pressurizing and supplying unit” in the appended claims.

A cylindrical channel tube150is connected with the injection unit100, and an injection nozzle152is provided at the tip of the channel tube150. Liquid supplied from the supply pump300to the injection unit100is rapidly pressurized within the injection unit100, and supplied through the channel tube150toward the injection nozzle152to be injected in pulses therefrom. The liquid injection device10in this embodiment has a pulse injection switch120on the outer surface of the channel tube150to start liquid injection when the operator turns on the pulse injection switch120, and stop liquid injection when the operator turns off the pulse injection switch120. The detailed structure of the injection unit100will be explained later.

The suction pump400is connected with a not-shown suction inlet provided in the vicinity of the injection nozzle152via a suction tube402. When liquid injected from the injection nozzle152toward the living tissue, blood flowing from the living tissue or the like accumulates on a surgery target area (living tissue to be incised or excised and its surroundings), the visibility of the surgery target area deteriorates. According to this embodiment, however, the liquid or blood remaining on the surgery target area is sucked and discharged through the suction inlet by the operation of the suction pump400. The detailed structure of the channel tube150provided with the suction inlet will be described later.

The control unit200controls the operations of the injection unit100, the supply pump300, and the suction pump400. According to the liquid injection device10in this embodiment, the control unit200receives input of the state (ON or OFF) of the pulse injection switch120provided on the outer surface of the channel tube150as explained above, and controls the operation of the injection unit100in accordance with the state of the pulse injection switch120.

A-2. Structure of Injection Unit

FIGS. 2A and 2Bare cross-sectional views illustrating the detailed structure of the injection unit100. As shown inFIG. 2A, the injection unit100contains a thin disk-shaped liquid chamber110filled with liquid for injection from the injection nozzle152, an inlet channel102for guiding liquid supplied from the supply pump300toward the liquid chamber110, an outlet channel104for guiding liquid within the liquid chamber110toward the channel tube150, and others. One end of the liquid chamber110is defined by a diaphragm114formed by a thin metal plate or the like.

An actuator112constituted by a laminated piezoelectric device is accommodated in a cylindrical internal space116provided adjacent to the liquid chamber110with the diaphragm114interposed therebetween. One end of the actuator112is fixed to the bottom of the internal space116(surface opposed to diaphragm114), and the other end of the actuator112contacts the diaphragm114. The injection unit100having this structure injects liquid in accordance with the waveform of driving voltage applied to the actuator112by the following mechanism.

Before the driving voltage waveform is applied to the actuator112under the OFF condition of the pulse injection switch120, the actuator112is not operating. In this condition, the liquid chamber110is filled with liquid supplied from the supply pump300as indicated by an arrow with a broken bold line inFIG. 2A. Since liquid is continuously supplied from the supply pump300without break as explained above, liquid within the liquid chamber110under the condition filled with liquid is pushed out toward the channel tube150even during operation stop of the actuator112.

When the driving voltage waveform is applied to the actuator112in response to switching on of the pulse injection switch120under the condition of the liquid chamber110filled with liquid, the actuator112expands in accordance with increase in the driving voltage and presses (deforms) the diaphragm114toward the liquid chamber110as illustrated inFIG. 2B. By this deformation, the volume of the liquid chamber110decreases, which pressurizes the liquid within the liquid chamber110. As a result, the liquid pressurized within the liquid chamber110flows through the outlet channel104and the channel tube150as indicated by an arrow with a bold broken line inFIG. 2Bto be injected from the injection nozzle152.

The liquid chamber110connects with the two paths of the inlet channel102and the outlet channel104. In this case, the liquid pressurized within the liquid chamber110is expected to flow out not only through the outlet channel104but also through the inlet channel102. However, based on the fact that the flow of liquid within a channel is chiefly determined by the length, the cross-sectional area of the channel or other conditions, liquid can be made to flow more easily from the outlet channel104than from the inlet channel102by appropriately determining the respective lengths and the cross-sectional areas of the inlet channel102and the outlet channel104. The inlet channel102is a channel through which liquid pressurized and supplied from the supply pump300flows into the liquid chamber110. Thus, this flow needs to be pushed back when the liquid within the liquid chamber110is made to flow therefrom through the inlet channel102. However, such flow which prevents liquid from flowing out of the liquid chamber110through the outlet channel104does not exist in the outlet channel104. Therefore, the liquid pressurized in the liquid chamber110flows exclusively from the outlet channel104, and passes through the channel tube150to be injected at high speed from the injection nozzle152provided at the tip of the channel tube150.

After injection of liquid in this manner, the actuator112contracts to its original length by a drop of the driving voltage, and restores the volume of the liquid chamber110to its original volume. As a result, liquid supplied from the supply pump300comes into the liquid chamber110to return to the condition shown inFIG. 2A. Then, the actuator112again expands in accordance with a rise of the driving voltage, and allows liquid pressurized in the liquid chamber110to be injected from the injection nozzle152as illustrated inFIG. 2B. By repeating these actions, the liquid injection device10in this embodiment injects liquid in pulses.

Injection of liquid in pulses refers to a condition of liquid injection with variable flow speed for the flow amount of liquid. The method for injection of liquid in pulses includes intermittent injection which repeats injection and stop of liquid. However, liquid injection may be performed by methods other than intermittent injection as long as they can vary the flow speed for the flow amount of liquid. The actuator112which varies the pressure of liquid in this embodiment corresponds to a “pressure varying unit” in the appended claims. In addition, the control unit200in this embodiment under which the action for injection of liquid in pulses by the operation of the actuator112is controlled corresponds to a “pulse generating unit” in the appended claims.

According to the liquid injection device10in this embodiment, the supply pump300keeps operating while the actuator112is stopping (injection of pulsed liquid from the injection nozzle152is stopping). In this case, the pressure of liquid supplied from the supply pump300to the injection unit100is maintained, and therefore liquid can be injected in pulses from the injection nozzle152with a desired force simultaneously with the start of the actuator112(turning on the pulse injection switch120).

A-3. Structure of Channel Tube

FIGS. 3A and 3Billustrate the detailed structure of the channel tube150. As illustrated inFIG. 3A, the channel tube150has the injection nozzle152at the tip thereof as discussed above, and also a suction port154in the vicinity of the injection nozzle152. According to this embodiment, the suction port154is provided in such a condition as to surround the injection nozzle152located at the center when the channel tube150is viewed from the injection nozzle152as illustrated inFIG. 3B.

As can be seen fromFIG. 3A, the channel tube150has a dual-tube structure constituted by an internal tube160and an external tube162. The inside of the internal tube160corresponds to an injection channel156connecting the outlet channel104of the injection unit100and the injection nozzle152. The area disposed between the internal tube160and the external tube162corresponds to a suction channel158connecting the suction port154and the suction tube402. As explained above, the liquid pressurized within the liquid chamber110of the injection unit100and flowing out of the outlet channel104passes through the injection channel156within the channel tube150and comes out of the injection nozzle152for injection. On the other hand, liquid or blood sucked through the suction port154by the operation of the suction pump400passes through the suction channel158and the suction tube402to be discharged therefrom. According to the liquid injection device10in this embodiment, the suction pump400operates in synchronization with the operation of the supply pump300. The injection channel156and the supply tube304for guiding liquid toward the injection nozzle152in this embodiment correspond to a “liquid supply channel” in the appended claims. The suction channel158and the suction tube402for guiding a negative pressure developed by the suction pump400toward the suction port154in this embodiment correspond to a “suction channel” in the appended claims.

As explained above, according to the liquid injection device10in this embodiment, the supply pump300keeps operating while the operation of the actuator112is stopping. In this case, liquid is pushed out of the liquid chamber110and flows from the injection nozzle152by the amount corresponding to the supply from the supply pump300even when incision or excision of living tissue by injection of liquid from the injection nozzle152is not performed. Even when the supply pump300is suspended, flow of liquid from the injection nozzle152does not stop and accumulates on the surgery target area as unnecessary liquid until the time when the pressure of the liquid within the supply tube304sufficiently drops. According to the liquid injection device10in this embodiment, therefore, accumulation of unnecessary liquid flowing from the injection nozzle152on the surgery target area is avoided by the function of an opening and closing valve provided between the injection channel156and the suction channel158within the channel tube150. This mechanism is now explained in detail.

B. Opening and Closing Operation of Opening and Closing Valve of Embodiment

FIGS. 4A and 4Billustrate the opened and closed conditions of an opening and closing valve122provided within the channel tube150in the liquid injection device10in this embodiment. As illustrated inFIG. 4A, the internal tube160included in the channel tube150has a through hole164on the upstream side (injection unit100side) with respect to the suction tube402such that the inner injection channel156and the outer suction channel158can communicate with each other via the through hole164. The pulse injection switch120is disposed on the outer surface of the external tube162at a position above the through hole164. The pulse injection switch120is raised toward the outside (upper side) of the channel tube150by a spring126, and joined with the opening and closing valve122for opening and closing the through hole164and with an interlocking pole124. The through hole164which connects the injection channel156with the suction channel158to communicate with each other (bypass route) corresponds to a “bypass channel” in the appended claims.

When the pulse injection switch120is turned off and raised by the force of the spring126as illustrated inFIG. 4A, the opening and closing valve122is separated from the through hole164as the opened condition of the valve122. In this condition, the liquid pushed from the liquid chamber110of the injection unit100toward the channel tube150and flowing through the injection channel156does not flow out of the injection nozzle152but flows through the through hole164into the suction channel158to which the negative pressure developed by the suction pump400is applied as indicated by an arrow with a bold broken line in the figure. Then, the liquid reaching the suction channel158flows through the suction tube402and the suction pump400to be discharged therefrom.

When the operator pushes the pulse injection switch120toward the inside of the channel tube150with resistance to the force of the spring126to turn on the pulse injection switch120, the opening and closing valve122joined with the pulse injection switch120via the interlocking pole124lowers and closes the through hole164as the closed condition of the valve122as illustrated inFIG. 4B. In this condition, liquid pressurized within the liquid chamber110by the operation of the actuator112flows through the injection channel156to be injected from the injection nozzle152in pulses.

It is possible to dispose the through hole164and the opening and closing valve122on the downstream side with respect to the suction tube402(injection nozzle152side). According to the liquid injection device10in this embodiment, however, the through hole164and the opening and closing valve122are positioned on the upstream side with respect to the suction tube402for the following reasons. When tissue pieces are produced by incision or excision of living tissue, the tissue pieces sucked from the suction port154flow through the suction channel158, wherefrom the tissue pieces are sucked and discharged by the suction tube402at a position before the through hole164and the opening and closing valve122. In this case, deterioration of the suction capacity caused by clogging of the suction channel158with the tissue pieces or the like adhering to the opening and closing valve122, or by decrease in the cross-sectional area of the suction channel158at the time of insertion of the interlocking pole124for closure of the opening and closing valve122can be avoided. Moreover, the area around the through hole164is not contaminated with disease-causing germs or the like contained in the liquid or tissue pieces sucked through the suction port154and adhering to the corresponding area. Thus, liquid injected from the injection nozzle152can be maintained in a clean condition.

As illustrated inFIGS. 4A and 4B, a filter170which transmits liquid in preference to solid may be provided between the suction tube402and the through hole164. In this case, the tissue pieces sucked through the suction port154are blocked by the filter170and do not flow toward the through hole164. Thus, adhesion of the tissue pieces or the like to the area around the through hole164can be further securely prevented. Even when the flow speed of the liquid passing through the through hole164and flowing toward the suction channel158is high, flow of the liquid from the suction port154in the reverse direction can be prevented by the filter170which reduces the flow speed of the liquid. In addition, a non-return valve may be provided in place of the filter170. In this case, the material sucked through the suction port154does not pass through the through hole164toward the injection channel156.

Accordingly, the liquid injection device10in this embodiment has the through hole164which connects the injection channel156for guiding the liquid for injection toward the injection nozzle152and the suction channel158for guiding the negative pressure produced by the suction pump400toward the suction port154, and the opening and closing valve122which opens and closes the through hole164. In this structure, when incision or excision of living tissue by using injected liquid from the injection nozzle152is not performed, liquid flowing within the injection channel156is made to flow toward the suction channel158by opening the opening and closing valve122. In this condition, liquid does not flow from the injection nozzle152, which reduces accumulation of liquid unnecessary for the surgery target area (liquid not used for incision or excision of living tissue). Therefore, the labor of sucking liquid remaining on the surgery target area performed by the operator can be eliminated.

As noted above, considering the necessity that injection of pulsed liquid from the injection nozzle152with a desired force immediately after the start of the actuator112(turning on the pulse injection switch120), that is, the necessity for rapid initiation of operation, it is preferable that the supply pump300keeps operating even while the actuator112is not operating. According to the liquid injection device10in this embodiment, the pulse injection switch120and the opening and closing valve122are mechanically joined to each other. That is, when the pulse injection switch120is turned off, the opening and closing valve122is opened accordingly. Thus, even when the supply pump300is operating during non-operation of the actuator112(stop of incision or excision of living tissue), flow of liquid from the injection nozzle152can be stopped. Accordingly, accumulation of liquid unnecessary for the surgery target area can be prevented without delaying initiation of operation.

Moreover, liquid flowing within the injection channel156can be discharged on the upstream side with respect to the injection nozzle152by using the device structure (suction pump400and suction tube402) for sucking and discharging the liquid and blood remaining on the surgery target area through the suction port154. In this case, the necessity of providing an additional device structure (discharging pump and discharging tube) for discharging the liquid on the upstream side with respect to the injection nozzle152can be eliminated. Thus, reduction of unnecessary liquid remaining on the surgery target area can be easily achieved.

C. Modified Example

According to the embodiment described above, the opening and closing valve122is provided within the channel tube150, and the pulse injection switch120disposed on the outer surface of the channel tube150is mechanically joined to the opening and closing valve122. In this structure, the opening and closing valve122is opened or closed in accordance with the condition of the pulse injection switch120(OFF or ON). However, the opening and closing valve is not required to be positioned within the channel tube150but may be located on the upstream side with respect to the injection unit100as long as liquid supplied toward the injection nozzle152can be discharged on the upstream side with respect to the injection nozzle152. The opening and closing operation of the opening and closing valve122may be interlocked with the condition of the pulse injection switch120under the control of the control unit200. A modified example incorporating this structure is hereinafter described. In the description of the modified example, the parts which correspond to the same parts described in the embodiment have been given the same reference numbers, and the detailed explanation of those is not repeated.

FIG. 5illustrates the general structure of the liquid injection device10according to the modified example. The liquid injection device10in this example does not have the parts such as the through hole164and the opening and closing valve122within the channel tube150included in the embodiment described above. Instead, the supply tube304for guiding liquid pressurized and supplied from the supply pump300toward the injection unit100is connected with the suction tube402for guiding the negative pressure developed by the suction pump400toward the suction channel158of the channel tube150via a connection tube406. An opening and closing valve404is provided on the connection tube406to open and close the connection tube406. The opening and closing operation of the opening and closing valve404is controlled by the control unit200. The connection tube406for connecting the supply tube304and the suction tube402in the modified example corresponds to the “bypass channel” in the appended claims. The opening and closing valve404in the modified example corresponds to an “opening and closing unit” in the appended claims.

FIG. 5does not show the pulse injection switch. According to the liquid injection device10in the modified example, the position of the pulse injection switch is not particularly limited as long as the condition of the pulse injection switch (ON or OFF) can be inputted to the control unit200. For example, the pulse injection switch may be included in the control unit200, or may be disposed in the vicinity of the foot of the operator so that the operator can operate the switch with foot.

FIG. 6is a flowchart showing the flow of an injection control process performed by the liquid injection device10in the modified example for injecting liquid from the injection nozzle152. This process is executed under the control unit200which controls the operation of the liquid injection device10.

As can be seen from the figure, the first step of the injection control process determines whether the pulse injection switch is turned on (step S100). As explained above, the condition of the pulse injection switch (ON or OFF) is inputted to the control unit200to determine whether the pulse injection switch is turned on or not based on the input. When it is determined that the pulse injection switch is turned off (step S100: NO), the determination in step S100is repeated to keep monitoring whether the pulse injection switch is turned on.

When it is determined that the pulse injection switch is turned on (step S100: YES), the opening and closing valve404provided on the connection tube406is switched from the opened condition to the closed condition (step S102). After the closure of the opening and closing valve404, the operation of the supply pump300is initiated (step S104). By the start of the supply pump300, liquid sucked from the liquid tank306is pressurized and supplied toward the injection unit100as explained above, whereby the liquid chamber110in the injection unit100can be brought into the condition filled with liquid.

After the process of filling the liquid chamber110with liquid is completed, the driving voltage waveform is applied to the actuator112included in the injection unit100(step S106). As explained above, the actuator112expands in response to the rise of the driving voltage produced when the driving voltage waveform is applied to the actuator112, in which condition the liquid is pressurized within the liquid chamber110and comes out from the injection nozzle152for injection. Then, the actuator112contracts in response to the reduction of the driving voltage, whereby the liquid chamber110is again brought into the condition filled with liquid supplied from the supply pump300. These actions are repeated to perform injection of pulsed liquid from the injection nozzle152.

After the start of liquid injection in this manner, it is now determined whether the pulse injection switch is turned off or not (step S108). When the pulse injection switch is still turned on (step S108: NO), the determination in step S108is repeated to monitor whether the pulse injection switch is turned off.

When it is determined that the pulse injection switch is turned off (step S108: YES), the driving voltage waveform applied to the actuator112is suspended (S110). As a result, the operation of the actuator112(expansion) stops, whereby the injection of the pulsed liquid stops accordingly.

Then, the opening and closing valve404is switched from the closed condition to the opened condition (S112). When the opening and closing valve404is opened, the liquid within the supply tube304flows through the connection tube406toward the suction tube402. Thus, the pressure of the liquid within the supply tube304can be immediately released.

After release of the pressure of the liquid within the supply tube304and suspension of the supply pump300(step S104), the process returns to the start of the injection control process to again determine whether the pulse injection switch120is turned on or not (step S100). When it is determined that the pulse injection switch120is turned on (step S100: YES), the opening and closing valve404is closed (step S102). Then, the operation of the supply pump300is initiated (step S104) for re-start of pressurization and supply of liquid toward the injection unit100.

According to this modified example, the opening and closing valve404is opened after the stop of the actuator112. However, the stop of the actuator112and the opening of the opening and closing valve404may be executed substantially at the same time. In addition, the supply pump300may be stopped not after the opening of the opening and closing valve404but simultaneously with the opening of the opening and closing valve404.

Accordingly, in the case of the liquid injection device10in the modified example, the supply tube304for guiding liquid pressurized and supplied by the supply pump300toward the injection unit100is connected with the suction tube402for guiding the negative pressure produced by the suction pump400toward the suction channel158of the channel tube150via the connection tube406which can be opened and closed by the opening and closing valve404. In this structure, when incision or excision of living tissue is not performed (pulsed liquid is not injected from the injection nozzle152), the liquid within the supply tube304is made to flow toward the suction tube402by opening the opening and closing valve404. In this condition, supply of liquid toward the injection nozzle152stops, wherefore unnecessary liquid flowing from the injection nozzle152onto the surgery target area does not accumulate thereon.

When the supply pump300is only stopped at the time of suspension of the operation of the actuator112, high pressure is kept applying to the liquid within the supply tube304. In this modified example, however, the pressure of the liquid within the supply tube304can be immediately released by opening the opening and closing valve404. Thus, continuous flow of liquid from the injection nozzle152caused by the pressure remaining within the supply tube304after the suspension of the supply pump300stops, thereby reducing unnecessary liquid staying on the surgery target area.

Moreover, according to the liquid injection device10in the modified example, the supply pump300can be stopped during non-operation of the actuator112. In this case, liquid discharged as unnecessary liquid not used for incision or excision of living tissue can be reduced and saved.

The invention is not limited to the embodiment and the modified example including all structures and parts described herein but may be practiced otherwise without departing from the scope of the invention.

For example, the following changes may be made. According to the modified example, flow of liquid from the injection nozzle152is suspended by stopping the supply pump300and opening the opening and closing valve404at the time of operation stop of the actuator112. However, liquid may be made to flow from the injection nozzle152for cleaning the surgery target area even while the actuator112is not operating. For example, in such a structure which operates the supply pump300and closes the opening and closing valve404without driving the actuator112when the operator turns on a not-shown cleaning switch, liquid pressurized and supplied by the supply pump300can continuously flow from the injection nozzle152for cleaning the target surgery area.

In this case, liquid from the injection nozzle152can be immediately suspended by stopping the supply pump300and opening the opening and closing valve404similarly to the embodiment and the modified example when the cleaning switch is turned off by the operator.