Patent Description:
High pressure liquid pumps can be used in many applications, such as machining and surgery. For example, waterjets can be used to resect tissue. Several surgical procedures have been developed in which waterjets can be used to resect tissue, such as prostate surgery to remove benign prostate hyperplasia and spinal surgery. With surgical procedures it is beneficial, and in some instances required, to maintain sterility of the fluid being used to resect tissue of the patient. Although pumps can be reused and sterilized, this can be time consuming.

One prior approach to maintaining sterility has been to provide a sterile pump cartridge that can be used for a single surgery and then replaced. For example, <CIT> describes high pressure pumping cartridges for medical and surgical pumping and infusion applications. However, the prior pump cartridges for surgical procedures can be less than ideal in at least some instances. A pump cartridge may comprise several moving components and shipping and storage of at least some prior pump cartridges can be less than ideal. For a high-pressure pump cartridge to work reliably, there are several technical challenges that should be met, and the prior pump cartridges can be more complex and have tighter tolerances than would be ideal in at least some instances.

Work in relation to the present disclosure suggests that the reuse of pump cartridges may not be appropriate in at least some instances, resulting in cartridges potentially being reused in a less than ideal manner. Also, at least some of the prior approaches can require more user skill than would be ideal. Some of the prior approaches may less than ideally utilize the forces available from a pump console that receives the cartridge.

In some instances, the fluid flow from the nozzle jet used in surgery or other applications can be less than ideal. Work in relation to the present disclosure suggests that this variability can be more pronounced with lower pump rates, which may result in increased pulse to pulse variability and the resection of material being less accurate and rougher than would be ideal.

In light of the above, it would be desirable to have improved methods and apparatus for delivering fluids such as sterile fluids for surgical procedures with waterjets that overcome at least some of the above limitations.

According to the invention, the a pump cartridge comprises a retention structure to retain a piston for shipping and storage, in which the piston can be decoupled from the retention structure to pump fluid. In the shipping and storage configuration, the piston may be positioned with the retention structure to allow sterilization gas to travel within a housing and into a cylinder distal to the piston, in accordance with some embodiments. When placed in the console for use in a pumping configuration, the piston can be decoupled from the retention structure to form a seal within the housing. In some embodiments, when the procedure has been completed, the pump cartridge can be decoupled from the console in a manner that disables the cartridge for subsequent use to prevent a non-sterile cartridge from being reused. In some embodiments, axial force from a pushrod of the console decouple the piston from the retention structure, which can allow increased amounts of force for decoupling and increased stability of the cartridge and associated components such as the pistons in the shipping and storage configuration. The cartridge may comprise a deformable valve seat to permit looser tolerances during manufacturing and can decrease valve leakage and improve performance. In some embodiments, the cartridge comprises a plurality of pistons to provide more uniform fluid flow rates through the nozzle. In some embodiments, the cartridge is configured to couple to a high-pressure line having suitable elasticity to decrease piston pulse to piston pulse variability of a fluid stream through a nozzle.

According to the invention, the a pump cartridge comprises a piston. A housing comprises a channel, an inlet, and an outlet, in which the channel comprises a cylinder shaped to receive the piston. An engagement structure is configured to couple the piston to a pushrod in response to axial movement of the pushrod or the housing.

In some embodiments, a pump console comprises a receptacle to receive a pump cartridge, and a locking structure to engage a fastener of the pump cartridge. A pushrod is configured to engage the pump cartridge, and an actuator is coupled to the pushrod. A processor is coupled to an actuator to move the pushrod, and the processor is configured to advance the pushrod into the cartridge in response to the locking structure engaging the fastener.

The claims define the scope of the invention.

A better understanding of the features, advantages and principles of the present disclosure will be obtained by reference to the following detailed description that sets forth illustrative embodiments, and the accompanying drawings of which:.

The following detailed description and provides a better understanding of the features and advantages of the inventions described in the present disclosure in accordance with the embodiments disclosed herein. Although the detailed description includes many specific embodiments, these are provided by way of example only and should not be construed as limiting the scope of the inventions disclosed herein, which is solely defined by the appended claims.

The pump consoles and cartridges as described herein can be used in many applications, such as the surgical resection of tissue, dentistry, cosmetic surgery, dermatology, ophthalmology, urology, surgical removal of tissue from organs, and industrial applications such as machining. The pump consoles and cartridges as described herein can be incorporated with many commercially available surgical systems. Although reference is made to surgical and healthcare applications, the presently disclosed pump cartridge and console will find applications in many fields, such as industrial applications including paint sprayers and the machining of parts.

The pump cartridge can be configured to generate high pressure fluid flow with relatively little leakage, allow fluid to enter the pump cylinders quickly little or no cavitation within the cylinder, high efficiency and rapid fluid expulsion from the cylinders.

With reference to <FIG>, a system that treats a patient with fluid stream energy is shown. The system <NUM> includes a treatment probe <NUM> and may optionally include an imaging probe. The treatment probe <NUM> may be coupled to an imaging console <NUM> and a base <NUM>. The patient treatment probe <NUM> and the imaging probe may be coupled to a common base <NUM>. The treatment probe <NUM> is coupled to the imaging console <NUM> with an arm <NUM>.

In some embodiments, the system <NUM> includes a display <NUM> for allowing a technician to visualize the location and orientation of the treatment probe <NUM>, such as when the treatment probe <NUM> is positioned inside a patient. The console <NUM> includes a pump <NUM> which is in fluid communication with the treatment probe <NUM> by one or more hoses <NUM>. The hose <NUM> may comprise a high-pressure line.

The pump <NUM> may be any type of suitable pump for pumping fluid, such as for example, a rotary lobe pump, a progressing cavity pump, a peristaltic pump, a rotary gear pump, a piston pump, a diaphragm pump, a screw pump, or some other type of fluid pump. In some embodiments, the pump is a piston pump and may be configured to drive one, two, or more pistons. As will be described hereinafter, a dual piston pump is shown and described, but this disclosure should not be so limited as any number of pistons can be used with the inventions described herein.

The pump includes a cartridge, that in some embodiments, is removable from the pump such as for cleaning, repair, or replacement as components wear over time through normal use. The pump cartridge, in some embodiments, includes a valve body housing one or more inlet valves, outlet valves, and fluid seals.

<FIG> and <FIG> show external views from different angles of a console <NUM> to receive a pump cartridge as described herein into system <NUM>. <FIG> shows a cross-sectional view of the console <NUM>. The console can be configured in many ways, and may comprise a stand-alone console, or can be integrated with a surgical or other system. The console comprises a cartridge receptacle <NUM> (also referred to herein as a loader, or a cartridge loader) sized and shaped to receive the cartridge <NUM>. The cartridge receptacle may comprise structures to receive structures of the cartridge as described herein, in order to fasten the cartridge to the receptacle. The receptacle can be configured for linear insertion of the cartridge <NUM> into the receptacle <NUM>, for example.

The console may comprise a pump motor <NUM> coupled to a crankshaft <NUM> with a transmission. Alternatively, or in combination, the transmission may comprise a crankshaft <NUM> and one or more connecting rods <NUM> coupled to one or more pushrods <NUM>. The crankshaft <NUM> can be coupled to the one or more pushrods <NUM>, e.g. a plurality of pushrods, with the connecting rods <NUM> positioned therebetween. The motor and transmission can be configured to drive each of the pushrods at a variable rate, for example within a range from about <NUM> to about <NUM>, and from a rate from about <NUM> to about <NUM>. The pushrods can be coupled to the pistons of cartridge <NUM> with engagement structures as described herein.

The console may comprise a movable component, such as an arm or clamp <NUM> to fasten the cartridge to the console when placed in the receptacle. The console may comprise a motor coupled to the movable component, e.g. a clamping motor <NUM>, in order to drive the movable component to a first position to fasten the cartridge in the receptacle, and a second position to allow placement of the cartridge in the receptacle and removal of the cartridge from the receptacle.

In some embodiments, the moveable component may comprise a plate, a gate, or a retainer to engage with the cartridge when the cartridge is placed in the receptacle and fully seated. For example, the cartridge may have one or more protrusions, and once the cartridge is seated within the receptacle, the moveable component can engage with the one or more protrusions to maintain the cartridge in an installed configuration. In the installed configuration, the connecting rods <NUM> of the console can engage with the pushrods of the cartridge.

The console may comprise a plurality of sensors. The console may comprise a sensor <NUM> to detect placement of the cartridge in the receptacle <NUM>. The console may comprise a sensor <NUM> to sense the movable component fastening the cartridge in the receptacle and may comprise a clamped sensor to detect the movable component clamping the cartridge in place. The plurality of sensors may comprise a home sensor <NUM> to detect the movable clamp component moving to a home or resting position. The plurality of sensors may comprise a sensor to sense an intermediate position in the cylinder, for example a mid-dead-center sensor <NUM> to indicate a mid-dead-center position of a piston in the cylinder, which is halfway between a top dead center position and a bottom dead center position. The plurality of sensors may comprise a first gate sensor <NUM> to detect an open configuration of the gate and a second gate sensor <NUM> to detect a closed configuration of the gate. The plurality of sensors may comprise a crankshaft position sensor <NUM>. The crankshaft position sensor <NUM> may comprise an optical sensor and may be used to verify that the pushrods are in the middle dead center, such as for loading the cartridge and coupling the pushrods with the pistons of the cartridge.

The console may comprise a sensor <NUM> to read a unique identifier of the cartridge. The unique identifier may comprise one or more of a QR code, a bar code, an RFID, or some other indicia, and the reader may comprise one or more of a QR code reader, bar code scanner or an RFID reader. The sensor can be coupled to a processor configured to read the unique identifier from the cartridge. The processor can be configured with instructions to determine if the cartridge is a valid cartridge. The processor may comprise a library of valid unique identifiers or be operatively coupled to a library of valid unique identifiers. The processor can be configured to allow a treatment to proceed in response to the unique identifier of the cartridge matching the unique identifier in the library. The library may comprise unique identifiers of previously used cartridges, and the processor configured with instructions not to proceed with treatment in response to the unique identifier of the cartridge comprising an identifier corresponding to a used cartridge.

Referring again to <FIG>, the console may comprise a gate <NUM> to retain cartridge <NUM> in position for pumping when the gate is closed. The gate can be moved to an open position to allow insertion and removal of the cartridge <NUM>. The gate <NUM> can be sized and shaped in many ways and may comprise a "U" or forked shape structure to engage the faster of the cartridge <NUM> as described herein. The console may comprise a guide such as a slot <NUM> along which gate <NUM> slides into a locking position to secure the cartridge <NUM>. In some embodiments, a second slot <NUM> is located on a second side of cartridge <NUM>. The gate may comprise a second extension <NUM> to slide in second slot <NUM> to engage an opposing fastener of cartridge <NUM> as described herein. The gate may be coupled to an actuator, such as a solenoid <NUM> to move the gate between open and closed positions.

The solenoid <NUM> may actuate in response to one or more parameters associated with the cartridge. For example, the solenoid <NUM> may actuate and move the gate to a closed position upon a limit switch being activate as the cartridge is fully inserted into the receptacle. The solenoid <NUM> may actuate and move the gate to a closed position upon a sensor reading a code on the cartridge. The code, which may be a QR code or some other indicia, may identify data associated with the cartridge, and may only be read once the cartridge is properly inserted into the receptacle. Similarly, the solenoid <NUM> may be actuated automatically upon completion of a treatment cycle. Alternatively, the solenoid <NUM> may be manually actuated, such as by pressing a switch or button.

The console may comprise a plurality of movable members such as pins <NUM> coupled to a plurality of springs <NUM>. Once the cartridge has been placed and the gate is in position in the closed configuration, the movable members press against a plurality of fasteners <NUM> of the cartridge <NUM>, which may comprise a fastener comprising a portion of the metallic housing as described herein. The movable members, e.g. pins <NUM>, can press the fasteners <NUM> against the gate <NUM> in order to secure the cartridge for advancement of pushrods into an engagement structure as described herein.

<FIG> shows a side view of the console as in <FIG> in an unclamped configuration. The clamp <NUM> comprises an arm and is shown in a first configuration, in which the motor, transmission, coupling rods, and pushrods are located away from the cartridge <NUM>. With advancement of the clamp <NUM> toward a second configuration in a direction indicated by arrow <NUM>, the pump motor <NUM> and transmission comprising crankshaft <NUM>, connecting rods <NUM> and pushrods <NUM> are advanced toward cartridge <NUM> in a direction indicated by arrow <NUM>. The clamp arm can be advanced with rotation of clamping motor <NUM>. The clamp <NUM> can be coupled to clamping motor <NUM> in many ways, for example with a threaded nut to move the clamp arm with rotation of clamping motor <NUM>. The pump motor <NUM> and transmission comprising the crankshaft <NUM>, connecting rods <NUM> and pushrods <NUM> can be supported on a carriage <NUM> to allow translation of these components toward cartridge <NUM> as described herein. The carriage <NUM> may comprise rails and sliders to allow the pump motor, transmission comprising the crankshaft, coupling rods and pushrods to translate between the clamped and unclamped positions. The clamp <NUM> may comprise an arm <NUM> that generally pivots about a pivot point <NUM> to advance the carriage and associated component toward cartridge <NUM>.

<FIG> shows a side view of the console as in <FIG> in a clamped configuration, in which the components supported on carriage <NUM> have been advanced in a direction indicated by arrow <NUM> so as to engage the cartridge <NUM> with the pushrods.

In some embodiments, the pushrods are positioned in an intermediate position between top dead center and bottom dead center (e.g. middle dead center) when the pushrods are advanced into the engagement structures and further advanced to break the pistons and engagement structures away from the retention structures as disclosed herein.

<FIG> shows a partial cutaway view of the console as in <FIG> and shows a pushrod <NUM> coupled to a piston of a cartridge as will be described hereinbelow. A position sensor <NUM> can be used to detect the presence and the proper position of a cartridge <NUM>. The position sensor <NUM> may be used to trigger the closing of the gate to secure the cartridge <NUM> in an installed configuration. The gate may be moved by any suitable mechanism, such as a motor, a solenoid, or manual positioning by an operator. In some embodiments, the cartridge <NUM> moves the position sensor <NUM> as it is inserted into the receptacle, which may trigger a switch that causes a gate, or some other retaining structure, to capture the cartridge in the installed configuration and hold the cartridge against the pumping force imparted by the control rods.

A processor can be coupled to one or more of each of the console sensors as disclosed herein to provide movement of the components of the console in response to readings from the sensors.

In some embodiments, the processor is configured to advance the pushrods into the cartridge a first distance to decouple one or more pistons of the cartridge from a retentions structure of the piston. The retentions structure may secure the pistons in a secure position, such as for shipping or storage. Once engaged by the pushrods, further advancement of the pushrods can liberate the pistons from the retention structures. In some cases, the pistons are liberated by breaking the retentions structures, or by forcing the pistons to disengage with an interfering portion of the retention structures or the valve case in order to move in a reciprocating motion. The pushrods are configured to advance to a top dead center and withdraw to a bottom dead center as they reciprocate by action of the motor.

In use, an operator inserts a cartridge into the receptacle. Once the cartridge is inserted fully, a sensor detects that the cartridge is inserted and a sensor can read the unique identifier indicated on the cartridge. A retaining structure, such as a plate or gate, may be actuated to slide into place and inhibit the cartridge from being removed from the receptacle. The pump motor <NUM> and transmission comprising crankshaft <NUM>, connecting rods <NUM> and pushrods <NUM> are advanced toward cartridge <NUM>. The pushrods coupled to the connecting rods of the motor engage the pistons of the cartridge. Further advancement of the pushrods liberates the pistons from their respective retention structures and the piston can then reciprocate in response to rotational operation of the motor.

Advancement of the pump motor and transmission may be performed by a lead screw in response to rotation of the clamping motor <NUM>. The clamping motor <NUM> may be operated under control of the processor and in response to the processor determining, based on signals from one or more sensors, that the cartridge is a correct cartridge and the cartridge has been fully inserted into the receptacle.

With reference to <FIG>, a process flow diagram for loading a cartridge, performing a pumping operation, and unloading a cartridge is shown.

At step <NUM>, an operator inserts a pump cartridge into the console, such as by inserting the cartridge into the receptacle of the console.

At a step <NUM>, a sensor reads an indicia on the cartridge. The sensor may comprise any suitable sensor such as a bar code scanner, an RFID scanner, or a QR code scanner, e.g. a camera.

In some embodiments, a second sensor is used to determine the position of the cartridge for capture. The second sensor is configured to generate a signal indicating that the cartridge has been placed at the location for capture, and the processor receives the second sensor signal as input to capture the cartridge with the gate when the cartridge has been placed at the capture location. The second sensor may comprise any suitable sensor such as a proximity sensor, a switch or a Hall effect sensor, for example.

At step <NUM>, a processor associated with the console identifies the cartridge and the position of the cartridge. This may be performed through any suitable sensor type, such as a limit switch, an optical sensor, a position sensor, or otherwise. The processor may utilize a sensor to determine indicia on the cartridge that may provide data associated with the cartridge such as the type of cartridge, the date of manufacture of the cartridge, material properties of the cartridge, or otherwise. In some embodiments, an optical sensor can be used to both read the indicia and determine the position of the cartridge.

At step <NUM>, the console captures the cartridge. This may be performed automatically in response to the processor determining that the cartridge is of a proper type and/or has been inserted properly into the console. The cartridge may be captured through any suitable structure as has been describe herein. In some instances, a gate moves into a position that interferes with removal of the cartridge. The gate may be actuated by a motor, a solenoid, or some other structure.

At step <NUM> the console engages the cartridge as described herein. In some embodiments, a clamping motor turns a lead screw which causes the transmission comprising the crankshaft <NUM>, connecting rods <NUM> and pushrods <NUM> to slide forward toward the cartridge. The pushrods <NUM> then couple to the pistons of the cartridge and rotation of the motor turns the crankshaft, which causes reciprocation of the connecting rods, the pushrods, and the pistons.

At step <NUM>, the console, under control of the processor, executes a pumping operation. The pumping operation comprises a speed and duration of activating the motor. A desired speed of the motor translates into a desired fluid pressure exiting the cartridge.

At step <NUM>, the console, under control of the processor, stops the pumping cycle and disengages from the cartridge. The disengagement may be performed by reversing the steps that cause the console to engage with the cartridge. For example, the console may activate the clamping motor in a reverse direction, which causes the transmission to withdraw from the cartridge and the pushrods may disconnect from the pistons.

At step <NUM>, the console releases the cartridge, such as by activating a solenoid or motor to open the gate, thereby allowing the cartridge to be removed from the console.

According to some embodiments, the cartridge may be electrically isolated from the source of power to the console. For example, the cartridge may have one or more components coupled thereto that are non-conductive. In some embodiments, one or more of the sensors are mounted to non-conductive materials, such as plastic. In embodiments in which one or more components of the cartridge are metal, the components that interact with the cartridge may each be electrically isolated. For example, protrusions on the cartridge used for capturing the cartridge within the console are metal in some embodiments. Accordingly, the gate, the pushrods, and the crankshaft may all be isolated from the source of electrical power to the console to avoid creating an electrical ground path through the cartridge.

With reference to <FIG>, the cartridge <NUM> may comprise components for pumping a fluid such as a liquid when coupled to the pushrods. The pump cartridge <NUM> may comprise a housing that comprises one or more components of a valve body <NUM>. Valve body <NUM> includes a proximal end <NUM> and a distal end <NUM>. The distal end <NUM> corresponds with a fluid outlet <NUM> and is configured for coupling with a delivery hose for delivering pressurized fluid to a nozzle, such as a nozzle of a treatment probe. The valve body may comprise a housing shaped with fluid inlets and an outlet for the delivery of pressurized fluid such as a liquid. The housing of valve body <NUM> may comprise one or more cylinders sized and shaped to receive pistons of cartridge <NUM> as described herein.

The valve body <NUM> includes fluid inlets 310a, 310b for coupling to a fluid source and providing one or more fluid inlets to the interior of the valve body <NUM>. In some instances, the fluid inlets 310a, 310b, are ports that provide fluid communication between the inside of the valve body <NUM> and ambient fluid outside the valve body <NUM>. For instance, a plenum may surround portions of the valve body <NUM> and provide a reservoir of fluid that may be drawn into the valve body <NUM> through the fluid inlets 310a, 310b. The fluid inlets 310a, 310b may alternatively be connected to fluid delivery hoses that supply working fluid to the valve body <NUM>.

The valve body <NUM> may include one or more coupling flanges 312a, 312b that facilitate the valve body <NUM> being secured within a pump cartridge. For example, the coupling flanges 312a, 312b may include through holes that accommodate a threaded faster that passes therethrough to securely affix the valve body <NUM> to a pump cartridge. Of course, other methods of securing the valve body <NUM> to a pump cartridge are contemplated herein.

The valve body <NUM> includes a plurality of valves, seals, piston sleeves, and elements for positioning, holding, and attaching the valve body to fluid paths, as will be further described hereinafter. The valve body <NUM> may be formed of any suitable material, such as any of a number of durable plastics, metals, or composite materials, or combinations of materials. In some embodiments, portions of the valve body are formed of steel, such as stainless steel, and more particularly, Stainless Steel <NUM>-<NUM>, which exhibits high corrosion resistance, good formability, strength, precision, and reliability. Of course, other suitable materials, including other metals or steels can be used to form portions of the valve body <NUM>.

As illustrated, the valve body <NUM> may define one or more cavities <NUM> for housing pistons internally thereto. The cavities <NUM> may define sleeves for pistons to ride in as will be discussed hereinafter.

<FIG> illustrates embodiments of a valve body <NUM> having a single output valve and two valve seats on the output valve. As described previously, the valve body <NUM> includes a housing <NUM> which defines a proximal end <NUM> and a distal end <NUM> and has one, two, or more fluid inlets 310a, 310b. The fluid inlet 310a is in fluid communication with a first fluid chamber <NUM>, and the fluid inlet 310b is in fluid communication with a second fluid chamber <NUM>. The fluid inlet <NUM> is separated from the first fluid chamber <NUM> by an inlet valve 430a that selectively allows fluid to enter the first fluid chamber <NUM> through the fluid inlet 310a. Similarly, an inlet valve 430b selectively allows fluid to enter the second fluid chamber <NUM> through the fluid inlet 310b. The inlet valves 430a, 430b can be any suitable unidirectional fluid valves, such as, for example, ball valves, flapper valves, diaphragm valves, check valves, gate valves, pinch valves, knife valves, disc valves, clapper valves, duckbill valves, leaf valves, umbrella valves, dome valves, cross-slit valves, or any other suitable valve configuration.

The first fluid chamber <NUM> and second fluid chamber <NUM> are selectively in fluid communication with fluid outlet <NUM> that delivers fluid to the distal end <NUM> and a fluid hose attached thereto, such as for delivering fluid to a treatment probe. The first fluid chamber <NUM> and second fluid chamber <NUM> are separated by an output valve <NUM> that selectively allows either the first fluid chamber <NUM> or the second fluid chamber <NUM> to be in fluid communication with the fluid outlet <NUM>. According to some embodiments, the output valve <NUM> is a shuttle valve in which a fluid blocking element moves freely between two valve seats. When the fluid blocking element is in a first position against a first valve seat, the first fluid chamber <NUM> is in fluid communication with the fluid outlet <NUM>. Similarly, when the fluid blocking element is in a second position against a second valve seat, the second fluid chamber <NUM> is in fluid communication with the fluid outlet <NUM>. The fluid blocking element may shuttle between the first valve seat and the second valve seat by fluid pressure, allowing fluid to flow therethrough from one of two sources, but prevent backflow from one source to the other.

Fluid pressure within the first fluid chamber <NUM> and the second fluid chamber <NUM> can be affected by reciprocating pistons slidably disposed within cylinders <NUM>, <NUM>. For example, when piston located within cylinder <NUM> moves distally from a first, retracted position, to a second, extended position, the fluid within the first fluid chamber <NUM> increases in pressure, thus causing the output valve <NUM> to allow the fluid from within the first fluid chamber <NUM> to flow therethrough and to the fluid outlet <NUM>. Concurrently, the second fluid chamber <NUM> fills with fluid as the piston within cylinder <NUM> moves proximally from an extended position to a retracted position. Thus, the fluid pressure of the opposing fluid chamber causes the output valve <NUM> to shuttle causing the filling chamber to be isolated while the pressurizing chamber delivers fluid to the fluid outlet <NUM>.

The efficiency of such a configuration is influenced by the shuttling stroke of the output valve <NUM>, with a shorter stroke providing more efficient pumping in terms of volume and pressure. In some instances, the output valve <NUM> is designed to maintain efficiency in fluid flow and inhibit pressure drops across the valve. This may be done, for example, by selecting a shuttle having a low mass and large cross section. In this way, the output valve <NUM> can be selected to minimally impact fluid volume and pressure.

The pistons are carried within a sleeve or cylinder <NUM>, <NUM> defined by the housing <NUM>. In some cases, the housing <NUM> has channels <NUM> formed therein configured to guide a piston and thus integrally form the cylinder <NUM>, <NUM>. In some embodiments, the channel <NUM> may carry a sleeve configured to guide the piston therein. While the description refers to a cylinder slidably disposed within a sleeve or cylinder <NUM>, <NUM>, the description should not be used to impute any specific cross-sectional geometry to the pistons or the cylinders <NUM>, <NUM>. For instance, while a cross section of the cylinders <NUM>, <NUM> may be circular, it could likewise alternatively be formed as hexagonal, octagonal, or some other geometric shape. Similarly, the pistons that are slidable disposed within cylinders <NUM>, <NUM> may be configured with a similar, or the same, cross sectional shape as the cylinders <NUM>, <NUM>. In some embodiments, the pistons and the cylinders <NUM>, <NUM> have the same cross-sectional shape and the pistons are sized to provide a clearance between an outer surface of the piston and an inner surface of the cylinder <NUM>, <NUM> to accommodate the piston sliding therein.

The channel <NUM> may be in fluid communication with the first fluid chamber <NUM> and has one or more seals to inhibit fluid leaking out of the housing <NUM>. There are a multitude of different configurations that provide for a fluid tight seal, some of which will be discussed hereinafter. Suffice it to say, any structure or configuration that provides a fluid tight seal of the housing can suitably be implemented within the embodiments described herein.

With reference to <FIG>, a valve body <NUM> has a housing <NUM> that defines one or more channels <NUM> within which ride a piston (not shown). The valve body <NUM> includes one or more fluid inlets 310a, 310b separated from one or more fluid chambers <NUM> by an inlet valve 430a, 430b. While two fluid inlets and two fluid chambers are illustrated, it should be appreciated that fewer or more fluid inlets and fluid chambers may be provided. In some embodiments, each fluid chamber may have more than on fluid inlet. For example, a fluid chamber <NUM> may communicate with a fluid source through two, three, or more fluid inlets 310a in order to provide sufficient fluid within the fluid chamber <NUM> for efficient pumping operation.

In some embodiments, the inlet valve <NUM> is a one-way valve that is operated by fluid pressure. In these embodiments, the hydrodynamics of the pistons moving within the cylinders causes fluid to enter the fluid chamber <NUM> via the fluid inlet 310a, and likewise causes fluid to expel through a fluid outlet <NUM>. The valve body <NUM> includes the fluid outlet <NUM> which may be selectively coupled to an output hose <NUM> for delivering pressurized fluid to a treatment site, such as through a treatment probe.

The fluid chambers <NUM>, <NUM> are each separated from the fluid outlet <NUM> by an outlet valve 510a, 510b. This is in contrast to the embodiments of <FIG> which included a single output valve <NUM>. The outlet valves 510a, 510b can be any suitable one-way valve such as, for example, ball valves, flapper valves, diaphragm valves, check valves, gate valves, pinch valves, knife valves, disc valves, clapper valves, duckbill valves, leaf valves, umbrella valves, dome valves, cross-slit valves, or any other suitable valve configuration. In some embodiments, the outlet valves 510a, 510b comprise a valve and a valve seat that allow fluid to flow therethrough in a fluid flow direction and inhibit reverse directional fluid flow therethrough. The outlet valves 510a, 510b can be positioned adjacent one another with a feature that inhibits them from contacting each other and sticking together, such as through hydrostatic force. The feature may be bumps or ridges formed on the valves themselves that inhibit the valves from making intimate surface contact with one another, or may be a stop formed in the housing <NUM> to prevent the outlet valves 510a, 510b from contacting one another. As described above, the outlet valves 510a, 510b can be any suitable valve now known or later developed that allow unidirectional fluid flow to selectively allow fluid to flow from one fluid chamber <NUM>, <NUM> to the fluid outlet <NUM> while preventing backflow of fluid to the opposing fluid chamber <NUM>, <NUM>.

In some embodiments, a spring <NUM> is disposed between the outlet valves 510a, 510b that biases the valves apart. As pressure increases against one outlet valve 510a, it compresses the spring and pushes the outlet valve 510a toward the opposing outlet valve 510b thus creating a fluid flow path from the cylinder <NUM> through the fluid outlet <NUM>. A spring located between the outlet valves 510a, 510b may urge the valves to close quicker which results in less regurgitation of fluid. In some embodiments, a spring is not provided, but rather, the outlet valves 510a, 510b are biased in one direction or another by hydrostatic forces. Similarly, a spring may be provided on the inlet valve to urge the inlet valve 430a, 430b to close quickly in the absence of positive fluid pressure.

The inclusion of multiple outlet valves 510a, 510b is believed to increase efficiency of the pumping cycle through the action of the output hose pressure influencing the open valve to close faster, and in some cases, before the opposing piston drives the opposing valve open. This may reduce premature closure of the opposing input valve and therefore improve pumping flow efficiency and provide for a smoother fluid pressure profile.

With reference to <FIG>, a valve body <NUM>, which may be substantially the same as valve body <NUM>, defines a first fluid chamber <NUM> coupled to a first fluid inlet <NUM> by an inlet valve <NUM>. As described, the inlet valve <NUM> may be any suitable one-way valve that allows fluid to enter the fluid chamber <NUM> from the fluid inlet <NUM>, but inhibits fluid flow in the other direction.

Similarly, the valve body <NUM> defines a second fluid chamber <NUM> coupled to a second fluid inlet <NUM> by a second inlet valve <NUM>. Of course, additional fluid chambers may be provided as desired to create alternative fluid pumping profiles.

The valve body <NUM> defines an outlet channel <NUM> through which fluid may leave the valve body <NUM>. The outlet channel <NUM> may be machined into the valve body <NUM>, may be a tube or hose coupled to the valve body <NUM> or may otherwise be formed or connected to the valve body <NUM>. The first fluid chamber <NUM> and the second fluid chamber <NUM> are in selective fluid communication with the outlet channel <NUM> through respective outlet valves <NUM>, <NUM>. In some embodiments, the outlet valves <NUM>, <NUM> are one-way valves that allow fluid to flow from the fluid chambers <NUM>, <NUM>, to the outlet channel <NUM>. Each outlet valve <NUM>, <NUM> comprises a valve seat that cooperates with a valve to engage with the valve seat to inhibit fluid flow therethrough. In some embodiments, the valve seat is formed of a ductile material to allow fluid pressure to cause the valve to deform the valve seat to form a more intimate surface contact between the valve and the valve seat. In some embodiments, forming the valve seat to have a surface area configured to contact the valve that is smaller than the cross-sectional area of the valve seat allows a higher contact pressure between the valve and the valve seat.

For example, if the valve seat has a generally annular cross-sectional area, forming the valve seat with a protruding conical shape, when pressurized, the water pressure pushing against the valve causes it to press on a small annular edge of the valve seat, thus causing the ductile material to plastically deform to cause an intimate surface contact with the valve. The valve seat may be formed during manufacture, such as by forming a chamfer on the inside diameter or the outside diameter of the valve seat.

The valve seat and/or the valve can optionally have a variety of configurations, such as D-shaped, star shaped, ovoid-shaped, disc shaped, triangular, four-fingered star, or some other shape. In some instances, the valve is sized and selected to reduce flow resistance and maximize flow volume. Maximizing the flow volume will reduce the likelihood of cavitation at the valves which maintains the output efficiency.

In the illustrated embodiments, a spring <NUM> biases each valve <NUM>, <NUM> in a closed configuration. The spring <NUM> may be chosen to have a relatively low spring constant such that the fluid pressure caused by the pistons extending distally into the cylinder easily overcomes the spring force and opens the respective outlet valve <NUM>, <NUM>. The spring <NUM> may be positioned between the outlet valves <NUM>, <NUM>, such that when one valve is open, the spring is compressed and exerts a restoring force on the open valve urging it closed.

As the pistons reciprocate, when a driving piston reaches its top dead center position, it no longer increases fluid pressure within the respective fluid chamber, but rather, pressure quickly equalizes before the driving piston reverses its direction of travel. At this point, the spring enhances the closing time of the open valve and prevents back flow of pressurized fluid from the fluid outlet <NUM>.

The spring <NUM> may optionally be a compression spring, a torsion spring, a leaf spring, or some other form of biasing member configured and located to urge the valves into their respective closed positions.

<FIG> and <FIG> show a valve comprising a tapered valve seat <NUM> and movable valve component <NUM>. The tapered valve seat as described herein can be used with a single cylinder pump or a pump comprising a plurality of pistons and cylinders as shown in <FIG>. The movable valve component <NUM> comprises a valve seat engaging portion <NUM>. The valve seat <NUM> can be inclined with respect to a surface of the movable component of the valve, for example at an angle of inclination <NUM>. The valve can be configured in many ways to provide increased pressure to valve seat <NUM>. For example, the valve seat may comprise a tapered end or a thin flat end, such as rim, to provide increased pressure and deformation of the valve seat from the movable valve component <NUM> engaging the valve seat.

The deformation of the valve seat can occur in relation to the geometry of the end of the valve seat and the movable valve component, which engages the end of the valve seat. The valve seat may comprise a ductile material, such as stainless steel. In some embodiments, the valve seat may comprise austenitic steel, such as <NUM> stainless steel, for example. A plurality of valve seats can be configured for deformation. For example, a first valve seat and a second valve seat may each comprises a ductile material in order to shape a surface of the first valve seat to the first movable valve component and the second valve seat to the second movable valve component. The first valve seat and the second valve seat may each comprises a material softer than the movable component. In some embodiments, the valve seat may be formed of <NUM> stainless steel, and the moveable component may be formed of a harder material, such as a martensitic steel, for example <NUM>-<NUM> stainless steel. Alternatively, the first valve seat and the second valve seat may comprise a material less ductile than the movable component. Each valve seat may comprise a generally tapered end to engage the movable component. The tapered end may comprise an angle of inclination <NUM> within a range from about <NUM> degree to about <NUM> degrees relative to plane defined by the movable component engaging portion of the valve seat. The range can be from about <NUM> degree to about <NUM> degrees, for example. In some embodiments, the angle of inclination is about <NUM> degree to about <NUM> degrees, and in some embodiments, is about <NUM> degrees.

As shown in <FIG>, repeated contact between the tapered valve seat <NUM> and the moveable component may cause a flat annular ring <NUM> to form on the valve seat. The annular ring <NUM> has a width R <NUM> that is dependent, at least in part, upon the material properties of the valve seat <NUM>, the moveable component, and the force at which the moveable component strikes the valve seat <NUM>.

In some embodiments, the valve seat <NUM> is formed of a material having a tensile yield between about <NUM> kPa (<NUM>,<NUM> psi) and about <NUM> kPa (<NUM>,<NUM> psi). In some embodiments, the moveable component is formed of a material having a tensile yield of from about <NUM> kPa (<NUM>,<NUM> psi) to about <NUM> kPa (<NUM>,<NUM> psi). In some instances, the pressure within the fluid chamber <NUM> may be about <NUM> kPa (<NUM>,<NUM> psi), which may result in a force on the valve seat of about <NUM> (<NUM> lbs). As shown by the experimental results and image of <FIG>, this may result in an annular ring <NUM> having a width R <NUM> of about. <NUM> inches). Through experimentation, this annular ring provided an acceptable seal of the moveable component against the valve seat <NUM>. The image shown in <FIG> was obtained by cutting a used valve seat to obtain the cross-sectional view shown.

In one experiment, the moveable component was formed of a hardened, polished <NUM>-<NUM> stainless steel and the valve seat <NUM> was formed of <NUM> stainless steel with a <NUM>-degree angle cone cut leaving the inner lumen edge higher than the outer edge. The <NUM>-degree angle cone interfaces with the hardened moveable component which, under the operating pressure of the system, deforms the conical valve seat <NUM> surface creating a sealing surface (e.g., the annular ring <NUM>), that matches the surface of the moveable component. The annular ring <NUM> may continue to deform until it reaches a surface area sufficient to support the moveable component without further plastic deformation of the valve seat <NUM>. In some cases, a terminal pressure of about <NUM> kPa (<NUM>,<NUM> psi) will result in an annular ring <NUM> about a. <NUM> inch) lumen having a width R <NUM> of about. <NUM> inches).

As can be seen, the deformation of the annular ring <NUM> causes a burr <NUM> to form toward the fluid inlet <NUM> inner chamber. The burr <NUM> may form as a result of cold-working, burnishing, or forging by the repeated colliding of the moveable component <NUM> and the valve seat <NUM> until the annular ring <NUM> reaches a surface area to support the moveable component without further deformation.

The moveable component <NUM> may comprise a maximum cross-sectional dimension <NUM> sized to fit in the fluid chamber <NUM> and a thickness <NUM> no more than the maximum cross-sectional dimension <NUM>.

<FIG> shows a movable valve component as in <FIG>. The moveable valve component <NUM> may comprise a profile <NUM> around a perimeter. The movable valve component and valve seat may comprise a plurality of movable valve components and a plurality of valve seats configured for each of valves <NUM>, <NUM>, <NUM> and <NUM>, for example. The movable valve component may define one or more channels <NUM> to allow fluid to pass through the channels from the cylinder to the outlet when the movable component is located away from the valve seat. For example, in embodiments where the valve comprises one or more of valves <NUM> or <NUM>, the profile of the movable valve component may define one or more channels to allow fluid to pass through the channels from the respective cylinder to the outlet <NUM> when the movable component is located away from the valve seat.

The valve seat engaging portion <NUM> can be sized and shaped to engage the valve seat. The channel portion of the movable valve component <NUM> can be sized and shaped to define the one or more channels <NUM>. The valve seat engaging portion <NUM> can be located radially inward from the channel portion. The perimeter <NUM> of the movable valve component <NUM> may corresponds to one or more of a star shape, a D shape, a polygon, a triangle, a rectangle, an ellipsoid, or a crescent, for example. In some embodiments the perimeter corresponds to an annular shape with an outer portion of the perimeter defined by an outer annular diameter and an inner portion of the perimeter defined by an inner annular diameter, with a plurality of grooves extending inwardly from the outer annular diameter to the inner annular diameter. In some embodiments, the valve seat engaging portion <NUM> comprises a diameter less than the inner annular diameter.

The hydraulic system as described herein may be characterized as an RC circuit in which the pressurized fluid has capacitance and the couplings, hoses, nozzles, and other physical components introduce resistance. Thus, the pressurized fluid stores energy as its flow is restricted. This induced hysteresis in the hydraulic system serves to provide a more consistent fluid pressure at the treatment end, which may be a treatment probe positioned within a patient. For example, the nature of two or more reciprocating pistons within a pump will provide a pulsating fluid flow having the same frequency as the reciprocating pistons, albeit with a slight lag due to fluid mass and induced resistance. The design of the outlet valves <NUM>, <NUM>, the selection of the outlet hose material, configuration, and length, in combination with all couplings will introduce resistance into the system which serves to smooth the pulsating frequency. In some embodiments, the resistance in the hydraulic system is designed to provide a smoother fluid flow profile than an unrestricted fluid flow profile. In this way, the working fluid at a tissue resection site may be delivered precisely, repeatably, and at a pressure that is relatively uniform over time.

Turning now to <FIG>, a valve body <NUM> is shown having structure to fluidically seal the channels <NUM>. The valve body <NUM> may be substantially similar to valve body <NUM> or <NUM>. Much of the fluid flow structure and apparatuses of the embodiments shown is substantially as previously described. As fluid enter the fluid chambers 704a, 704b, it is free to flow within the channels <NUM> formed in the housing. As used herein, the terms channel and cylinder are broad terms and may be used interchangeably. The terms refer to a void within the housing <NUM> configured to slidably accept a piston. In some embodiments, a channel integrally formed in the housing <NUM> provides the path for the piston. In other embodiments, a sleeve may be inserted into the channel to provide the path for the piston. In either case, the description herein is largely agnostic as to which piston supporting structure is present unless specified. Further, use of the term cylinder does not necessarily denote geometric structure, but rather, refers to a pathway that cooperates with a slidable piston to pressurize fluid.

The proximal end <NUM> of the housing <NUM> includes cooperating structure to inhibit fluid from leaking out of the proximal end <NUM> of the housing <NUM>. An O-ring <NUM> provides an annular static seal on the housing <NUM>. The O-ring <NUM> is compressed against the housing <NUM> by a sleeve <NUM>. The O-ring deforms to make surface contact with the sleeve <NUM> and the housing <NUM> to create a fluid seal. The O-ring <NUM> is formed of any suitable material, but in some instances, is formed of nitrile rubber, hydrogenated nitrile butadiene rubber, or some other suitable material exhibiting excellent strength, retention of properties after prolonged use, and wear resistance.

The sleeve <NUM> additional provides a dynamic seal against the piston (not shown). Once the piston is inserted into the channel <NUM> and beyond the sleeve <NUM>, the sleeve <NUM> is forced outwardly, thus compressing the O-ring <NUM> against the housing <NUM>. The sleeve <NUM>, by a restoring force exerted upon it from the compressed O-ring <NUM>, makes intimate surface contact with the piston to provide a fluid tight reciprocating shaft seal. The sleeve <NUM> is preferably formed of a suitable material that is lubricious to allow the piston to slide relative to the sleeve <NUM> while maintaining a fluid tight seal. In some embodiments, the O-ring <NUM> and sleeve <NUM> may be combined into a single seal structure, such as a reciprocating shaft seal having radial type inner diameter and outer diameter sealing lips.

A bushing <NUM> additionally cooperates with the O-ring <NUM> to fluidically seal the housing <NUM>. The bushing <NUM> further provides support and a pathway for the piston. A support washer <NUM> may be provided to add strength to the components and may be formed of metal or a high-strength polymer, or some other suitable material. A retainer <NUM> may be positioned within the housing <NUM> to secure the seal components in place, and may be formed as a steel snap ring.

The retainer <NUM> may also be a screw-in plug, such as a hollow set screw, or may be formed by crimping one or more components in place.

Additional seal arrangements are shown in the figures and accompanying description.

<FIG> illustrates another embodiment of a seal for a valve body <NUM>. Much of the fluid flow structure and apparatuses of the embodiments shown is substantially as previously described. The housing <NUM> defines recesses configured to support and engage one or more seal components. As illustrated, an O-ring <NUM> is provided and engages against a saddle sleeve <NUM> to provide a fluid tight seal between the channel <NUM> and the proximal end <NUM> of the housing <NUM> sleeve. The saddle sleeve <NUM> is configured to cooperate with the O-ring <NUM> to provide a compressive force to the O-ring <NUM> to cause the O-ring to form a seal against the housing <NUM>. The restoring force of the compressed O-ring <NUM> causes the saddle seal <NUM> to make surface contact with the piston and provide a fluid tight seal therewith. The saddle seal <NUM> has a parallel position relative to the piston, which allows the mating surfaces to be in intimate contact sufficient to provide the seal.

A bushing <NUM> guides the piston into the channel <NUM> and provides support to maintain coaxial orientation between the piston and the channel <NUM>. A retainer <NUM> may be provided, as has been described herein.

<FIG> illustrates another type of seal applicable to embodiments described herein. The valve body <NUM> includes a housing <NUM> as previously described, and may be substantially similar to valve body <NUM>. The housing defines a cavity for a cup seal <NUM>, a bushing <NUM>, and a retainer <NUM>. The cup seal <NUM> may be a U-cup seal which has a U-shaped profile and includes an outside static sealing lip <NUM> and an inside dynamic sealing lip <NUM>. This type of seal provides both the static and dynamic seal required by the reciprocating piston within the channel <NUM>. The cup seal may be formed of any suitable material, but in some instances, may be formed of nitrile, urethane, highly saturated nitrile, or polytetrafluoroethylene. In some instances, the cup seal <NUM> may optionally include an O-ring inside the cup to provide additional support for the seal and aid in providing a restoring force to bias the cup seal <NUM> against the piston.

<FIG> illustrates a valve body <NUM> having another arrangement of sealing structure to provide a fluid seal of the housing <NUM> at the proximal end <NUM>. Much of the fluid flow structure and apparatuses of the embodiments shown is substantially as previously described. As illustrated, an O-ring <NUM> is supported by a saddle sleeve <NUM>. A bushing <NUM> provides a guide for a piston and urges the piston to maintain a coaxial relationship with the channel <NUM>. This embodiment differs in design with previous embodiments, such as is illustrated in <FIG>, by the one-piece bushing which allows the elimination of the metallic support washer. In this instance, the housing <NUM> may define capturing structure to secure the bushing <NUM>, the saddle sleeve <NUM>, and the O-ring <NUM> in place. The capturing structure may be formed as grooves, bosses, protrusion, or some other structure integrally formed with, or attached to, the housing <NUM> to couple the sealing components within the housing <NUM>.

<FIG> illustrates a valve body <NUM> having a housing <NUM> that defines at least one channel <NUM>. Much of the fluid flow structure and apparatuses of the embodiments shown is substantially as previously described. The valve body <NUM> includes a seal at its proximal end <NUM>. The seal may comprise a cup seal <NUM>, which in some embodiments is a U-cup seal. The cup seal <NUM> may be annular and have a U-shaped cross section have two seal portions spaced to contact the housing <NUM> and a piston disposed in the channel <NUM>. The two seal portions comprise a static seal lip <NUM> and a dynamic seal lip <NUM>. The static seal lip <NUM> is biased against the housing <NUM> to inhibit fluid egress from within the channel <NUM> out the proximal end <NUM> of the valve body <NUM>. The static seal lip <NUM> does not move relative to the housing <NUM> thus providing a static seal. The dynamic seal lip <NUM> is biased against a piston extending therethrough and the piston moves axially with respect to the dynamic seal lip <NUM>, thus providing a dynamic seal against the piston. The piston is thus able to reciprocate along its axis while maintaining a fluid tight seal against the dynamic seal lip <NUM> of the cup seal <NUM>.

A bushing <NUM> provides support for the cup seal <NUM> and the piston (not shown). The bushing is held in the housing <NUM> by any suitable mechanism, but in some, embodiments is secured by fitting in grooves or capturing protrusions that cooperate with the bushing <NUM> to securely hold the bushing <NUM> in place. The bushing <NUM> provides support for the piston that extends therethrough and reciprocated within the channel <NUM>. The bushing may be formed of a lubricious material that provides for a relatively low friction sliding contact with the piston.

<FIG> illustrates a valve body <NUM> having a channel <NUM> defined by a housing <NUM>. Much of the fluid flow structure and apparatuses of the embodiments shown may be substantially as previously described. A seal <NUM> disposed at or near the proximal end <NUM> of the valve body <NUM> inhibits fluid leakage from within the housing <NUM>. As illustrated, an O-ring <NUM> is supported by a bushing <NUM>. The bushing <NUM> and O-ring <NUM>, in some instances, are annular and fit within a cylindrical cavity formed in the housing <NUM>. Once assembled, a piston extends from outside the housing <NUM> and through the bushing <NUM>. The piston and bushing <NUM> are disposed coaxially and the bushing <NUM> provides guidance and support to maintain the piston in its coaxial relationship with the bushing <NUM> and further, coaxial with the channel <NUM> formed in the housing <NUM>. The piston engages with the bushing <NUM> and biases the bushing <NUM> to expand in a radial direction. The bushing <NUM>, in turn, compresses the O-ring <NUM> against the housing <NUM>. The O-ring <NUM>, as it compresses, elastically deforms against the housing <NUM> to provide a static fluid-tight seal against the housing. The O-ring <NUM> additionally provides resistance against the bushing <NUM> by its restorative force resulting from compression, and biases the bushing <NUM> against the piston, thereby causing intimate surface contact between the inner surface of the bushing <NUM> and the outer surface of the piston, thus creating a dynamic fluid-tight seal between the piston and the bushing <NUM>, even as the piston reciprocates within the channel <NUM>.

The bushing <NUM> and O-ring <NUM> may be formed of suitable materials selected to have the advantageous characteristics described herein, such as wear resistance, seal characteristics, lubricity, ductility, spring constant, and other characteristics that make the sealing members suitable for their intended purposes. Of course, once the fluid is pressurized within the housing <NUM>, the fluid pressure will exert additional sealing force on the bushing <NUM> and the O-ring <NUM> to further improve the effectiveness of the seal members.

As illustrated in this, and other figures, the housing defines a first channel <NUM> configured to receive a piston slidably therein. A second channel <NUM> is formed in the housing, and has a diameter that is larger than the diameter of the first housing. The second channel <NUM> is configured to securely hold the sealing members, including any bushings, sleeves, retaining members, deformable seals, or other structure that effectuates a fluid tight seal and retaining the sealing members in their proper position and orientation.

<FIG> illustrates a cartridge <NUM> that incorporates a valve body <NUM> as has been substantially described herein. The cartridge <NUM> has a casing <NUM> that provides support for and covers at least a portion of the valve body <NUM>. The casing <NUM> provides a secure connection of the valve body <NUM> and may incorporate fasteners, clips, cooperating friction fit members, or other suitable structure that captures and secures the valve body <NUM> within the casing. In some embodiments, one or more of the coupling flanges <NUM> is captured by holes in the casing <NUM> to secure or aid in securing the valve body <NUM> into the casing <NUM>. One or more fluid delivery lines <NUM>, <NUM> can be coupled to the fluid inlets 1312a, 1312b to provide working fluid to the interior of the valve body <NUM>. In some embodiments, the working fluid is saline solution, deionized water, distilled water, or some other aqueous solution that may have additional therapeutic agents therein. The fluid delivery lines <NUM>, <NUM> can be coupled to any source of fluid, such as any of a number of medical fluid bags.

The cartridge <NUM> has one or more hose supports <NUM> to support the fluid delivery lines <NUM>, <NUM> to inhibit relative movement between the fluid deliver lines <NUM>, <NUM> and the cartridge <NUM>, to ensure a secure connection of the fluid delivery system to the cartridge <NUM>.

The cartridge <NUM> further has additional outlet hose supports <NUM> to support the outlet hose <NUM>. The outlet hose <NUM> may be attached to the valve body <NUM> through any suitable mechanism, but in some embodiments, is secured by a crimp j oint, a threaded coupler <NUM>, or a combination. Of course, other attachment mechanisms are contemplated herein, such as a luer lock, a clip-on fastener, or some other suitable mechanism.

As illustrated, pistons <NUM>, <NUM> are shown disposed within the casing <NUM> and only partially extending into the valve body <NUM>. As can be seen, the pistons <NUM>, <NUM> are appropriately sized to reciprocate within channels 1332a, 1332b formed in the housing of the valve body <NUM>.

The pistons <NUM>, <NUM> re shown in a transit position, or a configuration that is ready to be shipped, delivered, and installed into a pump. The pistons <NUM>, <NUM> are shown in a proximal, retracted position and engagement structure 1350a, 1350b configured to initially cooperate with a retention structure 1352a, b to secure the pistons in the illustrated transit position.

In this configuration, with the engagement structure 1350a, 1350b, coupled to the retention structure 1352a, 1352b, the piston is in a locked position and is not free to move relative to the valve body <NUM>. More specifically, the pistons <NUM>, <NUM> do not contact the seal lip or the seal structure, thus allowing communication with the interior of the valve body <NUM>, such as for allowing sterilant gas to enter the channels 1332a,b and the fluid chambers 1362a,b. Furthermore, by inhibiting contact between the pistons <NUM>, <NUM> and the seal structure <NUM> during manufacturing, shipping, and storage prior to use, the phenomenon of material weld and creep over time is eliminated or at least reduced, and the seal structure <NUM> remains intact until the cartridge <NUM> is put in use and the pistons <NUM>, <NUM> are allowed to advance into the channels 1332a, 1332b.

In some embodiments, the engagement structure 1350a is attached to the piston <NUM> through any suitable mechanism. In some cases, the engagement structure 1350a is connected to the piston <NUM> through a cooperating annular flange and groove. For instance, the piston <NUM> may have an annular groove formed therein, and the engagement structure 1350a may have an annular flange on an inner diameter that snaps into the annular groove formed in the piston <NUM>.

In the illustrated transit position, the engagement structure 1350a, 1350b is removably secured to the retention structure 1352a, 1352b. The retentions structure 1352a, 1352b may have a sloped inwardly extending protrusion that captures a surface of the engagement structure 1350a. An axial force causes the engagement structure <NUM> to be released from the retention structure 1352a as will be described hereinafter.

With reference to <FIG>, a cartridge <NUM> is illustrated that may be the same cartridge as illustrated in <FIG>, or may have slight variations, such as, for example, the sealing structure at the proximal end of the valve body may be of a different configuration than what is illustrated. As shown, the piston <NUM> is advanced into the channel and the engagement structure 1350a disengages from the retention structure 1352a. In some instances, one or both of the engagement structure 1350a and the retention structure 1352a elastically deform to allow the piston <NUM> to advance into the chamber.

As shown, the piston <NUM> is advanced to a top dead center position and is at the extent of its travel in a distal direction. The opposing piston <NUM> is at its bottom dead center position and is at the limit of its travel in a proximal direction. A motor may drive an output shaft that drives control rods or pushrods to convert the motors rotary motion into linear activation. The control rods may be out of phase with one another, such that when a first control rod pushes, the second control rod pulls in an opposite direction. The control rods can be coupled to the pistons by the engagement structure 1350a and can thereby reciprocate the pistons <NUM>, <NUM> within the channel.

With reference to <FIG> and <FIG>, a cutaway view of the cartridge <NUM> is shown and illustrates the orientation of the valve body <NUM>, the pistons <NUM>, <NUM>, the engagement structure 1350a, 1350b and the control rods <NUM>, <NUM> that are shown coupled to the engagement structure 1350a, 1350b to drive the pistons <NUM>, <NUM>. The cartridge <NUM> may be substantially the same as described above in relation to <FIG> or <FIG>. Some embodiments utilize control rods <NUM>, <NUM> that are coupled to drive the pistons <NUM> in two directions along the longitudinal axis of the piston. In other embodiments, a control rod <NUM> may be a pushrod, and only provides a power stroke to advance the piston <NUM> and the piston <NUM> retracts by another force, such as fluid pressure, a spring force, or some other force the causes the piston <NUM> to retract. However, the terms "control rod" and "pushrod" may be used interchangeably and refer to a transmission member that transfers rotation from a motor into linear reciprocal motion of the pistons.

One difference between the cartridges <NUM> shown in <FIG> and <FIG> is the structure used to couple the control rods <NUM> with the piston <NUM>. For example, in <FIG>, the engagement structure 1350a is securely connected to the piston <NUM> and is removably connected to the control rod <NUM>, while in <FIG>, the engagement structure 1650a, 1650b is securely connected to the control rod <NUM>, <NUM> and is removably coupled to the piston <NUM>, <NUM>. While either configuration of the engagement structure 1350a, 1350b or 1650a, 1650b will work, in some instances, locating the engagement structure on the piston allows the control rods to be withdrawn from the cartridge <NUM> and the cartridge <NUM> can be replace with another.

In use, a motor will drive an output shaft, which may be a crankshaft, or may be outfitted with lobes or some other type of cam structure, and cooperating couplings can connect the control rods to the lobes, cams, or crankshaft and convert the rotational output of the motor into linear reciprocating motion of the control rods. The control rods, when coupled to the pistons, cause the pistons to reciprocate within their respective channels. For example, as the motor drives the control rod <NUM>, the linear motion is transmitted to the piston <NUM> which reciprocates linearly within channel <NUM>. As the piston <NUM> moves proximally in the channel <NUM>, a vacuum is created by the withdrawal of the piston from the channel and working fluid is drawn into the fluid chamber <NUM> through the fluid inlet <NUM>. As used herein, the term "vacuum" does not refer to an absolutely vacuum, but rather, refers to a reduced pressure that causes fluid flow from an area of higher pressure into the fluid chamber <NUM> which has a lower fluid pressure caused by the withdrawing piston <NUM>. As one piston moves proximally and draws in fluid, the opposing piston <NUM> advances distally within its respective channel and increases the fluid pressure. The increased fluid pressure, as described elsewhere herein, opens the output valve <NUM> and expels the fluid through the output hose <NUM>.

The rotational nature of the motor will continue to drive the pistons in a reciprocating motion, with each piston drawing in fluid during its stroke from top dead center to bottom dead center, and expelling fluid through the fluid outlet <NUM> as the piston is driven from its bottom dead center position to its top dead center position. The pistons may be driven <NUM> degrees out of phase, such that in a system having two pistons, they are driven oppositely. Of course, other configurations may provide for more, or fewer, pistons and they can be driven by any drive mechanism and at any suitable frequency and phase shift. For example, in some embodiments, three pistons can be driven <NUM> degrees out of phase with one another and cooperate to provide a fluid flow through the output hose <NUM>. In some embodiments, four pistons can be driven <NUM> degrees out of phase with one another to provide an output fluid flow. In some embodiments, the motor is driven from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

With reference to <FIG> and <FIG>, a piston <NUM> is coupled to a control rod <NUM> by an engagement structure <NUM>. As can be seen, the engagement structure <NUM> is carried by the piston <NUM> by a groove <NUM> formed in the piston <NUM> and a cooperating annular protrusion <NUM> on the engagement structure <NUM>. The engagement structure <NUM> may be formed of any suitable material, such as any of a number of plastics, metals, composite materials, or a combination. In some embodiments, the engagement structure <NUM> is formed of a material that is able to elastically deform in order to expand to securely engage with the piston <NUM> and the control rod <NUM>. The illustrated structure of coupling a piston to a control rod may be usable in any embodiment described herein. For example, the engagement structure used with any embodiment described herein may have fingers that grasp the control rod <NUM>. As the control rod <NUM> is advanced to be coupled with the piston <NUM>, the fingers elastically deform outwardly to accept the distal end <NUM> of the control rod <NUM> and then resiliently return to their shape to capture the distal end <NUM> of the control rod <NUM>.

In the illustrated transit or shipping configuration, the engagement structure <NUM> is initially secure attached to the piston. The engagement structure <NUM> is additional held in a fixed position by interference with the retention structure <NUM>. The retention structure <NUM> has a sloped surface <NUM> that interferes with movement of the engagement structure <NUM>. In this initial transit configuration, the piston <NUM> is held in a fixed position and is inhibited from advancing into the channel and coming in contact with the seal members (not shown).

Prior to use of the cartridge, the cartridge is installed into the loader mechanism that connects the cartridge with the transmission that supplies energy from the motor to the pistons. As part of the installation of the cartridge, the control rod <NUM> is moved relative to the piston <NUM> and the distal end <NUM> of the control rod <NUM> contacts the engagement structure <NUM>. The control rod <NUM> and engagement structure <NUM> have cooperating structure that allow the control rod <NUM> to be coupled to the engagement structure, and therefore, in driving engagement with the piston <NUM>. The control rod <NUM> may have one or more grooves, slots, detents, or pockets that accept a protrusion or boss from the engagement structure <NUM> to secure the two devices together.

The engagement structure <NUM> may be coupled to the control rod <NUM> by advancing the cartridge linearly toward the control rods <NUM>. That is, the cartridge may move along the longitudinal axis of the piston to contact the control rod <NUM>. This may be done, for example, by manually pushing the cartridge toward the control rods, by a motor, a lever, a cam, or some other suitable mechanism, details of which will be discussed in further detail hereinafter. Of course, the cartridge may remain stationary and the control rods and optionally other supporting structure associated with the control rods may translate toward the cartridge to effectuate coupling of the control rods to the pistons.

A first axial force causes the engagement structure <NUM> to elastically deform and accept the distal end <NUM> of the control rod <NUM>. Protrusions <NUM> on the engagement structure <NUM> are forced outwardly as the control rod <NUM> initially contacts the engagement structure <NUM>, and then snap back into place as the protrusions <NUM> find purchase in the groove <NUM> formed in the control rod <NUM>.

Upon coupling the control rod <NUM> to the piston <NUM> via the engagement structure <NUM>, a second axial force, greater than the first axial force, causes the retention structure <NUM> to elastically deform outwardly as the sloped surface <NUM> is pushed outwardly by the engagement structure <NUM> being advanced into the cartridge.

In some embodiments, the engagement structure <NUM> is able to retract the piston with an amount of force within a range from about <NUM> pound to about <NUM> pounds without disengaging from the control rod <NUM>.

<FIG> shows the piston <NUM> after it has been coupled to the control rod <NUM> by the engagement structure <NUM>. As can be seen, the piston <NUM> has been advanced beyond the seal members <NUM> and the engagement structure <NUM> is free of the retention structure.

With reference to <FIG>, <FIG>, and <FIG>, a loader <NUM> is illustrated with a cartridge <NUM> installed therein. The loader <NUM> facilitates coupling of the cartridge <NUM> with the motor by way of a transmission. In some embodiments, the transmission comprises control rods <NUM> as has been described, which are driven by a motor.

The process of loading a cartridge begins with installing the cartridge <NUM> into the loader <NUM>, which may be done by manually inserting the cartridge into one or more recesses within the loader <NUM> that are configured to securely hold the cartridge <NUM>. Any suitable type of fastening method may optionally be used to add to the securement of the cartridge in the loader <NUM>, such as fasteners, levers, or locks, to name a few. <FIG> illustrates a cartridge <NUM> initially installed into the loader <NUM>, and as can be seen, the control rods <NUM> are not engaged with the engagement structure <NUM> or the pistons <NUM>.

<FIG> illustrates a first action of engaging the control rods <NUM> with the pistons <NUM>. The loader <NUM> facilitates relative displacement between the cartridge <NUM> and the control rods <NUM>. In some embodiments, the control rods <NUM> are advanced toward the cartridge <NUM>, such as by a lever, motor, cam, or some other actuator. In other embodiments, the cartridge <NUM> is advanced toward the control rods <NUM>, such as by manual force, a lever, motor, or cam. In any event, a linear force causes relative motion between the cartridge <NUM> and the control rods <NUM> until the control rods <NUM> contact the engagement structures <NUM>. A first force causes the control rods <NUM> to engage with the engagement structures <NUM>, and the components may be considered to "snap" together as the engagement structure <NUM> elastically deforms and quickly returns to its initial shape once the control rod <NUM> is inserted sufficiently to mate the cooperating structures.

Once the control rods <NUM> are "snapped" into the engagement structures <NUM> as illustrated in <FIG>, a second axial force causes the engagement structure <NUM> to disengage from the retention structure <NUM> as shown in <FIG>. In this configuration, the pistons <NUM> are now liberated from their fixed position and are free to slide within the channels in response to linear force from the control rods <NUM>.

In the configuration shown in <FIG>, one piston <NUM> is advanced to its top dead center position, the opposing piston is at its bottom dead center position, and the system is ready to begin pumping working fluid as has been previously described.

The loader <NUM> may comprise structure that is part of a larger console, and is especially suited to receive a cartridge <NUM> and further is configured to facilitate mating cartridge <NUM> with the transmission and the motor.

<FIG> shows a cartridge <NUM> after it has been in operation and has since been removed from the loader. The piston <NUM> is still coupled to the engagement structure <NUM>; however, the engagement structure has been uncoupled from the control rod (not shown). A cartridge will have a useful life, which may be based upon hours of operation, number of procedures, date of in-service, or some other metric. A cartridge may be removed from the loader and replaced with a new cartridge. In this way, the cartridge is a consumable item, while the remaining components of the pump, including the control rods, motor, loader, and console are durable components and are not typically replaced.

To remove the cartridge <NUM>, the control rod is withdrawn from the cartridge <NUM>. During the operation, a sloped surface <NUM> on the engagement structure contacts a mating surface <NUM> on the retention structure <NUM>. An applied force from the control rod causes the retention structure to interfere with further withdrawal of the engagement structure <NUM> and causes the engagement structure to deform outwardly, thus releasing the protrusions <NUM> from their purchase within the grooves of the control rod. The control rod is then able to be completely decoupled from the engagement structure <NUM> and removed from the cartridge.

As can be seen, the engagement structure <NUM> remains attached to the piston <NUM>, and is unable to be withdrawn from the cartridge <NUM> because the retention structure <NUM> prohibits its withdrawal. This also provides the additional feature that it becomes very difficult to re-use a cartridge <NUM> that has exceeded its useful life, and a simple visual check can verify whether the cartridge <NUM> has been previously used.

<FIG> illustrate a cartridge <NUM> having an active return on the piston. The piston <NUM> may be as substantially described elsewhere herein, and has a compression spring <NUM> that surrounds a bushing <NUM> that guides the piston <NUM> through its stroke. The bushing <NUM> may carry a forward retainer <NUM> that provides a bearing surface against which the spring <NUM> is compressible. A rear retainer <NUM> may be carried by either the piston <NUM> or the control rod <NUM> and provides a surface that engages the spring and provides a compressive force on the spring <NUM> as the control rod <NUM> is advanced into the cartridge <NUM>. Providing the rear retainer <NUM> on the piston <NUM> allows the control rod <NUM> to be completely withdrawn from the cartridge <NUM>, as desired. The spring <NUM> may be selected to have a desired spring constant, and may be selected to prevent "slapping" between the control rod <NUM> and the rear retainer <NUM>, especially at higher motor rpms.

In some embodiments, the spring <NUM> provides an amount of force to the piston within a range from about <NUM> pound to about <NUM> pounds between bottom dead center and top dead center of the piston in the cylinder. The amount of force may optionally be within the range from about <NUM> to <NUM> pounds, or from about <NUM> to <NUM> pounds.

The pushrod may carry a slider <NUM> that compresses the spring with advancement of the pushrod and piston, the slider coupled to a receiver to receive the piston and urge the piston toward the pushrod with retraction of the pushrod.

The control rod <NUM> may be configured such that it provides surface contact with the piston <NUM> and may not necessarily include structure that captures the piston and secures the two together. In other words, the control rod <NUM> may function strictly to push the piston <NUM> and not provide a force to return the piston <NUM>. The return force required to retract the piston to its bottom dead center position may be provided, in large part, by the spring <NUM>. The rear retainer <NUM> may optionally engage with, and perhaps capture, the piston <NUM>, but is not required to do so where there is an external force applied to the piston <NUM> to cause it to move from its top dead center to its bottom dead center locations.

The seals for inhibiting fluid leaks from the cartridge may be any suitable seal mechanism and arrangement, several of which have already been described.

<FIG> illustrate a cartridge <NUM> having a piston <NUM> carrying an engagement cap <NUM>. The engagement cap <NUM> may be designed to cooperate with the control rod <NUM> to provide a secure connection therebetween. In some embodiments, the engagement cap <NUM> has a radial ridge <NUM> that engages a radial groove <NUM> formed in the control rod <NUM>. The engagement cap <NUM> may be secured to the piston <NUM> by any suitable method, and may be attached to the piston <NUM> during manufacture. The engagement cap <NUM> may be connected to the control rod <NUM> by the application of a force that is transverse to the longitudinal axis of the control rod <NUM>. In other words, the cartridge can be forced downwardly onto the control rods to secure the pistons <NUM> and the control rods <NUM> together. The cartridge <NUM> may be manually inserted into the loader such as by pressing downward on the cartridge to couple the pistons <NUM> to the control rods <NUM>. The cartridge may alternatively be coupled to the loader by a motor, lever, hinge, crank, or some other manual or automated means.

<FIG> illustrate a cartridge <NUM> coupled to a loader <NUM>. The loader <NUM> may contain a yoke <NUM> that connects the control rods <NUM> to an actuator <NUM> that causes the control rods <NUM> to reciprocate at a desired stroke and frequency. The actuator <NUM> may be a rotary or linear travel actuator. As a non-limiting example, the actuator <NUM> may comprise a pinion gear having gear teeth and the control rod <NUM> (or the piston itself) may be formed with rack gear threads that engage with the pinion gear teeth to form a rack and pinion gear system. As the pinion gear is rotated clockwise and counterclockwise in rapid succession, the control rod <NUM> is caused to reciprocate linearly.

The actuator <NUM> may alternatively comprise a lead screw or a power screw that converts rotational motion of the motor into linear displacement of the control rods and pistons.

<FIG> illustrates a cartridge <NUM> having a dual piston arrangement as previously described. The pistons <NUM> may be coupled by a rocker arm <NUM> having a pivot point <NUM> disposed generally in between the pistons <NUM>. The rocker arm <NUM> may have protruding bosses <NUM>. One control rod <NUM> may push against the boss <NUM> of the rocker arm <NUM> causing the rocker arm <NUM> to pivot about the pivot point <NUM>. As one control rod <NUM> exerts a force on a boss <NUM> to drive the piston <NUM> distally within the cylinder, the opposing boss <NUM> causes the opposing piston to withdraw from the cylinder. Thus, the primary force that tends to withdraw the piston is applied by the control rod driving the opposing piston <NUM> and the withdrawing force is applied through the rocker arm <NUM>.

The cartridge <NUM> may be loaded into the console by dropping the cartridge <NUM> vertically downward into the console and engaging with suitable retaining structures of the console to secure the cartridge <NUM>.

<FIG> illustrates a cartridge <NUM> having one or more pistons <NUM> and one or more control rods <NUM>. The pistons <NUM> are coupled to the control rods <NUM> by an engagement structure <NUM>. The engagement structure <NUM> may securely be affixed to the piston <NUM> and control rod <NUM> through structure that captures an end of each respective rod. After use, the engagement structure <NUM> may be removed from the control rod <NUM> through an axial force that pulls the end of the control rod <NUM> out of the engagement structure <NUM>.

<FIG> illustrates structure configured for axial loading of the cartridge. The cartridge may have threads <NUM> formed on a shaft <NUM> thereof. The loader <NUM> may likewise have drawing threads <NUM> that engage with the cartridge threads <NUM> to draw the cartridge into the loader <NUM>. In some embodiments, the cooperating threads may be acme threads, which resist driving in a reverse direction, thereby providing positive retention of the cartridge in the loader.

<FIG> illustrates a cartridge <NUM> and an attachment mechanism to secure the cartridge <NUM> in a loader <NUM>. In the illustrated embodiments, a tapered wedge <NUM> seats within a correspondingly shaped pocket <NUM> formed in the cartridge <NUM>. The tapered wedge <NUM> may be associated with the console and may move relative to the cartridge <NUM> to insert into the pocket <NUM> and thereafter draw the cartridge <NUM> into engagement with the loader <NUM>.

<FIG> illustrates a cam <NUM> configured to draw a cartridge <NUM> into a loader. The cam <NUM> has a pivot <NUM> about which the cam <NUM> rotates. An outer surface of the cam <NUM> may have threads formed therein and a motor <NUM> may turn a gear that meshes with the threads formed on the cam. The cartridge <NUM> may have one or more protrusions <NUM> extending therefrom that can be captured by the cam. As the motor <NUM> turns the cam <NUM>, the cam <NUM> captures the protrusion <NUM> and pulls the cartridge <NUM> substantially linearly to secure the cartridge <NUM> relative to the loader.

<FIG> illustrates a mechanism for loading a cartridge <NUM>. The cartridge <NUM> may be placed within a receptacle <NUM> configured to receive and hold the cartridge <NUM>. A lever <NUM> is moveable between a first position in which the receptacle <NUM> is uncovered and open to receiving the cartridge, and a second position in which the lever <NUM> fastens and holds the cartridge <NUM> in place within the receptacle <NUM>. Once in place, the control rods <NUM> can advance and engage the pistons <NUM> associated with the cartridge <NUM>.

<FIG> illustrates a mounting path for engaging a cartridge <NUM> with a loader associated with a console. The cartridge <NUM> may have protruding bosses <NUM> that slide within a channel <NUM> formed within the loader. The channel <NUM> may define any suitable path, such as the one illustrated in which the cartridge <NUM> travels inward and then downward as it engages with the loader. Of course, other paths may be used with this concept.

<FIG> shows an equivalent circuit suitable for incorporation in accordance with some embodiments. With some applications such as surgery, the pump is connected to a nozzle with a fluid line. The pump comprises a source of fluid injection similar to the source of current I of an electrical circuit. The flow line can be configured to expand in response to pressure similar to capacitance C of a capacitor. Increasing the length of the flow line can increase the capacitance and decreasing the length of the flow line can decrease the capacitance. The nozzle may comprise a small opening providing a resistance to flow similar to a resistor R. Decreasing a diameter of the nozzle can increase the resistance and increasing the diameter of the flow line and decrease the resistance. The combination of the pump fluid injection current, fluid line capacitance and nozzle resistance can be configured to smooth out the flow from the pump so as to provide more uniform fluid flow through the nozzle. Based on the teachings disclosed herein, a person or ordinary skill in the art can determine the pump flow fluid injection, line capacitance, and nozzle resistance to provide improved stability of the flow of fluid such as a liquid from the end of the nozzle. Work in relation to embodiments disclosed herein suggests that a more uniform flow rate through the nozzle can provide improve smoothness to ablations such as tissue resection, for example.

In some embodiments, the positive displacement pump as described herein provides an amount of fluid that can vary with flow rate and pressure, and variables such as piston seal, valve seal, pressure and valve closure rate can result in a variable fluid flow characteristics that can be measured and incorporated into the fluid flow equivalent circuit. The fluid delivery line may comprise a conduit with compliance that can vary with pressure, and this can be incorporated into the fluid flow equivalent circuit. A cylindrical nozzle may comprise a resistance to flow that varies with flow rate, and this can be measured and incorporated into the fluid flow equivalent circuit. Fluid flow characteristics that can be influence the resistance include boundary flow conditions, the shape of the nozzle, and eddy current flow near the nozzle, which can increase the resistance at higher flow rates.

<FIG> shows a pump displacement suitable for smoothing in accordance with some embodiments. The sinusoidal motion of the crankshaft <NUM> can impart motion to the piston. Motion of the piston can be represented with a filling curve cosine function <NUM>. The filling curve cosine function <NUM> shows the fluid outflow from the cylinder. Portions of the filling curve cosine function <NUM> are shown above and below zero, corresponding to filling and emptying of the cylinder. The X-axis <NUM> indicates flow past the output valve, with a value of zero indicating zero flow. Near the bottom <NUM> of the filling curve indicates a point at which the piston changes direction, which results in inefficiency in the pumping cycle.

<FIG> shows flow per unit time suitable for smoothing in accordance with some embodiments. At about t=<NUM><NUM>, the piston starts moving in a direction to pump fluid out of the outlet. During initial pumping, the piston moves to express fluid from the outlet, and the pressure of the fluid increases to overcome internal resistance and fluid begins to flow through the outlet. As the piston nears the extent of its travel at about t=<NUM><NUM>, the flow rate out of the outlet slows and eventually becomes zero as the piston reverses direction and begins a filling cycle <NUM> of the cylinder. As the piston reciprocates, the fluid flow out of the nozzle approximates the curve shown in <FIG>.

<FIG> shows cumulative flow suitable for smoothing in accordance with some embodiments. At t=<NUM><NUM>, the piston begins pumping fluid through the output valve, and fluid is pumped through the output valve through the pumping cycle of the piston. At about t=<NUM><NUM>, the piston slows its travel, comes to a momentary stop, and reverses direction. This is represented in the graph by the slope of the curve gradually moving to zero <NUM>, indicating that no fluid is being pumped through the output valve. The region of zero slope corresponds to a filling cycle of the cylinder as the piston withdraws, thus filling the cylinder with fluid. The volumetric output data shown in <FIG> provides the material input to a resistance x capacitance equation resulting in pressure and jet velocity.

<FIG> shows displacement and flow from a dual cylinder pump, suitable for smoothing in accordance with some embodiments. The dual cylinder pump can provide fluid flow to the line more regularly, so as to decrease variations in fluid flow. For example, a dual cylinder pump can provide dual cylinders and pistons that operate out of phase with one another, such as by oscillating <NUM>° out of phase with one another, with one cylinder executing a pumping cycle while the other cylinder executes a filling cycle.

A first cylinder/piston can be approximated by a sine wave <NUM> and a second cylinder/piston can be approximated by a sine <NUM> wave <NUM> (e.g. a sine wave that is <NUM>° out of phase with the sine wave <NUM>). A velocity <NUM> of the first cylinder/piston is approximated by a curve that is out of phase with the sine wave <NUM>. Similarly, a velocity <NUM> of the second cylinder/piston can be represented by a curve <NUM> that is out of phase with the sine <NUM> wave <NUM>. Notably, the velocity curve <NUM> and the velocity <NUM> curve <NUM> are <NUM>° out of phase with each other, with one curve having a maximum when the second curve is at a minimum. The net result is a total flow rate <NUM> that does not drop below zero. While the total flow rate <NUM> through the output valve may be pulsatile, it is much smoother than a single piston configuration.

<FIG> shows flow from a dual cylinder pump suitable for smoothing in accordance with some embodiments. The total flow rate <NUM> of a dual cylinder pump remains positive, except for a brief time <NUM> where the flow rate from both cylinders cross at a flow rate of <NUM>. In some embodiments, fluid lines downstream of the fluid output valve may have some capacitance built into them, such that even where the pump is producing zero flow through the output valve, the compliance within the fluid lines provides continuous fluid flow, thus further smoothing the total fluid flow.

<FIG> shows cumulative flow from a dual cylinder pump suitable for smoothing in accordance with some embodiments. As illustrated, the total fluid flow through the output valve continues to rise as a dual cylinder pump operates. The dual cylinder configuration provides for a much smoother fluid flow in comparison with the single cylinder configuration as in <FIG>. The volumetric output data is the material input to a resistance x capacitance equation resulting in pressure and jet velocity.

<FIG> shows cumulative flow from a dual cylinder pump suitable for smoothing in accordance with some embodiments. A single cylinder pump total flow curve <NUM> is illustrated in comparison with a dual cylinder pump total flow curve <NUM>. As can be seen, the single cylinder pump total flow curve <NUM> exhibits periods of no flow due to the cylinder fill cycle, while the dual cylinder pump total flow curve <NUM> exhibits nearly continuous fluid flow, a much greater total flow per unit time, and a much smoother fluid delivery.

<FIG> shows a fluid pressure profile over time of a single piston pump operating at <NUM>. In a fluid circuit comprising an at least partially compliant delivery hose and a jet nozzle that provides a restriction on the outgoing fluid, the pressure accumulates and dissipates during the reciprocating piston cycles. The fluid delivery profile curve <NUM> shows that during piston retraction when the cylinder is being refilled with fluid, the output valve is closed thus isolating the cylinder from the downstream fluid circuit. The fluid pressure curve <NUM> oscillates in response to the pumping action and is smoothed by the compliant delivery hose and the restrictive nature of the jet.

<FIG> shows a fluid pressure profile over time of a dual piston pump operating at <NUM>. The fluid delivery profile curve <NUM> shows that two pistons operating <NUM> degrees out of phase results in a smoother fluid delivery pressure curve <NUM>. In other words, the amplitude (e.g., variance in output fluid pressure) is much lower for the dual piston pump as compared to the single piston pump, thus indicating a smoother fluid delivery output.

<FIG> shows a fluid pressure profile over time of a single piston pump operating at <NUM>. The fluid delivery profile curve <NUM>, having a much lower frequency as compared to the single piston pump operating at <NUM> of <FIG>, exhibits a much longer period. The fluid delivery pressure curve <NUM> illustrates that the single piston pump, when pumped at a frequency, generates an oscillating fluid delivery pressure.

In some embodiments, tissue or other material has an ablation threshold. This threshold for ablative resection can be dependent on the type of tissue. For example, collagenous tissue such as the capsule of the prostate may have a higher ablation threshold than the glandular tissue of the prostate. The threshold for ablative resection is related, at least in part, to the tensile strength and elasticity of the tissue being ablated. Tissue will typically have an ablation threshold, which defines a fluid pressure that, when exceeding the ablation threshold, will ablate the tissue, and when the fluid pressure is below the ablation threshold, will not ablate tissue. In some instances, as shown in <FIG>, the fluid delivery pressure curve <NUM> may fall below the ablation threshold.

In contrast, in <FIG> the fluid delivery pressure profile curve <NUM> illustrates a dual piston pump operating at <NUM>, and further shows that the fluid delivery pressure curve <NUM> does not drop below the ablation threshold <NUM> upon reaching steady state for a similar flow rate. The ablation threshold <NUM> may be different for various types of tissue and the pump can be configured based upon the type of tissue to be ablated. For instance, the pump can be run at a higher frequency, which results in an average fluid pressure delivery that is greater than the pump running at a lower frequency. Comparing the dual piston pump operating at <NUM> and <NUM>, it can be seen that the <NUM> fluid delivery pressure curve <NUM> is much higher on average than the <NUM> fluid delivery curve <NUM>.

As detailed above, the computing devices and systems described and/or illustrated herein broadly represent any type or form of computing device or system capable of executing computer-readable instructions, such as those contained within the modules described herein. In their most basic configuration, these computing device(s) may each comprise at least one memory device and at least one physical processor.

The term "memory" or "memory device," as used herein, generally represents any type or form of volatile or non-volatile storage device or medium capable of storing data and/or computer-readable instructions. In one example, a memory device may store, load, and/or maintain one or more of the modules described herein. Examples of memory devices comprise, without limitation, Random Access Memory (RAM), Read Only Memory (ROM), flash memory, Hard Disk Drives (HDDs), Solid-State Drives (SSDs), optical disk drives, caches, variations or combinations of one or more of the same, or any other suitable storage memory.

In addition, the term "processor" or "physical processor," as used herein, generally refers to any type or form of hardware-implemented processing unit capable of interpreting and/or executing computer-readable instructions. In one example, a physical processor may access and/or modify one or more modules stored in the above-described memory device. Examples of physical processors comprise, without limitation, microprocessors, microcontrollers, Central Processing Units (CPUs), Field-Programmable Gate Arrays (FPGAs) that implement softcore processors, Application-Specific Integrated Circuits (ASICs), portions of one or more of the same, a logic circuit, variations or combinations of one or more of the same, or any other suitable physical processor.

In addition, one or more of the devices described herein may transform data, physical devices, and/or representations of physical devices from one form to another. For example, one or more of the devices recited herein may receive image data of a sample to be transformed, transform the image data, output a result of the transformation to determine a 3D process, use the result of the transformation to perform the 3D process, and store the result of the transformation to produce an output image of the sample. Additionally or alternatively, one or more of the modules recited herein may transform a processor, volatile memory, non-volatile memory, and/or any other portion of a physical computing device from one form of computing device to another form of computing device by executing on the computing device, storing data on the computing device, and/or otherwise interacting with the computing device.

The term "computer-readable medium," as used herein, generally refers to any form of device, carrier, or medium capable of storing or carrying computer-readable instructions. Examples of computer-readable media comprise, without limitation, transmission-type media, such as carrier waves, and non-transitory-type media, such as magnetic-storage media (e.g., hard disk drives, tape drives, and floppy disks), optical-storage media (e.g., Compact Disks (CDs), Digital Video Disks (DVDs), and BLU-RAY disks), electronic-storage media (e.g., solid-state drives and flash media), and other distribution systems.

Unless otherwise noted, the terms "connected to" and "coupled to" (and their derivatives), as used in the specification and claims, are to be construed as permitting both direct and indirect (i.e., via other elements or components) connection. In addition, the terms "a" or "an," as used in the specification and claims, are to be construed as meaning "at least one of. " Finally, for ease of use, the terms "including" and "having" (and their derivatives), as used in the specification and claims, are interchangeable with and shall have the same meaning as the word "comprising.

The processor as disclosed herein can be configured with instructions to perform any one or more steps of any method as disclosed herein.

As used herein, the term "or" is used inclusively to refer items in the alternative and in combination.

Claim 1:
A pump cartridge (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) comprising:
a piston (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>);
a housing comprising a channel (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; 1331a; 1332b), an inlet (310a; 310b, <NUM>; <NUM>; 1312a; 1312b, <NUM>), and an outlet (<NUM>; <NUM>; <NUM>; <NUM>), the channel (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; 1331a; 1332b) comprising a cylinder (<NUM>; <NUM>) shaped to receive the piston (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>);
an engagement structure (1350a; 1350b, 1650a; 1650b; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) to couple the piston (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) to a pushrod (<NUM>) in response to axial movement of the pushrod (<NUM>) or the housing; and
a retention structure (1352a; 1352b; <NUM>; <NUM>; <NUM>) to retain the piston (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) for shipping and storage,
characterised in that the engagement structure (1350a; 1350b, 1650a; 1650b; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) is removably securable to the retention structure (1352a; 1352b; <NUM>; <NUM>; <NUM>).