Abstract:
A hydraulic pressure intensifier system ( 10 ) for developing a high pressure fluid jet that utilizes an electric motor ( 84 ) for both pressurizing a hydraulic fluid and for controlling the pressure and/or flow of the high pressure fluid jet developed by the system. The intensifier system also utilizes a return spring for retraction of the piston which allows the hydraulic fluid and the high pressure fluid to be separated by an air gap to minimize the potential for cross-fluid contamination. A high pressure hose ( 66 ) connected to the output of the intensifier includes a check valve ( 70 ) at its distal end rather than at the outlet of the intensifier to allow fluid to be drained out of the hose and into the intensifier upon system shut down for instantaneous stoppage of the jet.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/078,957 filed Jul. 8, 2008, which is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]    The present invention relates generally to pressure intensifiers and, more particularly, to pressure intensifiers for surgical and/or dental applications. 
       BACKGROUND  
       [0003]    New technologies to replace traditional surgical cutting tools such as scalpels and drills are in high demand. Laser-based tools, electrosurgical cutters, plasma jets, and fluid jets have all been introduced to improve various surgical and medical procedures. Fluid jet cutters have several characteristics that make it a popular technology. For example, there is little heat generated by fluid jets (as compared to a drill or laser, for example) and the effects of fluid jets can be extremely localized. 
         [0004]    Fluid jet cutters also excel at removing soft tissue due to the fact that high pressure jets tend to emulsify soft tissue and the emulsified tissue is easily transported by aspiration away from the surgical site. In contrast, competing technologies such as laser cutters and electrosurgical cutters remove tissue by ablation or electrothermal dissolution. Both of these effects tend to create collateral thermal damage and necrosis, which is generally unwanted and often intolerable for medical purposes. Accordingly, fluid jets have been employed for performing a variety of medical and/or dental procedures. 
         [0005]    For example, using a fluid jet to excise, emulsify, and aspirate soft tissue can be useful for some dental procedures. One feature of a fluid jet that makes it well suited to such dental procedures is that the high velocity liquid jet can be used to easily remove soft tissue, but is limited in its ability to cut or erode hard calcified tooth tissue. 
         [0006]    Existing fluid jet cutters generally include a high pressure intensifier for developing the high pressure fluid stream. Such intensifiers are typically pneumatically operated devices that include a T-shaped intensifier piston having a broad end which divides a drive bore into an actuating chamber and a retracting chamber. A bistable valve is connected to admit compressed air from an external source into the actuating chamber for driving the piston to translate. The narrow end of the piston is disposed in a fluid pumping chamber that is connected to a supply of fluid. The translating piston drives the fluid from the pumping chamber through a first check valve into a fluid jet nozzle which directs the high pressure fluid pulse to a tissue target. The bistable valve then switches to admit compressed air to the retracting chamber for driving the piston in reverse and allowing the pumping chamber to refill with fluid through a second check valve. 
       SUMMARY 
       [0007]    The present invention provides intensifier systems for developing a high pressure fluid jet that utilize an electric motor. According to one aspect, a hydraulic pressure intensifier system for developing a high pressure fluid jet utilizes an electric motor for both pressurizing a hydraulic fluid and for controlling the pressure and/or flow of the high pressure fluid jet developed by the system. The intensifier system can also utilize a return spring for retraction of the piston which allows the hydraulic fluid and the high pressure fluid to be separated by an air gap to minimize the potential for cross-fluid contamination. A high pressure hose connected to the output of the intensifier includes a check valve at its distal end rather than at the outlet of the intensifier to allow fluid to be drained out of the hose and into the intensifier upon system shut down for instantaneous stoppage of the jet and/or to prevent contaminated fluid from being sucked into the hose. 
         [0008]    A high pressure intensifier system in accordance with the invention can be designed to create high pressure water but could also be used to create high pressure fluids besides just water. The system can employ an oil over water intensifier, using 1000 psi oil pressure to generate 10,000 psi water pressure, for example. A stepper motor, or other suitable motor which may be AC, DC, brushless, servo, etc., drives a hydraulic pump for creating hydraulic pressure to act on a hydraulic drive piston during pressurization. Operatively coupled to the hydraulic piston is the intensifier piston, such that when they are pushed forward during a delivery stroke (also referred to herein as an intensification or discharge stroke), high pressure water is created in a cavity of the intensifier. Oil pressure in the hydraulic cavity is controlled using a low pressure transducer installed either in the hydraulic circuit, or a high pressure transducer installed in the fluid circuit, which gives feedback information to a PID (proportional integral derivative) loop or the like. The system can include a hydraulic solenoid valve for opening and closing the oil pressure path from the pump outlet to the hydraulic piston to thereby control pressure cycles. A pressure relief valve can be provided in the hydraulic circuit for prevention of system over-pressurization. The intensifier system can employ a spring to return the pistons back after reaching the end of the delivery stroke thereby allowing the intensifier cavity to refill with water (or other fluid to be intensified such as oil, saline solution, etc.) and be ready for another pressure intensification stroke. As will be appreciated, a two piston design can be provided in order to achieve continuous flow of high pressure water. 
         [0009]    A high pressure hose or the like can be attached to the end of the intensifier via suitable fittings for receiving and transferring the high pressure fluid to a point of use. At a distal end of the hose a check valve can be provided for preventing fluid from reversing direction and returning to the intensifier cavity. Such check valve can be especially useful during the recharge stroke (also referred to herein as a retraction stroke) when the intensifier piston is retracting and fluid is refilling the intensifier cavity as it will prevent backflow of fluid. In addition, after a delivery stroke any accumulated pressure in the hose can be dissipated back into the intensifier chamber upon release of hydraulic pressure resulting in extremely quick pressure shut-off at the end of the hose. This can reduce or eliminate contamination of the hose and/or intensifier cavity, and also can serve to maintain fluid in the hose that is ready for dispensing on the next delivery stroke such that the hose need not be primed thereby allowing very rapid pressure ramp-up. 
         [0010]    Accordingly, a pressure intensifier for developing a high pressure flow of fluid comprises a high pressure intensifier piston displaceable within a chamber of a high pressure intensifier cylinder between first and second positions to respectively discharge pressurized fluid from the chamber through an outlet on a delivery stroke and to intake fluid into the chamber through an inlet on a recharge stroke. A low pressure drive piston is supported for sliding movement within a low pressure cylinder and operatively coupled with the high pressure intensifier piston for displacing the high pressure intensifier piston towards the second position during the delivery stroke. A return spring is operatively coupled to at least one of the high pressure piston and the low pressure piston and configured to urge at least the high pressure piston towards the first position during the recharge stoke. 
         [0011]    More particularly, a sleeve can be operatively coupled to the low pressure piston for movement therewith and adapted for telescoping movement over an exterior surface of the high pressure intensifier cylinder during displacement of the high pressure piston by the low pressure piston. The return spring can at least partially surround the sleeve, with the sleeve thereby acting as a spring guide for guiding the spring during movement of the pistons. The sleeve, the low pressure piston, and the high pressure intensifier cylinder can together form therebetween a void that can vary in size depending on the position of the low pressure piston. The void can separate the fluid acting on the low pressure piston from the fluid in the high pressure intensifier cylinder to avoid mixing of the same. The return spring can be interposed between the low pressure piston and the high pressure intensifier cylinder and can be configured to be compressed during the delivery stroke when the low pressure piston is displaced towards the high pressure intensifier cylinder. The high pressure intensifier cylinder can be supported within the low pressure cylinder, and the intensifier can be used for intensifiying the pressure of a stream of fluid including water. 
         [0012]    In accordance with another aspect, a pressure intensifier system for developing a high pressure flow of fluid comprises a high pressure intensifier piston displaceable within a chamber between first and second positions to respectively discharge pressurized fluid from the chamber through an outlet on a delivery stroke and to intake fluid into the chamber through an inlet on a recharge stroke. A low pressure drive piston is supported for sliding movement within a cylinder and operatively coupled with the high pressure intensifier piston for displacing the high pressure intensifier piston towards the second position during the delivery stroke in response to pressurized fluid being supplied thereto. The system also includes a pump for supplying pressurized fluid to the low pressure drive piston, a motor for driving the pump, and a controller configured to control the motor in response to pressure sensed by a pressure sensor that senses the pressure of the pressurized flow. Alternatively, the controller could be configured to control the motor in response to pressure sensed by a pressure sensor that senses pressure in the hydraulic circuit. 
         [0013]    The controller can be configured to control a speed or torque output of the motor to modulate the pressure of the pressurized flow. The system can include an electrical limit switch associated with the low pressure drive piston that is configured to limit the advance of the low pressure drive piston on the delivery stroke. A conduit fluidly coupled to the outlet for receiving the pressurized fluid from the chamber can be provided, the conduit having at a distal dispensing end thereof a check valve permitting flow through the conduit from the chamber and restricting backflow into the conduit. This prevents contamination of the conduit when pressure is shut off, and also allows pressure remaining in the conduit to be bled back to the chamber. 
         [0014]    In accordance with another aspect, a pressure intensifier system for delivering a fluid comprises an intensifier unit for developing a high pressure flow of fluid, the unit including a high pressure piston displaceable within an intensifier chamber to discharge pressurized fluid through an outlet on a delivery stroke, and on a recharge stroke to admit fluid into the chamber through an inlet to refill the chamber, and a fluid conduit fluidly coupled to the outlet of the intensifier chamber for receiving high pressure fluid from the intensifier unit and for dispensing high pressure fluid at a dispensing end thereof connectable to a nozzle. The fluid conduit has a check valve at the dispensing end thereof remote the outlet for restricting backflow of fluid into the conduit when fluid is not being dispensed therefrom. A nozzle can be provided connected to the conduit, wherein the check valve restricts backflow of fluid from the nozzle into the conduit. The check valve can be a ball check valve or any other suitable type of check valve. An inlet check valve for restricting flow of fluid from the chamber out the inlet during the delivery stroke, and to permit flow of fluid through the inlet during the recharge stroke, can also be provided. 
         [0015]    In an exemplary embodiment, a linear actuator is operatively coupled to the high pressure intensifier piston for advancing the piston on the delivery stroke and retracting the piston on the recharge stroke. The linear actuator can include a ball screw assembly, wherein, for example, the output shaft has a screw portion having threads threadedly engaged with mating threads associated with the high pressure piston, and wherein the high pressure piston is fixed against rotation such that rotation of the output shaft in a first direction advances the piston and rotation of the shaft in an opposite direction retracts the piston. A controller can be configured to control the motor in response to sensed condition, such as a pressure sensed by a pressure sensor that senses the pressure of the high pressure fluid, or a position of the linear actuator. 
         [0016]    Further features of the invention will become apparent from the following detailed description when considered in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a schematic diagram of an exemplary pressure intensifier system in accordance with the invention. 
           [0018]      FIG. 2  is a perspective view of an exemplary pressure intensifier assembly in accordance with the invention. 
           [0019]      FIG. 3  is a top view of the pressure intensifier assembly of  FIG. 2 . 
           [0020]      FIG. 4  is an end view of the pressure intensifier assembly of  FIG. 2 . 
           [0021]      FIG. 5  is a cross-sectional view of the hydraulic circuit portion of the pressure intensifier assembly taken along the line A-A in  FIG. 4 . 
           [0022]      FIG. 6  is another end view of the pressure intensifier assembly. 
           [0023]      FIG. 7  is a cross-sectional view of the pressure intensifier assembly taken along the line B-B in  FIG. 6 . 
           [0024]      FIG. 8  is a cross-sectional view taken through an axial length of an exemplary hose assembly connectable to an outlet of the pressure intensifier assembly. 
           [0025]      FIG. 9  is a perspective view of an exemplary dual intensifier unit assembly for providing a continuous flow of intensified fluid. 
           [0026]      FIG. 10  is a perspective view of another exemplary pressure intensifier assembly having a screw drive in accordance with the invention. 
           [0027]      FIG. 11  is a cross-sectional view of the pressure intensifier assembly of  FIG. 10 . 
           [0028]      FIG. 12  is a perspective view of an exemplary dual head screw drive pressure intensifier assembly in accordance with the invention. 
           [0029]      FIG. 13  is a cross-sectional view of the exemplary pressure intensifier assembly of  FIG. 12 . 
           [0030]      FIG. 14  is a perspective view of an exemplary dual intensifier unit assembly in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    In  FIG. 1 , a pressure intensifier system for delivering a high pressure stream of fluid is indicated generally by reference numeral  10 . The system  10  generally includes a hydraulic circuit  12  for generating hydraulic pressure to act on a piston for pressurizing a fluid, such as water, in a fluid circuit  14 . In the following description the fluid of the fluid circuit  14  is water, but it will be appreciated that other fluids and/or suspensions can be pressurized by the intensifier without departing from the scope of the invention. 
         [0032]    The hydraulic circuit  12  includes a pump  16  driven by a motor  20  for pumping hydraulic fluid from a reservoir  24 . The pump  16  can be a fixed displacement pump, for example, configured to draw hydraulic fluid from the reservoir  24  through a filter  28  and supply the fluid via a pump outlet  30  to an outlet conduit  32  that is connected to a hydraulic cylinder  36 . The outlet conduit  32  is also connected back to an inlet  38  of the pump  16  via a normally open solenoid valve  40 . In addition, a pressure relief valve  44  connects the outlet of the pump  16  back to the pump inlet  38  for relieving pressure from the hydraulic circuit  12  in the event of overpressurization. 
         [0033]    In operation, the motor  20  drives pump  16  to supply hydraulic fluid to outlet conduit  32 . Since solenoid valve  40  is normally open, fluid in the outlet conduit  32  will be redirected back to the inlet  38  of the pump  16  until such time as the solenoid valve  40  is closed. Accordingly, until solenoid valve  40  is closed, little or no pressure is developed in outlet conduit  32 . Once the solenoid valve  40  is closed, pressurized fluid in the outlet conduit  32  is supplied to a hydraulic chamber  46  in hydraulic cylinder  36  and acts on a hydraulic drive piston  48 . As will be described in more detail below, the normally open solenoid valve  40 , which may be electronic, provides automatic shutoff of the intensifier if the power fails, operator turns off system, etc., since the hydraulic circuit  12  of the system  10  is very quickly depressurized when the solenoid valve  40  is open. Response time of the solenoid can be about 40 milliseconds, for example. 
         [0034]    As will be appreciated, when the solenoid valve  40  is closed, the pressurized fluid in the hydraulic circuit  12  acts on the hydraulic drive piston  48  causing a linear translation of the piston  48  to thereby displace an intensifier piston  52  in order to pressurize the fluid in the fluid circuit  14 . The fluid circuit  14  includes a fluid reservoir  54  for holding a supply of fluid to be pressurized. The fluid reservoir  54  is connected to intensifier cylinder  58  in which intensifier piston  52  is supported. An inlet check valve  62  is configured to permit flow from the fluid reservoir  54  to the intensifier cylinder  58  and restrict backflow of fluid from the intensifier cylinder  58  to the fluid reservoir  54 . The intensifier cylinder  58  has an outlet  64  to which a first end of a high pressure hose  66  is attached. A distal end of the high pressure hose  66  remote from the intensifier cylinder  58  includes an outlet check valve  70  for restricting backflow of pressurized fluid into the hose from a nozzle  74 . 
         [0035]    During operation of the fluid circuit  14  on a delivery stroke, the intensifier piston  52  is translated from the left to the right in  FIG. 1  as hydraulic fluid acts on the hydraulic drive piston  48 . The intensifier piston  52  acts on fluid in the intensifier cylinder  58  thereby compressing the fluid. The fluid is then supplied via intensifier cylinder outlet  64  to hose assembly  126  for delivery to a target location via hose outlet or nozzle  74 . Upon completion of the delivery stroke, a retraction stroke commences in which hydraulic fluid is no longer applied to the hydraulic drive piston  48  and solenoid valve  40  is opened thereby allowing both the hydraulic drive piston  48  and the intensifier piston  52  to translate back to the left in  FIG. 1 . To effect retraction, a spring or the like can be provided as will be described. In addition, pump  16  and motor  20  can be reversible for assisting in removing hydraulic fluid from the hydraulic chamber  46 . 
         [0036]    During the retraction stroke, outlet check valve  70  prevents backflow of fluid from the nozzle  74 . Accordingly, as negative pressure builds within the intensifier chamber  63 , fluid from the fluid reservoir  54  is drawn into the intensifier cylinder  58  via inlet check valve  62 . Upon completion of the retraction stroke, another delivery stroke can commence and the process can then repeat. 
         [0037]    As will be described in more detail below, a controller  80  can be provided for controlling the motor  20  in response to pressure sensed in the hydraulic circuit  12  by a pressure transducer  82  and/or pressure sensed in the fluid circuit  14  by pressure transducer  84 . 
         [0038]    Turning now to  FIGS. 2-8 , and initially to  FIG. 2 , an exemplary high pressure intensifier system assembly is generally indicated by reference numeral  110 . The intensifier assembly  110  has a housing  114  in which both hydraulic circuit components and fluid circuit components, for example as shown and described in connection with  FIG. 1 , are housed. A fluid inlet port  118  is provided for connection to a fluid reservoir and a high pressure fluid outlet port  64  is provided for connection to a hose assembly  126  which includes the hose  66  and outlet check valve  70  at a distal end thereof (not shown in  FIG. 2 ). The intensifier assembly  110  is designed such that the intensifier portion can be quickly replaced as a unit for replacement or repair. 
         [0039]    With reference to  FIGS. 3 and 4 , the intensifier assembly  110  generally includes two parts, the hydraulic pump system portion  130  (e.g., including the hydraulic circuit  12 ) and the intensifier assembly portion  134  (e.g., including the fluid circuit  14 ). The pump system portion  130  generally includes the hydraulic circuit components including the motor  20 , pump  16 , solenoid valve  40 , outlet conduit  32 , etc., shown in  FIG. 1 . A gasket, such as bellows gasket  141 , moves in response to changes in hydraulic oil level in reservoir  24  during system operation thereby allowing the pump portion of the assembly to be a closed hydraulic circuit. The intensification assembly portion  134  generally includes the components of the fluid circuit  14  of  FIG. 1  including the inlet check valve  62 , the intensifier cylinder  58 , etc. 
         [0040]    Turning to  FIG. 5 , which is a cross-section taken along the line A-A in  FIG. 4 , the internal details of the pump system portion  130  of the intensifier system assembly  110  are shown. In particular, motor  20  includes motor shaft  140  operatively connected to pump  16 . Pump  16  receives fluid from pump inlet  38  and supplies fluid to the pump outlet  30 . Pump outlet  30  is connected to the outlet conduit  32  which supplies fluid to the hydraulic cylinder  36  (not shown in  FIG. 5 ). Solenoid valve  40  connects the outlet conduit  32  back to the pump inlet  38 , and relief valve  44  is provided to relieve pressure from the outlet conduit  32  in the manner previously described. 
         [0041]    In  FIGS. 6 and 7 , the internal details of the pressure intensifier assembly  134  are shown.  FIG. 6  is an end view of the pressure intensifier assembly  134 .  FIG. 7 , which is a cross-section taken along the line B-B in  FIG. 6 , shows the hydraulic drive piston  48  supported for sliding axial movement within hydraulic cylinder  36 . Opposite the hydraulic piston  48 , an intensifier cylinder  58  is supported within the hydraulic cylinder  36  and receives the intensifier piston  52  which is operatively coupled to the hydraulic piston  48  for movement therewith. 
         [0042]    The intensification assembly portion  134  is secured to the hydraulic cylinder  36  via a quick-release mechanism  136  which includes locking balls  137 , a release collar  138 , and a spring  135 . As will be appreciated, the locking balls  137  and release collar  138  cooperate to lock and/or release the intensification assembly  134  from the hydraulic cylinder  36 . In the locked position of  FIG. 7 , the release collar  138  restricts radial expansion of the locking balls  137  thus preventing withdrawal of the intensification assembly  134  from the hydraulic cylinder  36 . Likewise, the spring  135  prevents accidental release of release collar  138  by biasing the collar towards the lock position. To release the intensification assembly  134  for withdrawal, release collar  138  is shifted rightward in  FIG. 7  against the bias of spring  135  such that the locking balls  137  can expand radially into an annular groove  139  in the release collar  138  thereby permitting the intensification assembly  134  to be withdrawn from the hydraulic cylinder  36 . The quick-release mechanism  136  allows the intensification assembly  134  to be quickly and easily removed for repair or replacement. 
         [0043]    A cylindrical sleeve  142  surrounds a portion of an exterior surface of the intensifier cylinder  58  and is configured to slide axially with the hydraulic drive piston  48  upon movement thereof during a delivery stroke as previously described. A return spring  144  is interposed between a radially outwardly extending shoulder  146  of the sleeve  142  and a radially outwardly extending shoulder  148  formed in an outer surface of the intensifier cylinder  58 . The return spring  144  is configured to be compressed during the delivery stroke and, upon a decrease in pressure in the hydraulic chamber  46  at the end of the delivery stroke, the return spring  144  is configured to act against the hydraulic drive piston  48  and/or intensifier piston  52  to carry out the retraction stroke. Unlike other intensifier systems that use hydraulic pressure to both extend and retract a hydraulic piston, the present embodiment facilitates automatic return of both pistons upon removal of the application of pressurized fluid to the hydraulic piston  48 . Further, providing the spring  144  over the outside of the intensifier cylinder  58  saves space by reducing over all system length. 
         [0044]    As will be appreciated the hydraulic drive piston  48  includes one or more seals  152  for sealing the piston  48  to the hydraulic cylinder  36 . Similarly a high pressure seal  156  is provided for sealing the intensifier piston  52  to the intensifier cylinder  58 . A pair of bushings  158  stabilize the intensifier piston  52  as it slides axially. 
         [0045]    As it is generally desirable to prevent mixing of the hydraulic fluid with the fluid in the fluid circuit  14 , an air gap  160  is provided between the hydraulic chamber  46  containing the hydraulic fluid and the intensifier chamber  63  containing the fluid to be pressurized. Accordingly, hydraulic fluid does not contact the intensifier piston at any time, unlike other intensifiers that have hydraulic fluid pushing an intensifier piston in both directions and hydraulic fluid in direct contact with the intensifier piston. 
         [0046]    The air gap  160  also serves at least two functions related to preventing mixing of the hydraulic fluid and the fluid in the intensifier chamber. First any leakage past either seals  152  or  156  into the air gap  160  can be drained out of the assembly via suitable drain ports, such as drain hole  166 , rather than result in mixing of the fluids. Second, the air gap  160  can make detection of a leak easier since, under normal operation, no fluid (hydraulic or otherwise) will exist in the air gap  160 . Thus, if fluid is detected in the air gap  160  one or more of the seals is likely leaking. Accordingly, a sight glass could be provided in place of, or in addition to, the drain hole  166  to facilitate detection of fluid in the air gap  160 . Alternatively, or in addition, one or more sensors could be provided for sensing the presence of fluid in the air gap  160 . The air gap  160  also prevents high pressure fluid from spraying out of the intensifier in the event the high pressure seals leak or otherwise fail. 
         [0047]    As previously described, in operation of the assembly pressurized hydraulic fluid is provided to the hydraulic cavity chamber  46  and acts upon hydraulic drive piston  48  to displace hydraulic drive piston  48  leftward in  FIG. 7 . The displacement of hydraulic piston  48  results in a corresponding displacement of the intensifier piston  52  which acts on fluid in the intensifier chamber  63  thereby pressuring such fluid. The inlet check valve  62  prevents fluid from escaping from the intensifier chamber  63  back to the reservoir  54  such that the pressurized fluid is forced into the hose assembly  126  for dispensing at a target. 
         [0048]    When the hydraulic drive piston  48  reaches full extension, pressure in the hydraulic circuit  12  is released via the opening of solenoid valve  40 . A limit switch on the hydraulic cylinder  36  can be provided for sensing such position of the drive piston  48  and automatically opening the solenoid valve  40 . The limit switch can be an electronic limit switch, for example, as opposed to the mechanical switches used on many hydraulic intensifiers. Such switch can be tripped by a magnet  168  integrated into the hydraulic piston  48 , or could also be a linear strip such that the system has variable full pressure time. 
         [0049]    Upon release of the hydraulic pressure on hydraulic piston  48  (e.g., via opening of solenoid valve  40 ), the spring  144  forces the hydraulic piston  48  and intensifier piston  52  rightward in  FIG. 7  thereby drawing fluid into the intensifier chamber  63  from the reservoir  54  through inlet  118  (see  FIG. 6 ) in preparation for a new intensification stroke. As noted, the pump  16  and motor  20  can be reversible to assist in removal of hydraulic fluid from the hydraulic chamber  46  during the retraction stroke. 
         [0050]    Turning to  FIG. 8 , the hose assembly  126  is shown in detail. The hose assembly  126  generally comprises a conduit  170  through which the pressurized fluid can flow, a hose nut  174  for coupling the conduit  170  to an outlet  64  of the intensifier pressure chamber, and a fitting  178  such as a quick disconnect fitting for coupling the conduit  170  to a hand tool or the like. Outlet check valve  70  is provided at the distal end of the conduit  170  remote from the intensifier chamber and acts to prevent backflow of fluid from downstream of the valve  70  from being drawn back into the conduit  170  on the retraction stroke of the intensifier assembly  134 . 
         [0051]    Referring back to  FIG. 1 , it will be noted that the output of the motor  20  can be controlled to control the pressure and/or flow output of the intensifier. To this end, a PID loop (proportional integral derivative) or PI loop, for example, can be configured to control the speed of the motor  20 , which then controls the flow rate and/or pressure of the output of hydraulic pump  16 , which in turn controls the flow rate and/or pressure of output of the intensified fluid dispensed from the intensifier chamber  63  and/or hose  66 . 
         [0052]    In this regard, pressure transducer  84  is provided for sensing the pressure of the pressurized fluid in fluid circuit  14  and generating a signal in response thereto. This signal is then fed to the controller  80  configured to control the motor  20  in response to the sensed pressure in order to deliver a desired pressure. For example, if the sensed pressure is below a desired pressure, the controller  80  will ramp up the speed of the motor  20  in order to increase the pressure applied to the hydraulic drive piston  48  and, in turn, to the intensifier piston  52 . If the sensed pressure is greater than the desired pressure, the controller  80  will decrease the speed of the motor  20  in order to decrease the pressure of the pressurized fluid. Accordingly, the system  10  acts essentially as a proportional hydraulic system but without a proportional control valve. 
         [0053]    It will be appreciated that pressure and/or flow of either the hydraulic circuit  12  (via pressure transducer  82 ) and/or the fluid circuit  14  (via pressure transducer  84 ) could be used for providing feedback to control the motor  20 . Further, both the speed and/or torque output of the motor could be used to achieve a desired output pressure and/or flow. 
         [0054]    Turning to  FIG. 9 , a dual intensifier assembly for providing a continuous intensified flow of fluid is indicated generally by reference numeral  200 . As will be appreciated, the unit  200  is essentially two systems, as described in  FIGS. 1-8 , joined together. The unit  200 , thus, includes first and second intensifier assemblies  202  and  204  each having a hydraulic assembly portion and an intensifier assembly portion as previously described. Although not shown, the units  202  and  204  can share a common housing. 
         [0055]    By alternating the delivery strokes of each intensifier assembly  202  and  204 , the unit  200  can supply a continuous intensified flow of fluid through a hose assembly or the like for dispensing at a target. Suitable controls can be provided for ensuring that when one assembly is on a retraction stroke, the other assembly is on a delivery stroke such that high pressure fluid is always available to be dispensed. The outlets of each unit may be fluidly coupled to a manifold to which a hose assembly as herein described is also attached, for example. 
         [0056]    It will further be appreciated that the hydraulic circuit as described above could be replaced by an electromechanical device for providing the linear velocity and force to create the intensified fluid. For example, a suitable electromechanical device could be an integrated motor (servo, etc) configured to turn a ball screw or the like for advancing the intensifier piston. 
         [0057]    Turning to  FIGS. 10-14 , and initially to  FIG. 10 , an exemplary intensifier assembly having a screw drive (e.g., a ball screw assembly) in accordance with the invention is indicated generally by reference numeral  300 . The assembly  300  generally includes a cylinder body  304  to which an intensifier portion  308  is coupled via a quick-release mechanism  310  or the like, and a motor  312  for driving the intensifier. As will be described below, the motor  312  in this embodiment replaces the hydraulic circuit for supplying the power to actuate the intensifier piston. The intensifier portion  308  is generally similar to the above-described intensifiers with respect to the manner in which fluid is drawn into the intensifier chamber via an inlet  316 , pressurized by the intensifier piston, and delivered to the outlet  320 . Accordingly, the details of the intensifier portion will not be described. 
         [0058]    Turning to  FIG. 11 , the internal features of the intensifier assembly  300  are shown. As mentioned, the intensifier portion  308  is generally similar to the previously described intensifier assemblies and includes an intensifier piston  324  movable within intensifier chamber  328  between first and second positions for drawing fluid into the chamber  328  and intensifying the pressure of the fluid for dispensing via outlet  320 . 
         [0059]    In this embodiment, the intensifier piston  324  is operatively coupled to a motor shaft screw of  332  of the motor  312  such that rotation of the screw  332  in a first direction advances the intensifier piston  324  and rotation of the screw  332  in the opposite direction retracts the intensifier piston  324 . To this end, the intensifier piston  324  has a bore having internal threads  336  threadedly engaged with external threads  340  of the screw  332 . The intensifier piston  324  can be fixed against rotation and supported for sliding axial movement within the cylinder body  304  by a retainer  344  and a bushing  348 . 
         [0060]    Accordingly, as the motor  312  spins the screw  332  in a first direction, the intensifier piston  324  is advanced within the intensifier chamber  328  to thereby discharge pressurized fluid in the manner previously described. Upon completion of such intensification stroke, the motor is reversed to thereby retract the intensifier piston  324  to refill/recharge the intensifier chamber  328  with fluid for the next intensification stroke. 
         [0061]    In the illustrated embodiment, the speed and/or torque of the motor  312  can be controlled in order to deliver a desired pressure. In this regard, a pressure transducer  352  (see  FIG. 10 ) can be provided for sensing the pressure of the pressurized fluid, and feeding a signal indicative of the pressure to a controller for controlling the current supplied to the motor  312 . As will be appreciated, limit switches can be used to set the stroke of the intensifier piston within the chamber. 
         [0062]    Turning now to  FIGS. 12 and 13 , a continuous flow dual head screw pump intensifier assembly is generally indicated by reference numeral  400 . In this embodiment, a pair of intensifiers  308  are alternately driven by a screw shaft of a motor  312  to thereby supply a continuous flow of intensified fluid. 
         [0063]    Referring to  FIG. 13 , it will be appreciated that in this embodiment a single motor  312  drives a pair of intensifier assemblies  308  coupled to respective cylinder bodies  304  via respective quick-release couplings  310 , for example. Accordingly, rotation of the screws  332  in a first direction advances one of the intensifier pistons  324  while retracting the other intensifier piston  324 . Reversing the rotation of the screws  332  reverses the movement of the respective pistons  324 . Thus, while one intensifier piston is on an intensification stroke, the other piston is on a recharge. The screws  332  can be part of a common shaft driven by the motor  312 . 
         [0064]    Turning now to  FIG. 14 , a dual intensifier assembly  500  is illustrated. In this embodiment, the dual intensifier assembly  500  includes two individual intensifier units  300  as described in connection with  FIGS. 10-11 , each having a respective motor  312 . To provide a continuous flow of intensified fluid during operation, one intensifier unit is configured to operate on an intensification stroke while the other intensifier unit is on a recharge stroke. 
         [0065]    Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.