Abstract:
Medical pumps for water jet surgery are known. The invention relates to a pump comprising at least two pistons provided with piston rods for displacing the pistons in cylinders and for coupling to a pump actuation device, a cylinder head for closing the cylinders, and valve means for respectively connecting a pressure chamber in the cylinder to at least one fluid inlet and at least one fluid outlet. Said fluid outlet is connected to the fluid inlet in a communicating manner by means of an adjustable pressure regulating valve, in such a way that the pressure in the fluid outlet can be limited to a predetermined maximum value so that operation of the pump can be.

Description:
RELATED U.S. APPLICATIONS 
       [0001]    Not applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       REFERENCE TO MICROFICHE APPENDIX 
       [0003]    Not applicable. 
       FIELD OF THE INVENTION 
       [0004]    The invention relates to a medical pump, in particular for water jet surgery. 
       BACKGROUND OF THE INVENTION 
       [0005]    Water jet surgery has been used for some time in liver surgery as this organ, like no other, has tissue structures of different firmness (parenchyma, blood vessels and bile ducts) and the applied water jet separates the tissue being cut, yet leaves the blood vessels and bile ducts undamaged. Naturally, a precise control of the cutting pressure is required for this. 
         [0006]    A further problem of water jet surgery is that the cutting medium must be totally sterile (e.g. Ringer solution) as the liquid comes into contact with body tissue in the closest and most intensive way possible. Ordinary problems such as high reliability, simplicity and economic manufacture must also be considered. 
         [0007]    A medical pump for water jet surgery is described in U.S. Pat. No. 6,216,573 B1, as well as DE 203 09 616 U1, which is disposable and thus used only once. The pump efficiency as well as its adjustment, however, are unsatisfactory. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The invention provides a medical pump, in particular for water jet surgery, which despite simple construction and suitability for single use facilitates improved cutting performance. 
         [0009]    According to the invention a medical pump comprises at least two pistons with piston rods for displacing the pistons in the cylinders and for coupling to a pump actuation device, a cylinder head for closing the cylinders in relation to the pistons, valve means for connecting the pressure chamber with at least one fluid outlet and at least one fluid inlet, whereby the fluid outlet interacts with the fluid inlet via an adjustable pressure control valve in such a way that the pressure in the fluid outlet can be limited to a predetermined maximum value. 
         [0010]    As the pump is operated with two piston/cylinder units, an improved and smoothed out pump capacity can be achieved. The construction is simple so that economic manufacture is possible. The already improved pumping of the working fluid is further improved by the pressure control valve as it can be smoothed out and at the same time be adjusted to the application requirements. 
         [0011]    The valve means and/or the pressure control valve comprise an elastic or elastically pressurized valve membrane. This enables very economic manufacture and high operational safety. 
         [0012]    The valve devices can also comprise two spring-loaded ball check valves, which again are simple to produce. 
         [0013]    The pressure control valve is preferably constructed as a power driven valve in such a way that the maximum value is adjustable by means of actuating power on a regulator of the pressure control valve. This special form facilitates coupling of the medical pump to the pump actuation device in an advantageous manner, where a particular specific spatial positioning of the pump in relation to the pump actuation device is not required. Because the pressure adjustment is not proportional to the travel but proportional to the force, coupling of the pressure control valve to a regulating unit is not position-dependent (which would require accurate adjustment of the pump), it is rather the position independent force with which the regulator activates the pressure control valve which is important. 
         [0014]    The pressure control valve is preferably arranged between fluid inlet and fluid outlet in such a way, that on exceeding the maximum value, fluid from the fluid outlet can be directed back to the fluid inlet. In this way the pressure can be adjusted independently of the quantity of pumped fluid. 
         [0015]    The pistons or pistons rods are preferably connected securely and in a sterile way via bellows, cup seal or similar non-slip seals to the cylinders. Germs can thus not be introduced despite sterile working fluid and sterile transmission pipes, which can be the case with pumps known hitherto. This danger is particularly great as due to piston displacement in the cylinders their back ends (in relation to the pressure chambers) are subjected to streams of ambient air and thus cylinders can be contaminated therewith in this area. 
         [0016]    The valve devices and/or pressure control valve are preferably housed in the cylinder head. This results in a simpler setup containing fewer parts. 
         [0017]    It is preferred that the cylinders are connected independently to the cylinder head. This simplifies manufacture. 
         [0018]    The outlet preferably has fittings for irreversible connection to a pressure hose. This avoids a faulty installation of the pump and also non-permissible re-use of the pump. 
         [0019]    The cylinder head preferably comprises holding devices, in particular lugs into which the catches engage, which are attached to the pump actuation device. No special measures are thus needed for mounting the pump to the pump actuation device. 
         [0020]    An accumulator is provided in a preferred embodiment and is connected to the fluid outlet in such a way that fluid pressure fluctuations at the fluid outlet are smoothed out due to a low pass function. This results in a further smoothing of the cutting jet and thus an improvement of the equipment cutting function desired. The accumulators are preferably situated in the cylinder head or connected therewith which simplifies the assembly of the entire arrangement. 
         [0021]    Embodiments of the invention will now be described by way of example with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0022]      FIGS. 1 to 3  are schematic block diagrams of different embodiments of the medical pump arrangements according to the invention. 
           [0023]      FIG. 4  is an exploded view of an embodiment of the pump. 
           [0024]      FIG. 5  is a side view of the pump shown in  FIG. 4 . 
           [0025]      FIG. 6  is a section along line VI-VI in  FIG. 5 . 
           [0026]      FIGS. 7 and 8  are partial sectional views through the medical pump in the pressure control valve area in two respective control positions. 
           [0027]      FIG. 9  is a perspective view of a cylinder head of the pump. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]    The same reference numbers will be used for the same parts and parts with the same function. 
         [0029]    A pump actuation device  10  is intended for the embodiment of the invention shown in  FIG. 1 , which encompasses a motor control  15  for the control of two motors  11 , 11 ′, which are connected via gearing  12 ,  12 ′ and clutch devices  13 ,  13 ′ to the piston rods  25 , 25 ′. One operator B can operate the motor control  15  with suitable switches (foot switch or finger switch), so that the motors  11 ,  11 ′ displace the piston rods  25 ,  25 ′ and thus the pistons  22 ,  22 ′ in the cylinders  21 ,  21 ′ of pump unit  20  alternately via the described train, so that the volume of the pressure chambers  16 ,  16 ′ of the pump unit  20  is alternately enlarged and reduced. 
         [0030]    In order to seal the pressure chambers  16 ,  16 ′ and the pistons  22 ,  22 ′ in relation to the cylinders  21 ,  21 ′ seals  23 ,  23 ′ are provided at the pistons  22 ,  22 ′. Moreover, the piston rods  25 ,  25 ′ maintain sterility with cup seals  24 ,  24 ′, which are firmly fixed to the cylinders  21 ,  21 ′ on the one hand and to the pistons rods  25 ,  25 ′ on the other. In this way germs from the ambient air, which without these cup seals  24 ,  24 ′ would settle on the internal walls of the cylinders  21 ,  21 ′ and pass through the seals  23 ,  23 ′, can neither mix with the working fluid nor find their way into the same. 
         [0031]    Suction valves  26 ,  26 ′ as well as pressure valves  27 ,  27 ′ are connected to the pressure chambers  16 ,  16 ′. The suction valves  26 ,  26 ′ are connected via a fluid inlet  6  to a reservoir  9  for the working fluid. The pressure valves  27 ,  27 ′ are connected to the pressure hose  5  via a fluid outlet  7 , which leads to an applicator  8 . The pump unit  20  forms a disposable part E together with the reservoir  9  including its contents, pressure hose  5  and applicator  8 , which is disposed of after each operation, so that the entire setup meets the highest sterility requirements possible. 
         [0032]    A butterfly valve  14  is intended for adjustment of pressure in this simple embodiment of the invention (which in addition to the motor control  15 ) facilitates adjustment of the fluid flow by operator B. 
         [0033]    The embodiment of the invention shown in  FIG. 2  differs from that in  FIG. 1  by virtue of the provision of a pressure control valve  35 , which with the aid of a valve membrane  36  can open and close a connecting channel between fluid outlet  7  and fluid inlet  6 . The membrane  36  is operated by an actuator  30  via a push rod  34  and a spring  33 , as well as a dynamometer  31 . The dynamometer  31  supplies a power proportional output signal to a controller  32 , via which an operator B can set a maximum pressure. Instead of a separate dynamometer  31  the operating current of the actuator  30  can also be measured which is also power proportional. 
         [0034]    This arrangement means that the fluid pressure can be accurately adjusted at the applicator  8 . Moreover, pressure fluctuations resulting from piston operation are smoothed out by the control valve  35 . The pressure control valve  35  owing to its construction operates with the membrane pressurised by fluid, in a power-controlled and not a travel-controlled manner. No pressure adjustment error can therefore occur even with dimension tolerances during coupling of the pump unit  20  to the pump actuation device  10 , as it is not the geometric dimensions (travel) which are important, but the power with which the pressure control valve  35  is operated. 
         [0035]    The embodiment shown in  FIG. 3  differs from the previously shown embodiments by virtue of the provision of an accumulator  40 , which comprises a cylinder  44  containing a piston  42  sealed by a seal  43 , which is pressurized by a spring  41 . A chamber situated above the piston is connected to the fluid outlet, so that with increasing pressure at the fluid outlet  7  the spring  41  is compressed and with decreasing pressure the spring  41  drives the piston  42 . In this way the pressure directed to the applicator  8  is smoothed out due to its low pass function. This accumulator  40  is arranged in a cylinder head  29  which seals the cylinders  21 ,  21 ′. It is also possible to combine the variants show here. In particular the pressure control valve  35  can be combined with the accumulator  40 . 
         [0036]      FIG. 4  shows a constructive embodiment of the pump device  20  in an exploded view. In this embodiment the pressure and suction valves  26 / 27  comprise balls  19 , which are pressed onto the valve seats via springs  18  (not visible in the illustration), in an arrangement that is known in principle. 
         [0037]    The cylinder head  29  has two sections to which the cylinders  21 ,  21 ′ are coupled, whereby the valves sit between the cylinders  21 ,  21 ′ and the cylinder head  29 . 
         [0038]    It can further be seen from  FIG. 4 , that the piston rods  25 ,  25 ′ have coupling projections  17 ,  17 ′ at their distal ends which serve to create mechanical connections with the coupling systems  13 ,  13 ′. 
         [0039]    The pistons in this embodiment of the invention are formed by the proximal ends of the piston rods  25 ,  25 ′ fitted with caps  28 , which simultaneously hold seals  23 ,  23 ′ firmly on the piston rods  25 ,  25 ′. 
         [0040]    The pressure hose  5  is fastened irreversibly to the cylinder head  29  via a connecting piece  37 , a crimping piece  38  and an internal pipe which is inserted into the pressure hose  5 , whereby after assembly of the connecting piece  37  (in a known way) in the cylinder head  29  by means of a catch  45 , the connecting piece is held irreversibly in the cylinder head  29 . 
         [0041]    From  FIGS. 5 and 6  details of the layout become clear in particular in relation to the construction of the suction valve  26 ,  26 ′ or the pressure valve  27 ,  27 ′ and especially the layout of the valve seats in the cylinder head  29  on the one hand and the relevant allocated cylinders  21 ,  21 ′ on the other. 
         [0042]      FIGS. 7 and 8  show a section through the pressure control valve  35 , which shows that the membrane  36  can be pressed by the push rod  34  onto a valve seat ( FIG. 7  shows the open position and  FIG. 8  the closed), so that between fluid outlet  7  and fluid inlet  6 , depending on the position of the membrane  36 , a more or less greater “short circuit” of the pump unit  20  is produced. As the membrane  36  is pressurized by the fluid outlet  7 , a power-controlled valve is present. 
         [0043]      FIG. 4  shows further construction related details of the cylinder head  29  and the valve devices (suction valve, pressure valve and pressure control valve) contained therein. Moreover,  FIG. 9  shows the lugs, which are coupled via the pump unit  20  to the pump actuation device  10  or they can be held firmly on the same. 
         [0044]    In an embodiment of the invention not shown here not only is the pressure control valve  35  a membrane valve, but also the two pressure valves  27 ,  27 ′ or suction valves  26 ,  26 ′ are designed as membrane valves instead of the ball valves shown here. This makes the arrangement even more economic. Finally, it is also possible to create the pump in such a way that not only are all the valves membrane valves but all the membranes are connected in one piece, so that the number of components is decreased still further. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
         E Disposable part 
         B Operator 
           5  Pressure hose 
           6  Fluid inlet 
           7  Fluid outlet 
           8  Applicator 
           9  Reservoir 
           10  Pump actuation device 
           11 , 11 ′ Motor 
           12 , 12 ′ Gearing 
           13 ,  13 ′ Clutch system 
           14  Butterfly valve 
           15  Motor control 
           16 , 16 ′ Pressure chamber 
           17 , 17 ′ Coupling projection 
           18  Spring 
           19  Ball 
           20  Pump unit 
           21 ,  21 ′ Cylinder 
           22 ,  22 ′ Piston 
           23 ,  23 ′ Seal 
           24 ,  24 ′ Cup seal 
           25 ,  25 ′ Piston rod 
           26 ,  26 ′ Suction valve 
           27 ,  27 ′ Pressure valve 
           28  Cap 
           29  Cylinder head 
           30  Actuator 
           31  Dynamometer 
           32  Controller 
           33  Spring 
           34  Push rod 
           35  Pressure control valve 
           36  Valve membrane 
           37  Connecting piece 
           38  Crimp tube 
           39  Internal tube 
           40  Accumulator 
           41  Spring 
           42  Piston 
           43  Seal 
           44  Cylinder 
           45  Catch 
           46  Lugs