Abstract:
The invention relates to a medical pump, especially for water jet surgery, in which a pump unit is assembled as a single use article and can be reversibly connected to a pump actuating device. Within the pump, the pump actuating device is also used to open up the connection between the pump unit and the pump actuating device.

Description:
FIELD OF THE DISCLOSED EMBODIMENTS 
     The disclosed embodiments relate to a medical pump, in particular for water jet surgery. 
     BACKGROUND 
     Water jet surgery has been used for some time in liver surgery, as this organ has tissue structures of different firmness (parenchyma, blood vessels and bile ducts) unlike any other organs and the applied water jet separates the tissue being cut (parenchyma) yet leaves the blood vessels and bile ducts undamaged. Naturally, precise control of the cutting pressure is required for this type of operation. 
     A further problem with 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. 
     Medical pumps for water jet surgery are known, for example, from U.S. Pat. No. 6,216,573 B1 and DE 203 09 616 U1, which comprise an exchangeable pump unit for single use, which can be connected to pump actuating devices. Changing of the pump devices is, however, very costly with the known setups. As relatively large forces are needed to generate high pressure with sufficient flow, the devices for connection of the pump device to the pump actuating devices must be very substantial so that they can maintain a “firm hold” on the pump device during operation. 
     SUMMARY 
     The disclosed embodiments include a medical pump wherein the connection between the pump unit and the pump actuating device is improved and easier to operate. 
     A medical pump according to disclosed embodiment includes a pump unit which is assembled as a single use article and which comprises at least one piston and piston rod for displacing the piston in an allocated cylinder defined by the pump unit; a pump actuating device comprising at least one controllable drive device and a motor control adapted to actuate the pump unit by displacing the at least one piston rod; holding devices which are adapted to open and close for reversible attachment of the pump unit to the pump actuating device; and clutch means which are adapted to open and close for reversible connection of the at least one piston rod to the at least one controllable drive device, wherein the at least one controllable drive device of the pump actuating device is further adapted to actuate the opening or closing of at least one of said holding devices or said clutch means. 
     In the disclosed embodiments, the drive device that pushes the piston back and forth additionally actuates or controls the holding devices and/or the clutch means as well. Simple operation by means of the drive device is thus possible and a large holding force can be exerted, as this is applied during opening to decouple the pump unit from the pump actuating device and not by the user. 
     The holding devices and/or the clutch devices are preferably snap fittings. The snap fittings are constructed so that closing of the holding devices and/or clutch devices can be achieved by snapping the holding devices and/or clutch devices in place and so that opening the holding devices and/or clutch devices can be achieved by means of the drive device opening the snap fittings. The energy required for connecting the pump device to the drive device can be generated very easily by the user. Opening is then carried out by the drive devices with a corresponding large holding force. In this way, only opening must be carried out by the drive devices but not closing as well. This simplifies the setup. 
     The snap fittings are preferably constructed so that the force required for closing is less than that for opening. 
     The drive device is preferably constructed so that the engagement devices fitted in the clutch devices are positioned at rest prior to attaching the pump unit to the pump actuating device so that, on connecting the pump unit to the pump actuating device, the engagement devices disengage from the piston rods and the clutch devices can be closed by actuating the drive devices. This means that the user does not have to carry out any great manipulation in relation to the pistons or piston positions in order to attach the pump unit to the pump actuating device. 
     In one preferred embodiment, two pistons with piston rods are provided in the cylinders and the pump actuating device is constructed to give alternate displacement of the pistons. This arrangement ensures an increased pump performance. In this embodiment, the pump actuating device is constructed either with two motors or a motor with controllable gearing preferably controllable such that the pistons can be displaced in one of two ways: (1) synchronously for alternate opening or closing of the holding device and/or the clutch devices and (2) alternately during normal pump operation. The pistons are operated alternately during (2) normal pump operation. A different modus operandi (e.g., synchronous operation) is selected for opening and closing of the holding device and/or the clutch devices using the same drive set as for normal pump operation. This results in a simplified setup of the pump. 
     The drive device is preferably a linear drive (or in an embodiment with two pistons, two linear drives) with shaft and motor so that the shaft is drivable in a controllable manner. Very accurate movements can be carried out via such linear drives, thereby protecting the pump with its piston/cylinder units. 
     The motor control is preferably constructed in such a way that the pistons can be displaced at a constant speed. This results in a smoother delivery of the medium to be pumped. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Disclosed embodiments are now described by way of example with reference to the accompanying drawings. 
         FIG. 1  is a schematic block diagram of a medical pump arrangement according to a disclosed embodiment. 
         FIG. 2  is an exploded diagram of an embodiment of the pump. 
         FIG. 3  is a perspective view of the pump actuating device with coupled pump unit. 
         FIG. 4  is a side view of a holding device. 
         FIG. 5  is a view similar to  FIG. 4 , partially-sectioned along the line V-V in  FIG. 6 . 
         FIG. 6  is a plan view of the holding device shown in  FIG. 4 . 
         FIGS. 7-9  are views similar to illustrations corresponding to those in  FIGS. 4-6 , showing the holding device in an open position. 
         FIG. 10  is an exploded drawing of the holding device showing its functional elements. 
         FIG. 11  is a perspective diagram of a sub-unit shown in  FIG. 10 . 
         FIG. 12  is an exploded drawing of the sub-unit shown in  FIG. 11 . 
         FIG. 13  is a perspective drawing of clutch means 
         FIG. 14  is a view of the clutch means shown in  FIG. 13  in a different displacement position. 
         FIG. 15  is an exploded view of one clutch means shown in  FIG. 13  and  FIG. 14 . 
         FIG. 16  is an exploded view of a sub-unit of the clutch means shown in  FIG. 13 . 
         FIG. 17  is a plan view of the clutch means shown in  FIG. 13  with coupled piston rods. 
         FIG. 18  is a front elevation of the clutch means shown in  FIG. 17 . 
         FIG. 19  is a view similar to  FIG. 17 , showing the clutch means in a different operational state. 
         FIG. 20  is a front elevation of  FIG. 19 . 
         FIG. 21  is a section along line XXI-XI in  FIG. 19 . 
     
    
    
     DETAILED DESCRIPTION 
     The same reference numbers will be used for the same parts and for parts with the same function. 
     In one disclosed embodiment depicted in  FIG. 1  a pump actuating device  10  is provided 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 ′. Ah operator B can operate the motor control  15  by means of suitable switches (foot switch or finger switch) so that the motors  11 ,  11 ′ alternately displace the piston rod  25 ,  25 ′ and thus the pistons  22 ,  22 ′ in the cylinders  21 ,  21 ′ of a pump unit  20  via the described train, so that the volume of the pressure chambers  16 ,  16 ′ of the pump unit  20  is alternately enlarged and reduced. 
     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 envisaged 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. 
     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  which leads to an applicator  8  via a fluid outlet  7 . 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. 
     A butterfly valve  14  is provided by means of which (in addition to the motor control  15 ) operator B can switch off the fluid flow completely. The embodiment shown in  FIG. 1  includes 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 , by means of which an operator B can set a maximum pressure. Instead of a separate dynamometer  31  the operating current of the actuator  30  can be measured which is also power proportional. 
     This layout 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 important point is that the pressure control valve  35  due to its construction operates with the membrane pressurized by fluid in a power-controlled and not a travel-controlled manner. No pressure adjustment error can therefore occur during coupling of the pump unit  20  to the pump actuating device  10  even with dimension tolerances as it is not the geometric dimensions (travel) which are important, but the power with which the pressure control valve  35  is operated. 
       FIG. 2  shows an exploded view of a construction embodiment of the pump device  20 . In this embodiment the pressure and suction valves  26 / 27  encompass balls  19  which are pressed onto the valve seats via springs  18  (not visible in the illustration) which principle is known. 
     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 . 
     It can further be seen from  FIG. 2 , that the piston rods  25 ,  25 ′ have coupling projections  17 ,  17 ′ at their distal ends which serve to create a mechanical connection with the coupling systems  13 ,  13 ′. 
     The pistons in this embodiment 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 ′. 
     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 (in a known way) the connecting piece  37  is held in the cylinder head  29  by means of a catch  45  which holds the connecting piece  37  irreversibly in the cylinder head  29 . 
       FIG. 3  shows a perspective illustration of the pump actuating device  10  with a coupled pump unit  20 . This illustration shows that the pump actuating device has a frame  65  to which the motors  11 ,  11 ′ are attached. They are constructed as reversing motors which drive the shafts  47 ,  47 ′ via cog belts  48 ,  48 ′ and gearing  12 ,  12 ′, so that the rotary movement of the motors  11 ,  11 ′ is translated into a linear movement. Attached to the shafts  47 ,  47 ′ are the clutches  13 ,  13 ′ to which the piston rods  25 ,  25 ′ can be coupled. The setup of the actuator  30  with the relevant push rod  34  is also visible in this illustration. 
     Moreover, the holding device  50  is attached to the frame  25  which is intended for holding the pump unit  20 . 
     The holding device is explained in more detail with the aid of  FIGS. 4-12 . 
     The holding device  50  encompasses jaw holder  52 ,  52 ′ with jaws  51 ,  51 ′ at the end, the jaws  51 ,  51 ′ being are constructed in such a way that they can engage with the lugs  46  ( FIG. 2 ) provided in order to hold the pump unit  20 . 
     The jaw holders  52 ,  52 ′—as shown in FIG.  4 —are positioned on the frame  65  via swivel pins and pretensioned in the closed position ( FIGS. 4-6 ) by means of springs  53  (see  FIG. 10 ). In order to insert a pump unit  20  this is pushed into the holding device  50  in such a way that the jaws  51 ,  51 ′ slip with front inclined surfaces over the lugs  46  of the pump unit  20  and are forced onto it. When the pump unit  20  has then been fully pushed on, the jaw holders  52 ,  52 ′ snap shut and the jaws  51 ,  51 ′ hold the pump unit  20  in this position until they are pushed apart again. 
     The mechanism for opening the holding device  50  or jaws  51 ,  51 ′ is explained with the aid of  FIGS. 10-12 . 
     The holding device  50  encompasses a holding block  54 , which has cylinder housings  56 ,  56 ′ at its front which correspond to the rears of the cylinders  21 ,  21 ′ of pump unit  20 . The fit can be seen easily when  FIGS. 2 and 10  are compared. 
     An opening slide  57  is fixed with fastening screws  59 ,  59 ′ to the cylinder housing  56 , whereby the opening slide  57  has elongated holes  60 ,  60 ′ so that it can be pushed back and forth. The opening slide  52  is pushed backwards, away from the pump unit  20 , by means of a spring  58 . 
     A rocker  52  which can be swiveled back and forth is fixed to the opening slide  57  by means of a rocker bearing  63  carrying symmetrically arranged tongues  64 ,  64 ′. The opening slide  57  has an opening tongue  61  at its front, facing the pump unit  20 . The opening tongue  61  has a height which corresponds to the distance between the internal surfaces of the jaw holders  52 ,  52 ′. On these inner surfaces of the jaw holders  52 ,  52 ′ opening ramps  55 ,  55 ′ have been attached in the displacement path of the opening tongue  61  in such a way that the opening tongue  61 , on meeting the opening ramps  55 ,  55 ′ and during further displacement in the direction of the pump unit  50 , pushes apart the jaw holders  52 ,  52 ′, so that they change from the position shown in  FIGS. 4-6  to the position in  FIGS. 7-9 . In this position (according to  FIGS. 7-9 ) the jaws  51 ,  51 ′ disengage from the lugs  46  on the pump unit  20  thus releasing it. Displacement of the opening slide  57  occurs as described as follows. 
     During a “normal” operation of the pump unit  20  the shafts  47 ,  47 ′ are moved back and forth alternately, so that in an end position of a shaft  47  or  47 ′ they hold the positions shown in  FIG. 6  or  17 . During these movements the holding blocks  72 ,  72 ′ are moved by the piston holders  70 ,  70 ′ at the end of the shafts  47 ,  47 ′ past the tongues  64 ,  64 ′ in such a way that the rocker  62  is either tilted anti-clockwise, as shown in  FIG. 6 , or in the other direction in which the holding blocks  72 ,  72 ′ are in the reverse position—projecting or pulled back, as shown in  FIG. 17 . These alternating movements of the piston holders  70 ,  70 ′ or the holding blocks  72 ,  72 ′ can thus be carried out to operate the pump without displacing the opening slide  57  in the direction of the pump unit  20 . 
     But when the shafts  47 ,  47 ′ are driven in such a way that both piston holders  70 ,  70 ′ or holding blocks  72 ,  72 ′ run side by side, the rocker  62  cannot be avoided during displacement (in the direction of the pump unit  20 ), so that both holding blocks  72 ,  72 ′ engage simultaneously with both holding tongues  64 ,  64 ′. As a result the opening slide  57  is pushed against the force of the spring  58  in its elongated holes  60 ,  60 ′ in the direction of the pump unit  50  when the piston holders  70 ,  70 ′ continue to move forward so that the opening tongue  61  slides over the opening ramps  55 ,  55 ′ thus forcing the jaw holders  52 ,  52 ′ apart. The engagement of the jaws  51 ,  51 ′ in relation to the lugs  46  on the pump unit  20  is released as a result. This opening of the holding device  50  thus occurs exclusively by means of the motors  11 ,  11 ′ and their corresponding control by means of the motor control  15 . 
     Below the effect or actuation of the clutch systems  13 ,  13 ′ is described in more detail with which the piston rods  25 ,  25 ′ are coupled to the piston holders  70 ,  70 ′ via their coupling projections  17 ,  17 ′. Attention is drawn in this respect to  FIGS. 13-21 . 
     The holding blocks  72 ,  72 ′ are screwed onto the shafts  47 ,  47 ′ as shown in  FIG. 15  and comprise insertion openings  77 ,  77 ′ into which the piston rods  25 ,  25 ′ can be inserted with their coupling projections  17 ,  17 ′. Springs  71 ,  71 ′ are attached to the holding blocks  72 ,  72 ′ in such a way that the spring ends  73 ,  73 ′ protrude into the insertion openings  77 ,  77 ′. The distance of the spring ends  73 ,  73 ′ is such that the piston rods  25 ,  25 ′ can be inserted into the insertion openings  77 ,  77 ′ with their coupling projections  17 ,  17 ′ and force the spring ends  73 ,  73 ′ apart until they snap shut behind the coupling projections  17 ,  17 ′. For this the coupling projections  17 ,  17 ′ have conical ends. After inserting the coupling projections  17 ,  17 ′ into the piston holders  70 ,  70 ′ the piston rods  25 ,  25 ′ are connected to the piston holders  70 ,  70 ′ and can neither be pushed nor pulled. 
     Between the displacement travel of the piston holders  70 ,  70 ′ or the holding blocks  72 ,  72 ′ a straddle lever  74  is attached on a swivel bearing  75  so that it can tilt, where on its upper and lower side it has straddle surfaces  76 ,  76 ′ on the side facing away from the pump unit  20 . On the other end, the end facing the pump unit  20 , swivel edges  78 ,  78 ′ are constructed on the straddle lever  74 . 
     The layout and dimensioning of the straddle lever  74  with its straddle surfaces  76 ,  76 ′ and swivel edges  78 ,  78 ′ is such that with alternating movements of the holding blocks  72 ,  72 ′ or piston holders  70 ,  70 ′, as shown in  FIGS. 13 and 17 , the straddle lever  74  is tilted either to one side or to the other side depending on which of the piston holders  70 ,  70 ′ or holding blocks  72 ,  72 ′ slide past it in the direction of the pump unit  20 . As result of this swivel action, the straddle surfaces  76 ,  76 ′ are swiveled in such a way that they do not engage with the spring ends  73 ,  73 ′ of the piston holder  70  or  70 ′ as they slide past. But when both piston holders  70 ,  70 ′ are pushed parallel next to each other in the direction of the pump unit  20  (see FIGS.  14  and  19 - 21 ) the straddle surfaces  76  or  76 ′ engage with the spring ends  73 ,  73 ′ (see in particular  FIGS. 20 and 21 ) so that these slide along on the (chamfered) straddle surface  76  or  76 ′ and are forced apart. As a result of this forcing apart the piston rods  25 ,  25 ′ previously attached to their coupling projections  17 ,  17 ′ (see holding position according to  FIG. 18 ) are released as shown in  FIG. 20 . After this with the same and simultaneous parallel movement of the piston holders  70 ,  70 ′ or holding blocks  72 ,  72 ′ the holding device  50  as well as the jaws  51 ,  51 ′ are forced open and thus their engagement with the lugs  46  of the pump unit  20  is released, the pump unit can be removed by the parallel displacement of the piston holders  70 ,  70 ′ as far as their front position facing the pump unit  20  without the user having to overcome any force. 
     The motor control  15  is furthermore constructed in such a way that after removal of a pump unit  20  from the pump actuating device  10 , both shafts  47 ,  47 ′ retract the piston holders  70 ,  70 ′. If the user inserts the pump unit  20  into the pump actuating unit  10 , it is only the force required for opening the holding device  50  that needs to be overcome. The piston rods  25 ,  25 ′ then protrude with their coupling projections  17 ,  17 ′ through the cylinder housing  56 ,  56 ′ into the pump actuating device  10 . The user can now control the motor  15  in such a way that the same moves the piston holders  70 ,  70 ′ in the direction of the pump unit  20  in a “coupling mode” until the coupling projections  17  or  17 ′ push apart the spring ends  73 ,  73 ′ and snap shut. This snapping process is carried out separately one after the other for both coupling projections  17  or  17 ′, so that the straddle lever  74  does not open the springs  71 ,  71 ′. 
     In disclosed embodiments, coupling of the pump unit  20  to the pump actuating device  10  is partially accomplished and decoupling is completely accomplished by means of the drive, which is provided for actuation of the pump itself. Separate drive devices are therefore not required to operate the pump actuation and the coupling/decoupling.