Not applicable.
Not applicable.
Not applicable.
The invention relates to a medical pump, in particular for water jet surgery.
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.
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.
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.
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.
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.
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.
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.
The valve devices can also comprise two spring-loaded ball check valves, which again are simple to produce.
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.
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.
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.
The valve devices and/or pressure control valve are preferably housed in the cylinder head. This results in a simpler setup containing fewer parts.
It is preferred that the cylinders are connected independently to the cylinder head. This simplifies manufacture.
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.
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.
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.
Embodiments of the invention will now be described by way of example with reference to the accompanying drawings.
The same reference numbers will be used for the same parts and parts with the same function.
A pump actuation device 10 is intended for the embodiment of the invention shown in
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.
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.
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.
The embodiment of the invention shown in
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.
The embodiment shown in
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
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′.
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.
From
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.
Number | Date | Country | Kind |
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10 2004 031 673.2 | Jun 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP05/06755 | 6/22/2005 | WO | 00 | 12/22/2006 |