Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1999-12-21
2001-03-20
Yasko, John D. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S070000, C604S140000
Reexamination Certificate
active
06203521
ABSTRACT:
This application claims priority of German Patent Application Number 198 59 135.7-35, filed Dec. 21, 1998, the entire disclosure of which is considered to be part of the present disclosure and is specifically incorporated by reference herein.
The present invention relates to an ejection device for the high-pressure ejection of a liquid or a liquid containing solid particles, comprising a pressure chamber wherein the liquid is received and which opens into an ejection opening and is delimited by a working piston which, upon application of a preferably elastic impact on its end facing away from the pressure chamber, is capable of transmitting a compression wave which may displace the pressure chamber-facing end of the working piston by a predetermined displacement stroke into the pressure chamber so that the volume thereof is reduced. The reduction in volume of the pressure chamber is significantly smaller than the volume of the pressure chamber. Further, the ejection device comprises a drive member which is capable of generating the elastic impact.
An ejection device of the above described type is known, for example, from EP 0 771 219, which describes said device as being specially designed for the ejection of precisely dosed, minute amounts of liquid, which may be in the range of cubic millimeters, so that it is particularly well-suited as a medical instrument for the injecton of minute doses of liquid drugs which are to be administered with high precision.
The ejection of such small amounts of liquid is achieved by the drive member transmitting only an elastic impact to the working piston so that the latter is not moved any further into the pressure chamber. That is, after having transmitted the impact, the drive member no longer exerts any external driving force upon the working piston so that the amount of liquid contained in the pressure chamber and defined by the working piston is not ejected in the way it would in a common syringe, but exclusively by means of the compression wave which is excited by the impact transmitted through the working piston. The working piston transmits a high-pressure pulse into the liquid present in the pressure chamber which causes the liquid to be ejected from the ejection opening at high pressure. The ejection pressure, and thus the volume or amount of liquid being ejected, may be precisely controlled by suitably adjusting the velocity of the drive member since said velocity determines the magnitude of the impact which is transmitted.
According to the ejection device described in EP 0 771 219, the volume of the pressure chamber considerably exceeds the stroke volume of the working piston so that a small, precisely dosed amount of liquid may be ejected regardless of the actual size of the pressure chamber.
To prevent the drive member from exerting any external force on the working piston after the impact has been transmitted, it is possible, for example, to stop the application of a driving force acting on the drive member towards the working piston as soon as the transmission of the impact starts, or to provide a stopper which prevents the drive member from exerting any force on the working piston after the impact has been transmitted.
The working piston is preferably made of a solid material which may transmit elastic shock waves with as little loss as possible, such as a metallic material. The drive member may be any impact-transmitting component, for example a drive piston, which may be accelerated within a drive pipe and is preferably coaxially aligned with the working piston. However, the drive member may also be designed other than as a piston, for example as a plate or a rocker arm which strikes on the working piston so that a driving impact is exerted thereupon.
The drive member may be moved pneumatically, hydraulically, mechanically, or electromagnetically, for example. The means driving the drive member may be designed such that they enable only a single working stroke of the drive member. However, the drive member may preferably be driven such that it successively transmits periodically repeated impact pulses so that the total amount of liquid being ejected may be controlled by suitably adjusting the number of repetitions. Preferably, the drive member is provided as a component which may be moved across an acceleration portion.
In the periodically operating ejection device described in EP 0 771 219, the working piston is returned to its starting position, i.e. the position it had prior to the elastic impact, after the liquid has been ejected, which is caused by the reflection of the elastic shock wave at the free end of the piston as well as by the reflection of the compression wave at the ejection end of the pressure chamber. The subsequent pressure drop in the pressure chamber resulting from said return motion causes liquid to be sucked into the chamber from a reservoir so that the device is immediately ready for the next ejection, thus enabling the successive ejection of predetermined doses of liquid.
The present invention provides an ejection device of the initially mentioned type which may be periodically operated independently of any liquid supply.
The ejection device according to the present invention is designed such that after the displacement of its leading end, the working piston is not returned to its starting position, i.e. the position it had before the transmission of the impact, but is progressively displaced into the pressure chamber by the repeated application of elastic impacts, with the distance of each single displacement being defined by the predetermined displacement stroke.
In the ejection device according to the present invention, the compression wave propagating through the working piston as the result of each impact transmitted thereto causes the working piston to be displaced into the pressure chamber by a certain distance, i.e. the predetermined displacement stroke, so that liquid is being ejected. The liquid supply is the amount of liquid initially present in the pressure chamber, which is then gradually squirted out from the pressure chamber. Thus, the pressure chamber of the ejection device according to the present invention is simultaneously used as a liquid supply chamber so that it is not necessary to provide an additional reservoir including supply lines to connect the reservoir to the pressure chamber, or any check valves to prevent the liquid in the pressure chamber from returning to the reservoir.
To prevent that the working piston reverses its motion and is pushed out of the pressure chamber as a result of the pressure increase in the pressure chamber and of the compression wave being to some extent reflected, which would result in air being sucked into the pressure chamber and thus render the operation of the device inaccurate, the masses of the movable components as well as the impact velocity of the drive member may be adjusted such that substantially the entire amount of impact strength is consumed for ejecting the liquid. Therefore, the frictional forces created between the working piston and its surrounding wall portions are sufficient to hold the working piston in its respective displaced position. Further, a check valve may be provided in the fluid connection between the pressure chamber and the ejection opening which enables the ejection of fluid while preventing air from being sucked into the pressure chamber. In this way, any reverse motion of the working piston is prevented.
Preferably, the ejection device according to the present invention is provided with linear reverse stopping means to support the working piston so that any reverse displacement thereof is prevented.
The linear reverse stopping means permit the movement of the working piston into the pressure chamber while blocking any reverse motion thereof caused by the compression wave being to some extent reflected at the end of the working piston facing the pressure chamber. In this way, the working piston is more reliably retained at the position it has at the end of the ejection process after the ejection process is ov
Menne Andreas
Merkle Wolfgang
Ferton Holding SA
Griffin & Szipl, P.C.
Yasko John D.
LandOfFree
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