Abstract:
A wick for an anesthetic evaporator is provided as a dimensionally stable wick body ( 14 ) transporting anesthetic by means of capillary force is provided. The wick body comprises a hollow cylinder as well as webs by which a gas-carrying cavity is formed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2008 045 081.2 filed Aug. 29, 2008, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a wick for an anesthetic evaporator. 
       BACKGROUND OF THE INVENTION 
       [0003]    Anesthetic evaporators for dispensing anesthetics frequently operate according to the “bypass principle,” according to which a partial gas flow is branched off from a bypass line connecting the evaporator inlet and the evaporator outlet and is enriched with anesthetic vapor in an evaporator chamber. The partial gas flow enriched with anesthetic vapor is again mixed at the evaporator outlet with the gas flow flowing through the bypass line via a dispensing valve, which is connected to a setting wheel for setting the concentration of the anesthetic released. Helically arranged wick tubes, through which the partial gas flow is passed, are used to evaporate the anesthetic in the evaporator chamber. A tubular wick jacket, which presses the wick tube onto a wick holder, on the one hand, and dips with its free end into the liquid anesthetic, on the other hand, and transports anesthetic to the wick tubes by capillary action, is pulled over the wick tubes. On the way through the wick tube, the partial gas flow is enriched with anesthetic vapor up to the saturation limit. An anesthetic evaporator of this type is known from DE 25 07 262 B (corresponding to U.S. Pat. No. 4,075,297 which is incorporated by reference). 
         [0004]    A wick tube as is used in the prior-art anesthetic evaporator can be manufactured at a high cost and requires a rather substantial manufacturing effort. Thus, wick material must at first be placed around a coil and fastened in the wick tube. The wick tube is then placed round the wick holder of the anesthetic evaporator such that the gas inlet for the partial gas flow into the evaporator chamber is located at the beginning of the wick tube and is not obstructed by wick material. When the wick jacket is subsequently pushed over the wick tube, the wick tube must not be displaced in relation to the wick holder. 
       SUMMARY OF THE INVENTION 
       [0005]    The basic object of the present invention is to improve a wick of this type such that it can be manufactured at a low cost and can be mounted in a simple manner. 
         [0006]    According to the invention, a wick is provided for an anesthetic evaporator. The wick comprises a dimensionally stable wick body transporting anesthetic by means of capillary force. 
         [0007]    According to another aspect of the invention, a wick is provided for an anesthetic evaporator. The wick comprises a dimensionally stable wick body including porous means for transporting anesthetic by means of capillary force. The dimensionally stable wick body defines a gas cavity for passage of gas through the porous means for saturation of gas with transported anesthetic. 
         [0008]    The wick body may advantageously comprise a hollow cylinder. The gas cavity may advantageously be defined by webs made in one piece with the wick body. 
         [0009]    According to another further aspect of the invention, an anesthetic evaporator is provided comprising an evaporator pot defining an evaporator chamber and a compensator with an evaporator chamber gas inlet and a dispensing gas passage leading from the evaporator chamber. A wick is provided adjacent to the evaporator pot and the compensator, the wick comprising a dimensionally stable wick body including porous means for transporting anesthetic by means of capillary force and with the dimensionally stable wick body defining a gas cavity for passage of gas through the porous means for saturation of gas with transported anesthetic. 
         [0010]    The advantage of the present invention is the design of the wick as a preferably one-piece, porous, dimensionally stable wick body, which can be directly connected to the corresponding connection component of the anesthetic evaporator. It is especially advantageous according to the invention to make gas ducts for passing through breathing gas in one piece with the wick body. The gas ducts are formed by webs, which are arranged either on the outside or on the inside of the wick body and are preferably manufactured as one assembly unit with the wick body. The gas ducts preferably extend helically at the wick body. However, routing the gas via a plurality of gas ducts, which are located one on top of another and are connected to each other, is possible as well. The wick body is preferably designed as a hollow cylinder or as a solid cylinder. 
         [0011]    Other advantages of the wick according to the present invention are improved space utilization within the anesthetic evaporator, smoother surfaces to reduce flow resistances, simpler mounting and better thermal coupling of the wick body with the compensator of the anesthetic evaporator, with which the temperature effect is compensated. 
         [0012]    It is especially advantageous that the wick body according to the present invention including the gas ducts can be manufactured from one piece. It may be an injection molding manufactured in a mold or a sintered shaped wick part. The gas-carrying area is formed here by a helical recess in the form of a groove in the shaped wick part. The liquid transport takes place by capillary action within the porous material. The capillary action can be varied by varying the density and the thickness of the wick body. As an alternative, the wick body may also be manufactured as a foam part or foamed part. Materials that are resistant to the anesthetics used are to be selected as the material for the wick body. Especially suitable are polyethylene, polypropylene, polytetrafluoroethylene, polyamide, special steel or even mixtures of these materials. Depending on the anesthetic used, bronze, copper, brass as well as sintered glass or sintered ceramic materials are suitable as well. The wick body is manufactured such that a sintered material is pressed from a preferably spherical granular product. The sintered compact is dimensioned such that its mean or typical pore size has a value of less than or equal to 30 μm. As an alternative to granular material, the wick body may also consist of an agglomeration of fine wires or fiber-like materials. 
         [0013]    It is especially advantageous to arrange sealing lips, which come into contact either with the evaporator pot in the case of webs located on the outside or with the wick holder in case of webs located on the inside or with the compensator, at the webs pointing outwardly or inwardly, with which the gas ducts are formed. Gas tightness of the gas-carrying ducts against the evaporator pot or the wick holder or compensator is achieved in this manner so that the gas flows all the way through the gas ducts rather than flowing past the gas ducts at right angles to the longitudinal axis. Improvement of anesthetic uptake can be achieved by arranging obstacles within the gas ducts, because a turbulent flow develops as a result. 
         [0014]    Gas-carrying ducts are provided within the wick body in another advantageous embodiment in order to enrich the gas flow with anesthetic vapor. Since the gas-carrying ducts are surrounded by the wick material on all sides in this embodiment, especially good saturation with anesthetic vapor is achieved. 
         [0015]    One exemplary embodiment of the present invention is shown in the figures and will be explained in more detail below. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    In the drawings: 
           [0017]      FIG. 1  is a schematic longitudinal sectional view of an anesthetic evaporator according to the invention; 
           [0018]      FIG. 2  is a view showing a wick body with gas-carrying ducts located on the inside as well as the evaporator pot and compensator of an anesthetic evaporator, according to an embodiment of the invention; and 
           [0019]      FIG. 3  is a view showing a wick body with gas-carrying ducts located on the outside as well as the evaporator pot and compensator of an anesthetic evaporator, according to another embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Referring to the drawings in particular,  FIG. 1  schematically shows an anesthetic evaporator according to the invention. An evaporator pot  5  defines an evaporator chamber  6 , The evaporator pot  5  is located under an evaporator upper part  2  with a dispensing cone  3  for dispensing breathing gas saturated with anesthetic vapor and with a setting wheel  4  connected to the dispensing cone  3 . The invention provides an anesthetic evaporator wick structure  100  comprised of a cylindrical wick body ( 14 ,  21 ) and helically extending cavity  16  (shown schematically as a vertically extending box in  FIG. 1 ) described below. The dimensionally stable wick body  14 ,  21  is porous and transports anesthetic by means of capillary force. The evaporator wick structure  100 , namely the cylindrical wick body  14 ,  21  is designed in terms of its principal geometry as a hollow cylinder. 
         [0021]    The anesthetic evaporator wick structure  100  is provided radially outwardly of a compensator  8  and extends into the evaporator chamber  6 . The anesthetic evaporator wick structure  100  dips into liquid anesthetic  11  in the chamber  6 . The anesthetic  11  is transported by capillary transport to the helically extending cavity  16  . The breathing gas to be enriched with anesthetic helically extending cavity  16  via the evaporator chamber inlet bore  7  and leaves same via an outlet opening  13 . 
         [0022]      FIG. 2  shows a longitudinal section of a cylindrical wick body  14  according to the present invention, which is designed as a hollow cylinder. The wick body  14  has, on its inside, helically extending webs  15 , by which the likewise helically extending cavity  16  is formed, which acts as a gas duct for the breathing gas to be enriched with anesthetic  11 . Sealing lips  17 , which are in contact with the compensator  8 , are arranged at the free ends of the webs  15 . The outer surface  18  of the wick body  14  is in contact with the evaporator pot  5 . The underside  19  of the wick body  14  dips into the anesthetic  1   1 , and is brought by capillary transport within the wick body  14  into the area of the webs  15 . The breathing gas flows, beginning from the evaporator chamber inlet bore  7 , through the cavity  16  and into the evaporator chamber  6 ,  FIG. 1 . 
         [0023]      FIG. 3  shows an alternative embodiment of a wick body  21 , in which the webs  15 , which form the gas ducts, are arranged on the outside of the wick body  21 . The inner surface  20  of the alternative wick body  21  is in contact with compensator  8 ,  FIG. 1 . The free ends of the webs  15  have sealing lips  17 , which are in contact with the evaporator pot  5 . Gas tightness of the cavity  16  against the evaporator chamber  6  is thus achieved. 
         [0024]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.