Abstract:
An expiration cassette is removably insertable in a receiving section of a ventilator and contains a gas passage, an expiratory valve and a flow meter. The expiratory cassette also has a locking mechanism for locking and unlocking interaction with a receiving section in the ventilator.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an expiration cassette for a ventilator. 
     2. Description of the Prior Art 
     One problem encountered with ventilators involves their disassembly for cleaning and subsequent re-assembly. This particularly concerns the ventilators expiration section that can include an expiratory valve, a flow meter, a pressure gauge, filters etc. 
     A simple, sturdy device, allowing replacement of the expiratory components for cleaning in a simple operation, is therefore needed. Ensuring correct reassembly of the cleaned ventilator parts after cleaning (or of dean parts) is also important in this context. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to achieve a device which solves the above need. 
     The above object is achieved in accordance with the principles of the present invention in a expiration cassette that is removably insertable in a receiving section of a ventilator, the expiration cassette having a gas passage, an expiratory valve and a flow meter, and further having a locking mechanism for locking and unlocking interaction with the receiving section in the ventilator. 
     Placing the desired components, such as a valve, flow meter, pressure gauge etc. for the ventilator&#39;s expiration section in a cassette reduces the need for disassembly for cleaning. The entire cassette is appropriately devised for cleaning as a single unit. The cassette itself is disassembled only in exceptional instances. 
     Correct insertion of the cassette into the ventilator is assured with a locking mechanism that interacts with a receiving section in the ventilator. 
     The locking mechanism in one preferred embodiment has a pushbutton on the top of the cassette. The pushbutton can move between an open position in which the cassette can be removed from the receiving section and a closed position in which the cassette is locked into the receiving section. A spring, or the equivalent, is arranged to act on the pushbutton with a force exerted toward the locking position. The pushbutton interacts with one boss or, preferably, two bosses that are mechanically connected to the pushbutton. In the pushbutton&#39;s locked position, the bosses project beyond the outer edge of the expiration cassette. In the pushbutton&#39;s open position, the bosses are inside the outer edge of the expiration cassette. The bosses interact with openings in the receiving section to lock the cassette in place. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a ventilator with an expiration cassette according to the invention. 
     FIG. 2 shows a locking mechanism in an expiration cassette interacting with a receiving section in the ventilator. 
     FIG. 3 shows the expiration cassette and receiving section of FIG. 2 from another angle. 
     FIG. 4 shows an alternative locking mechanism in the expiration cassette of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a ventilator  2  which can be connected to one or more gas sources via gas connections  4 A,  4 B. The gases can be regulated and mixed in a gas mixer  6  and passed through the inspiratory section  8  of the ventilator  2  to a first connection  10  for a breathing system (not shown). 
     It should be noted that the term ‘ventilator’ refers in principle to all types of apparatuses capable of providing breathing assistance, i.e. respirator, anaesthetic machines etc. 
     The ventilator  2  also has a second connection  12  for the breathing system, whereby gas is carried to the expiratory section of the ventilator  2  in which an expiration cassette  14  is arranged. The gas subsequently leaves the ventilator  2  through an evacuation  16 . 
     The expiration cassette  14  is equipped with a handle  18  to facilitate handling and a pushbutton  20  for disengaging the expiratory cassette  14 . The pushbutton  20  also serves as an indicator showing that the expiration cassette  14  is correctly connected to the respirator  2 . This function is described in greater detail in conjunction with FIG.  2 . 
     FIG. 2 schematically shows a locking mechanism to lock the expiration cassette  14  in a receiving section  22  in the ventilator. In addition to the pushbutton  20 , the locking mechanism includes a first boss  24 A and a second boss  24 B that respectively interact with a first opening  26 A and a second opening  26 B, a first mechanical coupling  28 A and a second mechanical coupling  28 B, a rod  30  and a spring  32 . The rod  30  is attached to the pushbutton  20  (or is an integral part of the pushbutton), and the movement of the pushbutton  20  is transmitted to the bosses  24 A,  24 B (whose movement is perpendicular to the direction of movement of the pushbutton  20 ) by the mechanical couplings  28 A,  28 B. 
     Transmission of the movement can be performed with any known mechanical transmission providing simultaneous movement of the pushbutton  20  and the bosses  24 A,  24 B (and vice-versa). Direct transmission is preferable; since friction-fit transmission could result in impaired functionality caused by e.g. wear etc. 
     A rack and pinion design has been indicated in the version shown in FIG.  2 . 
     The spring  32  strives to force the pushbutton  20  to assume its upper position (shown in FIG.  2 ), i.e. the locked position. 
     In disassembly, the pushbutton is depressed to its lower position, i.e. the open position, whereupon the bosses  24 A,  24 B are retracted inside the outer edge of the expiration cassette  14 , and the expiration cassette  14  can be removed. 
     When the expiration cassette  14  is inserted into the receiving section  22 , the bosses  24 A,  24 B are pressed inward by the walls of the receiving section  22 , whereupon the pushbutton  20  is forced down (towards its lower, open position). When the bosses  24 A,  24 B pass below the upper part of the openings  26 A,  26 B, they are forced into the openings because of the pressure of the spring  32  on the pushbutton  20 . The pushbutton  20  then assumes its upper position, thereby clearly indicating that the expiration cassette has been correctly inserted. 
     A gas passage  34  for gas flowing through the expiration cassette  14  is also shown in FIG.  2 . 
     FIG. 3 shows another feature of the expiration cassette  14 . FIG. 3 shows the expiration cassette  14  from the side, during insertion into or removal from the receiving section  22 . Here, the expiration cassette  14  is held by the handle  18 . 
     The receiving section  22  has a stop  36  arranged to interact with the rear end  38  of the expiration cassette  14 . In this instance, the locking mechanism (the boss  24 A is visible) is arranged at the front end  40  of the expiration cassette  14 . 
     The stop  36  prevents the rear end  28  of the expiration cassette  14  from being lifted out of the receiving section  22 . 
     At the same time, the bottom  42  of the receiving section  22  is devised with a raised area  44  (exaggerated in the figure). The raised area makes it necessary for some force to be used, when the expiration cassette  14  is inserted, before the bosses  24 A,  24 B are able to slip into the openings. This elastic tension therefore facilitates removal of the expiration cassette  14 , as its front end  40  is raised somewhat as soon as the pushbutton  20  is depressed to cause the bosses  24 A,  24 B to retract inside the outer edge of the expiration cassette  14 . 
     The gas passage  34 , an expiratory valve  46  and flow meter  48  contained in the cassette  14  are shown in FIG.  3 . 
     FIG. 4 shows an alternative version of the locking mechanism in the expiration cassette  14 . Components identical to those described above have the same designations. The alternative version has a pushbutton  20 , a rod  30 , a first boss (or piston)  24 A, a second boss  24 B, a first rotating body  50 A, a second rotating body  50 B and a leaf spring  52 . 
     When the pushbutton  20  is depressed, the leaf spring is pushed down, and the bosses  24 A,  24 B are rotated with the rotating bodies  50 A,  50 B. The bosses  24 A,  24 B are accordingly moved in toward the outer edge of the expiration cassette  14 , and the expiration cassette  14  can be detached. 
     When the expiration cassette  14  is inserted, the expiration cassette  14  is pressed down into the receiving section  22 . The bosses  24 A,  24 B are forced out to the outer edge of the expiration cassette  14 , and the pushbutton  20  is pulled down via the rotating bodies  50 A,  50 B and the leaf spring  52 . When the expiration cassette  14  has been pushed down far enough, the bosses  24 A,  24 B are moved out into the openings  26 A,  26 B by the leaf spring&#39;s  52  resilient force, and the pushbutton  20  is lifted to indicate a locked position for the expiration cassette  14 . 
     Other versions of the described embodiment can incorporate one boss instead of two. A single such boss can be arranged on the front of the expiration cassette. The pushbutton  20  can be arranged so it is raised in the locked position and on a level with the top of the expiration cassette in the open position. The pushbutton  20  can be replaced with a lever or the equivalent for achieving movement between two positions. Instead of having a raised area in the bottom of the receiving section, the bottom could instead be sloping or devised with spring-loaded rods that have to be depressed when an expiration cassette is connected. Alternatively, the expiration cassette can be devised with a raised area, a sloping area or an area with spring-loaded rods in order to achieve the effect of built-in elastic tension when the expiration cassette is inserted in the receiving section. As already noted, other mechanical systems for transmitting perpendicular motion can be utilized. 
     Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.