Abstract:
A directional valve for respiratory devices has a valve body and a valve seat whose contact surface with the valve body is primarily horizontal. In order to enhance and reinforce the directional valve&#39;s operation, the valve body contains a ferromagnetic material, preferably permanently magnetized, a coil is magnetically couplable to the valve body, a source of current is connected to the coil, and a control unit controls the source of current in order to regulate current through the coil to magnetically couple the coil to the valve body, in one or both of the closing and opening directions.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a directional valve suitable for use in respiratory devices, the directional valve being of the type having a valve body and a valve seat with the contact surface with the valve body being substantially horizontal. 
     2. Description of the Prior Art 
     Directional valves are used in respiratory devices, anaesthetic machines in particular, to channel the direction of gas flow. One directional valve is generally installed in the anaesthetic machine&#39;s inspiratory line and one directional valve in its expiratory line. Ideally, the directional valves should not affect expiratory resistance and inspiratory resistance for the patient nor interfere with measurements of flow in the anaesthetic machine. A conventional way to meet these conditions has been to devise directional valves with the lowest possible opening pressure. Such valves therefore generally are devised as disk valves, i.e. the directional valve has a disk-shaped valve body that rests loosely on a valve seat. 
     This type of directional valve has disadvantages. One disadvantage arises because moist gas is present in the anaesthetic machine. The valve body sometimes becomes wet, leading to surface tension that increases the opening pressure. 
     Other disadvantages are due to the shape of the valve body. If it is devised as a soft, lightweight disk, retrograde leakage could occur. Moreover, the valve body could be deformed enough by high back pressures to be pushed down into the valve opening. This would naturally be a serious problem, since the directional valve would then stop working. Retrograde leakage can be reduced by the use of a heavier directional valve, but this would naturally increase the valve&#39;s opening pressure, and the valve body might then start wobbling. Stiff valve bodies (usually ceramic disks) could start to leak because of the deposition of calcium particles etc. on the valve seat. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a directional valve that solves the aforementioned problems. 
     The above object is achieved in accordance with the principles of the present invention in a directional valve for a respiratory device, having a valve body and a valve seat, the contact surface of the valve seat with the valve body being substantially horizontal and the valve body containing ferromagnetic material, and the directional valve further having at least one coil which is magnetically couplable to the valve body, a source of current connected to the coil, and a control unit which regulates the current source to control the current through the coil so that the coil is magnetically coupled to the valve body in one or both of a closing direction and an opening direction. 
     When the valve body contains a ferromagnetic material and two coils are arranged with one coil on top of the valve body and one coil underneath the valve body, the valve body can be made to press against the valve seat or alternately lift off the valve seat by regulating the current flowing through the respective coils. 
     The directional valve can be operated as a servo system in an embodiment wherein the valve body contains a permanently magnetized material and a coil encircles the valve body and valve opening (to achieve the strongest possible magnetic coupling between the coil and the valve body). When the directional valve is to be in the closed position, a current is applied across the coil, generating a magnetic field that presses the valve body harder against the valve seat. This would accordingly reduce the risk of leakage. 
     When the directional valve is to be in the open position, the current is reversed, causing the electromagnetic field to lift the valve body. A minimal opening pressure is then achieved. 
     In the event of any loss of current, the directional valve would operate in the same way as a conventional directional valve. Directional valve operation is not interrupted. This is an important safety feature when the valve is used in anaesthetic machines and other respiratory devices. 
     Current through the coil is regulated from a source of current that is regulated, in turn, by a control unit. In principle, the control unit could regulate the source of current in such a way that directional valve operation parallels the respiratory device&#39;s inspiratory and expiratory phases. The directional valve in the inspiratory line would then be open during inspiration and closed during expiration (and the reverse for the directional valve in the expiratory line). This kind of simplified regulation is only possible in certain limited conditions, e.g. no bias flow is used and the patient is not breathing spontaneously. 
     More refined regulation, tailored to different phases of respiration, e.g. during anaesthesia, is possible. The control unit therefore can control the source of current by sensing the valve body&#39;s position. This can be achieved by inductive sensing of the coil. Alternatively, the EMF generated by the valve body&#39;s movements can be sensed and employed for controlling the source of current. Any deformation of the valve body can even be sensed from changes in inductance. 
     Other parameters can also be used for regulation, for example, the pressure gradient between the inlet and outlet sides of the directional valve and flow through the directional valve. These parameters can be obtained either by providing the directional valve with a pressure gauge or a flow meter or by utilizing measurement signals from existing pressure gauges or flow meters in the respiratory device. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a respiratory device incorporating directional valves according to the invention. 
     FIG. 2 shows a first embodiment of the inventive directional valve. 
     FIG. 3 shows a second embodiment of the inventive directional valve. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a respiratory device  2  connected to a patient  4 , in the conventional, known fashion, by an inspiratory line  6 , a patient line  8  and an expiratory line  10 . The respiratory device  2  can e.g. be an anaesthetic machine, and the patient line  8  can be a tracheal tube and Y-piece. 
     A first directional valve  12  is arranged in the inspiratory line  6  (or between the inspiratory line  12  and the patient line  8 ), and a second directional valve  14  is arranged in the expiratory line  10  (or between the expiratory line  10  and the patient line  8 ). 
     The function of the directional valves  12 ,  14  is mainly to achieve one-way passage of gas through the lines  6 ,  8 ,  10 ; therefore they must not allow any retrograde leakage. At the same time, it is undesirable for the directional valves  12 ,  14  to create any additional respiratory resistance for the patient  4  during inspiration and expiration. They must therefore open easily in the forward direction. 
     FIG. 2 shows a first embodiment of the first directional valve  12  (the second has an identical construction). In this instance, the inspiratory line  6  is connected to the inlet side of the first directional valve  12 , and the patient line  8  is connected to the outlet side of the first directional valve  12 . The first directional valve  12  has an essentially, horizontal valve seat  16 . A valve body  18  rests on the valve seat  16 . In this embodiment, the valve body  18  is disk-shaped, but other designs are possible. The surface of the valve body  18  in contact with the valve seat  16  is preferably made of a soft material. A hood  20  encircles the valve seat  16  and the valve body  18 . The hood  20  is preferably transparent to permit visual inspection by the operator. 
     A coil  22  surrounds part of the first directional valve  12  for magnetic coupling to the valve body  18  that contains, or consists of, a permanently magnetized ferromagnetic material. When a current is applied to the coil  22  from a source of current  24 , the valve body  18  is either pressed against the valve seat  16  or lifted off the valve seat  16 , depending on the direction of current in the coil. The basic functions of the directional valve  12  accordingly can be maintained without loss in the event of a power failure. This is extremely important to patient safety. 
     The source of current  24  is regulated by a control unit  26  on the basis of suitable control parameters. Some of these control parameters can be obtained from changes in EMF, induction etc. in the coil  22  occurring when the valve body  18  is affected by gases in the lines  6 ,  8 . Determination of these parameters can be performed by e.g. measuring voltage across the coil  22  with a voltmeter  28  and sending the measured value to the control unit  26 . (Alternatively or as a complement, current in the coil  22  can be measured inductively by sensor  48  and the measured value sent to the control unit  26 .) 
     Referring again to FIG.  1 . The control unit  26  in the depicted embodiment is integrated into the respiratory device  2  and controls a first source of current  24 A for regulating the first directional valve  12  and a second source of current  24 B for regulating the second directional valve  14 . Alternatively, a separate control unit (in the form of a microchip or the equivalent) can be integrated into the respective directional valves  12 ,  14 . 
     Additional opportunities for obtaining control parameters are provided with a first flow meter  30  in the inspiratory line  6 , a second flow meter  32  in the expiratory line  10 , a first pressure gauge  34  in the inspiratory line  6 , a second pressure gauge  36  in the patient line  8  and a third pressure gauge  38  in the expiratory line  10 . Flow through the respective directional valves  12 ,  14  or the pressure gradient between the inlet and outlet sides of the respective directional valves  12 ,  14  can be determined and used by the control unit  26  for regulating the directional valves  12 ,  14 . 
     The flow meters and pressure gauges  30 ,  32 ,  34 ,  36 ,  38  can be formed by components integrated into the directional valves  12 ,  14  or of components in the respiratory device  2  (or any combination thereof). 
     Regulation is suitably performed in such a way that the control unit  26 , via the sources of current  24 A,  24 B and with the aid of the parameters, regulates the directional valves  12 ,  14  by reinforcing their natural positions (open-closed) in every phase of the respiratory cycle. For many applications, the control unit  26  can suitably be supplied even with information from the respiratory device&#39;s control system on the respiratory cycles etc. Alternatively, the control unit  26  can even be an integral part of the control and regulatory system of the respiratory device  2 . 
     FIG. 3 shows a second embodiment of the directional valve  12 . As in the first embodiment, the inspiratory line  6  is connected to the inlet side of the directional valve  12 , and the patient line  8  is connected to the outlet side of the first directional valve  12 . The first directional valve  12  has a mainly horizontal valve seat  16 . A disk-shaped valve body  18  rests on the valve seat  16 . The valve body  18  preferably is made of a soft material at points at which it is in contact with the valve seat  16 . A hood  20  encircles the valve seat  16  and valve body  18 . The hood  20  is preferably transparent to permit visual inspection by the operator. 
     In this second embodiment, the direction valve  12  contains a first coil  40 , arranged below the valve body  18 , and a second coil  42 , arranged above the valve body  18 . The valve body contains, or consists of, a ferromagnetic material. 
     A current can be applied to the first coil  40  from a first source of current  44 , and a current can be applied to the second coil  42  from a second source of current  46 . The sources of current  44 ,  46  are regulated by a control unit  26  on the basis of suitable control parameters in the same way as in the first embodiment. These parameters can be obtained from a voltmeter  28 , straight from the sources of current  44 ,  46  or in some other way described above, such as with inductive sensors  48 . The sources of current  41 ,  46  in this embodiment are regulated differently, since current is alternately applied to the first coil  40  and the second coil  42  respectively. 
     Other embodiments of the directional valves are possible. For example, the coil(s) can be located in other ways with retention of the same functions. 
     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.