Patent Application
20110100362
The invention relates to the technical field of gas mixers. Specifically, the invention relates to gas mixers used for the artificial respiration of patients.
As a rule, gas mixers conventionally used in the field of intensive medicine are based on complex mechanical pressure controllers (Dräger, and others), which are adjusted by means of mechanical rotary switches. Alone an adjustment error thereof is frequently greater than the required accuracy in the gas mixture.
Flow controllers as a combination of gas flow sensor and proportional valve are known and customary in the trade. Gas mixers or gas dosing devices as parallel connection of flow controllers are known as discrete assemblies.
It is the object of the invention to provide a compact pneumatic shunt resistance and a compact gas mixer.
This object is achieved with the subject matters of the independent claims.
Preferred embodiments of the invention are defined in the dependent claims.
An advantage of a flow through a gap is that the flow is laminar. This results in a characteristic curve which is linear over large regions.
An advantage of the use of a gap between a cylindrical measurement cavity and a cylindrical resistor is the easy manufacturability, for example, by drilling, injection molding or turning.
A gap of a uniform width advantageously permits a large linear region. Advantageously, this is achieved with the coincidence of the rotational axes of the resistor and the measurement cavity.
If the resistor is part of an insert, which is screwed into the block by means of a thread, the flow resistance of the shunt resistance can be readily adapted to the requirements by different inserts.
An O-ring provides for the pressure tightness in an easy manner.
A gas mixer comprising a block with the most important pneumatic connections and to which as many valves and sensors as possible are directly fixed and pneumatically connected requires little space and is easy to mount because the number of tubes is reduced as fewer tubes are required.
Advantageously, a pneumatic shunt resistance according to the invention can be integrated in the block of the gas mixer, thereby simplifying the adaptation of the gas mixer to gas sources which provide different pressures.
A sword insert provides for a fast and complete mixing of the gases to be mixed. This is particularly advantageous if gas sensors are used, so as to avoid faulty measurements.
The constriction together with a storage volume, which is connectable to the connection connected in parallel to the gas outlet, forms a pneumatic low pass, which increases the stability of the control loops, even if different amounts of gas are delivered at the outlet during the inspiration and the expiration.
Advantageously, an oxygen sensor can be calibrated with the aid of the synthetic air supplied thereto, and it can verify the oxygen concentration of the mixed gas upon switching over a corresponding switch valve.
The use of additional blocks advantageously permits the adaptation of the gas mixer to different requirements. By using like component parts in different apparatus the manufacturing costs can thus be reduced due to the larger scale manufacture.
With the aid of the second additional block it is advantageously possible to provide the upstream outlets with a specific pressure level from the basic block and to adjust a pressure or throughput level for the respirator connection separately.
A preferred embodiment of the invention will be explained in more detail below by means of the accompanying drawings. In the drawings:
In the section illustrated in
As compared to other flow resistances, the pneumatic shunt resistance according to the invention allows the formation of a laminar flow in a very easy manner. By replacing the insert 3 by another insert having a cylinder 13 with a slightly different radius the dimension of gap 5 can be adapted to the flow range, so that a high variability is obtained without having to make alterations to block 2.
The basic adaptation is accomplished by the choice of the measurement bore 6 relative to the gas-containing bore 4.
The pressure drop can be sensed at the measurement bore 6 through cross holes 12, sensor connection bores 11 and sensor connections 10. To the sensor connections 10 either a flow sensor or a differential pressure sensor may be connected, which extends the pneumatic shunt resistance 1 to a flow sensor.
The gas mixer comprises a basic module 109, a first additional module 139 as well as a second additional module 169. The core pieces of the modules are comprised of a basic block 110, a first additional block 140 and a second additional block 170, respectively. The implementation in milled and drilled blocks, e.g. of anodized aluminum, guarantees a compact construction. The required but non-illustrated circuit board is situated in parallel with respect to and directly below the blocks. The assembly time is significantly reduced as compared to discretely constructed gas mixers because the gas mixer according to the invention requires fewer tubes for connecting the required valves and sensors by tubes.
In the simplest embodiment the gas mixer is comprised of a basic module in which the mixing of two gas flows is realized.
The oxygen connection 111 is, as the name implies, provided for the connection to oxygen. At air connection 121 artificial air or air compressed by a compressor is supplied. In the embodiment shown in
Each of the two gas flows first passes through a pressure sensor 112 and 122, respectively, in which the pressure on the oxygen connection 111 and the air connection 121, respectively is measured. Then, each gas flow passes through a combination of a proportional valve 113 and 123, respectively, and a gas flow sensor 114, 115, 116, 117 and 124, 125, 126, 127, respectively. Each gas flow sensor is comprised of a pneumatic shunt resistance as was explained by means of
Next, the two gas flows are mixed in the cross hole, in which a sword insert 133 is provided. To achieve a good and fast mixing, the sword insert 133 causes the gas coming from the air connection 121 to flow first to the left in the upper half (compare
If two gas flows each having a constant flow are joined, a new gas flow likewise having a constant flow is created. Alternatively it is also possible to adjust a specific target pressure at the gas outlet 137 by means of a pressure sensor 138 mounted at the mixing location.
By a connection 135 a non-illustrated compensation reservoir may be connected so that the constriction 136 and the compensation reservoir form a pneumatic low pass. This low pass reduces cross interferences affecting the control loops if, for example, during the inspiration and expiration different amounts of gas are delivered at the gas outlet 137.
The valves for the airway and the inserts 117 and 127 may be exchanged depending on the case of application, thereby permitting an optimum control of both the supply of compressed air from the bottle or the hospital system (2-7 bar) and poorly compressed air from a compressor (150 mbar).
On the inlet side a first additional module 139 may be mounted, by means of which, as an alternative to air, up to two other gases may be connected simultaneously, e.g. nitrous oxide at the nitrous oxide connection 141 or inert gas such as helium or xenon at the inert gas connection 151. By means of the pressure sensors 143 and 153, respectively, which are connected by the connections 142 and 152, respectively, the input pressure may be verified, for example, to indicate an empty gas bottle by means of an alarm. A series connection of switch valves 144 and 145 makes sure that always only one of the three gases is mixed with oxygen. If the first additional module 139 is connected, the airway is interrupted by an interrupter 130 to avoid a pneumatic short-circuit of the switch valve 145. If the first additional module 139 is not necessary, the connection openings in the basic block are tightly sealed.
Instead of the first additional module 139 a valve 131 and a connection for an oxygen sensor 132 may be mounted on the basic block 110. Merely because of the dimensions of the components is it impossible in the currently considered embodiment of basic block 110 to mount both the valve 131 and the first additional module 139 simultaneously. This is why
A second additional module 169 with the second additional block 170 can be connected on the outlet side. The second additional module 169, again, includes a gas flow sensor comprising the pneumatic shunt resistance according to the invention with insert 178, a flow sensor outlet 175 and a flow sensor inlet 176, to which a flow sensor 177 may be connected, a proportional valve 174 and a connection 185 for a pressure sensor 179 to allow the adjustment of the flow to or the pressure at the respirator connection 187 independently of the flow through and pressure at the gas outlet 137.
Besides, the second additional module 169 has an injector connection 186, which may directly be supplied with gas from the oxygen connection 111 or the air connection 121 via the valve 173 and the switch valve 134. Alternatively, the flow through the injector connection 186 can be limited by a valve 172 and a capillary 171. The capillary may have an opening, for example, of 0.3 mm.
Moreover, the second additional module 169 includes a hand-operated respirator connection 188, which may be connected by a valve 181 to the gas outlet 137. Finally, the second additional module 169 includes a nebulizer connection 189, which may connected by a capillary 184 and a valve 183 to the gas outlet 137. The capillary 184 may have an opening, for example, of 0.8 mm.
In one embodiment, the pressure sensors 112, 122, 138, 143, 153 have a measurement range of 0 to 7 bar. In this embodiment the pressure sensor 179 has a measurement range of 0 to 300 mbar. The valves 131, 172, 173 and 183 have a nominal width of 0.7 mm. The valves 134, 144, 145 and 181 have a nominal width of 1.5 mm.
The gas mixer was developed for the production of gas mixtures for respiration, but can be applied for plenty of other gas mixture functions.
The invention was explained in more detail by means of preferred embodiments above. A person skilled in the art will appreciate, however, that various alterations and modifications may be made without departing from the spirit of the invention. Therefore, the scope of protection will be defined by the accompanying claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 038 349.1 | Aug 2005 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE2006/001352 | 8/2/2006 | WO | 00 | 4/21/2010 |
