Abstract:
An air supply system comprises a compressed air generation device which is connected to a line system which conveys air and the capacity of which is a multiple of a nominal requirement for air used for medical purposes. The compressed air generation device is moreover connected via a line system to a low priority air consumer. To ensure that the air intended for medical purposes has priority, a device sensitive to pressure or volumetric flow rate is provided in the line system which conveys the air intended for medical purposes, which device restricts or shuts off the flow of air in the line system conveying the lower priority air when the pressure or the volumetric flow rate in the line system which conveys the air intended for medical purposes drops below a specific value.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to German Patent Application 10 2012 001 138.5 filed Jan. 22, 2012. The full disclosure of this earlier application is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to an air supply system for the medical sector and to a method for operating such a system. 
         [0004]    2. Description of Related Art 
         [0005]    In many countries multiply redundant systems are required for producing air which is used for clinical medical applications. In Germany, for example, triple redundancy is required. Triple redundancy means that the capacity of the compressed air generation device is three times the capacity for which the air supply system is designed in the medical application. 
         [0006]    In known air supply systems of the above-mentioned type, the capacity of the compressed air generation device remains largely unused. This means that air generation is associated with comparatively high costs. 
       SUMMARY OF THE INVENTION 
       [0007]    An object of the present invention is to provide an air supply system of the above-mentioned type and a method for the operation thereof with which more inexpensive operation is possible. 
         [0008]    Said object may be achieved with regard to the air supply system in that an air supply system for the medical sector is provided which comprises
       a) a compressed air generation device having an air generation capacity which is, for safety reasons, a multiple of a nominal requirement for air used for medical purposes;   b) a first line system connected to the compressed air generation device and configured to convey the air used for medical purposes;   c) at least one second line system connected to the compressed air generation device and connected to a lower priority air consumer so as to convey lower priority air to the lower priority air consumer; and   d) a monitoring and controlling device that
           is sensitive to pressure or volumetric flow rate in the first line system; and that   restricts air flow in the at least one second line system when the pressure or the volumetric flow rate in the first line system drops below a first specific value.   
               
 
         [0015]    The invention thus makes use of the compressed air generation device&#39;s redundant capacity at those times when it is not required in order to supply another consumer with compressed air. The latter compressed air is, however, of lower priority than the air used for medical purposes such that restricting or even cutting off flow has no serious disadvantages for the consumer, i.e. restricting or even cutting off flow is thus acceptable if the corresponding capacity of the redundant compressed air generation device is required for medical purposes, for example due to a fault. To state an example, in the event of a nominal requirement for air used for medical purposes of 500 litres per minute, it was previously necessary according to the prior art to provide a compressed air generation device with a capacity of 1500 litres per minute, meaning that the redundant capacity of 1000 litres per minute remained unused. According to the invention, however, the 1000 litres per minute of capacity which are not normally required for the medical application may now be used for the lower priority consumer until all or some of these 1000 litres are required for the medical application. Overall, this makes generating compressed air very much more inexpensive. 
         [0016]    In one advantageous embodiment of the air supply system, the lower priority air is supplied to a dental consumer. Hospital or similar facilities often have medical and dental consumers in relatively close proximity to one another. Dental consumers are typical of such lower priority consumers, in which reducing or even cutting off the compressed air supply may, if necessary, be accepted. 
         [0017]    The pressure-sensitive monitoring and controlling device conveniently comprises at least one pressure switch in the line system which conveys the air intended for medical purposes, and a controllable restrictor directly or indirectly actuatable by said pressure switch in the line system which conveys the lower priority air. “Direct” actuation would in particular be actuation which operates purely mechanically between the pressure switch and the restrictor. Indirect actuation would operate with electrical signals by means of an appropriate control device. 
         [0018]    It is particularly advantageous if the monitoring and controlling device sensitive to pressure or volumetric flow rate completely shuts off flow of air in the line system which conveys the lower priority air when the pressure or volumetric flow rate drops to a second specific value which is lower than the first value. In this development, air supply to the lower priority consumer is influenced in two steps: the air supply is firstly just restricted and only completely shut off if restriction is not sufficient. 
         [0019]    It is advisable for the monitoring and controlling device sensitive to pressure or volumetric flow rate to generate a warning signal when the pressure or volumetric flow rate drops below the first and/or second value. This warning signal may, on the one hand, be electronically processed and stored in order to document operation of the air supply system and permit fault analysis. On the other hand, the warning signal in the form of an acoustic and/or optical signal may indicate to operating personnel that a fault has occurred, so that said fault may be remedied. 
         [0020]    For safety reasons, an advantageous embodiment of the invention is one in which at least two series-connected restriction and/or shut-off valves are located in the line system which conveys the lower priority air. If one of these valves fails, functionality of the air supply system is nevertheless maintained. 
         [0021]    With regard to the method, the above-stated invention may be achieved by a method comprising the following steps:
       a) Providing an air supply system that is configured to be used for medical purposes and comprises, for safety reasons, a compressed air generation device having a capacity which is a multiple of a nominal requirement for air used for medical purposes;   b) Monitoring a pressure or a volumetric flow rate in a first line system which conveys the air used for medical purposes;   c) Branching off an air flow from the compressed air generation device and using the air flow for lower priority purposes, provided the pressure does not drop below a first specific value; and   d) Restricting the air flow for lower priority purposes when the pressure or the volumetric flow rate drops below the first specific value.       
 
         [0026]    The advantages of the method according to the invention correspond mutatis mutandis to the above-stated advantages of the air supply system according to the invention. The preferred developments of the method according to additional further embodiments of the present invention which also have their analogue in corresponding exemplary embodiments of the air supply system which have already been discussed above. 
         [0027]    One variant of the method according to the invention which merits particular mention is distinguished in that restriction and shutting off of flow in the line system which conveys the lower priority air is not ceased until the pressure or volumetric flow rate in the line system which conveys the air intended for medical purposes has risen above the first value and manual approval has been provided. Manual approval ensures that the air supply system only returns to normal operation once it has been ensured that the fault has been recognised by operating personnel and suitable action has been initiated. 
         [0028]    It is to be understood that the aspects and objects of the present invention described above may be combinable and that other advantages and aspects of the present invention will become apparent upon reading the following description of the drawing and detailed description of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    An exemplary embodiment of the invention is described in greater detail below with reference to the attached drawing in which  FIG. 1  is a schematic block chart of an air supply system for the medical sector. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0030]    While this invention is susceptible of embodiment in many different forms, there is shown in the drawing and will herein be described in detail one or more embodiments with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. 
         [0031]    Reference throughout this description to features, advantages, objects or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, any discussion of the features and advantages, and similar language, throughout this specification may, but does not necessarily, refer to the same embodiment. 
         [0032]    In one embodiment, the air supply system, denoted overall with reference numeral  1 , comprises three branches, namely an inlet branch  2 , a branch  3  for providing compressed air for medical purposes, hereinafter “medical branch” for short, and a branch  4  which generates compressed air for a dental consumer, hereinafter “dental branch” for short. The dental branch  4  here serves as an example of a branch in which compressed air is provided for purposes which are of a lower priority than the medical purposes and may thus in an emergency be supplied with compressed air with subordinate priority. 
         [0033]    The inlet branch  2  comprises those components which are conventional for compressed air supply systems, namely a compressor unit  5 , which draws air in from the atmosphere via a line  6  and compresses it, for example, to 12 bar, and a first air treatment unit  7 , to which the compressed air from the compressor unit  5  is supplied via a line  8 . The compressor unit  5  may contain a plurality of compressors connected in parallel which can be switched on as a function of the requirement for compressed air. The first treatment unit  7  comprises a filter and a water separator and optionally a pressure accumulator. In the terminology of the claims, the inlet branch  3  constitutes a compressed air generation device. 
         [0034]    The air conditioned in this manner is supplied by the first treatment unit  7  to the medical branch  3  via a line  9 . It passes here firstly into a second treatment unit  10 , in which the air is for example doubly redundantly dried and has dust, dirt, other particles and aerosols removed from it with filters of various pore sizes. The compressed air which has in this way been made suitable for medical purposes passes via a further line  11  into a measurement device  12  in which various air parameters, in particular system pressure, dew point and optionally the concentrations of specific gases, are measured. Details in this respect are not of relevance in the present connection. 
         [0035]    The compressed air is supplied from the measurement device  12  via a bifurcating line  13  to two pressure-reducing valves  14 ,  15 . The pressure-reducing valves  14 ,  15  reduce the system pressure to two values, as are generally required in hospitals or similar facilities: pressure-reducing valve  14  delivers compressed air with a relatively high pressure of for example 8 bar to the line  16 , while pressure-reducing valve  15  delivers compressed air with a relatively low pressure, for example 6 bar, to the line  17 . These units are preferably of doubly redundant construction. 
         [0036]    The compressed air leaving the first treatment unit  7  is supplied not only via the line  9  to the medical branch  3  but also via a line  18  branched therefrom to the dental branch  4 . Branching at this point upstream of the second treatment device  10  ensures that the air supplied for medical purposes does not suffer microbial contamination. 
         [0037]    The dental branch  4  substantially comprises a pressure accumulator  19 , from which a line  20  passes to the dental consumer via three motor-actuated, for example magnetically or compressed air-actuated, valves  21 ,  22 ,  23 . Valve  21  is a restriction valve, while valves  22  and  23  are shut-off valves. The values used for this purpose are preferably 2/2 way NC valves which are closed when in the idle state. The function of these valves  21 ,  22 ,  23  will become clear further below. 
         [0038]    The system pressure, namely the pressure which prevails downstream from the first treatment unit ( 7 ), is monitored by three pressure switches  24 ,  25 ,  26 . The various pressure switches  24 ,  25 ,  26  respond at different pressure values: pressure switch  24  responds at 10 bar, while pressure switches  25  and  26  both respond at approx. 9.5 bar. It would also be conceivable for pressure switch  26  to have a response pressure which is somewhat lower than that of pressure switch  25 . 
         [0039]    Pressure switches  24 ,  25 ,  26  are functionally connected to the valves  21 ,  22 ,  23  via a control device  27 . The output signals from pressure switches  24 ,  25 ,  26  which are generated when the pressure at the respective pressure switches  24 ,  25 ,  26  drops below the response pressure are supplied via electrical lines  28 ,  29 ,  30  to the control device  27 . In turn, the latter actuates valves  21 ,  22 ,  23  via electrical lines  31 ,  32 ,  33  in the manner described further below. In addition, the control device  27  may also trigger an alarm device  35  via a line  34 . Finally, a manual confirmation device  36  is provided which is capable of transmitting a signal to the control device  27  via an electrical line  37 . 
         [0040]    The control device  27  is now programmed such that the pressure switches  24 ,  25 ,  26 , the valves  21 ,  22 ,  23 , the alarm device  35  and the manual confirmation device  36  interact as follows in various operating states of the compressed air supply system  1 : 
         [0041]    The starting point for consideration may be an operating state in which the system pressure in lines  9  and  18  is above the response pressure of pressure switch  24 , for example at 12 bar. This means that sufficient compressed air, which may be delivered via lines  16 ,  17 , is available for medical purposes. Valves  21 ,  22 ,  23  are open and permit unhindered passage of air to the dental consumer, which has a maximum air consumption of less than ⅔ of the generation capacity. 
         [0042]    If the system pressure  9  now drops due to increasing quantities of compressed air being drawn off, whether via the medical branch  3  or the dental branch  4 , said pressure drop is firstly identified in the measurement device  12 . Providing the system pressure remains above the response pressure of the first pressure switch  24 , namely in the case of the numerical values stated above by way of example of between 11 and 12 bar, system pressure is firstly restored by successively switching on all the compressors in the compressor unit  5 . 
         [0043]    In the example, the installation is dimensioned such that the medical branch  3  consumes approx. ⅓ and the dental branch  4  approx. ⅔ of the maximum possible generation capacity. If there are no faults in either of the two branches  3 ,  4 , maximum possible consumption is less than the delivery capacity, such that the necessary system pressure may be maintained. 
         [0044]    If, due to a fault in one of the consumer branches, withdrawal of compressed air rises further or if there is a fault in the generator unit and the consequent drop in system pressure can no longer be compensated in the compressor unit  5 , the first pressure switch  24  responds at the pressure of 9.5 bar which has already been mentioned and transmits a signal to the control device  27 . The latter in turn activates the restriction portion of the restricting first valve  21  via the electrical line  31 , such that withdrawal of compressed air via the dental branch  4  is at first reduced. If the system pressure in line  9  builds back up during flow restriction, pressure switch  24  stops transmitting its signal to the control device  27 ; via the electrical line  31 , the control device  27  effects displacement of the gate of the valve  21  and the passage portion of the valve  21 , which does not restrict flow, is introduced into the line  20 . This process involving the response of the pressure valve  24  and actuation of the first valve  21  may be documented by storing corresponding warning signals and may optionally be forwarded to a higher-level controller for further processing. 
         [0045]    If the system pressure in the line  9  does not any longer build up to the required value even when withdrawal of dental air is restricted by appropriate switching of the valve  21 , but instead continues to drop further below the response pressure of pressure switches  25 ,  26 , namely in the present example below 9.5 bar, these pressure switches  25 ,  26  apply corresponding signals to the control device  27  via the electrical lines  29  and  30 . Said control device, acting via the electrical lines  32  and  33 , causes the valves  22 ,  23  to close. At this point, no further compressed air may be withdrawn for dental purposes. At the same time, the alarm device  35  is actuated, such that operating personnel are alerted to the fault. 
         [0046]    For safety reasons, the valves  22 ,  23  are no longer opened automatically even when the system pressure in line  9  rises again and exceeds the response pressure of pressure switches  25 ,  26 . Even when the response pressure of the first pressure switch  24 , namely 10 bar, is reached and exceeded, the control device  27  no longer switches the valves  21 ,  22 ,  23  into the open position. Instead, this only occurs once an approval signal is supplied to the control device  27  by manual actuation of the manual confirmation device  36 . The approval signal then causes valves  21 ,  22 ,  23  to open and so allows the compressed air supply device  1  to return to normal operation. 
         [0047]    It is to be understood that additional embodiments of the present invention described herein may be contemplated by one of ordinary skill in the art and that the scope of the present invention is not limited to the embodiments disclosed. While specific embodiments of the present invention have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying claims.