Abstract:
A heat therapy device including a care unit presenting a lying surface for supporting an infant, a hood which is moveable between a closed position covering the care unit and an opened position clearing the top of the care unit, a radiation heater arranged to irradiate the lying surface in the opened position of the hood, a convection heater, and control units which are configured and arranged to control the operation of the radiation and convection heaters, wherein the control units are configured and arranged to control the operation of the convection heater as a primary heater when the hood is in the closed position and to control the operation of the radiation heater as the primary heater when the hood is in the opened position.

Description:
FIELD OF THE INVENTION 
     The invention relates to a heat therapy device comprising a care unit having a lying surface for supporting an infant, a hood which is moveable between a closed position covering the care unit and an opened position clearing the top of the care unit, a radiation heating arranged such that it can irradiate the lying surface in the opened position of the hood, a convection heating, and control units which are configured and arranged to control the operation of the radiation and convection heatings, wherein the control units are configured and arranged to control the operation of the convection heating as a primary heating when the hood is in the closed position and to control the operation of the radiation heating as the primary heating when the hood is in the opened position. 
     BACKGROUND OF THE INVENTION 
     A heat therapy device of this kind is known from DE 20 2005 021 580 U1. The heat therapy device comprises a care unit having a lying surface for supporting an infant. Furthermore, a hood is provided which is moveable between a closed position covering the care unit and an opened position clearing the top of the care unit. Furthermore, a radiation heating is provided which can irradiate the lying surface of the care unit in the opened position of the hood. In addition, a convection heating is provided which serves to maintain the temperature within the care unit at a desired level when the hood is in the closed position. The operation of the radiation heating and the convection heating is controlled by control units. The control units are arranged such that the convection heating is controlled as a primary heating when the hood is closed and that the operation of the radiation heating is controlled as primary heating when the hood is in the opened position. In addition it is mentioned that the radiation heating may be heated up before the beginning of an opening step of the hood, in order to reach the desired temperature faster after the hood is opened. From U.S. 2002/0161276 A1 a heat therapy device is known which is arranged to pre-heat the convection heating before the hood is closed. 
     Such heat therapy devices are also referred to as “hybrids” which can operate as an incubator in the closed position of the hood and can be operated in the opened position of the hood for open therapy care. 
     Analytical investigations of the heat balance of an infant during the transition from the closed care to the open care mode or vice versa show that the infant cools off during opening of the hood because the air temperature and the air humidity are decreasing rapidly and because the warm, protecting walls of the hood are removed. 
     EP 1 124 403 B1 describes a heat therapy device. If the hood is in the closed position (incubator operation) the radiation heating is automatically switched off. Conversely, the convection heating is automatically switched off when the hood is lifted up. Furthermore, the radiation heating is, when it is initially switched on, operated with increased power for a given heating-up period, which increased power is larger than 100% of the nominal power of the lamp. This is disadvantageous because this reduces the lifetime of the radiation heating. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to adapt a heat therapy device of the above described type in such a manner that the cooling off of the infant during transition from opened to closed care mode and vice versa is minimized. 
     This object is solved by a heat therapy device according to the present invention. 
     According to the invention the control units are arranged such that, when the hood is closed, the radiation heating (heater) is operated in a standby mode, and that, when the hood is opened, the convection heating (heater) is operated in a standby mode. In this manner the operating temperature and a sufficient heating output is obtained very quickly by switching over between convection heating and radiation heating as the primary heating. In order to further accelerate a quick transition from convection heating to radiation heating or vice versa from the radiation heating to the convection heating, the control units are configured and adapted according to the invention such that with the beginning of the opening of the hood the radiation heating is operated at a given maximum heating output for a given heating-up period and such that after expiration of the heating-up period, a transition is made to the controlled operation of the radiation heating. Conversely the control units cause, after the beginning of the closing of the hood, that the convection heating is operated for a predetermined heating-up period at a given maximum convection heating output, and that after expiration of the heating-up period it is changed over to the controlled operation of the convection heating as the primary heating. 
     In any case the maximum radiation heating output and the maximum convection heating output do not exceed the maximum nominal heating output but are lower than or equal to the respective nominal output of the heatings. 
     In this manner the primary heating (radiation heating in the opened care mode and convection heating in the closed care mode) is brought to the desired heating output very quickly, wherein after this increased heating-up period or boost period the primary heating is caused to transit to an operation with a closed control loop in which the primary heating is controlled according to the desired temperature. With the heat therapy device according to the invention it is possible to keep the temperature change below ±0.5° C. upon changing the care mode. Thus, cooling down of a newborn baby is reduced compared to heat therapy devices of the prior art. 
     In a preferred embodiment the control units are configured and adapted to operate the radiation heating for a hood heating-up period which is shorter than the heating-up period of the convection heating, at an increased hood heating output in order to quickly raise the temperature of the hood, and to reduce the power input for the radiation heating after expiration of the hood heating-up period, and to operate the convection heating for the remaining heating-up period at a predetermined maximum convection heating output. In this manner the cooled-down hood is heated up while it is closed so that, when the hood reaches the closed position, it is already heated up. The hood heating-up period can be the same as the time period needed for closing the hood or may be longer. 
     In a preferred embodiment the control units are configured and adapted to reduce the power input to the convection heating during the heating-up period of the radiation heating such that the sum of the radiation heating output and the convection heating output does not exceed a predetermined threshold. 
     In a further preferred embodiment the control units are configured and adapted to reduce the power supply for the radiation heating during the heating-up period of the convection heating such that the sum of convection heating output and radiation heating output does not exceed a predetermined threshold. 
     In a preferred embodiment the convection heating is provided with a fan for distributing the heated air, wherein the control units are configured and adapted to reduce the power input to the fan during the heating-up period of the radiation heating. 
     When the control units are described in the present specification as “configured and adapted” to perform certain heating strategies this includes an adaption by programming or by provision of hard-wired control circuits or combinations of the options mentioned. 
     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 
       In the drawings: 
         FIG. 1  is a schematic block diagram of a heating therapy device; 
         FIG. 2  is a graphic view showing the heating outputs as a function of time during the transition from incubator operation with closed hood to open care with opened hood; 
         FIG. 3  is a graphic view showing the heating output as a function of time during the transition from open care of the heating therapy device to incubator operation with closed hood; 
         FIG. 3 a    is a graphic view showing the heating output as a function of time as in  FIG. 3  for an alternative embodiment; 
         FIG. 4  is a graphic view showing the number of revolutions of the fan as a function of time during the transition between incubator operation to open care and back to the incubator operation; and 
         FIG. 5  is a graphic view showing the heating output of the evaporator as a function of time during the transition from incubator operation to open care and back to incubator operation. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The heating therapy device as shown in  FIG. 1  has a mattress  5  which presents a lying surface and which is surrounded by side walls. The upper opening between the side walls may be closed by a hood  1  which is shown in  FIG. 1  both in the closed position as well as in the opened position and with an intermediate double arrow which indicates the transition from incubator operation to open care and vice versa. 
     When the hood is closed the convection heating (heater)  2  forms the primary heating source. The convection heating  2  is controlled by an air temperature controller  60 . An air temperature input unit  62  and an air temperature sensor  24  are connected to the air temperature controller  60 . When the hood  1  is closed the air temperature controller  60  controls the air temperature under the hood to the input desired air temperature value. 
     Furthermore, there is a radiation heating (heater)  4  which is mounted on a central column above the lying surface of the mattress  5 . The operation of the radiation heating  4  is controlled by skin temperature controller  80 . A skin temperature input unit  82  and a temperature-sensor  26  are connected to the skin temperature controller  80 . When the hood is in the opened position the skin temperature controller  80  controls the radiation heating  4  such that the desired temperature is maintained. 
     In the mattress  5  there is in addition a mattress heating  6  which is controlled by a mattress temperature controller  40 . A mattress temperature input unit  42  and a mattress temperature sensor  30  are connected to the mattress temperature controller  40 . 
     In addition a humidifier  7  is provided which is controlled by a humidity controller  50 . A humidity input unit  52  and a humidity sensor  22  are connected to the humidity controller  50 . 
     A skin temperature controller  80  is connected to the convection heating  2  and the radiation heating  4 , which skin temperature controller  80  coordinates the operation of the two heatings and into which a measuring value of the skin temperature sensor  26  as well as an input from the skin temperature input unit  82  are supplied. 
     Furthermore, a fan  8  belongs to the convection heating which is controlled by the venting controller  70 . 
     The control units are configured and adapted in the manner described in the following to control the operation of the heatings during the transition from incubator operation (closed hood) to open care and vice versa. 
       FIG. 2  shows the control of the heating output first in the incubator mode, then after opening of the hood  1  during a heating-up period and a subsequent phase of open care in which the heating output of the radiation heating  4  is controlled. According to the invention the radiation heating  4  is not switched off during incubator operation (closed hood), but is operated with a low predetermined heating output in a standby mode. During the incubator operation the output of the convection heating  2  is constant and indicated by the dashed line. Then a transition is to be performed from incubator operation to open care operation. For this purpose the hood  1  is moved away from its closed position over the lying surface so that the radiation cone of the radiation heating  4  is directed to the mattress  5  and is not obstructed by the hood. As shown in  FIG. 2 , at the beginning of the opening operation of the hood  1  the radiation heating  4  is operated during a predetermined heating-up period at a predetermined maximum radiation heating output. In this heating-up period the power supply to the convection heating  2  is reduced such that the sum of the reduced convection heating output and the maximum radiation heating output does not exceed a predetermined maximum total power P max . The heating-up period lasts longer than the opening operation of the hood  1 . After the heating-up period the radiation heating  4  is controlled by skin temperature controller  80 . During this period the radiation heating output slowly decreases and approaches a permanent operation value. At the same time the heating output of the convection heating  2  slowly increases to the level of the standby mode. 
       FIG. 3  illustrates the control of the heating output first in an open care phase in which the convection heating is operated at a low level in a standby mode, while the primary heating output is provided by the radiation heating  4 . During the transition to the incubator operation the hood  1  is brought into the closed position. At the same time, with the beginning of the closing movement of the hood, the convection heating is operated for a predetermined heating-up period with a predetermined maximum convection heating output, wherein in this example the heating-up period is somewhat longer than the time span for closing the hood. While the convection heating is operated at a maximum convection heating output the radiation heating is operated with reduced power such that the total heating output provided by the convection heating and the radiation heating does not exceed a predetermined value P max . After the end of the heating-up period the controller brings the convection heating again to a controlled operation in which the output of the convection heating is controlled by skin temperature controller  80 . Thereafter the heating output of the convection heating slowly decreases to an end value by the control of the heating output, while the heating output of the radiation heating  4  slowly increases to a predetermined value for the standby mode. 
     In the illustrated embodiment the heating output of the radiation heating  4  may also be controlled by a radiation heating controller  90  having a heating output input  92 . Likewise, the air temperature may be set via an air temperature input  62  to an air temperature controller  60  in order to control the convection heating based thereon alone. 
     The heat therapy device is further configured and adapted to reduce the number of revolutions of the fan while transitioning from incubator mode to open care mode to a predetermined standby mode value which is designated as RPM trans-STDBY  in  FIG. 4 . After termination of the open care phase the convection heating again undergoes the transition to a heating-up period with maximum heating output, wherein at the same time the number of revolutions of the fan is increased to the operation value, as shown in  FIG. 4 . 
     The heat therapy device is further adapted to decrease the heating output of an evaporator  7  for providing the desired air humidity to a standby level. At the beginning of the closing operation of the hood during the transition to the incubator operation the evaporator  7  is then operated for a predetermined time span at a maximum heating output value in order to bring the provided humidity to the desired value as fast as possible. After the predetermined time span with the maximum heating output of the evaporator the humidity controller  50  takes over control of the evaporator  7 , wherein the desired humidity is input to humidity input  52 . This operation mode of the evaporator during the transition from incubator operation to open care mode and vice versa is illustrated in  FIG. 5 . 
     In  FIG. 3 a    an alternative embodiment of the heating outputs as a function of time for a heat therapy device is shown during the transition from open care mode to incubator operation. In contrast to the embodiment of  FIG. 3  here the convection heating is brought to the maximum convection heating output only after expiration of a hood heating-up period, wherein during the hood heating-up period, which begins with the begin of the closing operation of the hood, the radiation heating is operated with increased heating output in order to directly heat up the hood during the transition to the incubator operation. The hood heating-up period is in the illustrated embodiment longer than the time span needed for the closing operation of the hood. During the hood heating-up period the convection heating is adjusted to a slightly decreased value compared to the standby mode such that the total heating power from the radiation heating and the convection heating does not exceed the maximum heating output. 
     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. 
     REFERENCES NUMERALS 
     
         
           1 . Hood 
           2 . Convection heating 
           4 . Radiation heating 
           5 . Mattress 
           6 . Mattress heating 
           7 . Humidifier 
           8 . Fan 
           22 . Humidity sensor 
           24 . Air temperature sensor 
           26 . Temperature sensor 
           30 . Mattress temperature sensor 
           40 . Mattress temperature controller 
           42 . Mattress temperature input unit 
           50 . Humidity controller 
           52 . Humidity input unit 
           60 . Air temperature controller 
           62 . Air temperature input 
           80 . Skin temperature controller 
           82 . Skin temperature input unit 
           90 . Radiation heating controller 
           92 . Heating output input