Abstract:
A meal trolley has an insulated casing and food dishes or plates supported therein for cooling and heating by thermochemical reactions. The reagents of the chemical reactions are stored in containers and reservoirs carried by the trolley and selectively connected to provide the self-contained cooling or heating.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART 
     The invention relates to trolleys and more particularly to trolleys for transporting or conveying prepared foods with cooling and/or warming thereof. The trolleys are ud, for example, in hospitals and retirement homes and in various means of public transportation. 
     A trolley of this type is already known from FR-A-2 684281 and from WO-97/09575. The trolley comprises a casing with a heat insulating wall inside which the food dishes are mounted. Means are provided for defining a first zone and a second zone, and these defining means may be a heat insulating partition or may be a virtual partition represented by the fact that the food dishes are covered with a dish-cover made of a heat insulating material, all the parts under the dish-cover on the one side of the trolley representing the first zone and on the other side the second zone. The first zone is generally designed to receive part of the dishes on which food is deposited intended to be consumed cold. It consists of a zone which must be kept at a low temperature, usually at around 3° C. On the other hand, the second zone is intended to receive food which must be consumed hot. This zone is first of all kept at a cold temperature of 3° C. for example, and then before the meal is consumed, is brought to a higher temperature, in particular 65° C. so that the food is reheated and may be served hot. To this end, the trolley includes a first device for cooling the first zone, a second device for cooling the second zone and a device for heating the second zone. 
     The disadvantage of trolleys known up to now is that devices for cooling by a refrigerating fluid or by absorption, both for the first zone as well as for the second zone, are operating as soon as they are put onto the trolley, even though they are not to be used at this time. As they can only provide a limited cooling capacity, they must be put on the trolley at the last moment or adapted to have the capacity to provide less cooling, so that the trolley can only keep food cold for a shorter time. 
     SUMMARY OF THE INVENTION 
     According to the invention, each cooling device comprises a first container for a gas, and optionally a first solid reagent capable of reacting with the gas, and a second container for a second solid reagent capable of reacting with the gas and which, if a first solid reagent is provided, is able to react more vigorously with the gas than the first solid reagent. The containers communicate with each other via a conduit provided with a valve. The first container of the first cooling device is placed in the first zone, while the second container of the first cooling device is placed outside the two zones. The first container of the second cooling device is placed in the second zone, while the second container of the second cooling device is placed outside the two zones. 
     The cooling devices operate by a thermochemical process, and they are actuated when the valve is opened. In this manner, the capacity of the cooling devices to produce cooling is only used deliberately and selectively. 
     According to one particularly preferred embodiment, the heating device comprises a first reservoir for a gas and optionally a first solid product able to react with the gas and a second reservoir for a second solid product able to react which, if a first solid product is provided, is able to react more vigorously with the gas than the first solid product, communicating with each other via a conduit provided with a valve, the first reservoir being placed outside the two zones, while the second reservoir is placed in the second zone. 
     The same advantages are thus obtained for the heating device as for the cooling devices, with the supplementary advantage that since the heating device is in this case entirely self contained and mounted on board the trolley, it is possible to operate it in at any moment whatsoever without being dependent on a source of electrical power at a fixed point. The heating can be started while the food dishes are carried in the trolleys. This enables the waiting time to be reduced. 
     In accordance with a second embodiment, it is possible to individualize more satisfactorily the cooling and/or heating of prepared dishes placed on the various plates. To that end, individual cooling and/or heating zones are provided for each prepared dish in order to obtain individual cooling or individual cooling and/or heating. 
     The gas may be ammonia or its derivatives, in particular alkylamines with C 1  to C 8 , for example monomethylamine, dimethylamine, but also water, CO 2 , SO 2 , SO 3  or H 2 . The solid adsorbent reagent may be a salt, such as a halide, a pseudohalide, a carbonate, a sulfate, a nitrate, an oxide or a metallic nitride, which, preferably, is in a natural expanded graphite matrix. The endothermicity of the reaction gives the desired cooling. As metals of salts constituting the solid reagents, use may in particular be made of the salts of the alkaline earth metals, zinc salts, manganese salts, iron salts and nickel salts. As a salt, reference may in particular be made to MnCl 2 , SrCl 2 , SrBr 2  to maintain the temperature at 3° C. and NiCl 2 , MgCl 2 , MgBr 2  and NiBr 2  to maintain the temperature at −20° C. When couples of reagents or solid products are provided, these may be for example NICl 2 , MgCl 2 , MgBr 2 , NiBr 2 , NiCl 2 , NiBr 2  according to the desired temperatures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings, given solely by way of example: 
     FIG. 1 is a sectional view of a trolley according to the invention; 
     FIG. 2 is a partial sectional view of a variant of the trolley according to the invention; 
     FIG. 3 is a sectional view along the line III—III of FIG. 2; 
     FIG. 4 is a top plan view of the cooling device used in the variant of FIG. 2; and 
     FIG. 5 is a top plan view of the combined cooling and heating device used in the variant of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The trolley shown in FIG. 1 has a casing  1  with an interior heat insulating partition  3  on which are mounted food dishes or plates  2 . The plates  2  are spread out horizontally while being superimposed. They pass through the heat insulating partition  3  so that each plate includes a depression situated in a cold zone  4  and a depression situated in a zone  5 , referred to as the cold/hot zone since it must be kept initially at a cold temperature and then brought, for example, to 65° C. 
     To this end, cooling devices are provided at each side of the casing  1 , which extend outside the plane of FIG.  1 . 
     The cooling device of the cold zone  4  includes a first container  7  filled with NH 3  and BaCl 2 . This first container communicates via a conduit  8  provided with a valve  9  with a second container  10  filled with MnCl 2 . 
     Similarly there is a first container  11 , filled with BaCl 2 , in the zone  5  and a second container  12 , filled with MnCl 2 , located remote of the zone  5 . The containers  11  and  12  communicate with each other via a conduit  13  provided with a valve  14  to provide the second cooling device. A heating device is also situated beside this cooling device, only on the side of the zone  5 , having a reservoir  15  filled with MnCl 2  communicating with a reservoir  16  filled with BaCl 2  via a conduit  17  provided with a valve  18 . The zone  4  is farther away from the container  10  than from the container  7 . The zone  5  is farther away from the container  12  than from the container  11  and is farther away from the reservoir  16  than from the reservoir  15 . The containers  10  and  12  and the reservoir  16  are located outside the casing, whereas the other containers and reservoir are located inside the casing. 
     In the embodiment of FIG. 1, each first container and/or first reservoir extends substantially perpendicularly to the plates. In accordance with another aspect of the invention, it is possible to stop the heating means by turning a valve. 
     In FIG. 2, the trolley comprises a casing  20  with a heat insulating wall enclosing mounted food dishes or plates  21 , only two of these plates being represented. Each depression in a given plate is covered with a dish-cover  22  made of heat insulating material. The dish-covers  22  determine a cold zone and a warm zone, on the one hand for the cold depressions and on the other hand for the warm depressions of the plate. More particularly, a sub-container  23  is provided under each cold depression of the plate  21 . Under each hot depression of the plate  21 , both a sub-container  24  and a sub-reservoir  25  are provided and interlaced as shown in FIG. 5 for respectively providing cooling and heating. 
     FIG. 4 represents one of the sub-containers  23 . The sub-container  23  has seven fingers  26  connected by a manifold  27 . The manifold  27  extends to a conduit  28  having a valve  29  and arranged to communicate with a reservoir  30 . The reservoir  30  contains MnCl 2  and the sub-container  23  contains BaCl 2 . 
     As shown in FIG. 5, the sub-container  24  has only six fingers  26 , but it is otherwise similar to the sub-container  23 . Accordingly, the fingers  26  are connected by the manifold  27  and conduit  28  including valve  29  to the reservoir  30 . 
     As also shown in FIG. 5, the sub-reservoir  25  has five fingers  31  connected to a common collector  32 . The collector  32  is connected by a conduit  33  having a valve  34  to a reservoir  35 . The fingers  31  contain MnCl 2  and the reservoir  35  contains BaCl 2 . The fingers  26  are interlaced with the fingers  31 . 
     FIG. 3 is a sectional view along the line III—III of FIG.  2 . The food dishes or plates  21  are stacked to either side of a service duct  36  in which the reservoirs  30  and  35  are housed. This service duct is separated from the zones where the plates are situated by heat insulating partitions  37 . 
     Another embodiment consists of positioning the reservoir  16  in the zone  4  and the reservoir  15  in the zone  5 . This enables the zone  4  to be kept cold provided the operation of the device  7 ,  10  is shut down, which prevents heat from being discharged to the environment, when the temperature is raised again.