GB2281775A

GB2281775A - Food cooling system using carbon dioxide snow

Info

Publication number: GB2281775A
Application number: GB9418148A
Authority: GB
Inventors: Clive Stewart Cumner; Roy Mellick
Original assignee: MG GAS PRODUCTS Ltd
Current assignee: MG GAS PRODUCTS Ltd
Priority date: 1993-09-09
Filing date: 1994-09-08
Publication date: 1995-03-15
Anticipated expiration: 2014-09-08
Also published as: GB2281775B; GB9318715D0; GB9418148D0

Abstract

In a carbon dioxide snow delivery system (1) comprising a number of horizontally supported carbon dioxide delivery horns, each delivery horn has a snowing nozzle mounted at one end arranged to be connected to a supply of liquid carbon dioxide and has an outlet orifice at the other end coupled to a complementary carbon dioxide output slot (4) formed in a face plate (3). The face plate (3) is adapted to close an open end of a compartment when the compartment is positioned substantially adjacent the face plate (3) so that the carbon dioxide delivery horns can direct streams of carbon dioxide gas and entrained carbon dioxide snow onto food supported at different levels inside the compartment to cool the inside surfaces of the compartment and dose the food with carbon dioxide snow. Preferably, the compartment is an airline trolley. At least part of the face plate (6) may be movable vertically to adjust the respective heights of the slots (5). <IMAGE>

Description

FOOD COOLING SYSTEM To ensure prepared food retains its freshness until it is served or put out for display some time later the food must be kept cool. Usually this is done by storing the food in a refrigerator. However, there are instances when refrigerators are not available. One area of particular interest where refrigerators are not usually available is in the airline industry where large amounts of food are prepared for serving in flight from trays held within airline trolleys. A convenient system of keeping prepared food cool is also of interest to other food handlers such as outside caterers.

It is known to cover food held on trays within a compartment with carbon dioxide snow. GB-A-2,259,357 describes a snowing gun which is especially useful for directing a flow of carbon dioxoide gas and entrained carbon dioxide snow into a series of compartments such as the interior of an airline trolley to chill food held on trays within the trolley which are intended to be served sometime later during a flight. However, the process is time consuming because each tray within the trolley has to be treated separately.

According to the present invention, a carbon dioxide snow delivery system comprises a number of horizontally supported carbon dioxide delivery horns, each delivery horn having a snowing nozzle mounted at one end arranged to be connected to a supply of liquid carbon dioxide and having an outlet orifice at the other end coupled to a complementary carbon dioxide output slot formed in a face plate, wherein the face plate is adapted to close an open end of a compartment when the compartment is positioned substantially adjacent the face plate so that the carbon dioxide delivery horns can direct streams of carbon dioxide gas and entrained carbon dioxide snow onto food supported at different levels inside the compartment to cool the inside surfaces of the compartment and dose the food with carbon dioxide snow.

Preferably, the face plate forms one face of an at least partially enclosed compartment.

Preferably, the face plate of the at least partially enclosed compartment is adapted to receive and enclose an open end of a compartment such as an airline trolley to enable the trolley to lie substantially adjacent the plurality of complementary carbon dioxide output slots to ensure that the majority of the carbon dioxide gas and snow enters the trolley.

Preferably, the delivery system further comprises means to activate the production of carbon dioxide snow only when the trolley is in a pre-determined position relative to the face plate of the at least partially enclosed compartment.

The production of carbon dioxide may be activated by manual operation of, for example, a switch, but preferably the switching operation is carried out automatically when the trolley is detected as being in position.

Typically, although, for example, the width of airline trolleys are standard, there is some variation in height between models. Preferably, therefore, at least part of the face plate of the at least partially enclosed compartment is arranged to be capable of moving so that the vertical position of at least one output slot along with its respective carbon dioxide delivery horn can be adjusted to suit the particular height of a trolley. Preferably, the movable section of the face plate is arranged to be driven by a hydraulic or pneumatic piston and cylinder assemblies to adjust the vertical position of the moveable section. The piston assembly may be manually actuated by means of a control switch.

Preferably, each carbon dioxide snowing nozzle is connected to the liquid carbon dioxide supply via an electrically actuated solenoid valve. Preferably, the connection between the carbon dioxide snowing nozzles and the liquid carbon dioxide supply further comprises a gas/liquid separator. Preferably, the gas/liquid separator is of the float type.

Preferably, once actuated, the solenoid valves remain open for a pre-determined period of time and then automatically close to stop the production of carbon dioxide snow.

Preferably, the delivery horns are generally rectangular in cross-section and the cross-sectional area increases from the one end where the carbon dioxide snowing nozzle is mounted to the other end where the outlet orifice is situated.

Preferably, each delivery horn is heated to ensure carbon dioxide snow does not adhere to the inside surface of the horns.

The carbon dioxide delivery system of the present invention enables the rapid dispensing of carbon dioxide snow onto trays of food within, for example, airline trolleys. A trolley filled with trays of food is opened at one end and simply pushed into place against the face plate of the enclosed compartment of the carbon dioxide snow delivery system whereupon the output of cold carbon dioxide gas and entrained carbon dioxide snow is activated.

The positions and dimensions of the carbon dioxide output slots are arranged to correspond to the known heights of trays held within an airline trolley so that each slot can direct carbon dioxide snow and gas onto a number of trays held within the trolley at different heights. However, if necessary, the position of one or more output slots may be adjusted.

A ten second burst of carbon dioxide snow is generally sufficient to cover each tray supported within a series of compartments within a trolley before the trolley is withdrawn and the open end securely closed. The amount of snow required is dependent on, amongst others, ambient temperature and food transit time.

The carbon dioxide gas is extremely cold and provides an initial cooling of the inside of the trolley and the food. The solid carbon dioxide slowly sublimes within the closed trolley to provide an additional delayed cooling effect over a period of several hours.

An example of a carbon dioxide snow delivery system in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of the outside of the housing of the carbon dioxide snow delivery system; Figure 2a shows a view of the arrangement of a pair of carbon dioxide delivery horns; Figure 2b shows a perspective view of a carbon dioxide delivery horn; Figure 3 shows an adjustable plate including a pair of horizontally configured carbon dioxide output slots; Figure 4 shows a sectional plan view of the arrangement of a trolley and the carbon dioxide delivery system; and Figure 5 illustrates the output of carbon dioxide gas and entrained carbon dioxide snow from the carbon dioxide snow delivery system of the present invention.

Figure 1 shows a carbon dioxide snow delivery system 1 which comprises an enclosed compartment 2, a front face 3 which comprises four vertically orientated carbon dioxide output slots 4 and a pair of horizontally orientated carbon dioxide outlet slots 5. The carbon dioxide output slots 5 are formed on a plate 6 (see Figure 3), the height of which may be adjusted by means of control switches 8 operatively connected to a hydraulic piston and cylinder assembly 9.

The carbon dioxide output slots 4, 5 co-operate with the output orifices 12 of six carbon dioxide delivery horns 7 mounted within the housing 2.

The housing 2 further comprises micro-switches 10 and 11 which are operated when the open end of a trolley is brought into position adjacent the front face 3 and carbon dioxide output slots 4, 5.

In this example, the carbon dioxide delivery horns 7 are mounted in pairs. This is illustrated in Figures 2a and 2b. Each delivery horn 7 comprises a hollow tube 13 which is rectangular in cross-section. The cross-sectional area of each tube 13 increases towards the carbon dioxide output orifice 12. A carbon dioxide snowing nozzle 14 is mounted at one end of the tube 13. In this example, the carbon dioxide snowing nozzle is a an Amal carburettor jet.

The nozzles 14 may also be formed by drilling a hole of a suitable diameter in a purpose made stainless steel outlet (not shown).

A pipe 15 connects a pair of delivery horns 7 to a solenoid valve 17 and a floating type gas/liquid separator 16. A 18 connects the gas/liquid separator 16 and valve 17 to a liquid carbon dioxide supply source 19 which typically stores liquid carbon dioxide at a pressure of 2 MPa and at a temperature of -18 C.

An electrical cable 20 connects the solenoid valve 17 to a control box (not shown) which sends the necessary electrical signals to control the operation of the valve 17. Opening the valve 17 allows liquid carbon dioxide to travel from the liquid carbon dioxide supply vessel 19 through the gas/liquid separator 16 and thereon to the carbon dioxide snowing nozzles 14. The sudden decrease in pressure when the liquid carbon dioxide exits the nozzles 14 causes the liquid carbon dioxide to change phase instantly to a mixture of cold carbon dioxide gas and solid carbon dioxide (snow). The size of the snow particles is increased as the particles stick together as they travel along the delivery horn 7 propelled by the carbon dioxide gas. Finally, the mixture of carbon dioxide gas and snow entrained in the gas exits the outlet orifice 12.

The dimensions of the delivery horns 7 are chosen to maximise the production of the solid carbon dioxide snow which typically represents 40 to 50% of the original carbon dioxide liquid, the remainder being formed as carbon dioxide gas.

A feature of the present invention is that the height of the horizontally orientated slots 5 and their respective pair of horizontally mounted delivery horns 7 is capable of being altered to match a particular trolley.

The plate 6, shown in Figure 3, is connected by a bracket assembly 21 to the hydraulic piston 9. Actuation of the piston 9 by pressing the control switches 8 alters the position of the plate 6 in the vertical sense and thus the height of the slots 5 relative to the base of the housing 2.

The delivery horns 7 are fixed to the plate 6 in the region of the slots 5 so that the output orifices 12 are aligned with the slots 5. The associated solenoid valve 17, gas/liquid separator 16 and connectors are capable of moving with the delivery horns 7.

In practice, all the components within the housing 2 are lagged with foam/rubber insulation to prevent heat being absorbed by the carbon dioxide. Absorption of heat by the liquid carbon dioxide in the pipes tends to cause the production of unwanted carbon dioxide gas. Hence the gas/liquid separator 16 is provided to ensure that only liquid carbon dioxide reaches the output nozzles 14. Each carbon dioxide delivery horn 7 may be wrapped in a resistive heating mat (not shown) connected to a DC supply to warm the delivery horns 7, thereby ensuring carbon dioxide snow does not stick to the inside surface of the horn 7.

The principle of operation of the carbon dioxide snow delivery system according to the present invention is as follows.

As shown in Figure 4, a trolley 22, including a series of filled with trays of food and/or drink 25, is opened at one end and brought into close proximity with the front face 3 of the carbon dioxide snow delivery system.

Further advancement of the trolley towards the front face causes the leading edges of the trolley to abut against switches 10 and 11. Only when both switches 10, 11 are activated is the trolley in the correct position to ensure the majority of carbon dioxide snow enters the trolley compartment 24 as the open end of the trolley 22 and the folded back doors 23 are then shrouded by the front of the carbon dioxide delivery system. The production of carbon dioxide snow then commences.

The control box (not shown) senses that the trolley is in position and sends a control signal to the solenoid valves 17 to open the path between the snowing nozzles 14 and liquid carbon dioxide supply 19. As explained above, a mixture of carbon dioxide gas and entrained carbon dioxide snow exits the output slots 4, 5 and covers the contents of the trolley compartments.

After a pre-determined period of say ten seconds, a control signal shuts the solenoid valves and thereafter the trolley can be withdrawn and the trolley compartment closed.

The amount of snow required is dependent on, amongst others, the ambient temperature and food transit time and a timer may be provided to adjust the period of snow delivery.

If the trolley is withdrawn bvefore the end of the snow delivery period, the micro-switches 10, 11 automatically shut off the solenoid valves 17.

The height of the output slots 5 can be adjusted to suit a particular trolley. The output slots 4 are positioned to match the heights of trays 25 held within the majority of conventional airline trolleys.

Finally, Figure 5 illustrates the production of carbon dioxide snow (a trolley is not illustrated for simplicity).

Claims

1. A carbon dioxide snow delivery system (1) comprising a number of horizontally supported carbon dioxide delivery horns (7), each delivery horn (7) having a snowing nozzle (14) mounted at one end arranged to be connected to a supply of liquid carbon dioxide (19) and having an outlet orifice (12) at the other end coupled to a complementary carbon dioxide output slot (4, 5) formed in a face plate (3), wherein the face plate (3) is adapted to close an open end of a compartment (22) when the compartment (22) is positioned substantially adjacent the face plate (3) so that the carbon dioxide delivery horns (7) can direct streams of carbon dioxide gas and entrained carbon dioxide snow onto food supported at different levels inside the compartment to cool the inside surfaces of the compartment and dose the food with carbon dioxide snow.

2. A carbon dioxide snow delivery system according to claim 1, wherein the face plate (3) forms one face of an at least partially enclosed compartment (22).

3. A carbon dixode snow delivery system according to claim 2, wherein the face plate (3) of the at least partially enclosed compartment (22) is adapted to receive and enclose an open end of a compartment (22) to enable the compartment to lie substantially adjacent the plurality of complementary carbon dioxide output slots (4, 5) to ensure that the majority of the carbon dioxide gas and snow enters the compartment (22).

4. A carbon dioxide snow delivery system according to any preceding claim, wherein the compartment is an airline trolley (22).

5. A carbon dioxide snow delivery system according to claim 4, further comprising means (10, 11) to activate the production of carbon dioxide snow only when the trolley (22) is in a pre-determined position relative to the face plate (3) of the at least partially enclosed compartment (22).

6. A carbon dioxide snow delivery system according to claim 4 or 5, wherein at least part (6) of the face plate (3) of the at least partially enclosed compartment is arranged to be capable of moving so that the vertical position of at least one output slot (5) along with its respective carbon dioxide delivery horn (7) can be adjusted to suit the particular height of a trolley (22).

7. A carbon dioxide snow delivery system according to claim 6, wherein the movable section of the face plate is arranged to be driven by a piston and cylinder assembly (9) to adjust the vertical position of the movable section (6).

8. A carbon dioxide snow delivery system according to any preceding claim, wherein each carbon dioxide snowing nozzle (14) is connected to the liquid carbon dioxide supply (19) via an electrically actuated solenoid valve.

9. A carbon dioxide snow delivery system according to any preceding claim, further comprising means to heat the surface of each carbon dioxide delivery horn (7).

10. A carbon dioxide snow delivery system according to any preceding claim, wherein the delivery horns (7) are generally rectangular in cross-section and the crosssectional area increases from the one end where the carbon dioxide snowing nozzle (14) is mounted to the other end where the outlet orifice (4, 5) is situated.

11. A carbon dioxide snow delivery system substantially as shown in or described with respect to Figure 1 to 5 of the drawings.