GB2193870A - Removal of substances from containers - Google Patents

Abstract

A highly viscous (or solid) substance is removed from a packaging container (22) by heating the substance with microwaves to lower its viscosity. A field pattern of microwaves produced by a magnetron (27) is set up in the space (21) above the magnetron and in a part of the substance, thereby reducing the viscosity of that part of the substance. This part of reduced viscosity is then made to flow out of the microwave field pattern from the container (22). This flow may be by means of a pump (29) connected to a tube (25) having a head (24) connectable with an outlet of the container (22). A temperature sensing means in the form of a plate including a pyroelectric plastics material may be located beneath the container to allow monitoring of the temperature of the heated substance, so that the microwave input may be appropriately controlled. Air may be injected into the container during the removal process, and similarly a solvent for the substance may be provided by solvent inlet (50) for injection into the container. <IMAGE>

Description

SPECIFICATION Removal of substances from containers The present invention relates to the removal of a substance from a container. It is particularly appropriate when the substance is a highly viscous liquid, but the present invention is also applicable to solids.

When a liquid which is highly viscous at normal temperatures is stored in a container, it is very difficult to remove the liquid from the container, particularly as part of a commercial process. An example of such a viscous liquid is meat extract, which is produced as a by-product in the production of corned beef, and contains approximately 82% solid material. Such meat extract is used in the manufacture of soups, or as a base for savoury flavours. Meat extract has a very high viscosity at room temperature, but becomes increasingly mobile as the temperature increases. Therefore, it is customary to remove meat extract from a container in which is stored for transport by heating. Of course, it must not be heated too much or the amino acids and peptides etc. within it will be broken down.Furthermore, the meat extract has a high value and so it is important to remove as much as possible from any container.

In practice what is currently done is to heat the container of meat extract in an oven until its temperature has been raised sufficiently.

Since the extract has a high heat capacity, this may take a long time, e.g. approximately 5-6 hours. Hence deiays are inherent in any commercial use. Furthermore, the container must be removed from the oven to enable the meat extract to be poured from it, and the extract then cools and its viscosity increases. This usually results in a residue of extract remaining in the container which must be removed by soaking with e.g. hot water or suitable solvent, which again is time consuming.

The present invention seeks to overcome this problem, and so provide a technique whereby viscous liquids or solids can be removed from a container more easily. The idea underlying the present invention is to heat the liquid (or melt the solid) in the container using microwaves, until it is sufficiently fluid for it to flow or be pumped from the container. In practice, the removal of substance which is sufficiently fluid will occur simultaneously with the continued heating of insufficiently fluid material in the container.

Heating by microwaves is much more rapid than heating within a stove, because it does not depend on heat conduction through the mass of viscous liquid, and therefore enables the liquid to reach more quickly a temperature at which it is relatively fluid. As a development of this, it is possible for the microwave pattern which heats the substance to be established selectively in only a part of that substance. Then that part is heated first.

Thus, for example, it is possible selectively to heat that part of the substance adjacent the outlet of the container, so that it flows from the container, and the remaining substance within the container flows into that part vacated.

The container may be rigid, but it is preferred for the substance to be bounded by a flexible wall of the container. This enables the container more easily to take up changes in shape as the substance is heated. The flexibility of such a flexible wall may be selected in dependence on the particular application. Normally, however, a plastics material, possibly with a suitable coating, will be used. When the substance is enclosed in a flexible container, it is desirable that the container is housed within a more rigid outer carton providing strength, ease of storage, and a decorative base.

One problem with both rigid and flexible containers is that, as the substance is removed, there may be a pressure drop within the container making it increasingly difficult to remove the substance. To overcome this it is possible to provide means for injecting a gas into the container, to compensate for the pressure changes. That means is preferably integral with the head of an outlet pipe for the fluid substance. Means may also be provided, preferably integrally with the head for removal of fluid substance, for spraying a hot solvent, such as water, within the container to assist in the removal of any residue.

Two or more such containers may be provided in a single unit, so that the initial heating of one may be carried on while fluidised substance is removed from the other.

As mentioned above, it may be important that the substance is not heated too much (if the substance is meat extract it will be degraded by overheating). Therefore, there are preferably means for detecting the temperature of the substance as it is heated by the microwaves. Positioning temperature detectors within a microwave field pattern makes it difficult accurately to detect the temperature, and therefore use may be made of the establishment of a selective field pattern to position the temperature sensor(s) approximate to, but outside, the microwave field pattern. The temperature sensor(s) may be suitable thermistors, but it is also considered possible to use a temperature sensor formed by a layer of pyroelectric plastics material, such as PVdF.That plastics material may itself form a support plate for the container, with the tube through which substance is removed then passing through that support plate.

With the provision of such temperature sensors, the microwaves may then controlled in order to achieve the desired heating of-the substance.

Normally, a pump connected by a suitable tube to the container will be used to remove the substance from the container, but in certain cases (e.g. where contamination is not a problem) it may be possible simply to use gravity to cause the fluid substance to flow from the container.

Embodiments of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a schematic view of a first embodiment of the invention, showing an apparatus for removal of viscous fluids from a single container; Fig. 2 shows a general view of a second embodiment of the invention; Fig. 3 shows a sectional view of the second embodiment shown in Fig. 2; Fig. 4 shows a detail of a temperature sensor for the embodiment of Fig. 2; Fig. 5 shows a fluid circuit diagram for the embodiment of Fig. 2; and Fig. 6 shows a third embodiment of the invention, which several containers are provided.

Referring firstly to Fig. 1, a container 1 for a highly viscous liquid comprises a generally square rectangular polyethylene box with an outlet 2. Other materials may be used to form the container 1, as discussed above, but they must not weaken too much when the temperature of the substance in the container is raised. The outlet 2 is connected via a head 3 to a tube 4 leading to a pump 5. The container 1 is itself contained within an outer housing 6 of e.g. cardboard or similar material. The housing 6 acts as a relatively rigid support for the (more flexible) container 1.

For transport, the housing 6 protects the container 1, and fitting a cap at the opening in the container (at connection 3) may also enable the housings 6 and their enclosed containers 1 to be stacked.

To remove a viscous liquid in the container 1, the housing 6 is inverted to the position shown in Fig. 1, and the tube 4 connected to the container 1 via the head 3. Microwaves generally indicated at 7 are then incident on the container, and its enclosed substance, to cause heating of that substance. The frequency of the microwaves 7 is determined by the dielectric characteristics of the substance to be heated. For viscous liquids, such as meat extract, it is desirable that the extract is raised to a temperature approaching 100"C and this will cause some softening of the polyethylene walls of the container 1. However, the housing 6 prevents collapse of the container 1, as it is made of a material which does not soften at such elevated temperatures.

Once the viscous liquid in the container 1 has reached a suitable temperature, the pump 5 is activated to draw the liquid through the pipe 4 to the point where the liquid is to be used.

The pump may be stopped during the removal process, and air pumped into the container 1, to compensate for the reduction in pressure created within the container by the removal of the substance. Thus, as shown in Fig. 1, a pipe 9 extending to an outlet 10 may be provided for injecting air, or other gas, into the container. In a further development, this pipe 9 and outlet 10 may also be used to inject solvent into the container, to remove residue of the substance. The choice of solvent sprayed into the container in this way will depend on the substance to be removed; hot water may be used for the removal of meat extract. Alternatively, of course, separate air and solvent inlets may be provided.

The heating of the liquid in the container 1 by the microwaves 7 may be controlled so that the temperature of the liquid is maintained at a temperature suitable to keep it fluid until virtually all the liquid has been removed. Alternatively, by controlling the microwave pattern (and therefore the heating pattern), it is possible to heat only that part of the substance closest to the outlet so that it can be pumped off first. Then the remaining substance then sinks into the vacated part of the container, so that that substance is then heated.

Means may be provided proximate the container for detecting the temperature of the substance, and it is desirable that such temperature sensor is placed outside the microwave field pattern.

Figs 2 to 5 show a second embodiment of an apparatus incorporating the present invention. The apparatus as shown, the apparatus has a body 20 with a cavity 21 at an upper part for receiving a container 22 containing substance to be removed from the container 22. The cavity 21 has ledges 23 on the sides thereof, and at the base is a head 24 connected to a tube 25 through which the substance flows after it has been heated.

The container 22 is first placed adjacent the cavity 21, as shown in Fig. 2, and then the head 24 is pulled from the cavity, the tube 25 extending upward, and connection is made between the head 24 and an outlet of the container 22. Then, the container 22 is slid, and rotated, until it is resting on the ledges 23 of the cavity 21 and a cover 26, with a cavity therein, is lowered to enclose the container 22.

As shown in Fig. 3, a magnetron 27 is located directly beiow the cavity 21, which generates microwaves which heat the substance in the container 22 (shown enclosed within the cover 26 in Fig. 3).

It is possible, by providing suitable microwave waveguides for a selected microwave pattern to be set up within the cavity 21, and hence in the substance within the container 22. Suitable waveguides 28 are shown at the bottom of the cavity 21 in Fig. 2.

It can be seen that the tube 25 extends to a peristaltic pump 29 for pumping the substance through the tube 25, and out of the body 20. Since the substance will cool as it passes through the tube 25, it is possible to provide additional heating means 30 adjacent the pipe.

As was mentioned with reference to Fig. 1, it is desirable that suitable temperature sensor(s) be provided for detecting the temperature of the substance within the container. If a selective microwave pattern is established, it is possible to use thermistors placed outside that pattern but Fig. 4 shows an alternative arrangement in which the container 22 is supported on a support plate 40. The tube 25 extends through an aperture 41 in that support plate. The support plate 40 is formed by a thin layer of pyroelectric polymer material such as PVdF, having electrodes on each side of the layer across which an output voltage is generated, corresponding to the temperature.

Preferably, a black, radiation absorbing, layer is provided on the surface of the support plate 40 adjacent the container 22. Infra-red radiation from the substance is then detected by the pyroelectric polymer, and monitoring the output voltage across the electrodes enables detection of the temperature. This detection may be used to control the microwaves, so that the substance is not heated.

As shown in Fig. 4, the support plate 40 may itself be supported on the ledges 23 within the cavity 21.

As shown in Fig. 3, in addition to the tube 25, an additional conduit 50 may extend into the head 24. This conduit has two functions, to permit the injection of air into the container to compensate for pressure changes as the substance is removed, and also to inject solvent to remove residue. Fig. 5 shows the circuit diagram for this. There, air may pass through a suitable inlet valve 51, and a filter 52 to a further valve 53. That valve 53 is also connected via a filter 54 to a pump 55 for solvent. The valve 53 is connected via a one-way valve 56 to the conduit 50, and the valve 53 allows selection of either air or solvent, for passage via the valve 56 into the conduit 50, and so through the head 24 into the container.

As shown in Fig. 5, the supply of air may also be connected via valves 57 to the telescopic arms 58 which, as can be seen from Fig. 1, support the cover 26. Thus, the raising and lowering of the cover 26 over a suitable container 22 may be controlled from the air supply as is used to control the pressure in the container. Furthermore, by having both arms 58 linked to a common air supply, it can be ensured that the arms move in synchronism, so that the cover 26 does not twist as it is raised and lowered.

The circuit of Fig. 5, and indeed the operation of the magnetron 27 and any temperature sensor arrangement, may be controlled by a central microprocessor system, with instructions being suitably programmed from e.g. a control panel 60.

Fig. 6 shows an alternative arrangement in which two units 71,72 each generally corresponding to the arrangement shown in Fig. 1, are provided in a single assembly. Each has an associated pump 73 and outlet pipe 74. A magnitron 75 is provided in the assembly, to generate microwaves for heating viscous liquids, or solids, in the containers of the units 71,72. Thus the viscous liquid in unit 71 may be heated, and when that liquid has reached a suitable temperature, it may be pumped out of the corresponding outlet 24. Simultaneous with this pumping, the liquid in the other container 72 may be heated. Once all the liquid has been removed from unit 71, it may be replaced by a corresponding full unit, which may then in turn be heated whilst liquid from the unit 72 is removed. In this way, a relatively continuous removal process may be achieved, in contract with the batch processing of the known systems.

Although the present invention has been described with reference to the removal of meat extract from containers, the present invention is applicable to the removal of any viscous liquid which reduces in viscosity to a significant extent when it is heated, or to removal of a solid.

Claims (13)

1. A method of removing a solid or highly viscous substance from a container in which a pattern of microwaves is established in at least a part of the substance, to heat that part of the substance so as to reduce its viscosity, and the heated substance is caused to flow out of the microwave pattern from the container.

2. A method according to claim 1, wherein the pattern of microwaves is established in only a selected part of the substance adjacent an outlet of the container.

3. A method according to claim 1 or claim 2, wherein at least one temperature sensor is located proximate the container, outside the pattern of microwaves.

4. A method according to any one of the preceding claims, wherein air in injected into the container during the removal of the substance.

5. A method according to any one of the preceding claims, wherein a solvent for the substance is injected into the container during the removal of the substance.

6. A method of removing a solid or a highly viscous liquid from a container, substantially as any one herein described with reference to the accompanying drawings.

7. An apparatus for removing a solid or highly viscous substance from a container, having means for supporting the container, means for establishing a pattern of microwaves within the container, a tube having a head connectable with an outlet of the container, the tube extending to a point outside the microwave pattern.

8. An apparatus according to claim 7 having temperature sensing means proximate the means for supporting the container.

9. An apparatus according to claim 8 wherein the temperature sensing means is a plate including a pyroelectric plastics material, and the tube extends through that plate.

10. An apparatus according to any one of claims 7 to 9 having means for heating the pipe outside the microwave pattern.

11. An apparatus according to any one of claims 7 to 10 wherein the tube extends to a pump.

12. An apparatus according to any one of claims 7 to 11 wherein there is a first cavity below the means for supporting the container, which first cavity contains the head of the tube, and a second cavity within a cover of the apparatus, which second cavity is for enclosing the container; the cover being movable towards and away from the means for supporting the container.

13. An apparatus for removing a solid or highly viscous liquid from a container substantially as herein described, with reference to Fig. 1, or Figs 2 to 4, or Fig. 5 of the accompanying drawings.