GB2272273A

GB2272273A - Apparatus for washing and drying containers

Info

Publication number: GB2272273A
Application number: GB9223531A
Authority: GB
Inventors: Frank N Carrick; Andrew Philpotts
Original assignee: AGMA PLC
Current assignee: AGMA PLC
Priority date: 1992-11-10
Filing date: 1992-11-10
Publication date: 1994-05-11
Also published as: GB9223531D0

Abstract

An apparatus for drying thermoplastic containers 28 individually on retail premises, after the containers have been washed and prior to refilling, comprises a drying chamber 2, on air inlet 16 to supply hot air to the drying chamber from a pump 3, and an upwardly projecting air outlet tube located within the drying chamber. The outlet tube projects into the container and is connected to the intake of the pump 3. In use, the container to be dried is inverted and the upwardly projecting air outlet tube is inserted into the container. This configuration provides rapid drying at low temperatures, making it suitable for drying containers formed from thermoplastics such as polyethylene. The apparatus optionally also comprises a washing chamber 1 for washing the thermoplastic container in which a pumps pumps water through a line 12 projecting upwardly into a container, chemicals being added to the water from reservoir 14 by a pump 13. <IMAGE>

Description

APPARATUS FOR WASHING AND DRYING CONTAINERS The present invention relates to an apparatus for washing and drying containers, in particular bottles formed from thermoplastic materials.

Containers formed from thermoplastic materials such as polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) are very widely used for packaging consumer products. The containers usually have a capacity of 10 ml to 1000 ml and are injection moulded or blow moulded in one piece, most often in the form of a bottle having a threaded neck for attaching a screw top. These containers have many practical advantages. The chief objection to containers of this type is that they are normally used only once. Disposal after use of the empty containers, most of which are not biodegradable, presents environmental problems. Moreover, public attitudes have changed and it is now considered unacceptable to waste natural resources by throwing away perfectly serviceable containers after they have been used only once.

The problem of disposing of plastic containers has been addressed in several ways, including incineration in power plants and recycling. Incineration presents environmental problems in itself, and recycling is difficult because of the need to separate out metal and paper from the various kinds of thermoplastic present in domestic rubbish.

An alternative solution - is to reuse the thermoplastic containers by washing them out after use and then refilling them with either the original product or something different. For example, one manufacturer of fabric softener currently sells refills for its plastic containers, the refills being packaged in paper Tetrapake cartons. This can only be regarded as a partial solution, as the empty refill cartons themselves must still be disposed of.

The optimum solution from the environmental point of view would be for retailers to refill, at the point of sale, thermoplastic containers brought in by customers. In order for this to be possible the retailer must be assured that the empty thermoplastic containers are clean inside.

Without this assurance the retailer cannot provide any warranty as to the amount or quality of the refill being supplied.

At present retailers can only rely on the goodwill of their customers to ensure that reusable thermoplastic containers are properly cleaned inside. Currently existing bottle washing equipment has been developed for cleaning glass bottles in dairies and breweries. It is quite unsuitable for use on retail premises for washing individual thermoplastic containers brought in by customers. In particular, existing equipment cannot handle a wide variety of shapes and sizes of container on an individual basis.

Moreover, existing equipment carries out washing and/or drying at temperatures up to 1O00C, which is hot enough to cause deformation of thermoplastic containers. However, lowering the drying temperature in conventional bottle washing and drying equipment results in unacceptably long drying times, even when so-called chemical rinse-aids are used to accelerate the shedding of water.

Accordingly, it is an object of the present invention to provide a drying apparatus that can be installed in ordinary retail premises and that will dry thermoplastic containers after they have been washed out quickly and at temperatures low enough to prevent softening or deforming the thermoplastic containers.

It is a further object of the present invention to provide an integrated washing and drying apparatus for thermoplastic containers that incorporates a drying apparatus as above.

The present invention provides a drying apparatus, a washing and drying apparatus, and a process for drying thermoplastic containers as claimed in the accompanying claims.

An embodiment of the present invention will now be described further, by way of example, with reference to the accompanying drawing. The drawing shows a schematic crosssection through a washing and drying apparatus according to the present invention.

Referring to the drawing, the washing and drying apparatus comprises a washing chamber 1, a drying chamber 2, an air pump 3, a water tank 4, a water pump 5, a mains water supply 6, a condenser 7 and a drain 8. The directions of flow of water and air are indicated by means of arrows.

The washing chamber 1 is a watertight chamber having a hinged lid 9. The washing chamber 1 has a liquid inlet 10 in the form of a tube projecting upwardly from the base of the container and a liquid outlet 11 connected to the drain 8. The liquid inlet 10 is connected through washing water line 12 to the low pressure water pump 5. Also connected to the washing water line 12 is a positive displacement chemical injection pump 13 connected to a reservoir 14 of a chemical cleaning and sanitising agent.

The drying chamber 2 is a substantially airtight chamber having a hinged lid 15. The drying chamber 2 has an air inlet 16 adjacent to a side wall of the drying chamber 2.

The air inlet 16 is connected through an air supply line 17 to the exhaust 18 of the air pump 3-. An electric heater 19is situated in the air supply line to heat the air, the electric heater being rated up to 1 kW and operatively associated with a power output control means (not shown).

The drying chamber 2 is also provided with an air outlet 21 in the form of a tube projecting upwardly from the base of the drying chamber. The top end 30 of the air outlet 21 is provided with crenellations to permit air flow into the air outlet tube even when the top end of the air outlet tube is resting against the base of a container. The same effect may be achieved by providing apertures in the air outlet tube adjacent to the top end of the air outlet tube. The air outlet 21 is connected through an air exhaust line 22 to the condenser 7 and thence to the air intake 23 of the air pump 3. A temperature control sensor 20 is positioned in the air exhaust line 22 close to the drying chamber 2 and is connected to the power output control means associated with the electric heater 19. The condenser 7 is a sealed unit immersed in the water tank 4 for cooling.The condenser 7 is provided with a condensate removal line 24 which is connected through vacuum lock 25 to the drain 8. The drying chamber 2, gas pump 3 and condenser 7 together constitute a substantially airtight closed loop gas flow system.

The washing and drying apparatus is provided with a number of interlocks in order to make it suitable for use by unskilled staff on retail premises. There are interlocks on the lids 9, 15 of the washing chamber 1 and the drying chamber 2. There is also a high temperature cut-out 26 adjacent to the electric heater 19. An effluent quality sensor and trip 27 is provided in the liquid outlet 11 of the washing chamber 1. Washing water is pumped through the liquid outlet 11 at a rate normally in the range of from 1 to 10 litres/minute, and preferably 2 to 6 liters/minute.

The temperature of the washing water is normally close to the ambient temperature, typically 5 to 25 degrees C.

In operation, the washing and drying apparatus is used as follows. First, the thermoplastic container 28 to be cleaned is inverted and placed in the washing chamber 1 so that the liquid inlet 10 is inserted inside the inverted thermoplastic container 28. The lid of the washing chamber is closed and the low pressure water pump 5 is activated to pump washing water into the thermoplastic container 28. The positive displacement chemical injection pump 13 simultaneously introduces a predetermined and tamper proof amount of the chemical cleaning and sanitising composition into the washing water flow.

The chemical cleaning and sanitising composition should preferably provide good detergent and disinfectant properties with minimal foaming. Preferred compositions comprise a detergent, a wetting agent and a disinfectant.

The detergent may be any common detergent, preferably a lowfoam detergent. The wetting agent is highly desirable for cleaning and disinfecting containers formed from hydrophobic thermoplastics such as polyethylene. The preferred disinfectant is hydrogen peroxide (5-10 vols strength) on account of its environmental acceptability, clean decomposition into water and oxygen, and non-foamability.

Alternatively, a low-foaming organic biocide such as a polymeric bi- or diguanide disinfectant may be used. Yet another alternative disinfectant is an inorganic peroxy compound such as sodium.persulphate.

The washing procedure described above washes only the inside of the thermoplastic container. This makes the process especially suitable for washing thermoplastic containers on shop premises prior to refilling because the process does not dislodge labels stuck to the outside of the container.

The washing procedure is continued for a predetermined time in the range of from 10 seconds to 5 minutes, and preferably 1 to 2 minutes. The thermoplastic container 28 is them removed from the-washing chamber 1 and placed in the drying chamber 2. The thermoplastic container is inverted and positioned so that the end 30 of the air outlet 21 is inside the container and preferably near the base of the container 28. More preferably the top end 30 of the air oulet tube 21 rests against the base of the inverted container 28 so that the air outlet tube 21 is also functioning as a support spigot for the container 28. This removes the need for alternative support means for the inverted thermoplastic container and renders the drying apparatus suitable for use with a wide range of thermoplastic container sizes.

Moreover, especially rapid drying is obtained in this configuration.

The lid 15 of the drying chamber 2 is then closed and the air pump 3 is started. Air from the air pump 3 passes through the air supply line 17 where it is heated by the electric heater 19. The heated air then passes through the air inlet 16 into the drying chamber 2. The air is drawn up through an annular gap defined between the neck 29 of the thermoplastic container and the air outlet tube and into the interior of the thermoplastic container where it dries the interior of the thermoplastic container. The humidified air then exits the drying chamber through the air outlet 21.

The crenellations or apertures at the end of the air outlet tube 21 permit air to flow freely into the outlet tube 21 even though the end 30 of the air outlet tube 21 is resting against and supporting the base of the container 28. The rate of flow of the air is normally in the range of 10 to 100 liters/minute and preferably 40 to 70 liters/minute.

Air that has passed through the drying chamber 2 flows down the air exhaust line 22 past the temperature control sensor 20. The output of the temperature control sensor 20 is used to regulate the power input to the electric heater 19, thereby controlling the temperature of the air leaving the drying chamber 2. The temperature of the air leaving the drying chamber 2 is selected to be as high as possible without causing softening and consequent deformation of the thermoplastic container. In practice, this usually implies a temperature of the air leaving the drying chamber of 50 - 550C, since low density polyethylene containers start to soften at about 550C.

The humidified air from the drying chamber passes down the air exhaust line 22 to the condenser 7. The dehumidified, cool air leaving the condenser flows into the air intake 23 of the air pump 3.

The drying apparatus provides rapid drying of thermoplastic containers. Containers having a capacity of up to 1000 ml can be dried by means of this apparatus within two minutes, making the apparatus especially suitable for use on retail premises.

The exceptional speed of drying obtained with the drying apparatus according to the present invention is due to the configuration of the air flow. It has been found, surprisingly, that suction from inside the container while the container is inverted and warm air is supplied outside the container provides very rapid drying. Especially rapid drying is achieved when the end of the air outlet tube rests against the base of the inverted thermoplastic container.

In contrast, blowing warm air into the container while it is inverted results in much slower drying at the low temperatures required for drying thermoplastic containers.

The drying apparatus according to the present invention also achieves faster drying than the use of centrifuges or air knives at similar temperatures.

The above embodiment of the present invention has been described by way of example only. Many other embodiments falling within the scope of the claims will be apparent to the skilled reader.

Claims

CLAIMS:

1. A drying apparatus for drying a thermoplastic container, the apparatus comprising: an air pump having an air intake and an air exhaust; a drying chamber; air supply means to supply air to the drying chamber; a heater operatively associated with the air supply means to heat the air being supplied to the drying chamber; and air evacuation means to evacuate air from the drying chamber, said air evacuation means being connected to the air intake of the air pump and comprising an upwardly projecting air outlet tube located within the drying chamber.

2. A drying apparatus according to claim 1 wherein the upwardly projecting outlet tube is substantially vertical.

3. A drying apparatus according to claim 1 wherein a top end of the air outlet tube located within the air outlet tube located within the drying chamber is crenellated, or the outlet tube is provided with apertures adjacent to the said top end.

4. A drying apparatus according to claim 1, 2 or 3 wherein the air supply means to supply air to the drying chamber is connected to the air exhaust of the air pump to provide a substantially closed air flow loop between the air pump and the drying chamber.

5. A drying apparatus according to any preceding claim wherein the evacuation means comprises a condenser.

6. A drying apparatus according to any preceding claim further comprising a temperature sensor operatively associated with the heater.

7. A washing and drying apparatus for washing and drying a thermoplastic container, the apparatus comprising a drying apparatus according to any of claims 1 to 6 and a washing apparatus, said washing apparatus comprising: a washing chamber; an upwardly projecting water inlet tube located within the washing chamber; and means to supply a flow of washing water to the water inlet tube.

8. A washing and drying apparatus according to claim 7 wherein the means to supply a flow of washing water to the water inlet tube comprises a water tank and a water pump.

9. A washing and drying apparatus according to claim 8 further comprising injection means to inject a chemical cleaning and/or disinfecting agent into the flow of washing water.

10. A washing and drying apparatus according to claim 9 wherein the injection means comprises a positive displacement chemical injection pump and a reservoir of the chemical cleaning and/or disinfecting agent.

11. A washing and drying apparatus according to claim 9 or 10 wherein the chemical cleaning and/or disinfecting agent comprises a detergent, a wetting agent and a disinfectant.

12. A washing and drying apparatus according to claim 11 wherein the disinfectant comprises hydrogen peroxide.

13. A washing and drying apparatus according to claim 11 wherein the disinfectant comprises a polymeric bi- ir diguanide.

14. A method of drying a thermoplastic container using a drying apparatus according to any of claims 1 to 6, the process comprising the steps of: opening the drying chamber; inverting the thermoplastic container and placing the thermoplastic container inside the drying chamber with the top of the upwardly projecting air outlet tube inserted into the container; closing the drying chamber; and starting the air pump.

15. A process according to claim 14 wherein the top of the upwardly projecting air outlet tube is inserted into the container near the base of the container.

16. A process according to claim 14 or 15 wherein the top end of the upwardly projecting air outlet tube is in contact with the base of the thermoplastic container.

17. A process according to claim 14, 15 or 16 wherein the temperature of the air leaving the drying chamber is maintained below 550C.

18. A drying apparatus substantially as hereinbefore described with reference to the accompanying drawing.

19. A washing and drying apparatus substantially as hereinbefore described with reference to the accompanying drawing.

20. A process of drying a thermoplastic container substantially as hereinbefore described with reference to the accompanying drawing.