GB2311353A

GB2311353A - Cleaning apparatus used for processing elastomeric materials

Info

Publication number: GB2311353A
Application number: GB9704445A
Authority: GB
Inventors: Christine Kay Horner
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-03-21
Filing date: 1997-03-04
Publication date: 1997-09-24
Anticipated expiration: 2017-03-04
Also published as: GB2311353B; GB9605962D0; GB9704445D0

Abstract

A machine part, such as apparatus used for processing polyurethane, is cleaned by flushing with a mixture of water and a surfactant at elevated temperature and pressure. The machine part may be flushed with pressurised air after cleaning. Water and surfactant in vessel 12 is pressurised by air 14 and passed through a heat exchanger 218 to the machine part 10 at 20-2000psi and 20-95 C. The heat exchanger 18 can also be used to heat the pressurised air.

Description

CLEANING METHOD AND APPARATUS This invention concerns a method and apparatus for cleaning machine parts ofthe kind (hereinafter termed ofthe kind referred to) which have hitherto been cleaned by use of solvents such as methylene chloride, particularly, though by no means exclusively, suitable for machines such as equipment which processes and becomes contaminated by elastomeric materials such as polyurethane for example.

The use of solvents is subject to ever more stringent procedures providing for recovery for environmental reasons including minimising damage to the ozone layer in the stratosphere.

According to one aspect of the present invention there is provided a method for cleaning a machine part of the kind referred to comprising the step of flushing it with a mixture of water and surfactant at elevated temperature and pressure.

The mixture may be at a pressure in the range 20 to 2000 psi.

The mixture may be at a temperature in the range 20 to 95"C.

The method may comprise the further step of flushing said machine part with pressurised hot or cold moisture free air.

According to a second aspect of the present invention there is provided apparatus for cleaning a machine part of the kind referred to comprising: a pressure vessel adapted to contain mixture of water and surfactant; means for supplying pressurised air to the pressure vessel; and a heat exchanger means connected between said pressure vessel and said machine part, the connection to said machine part having flow controlling valve means; wherein the pressurised air pressurises the mixture of water and surfactant and the heat exchanger means elevates the temperature of said pressurised mixture for supply to the machine part.

The pressure vessel may be connected to the heat exchanger means via preheating means for heating the pressurised mixture.

The pressure vessel may include a heating element.

The heat exchanger means may be connected to the valve means via pumping means, said pumping means increasing the pressure ofthe pressurised mixture.

The means for supplying pressurised air may also be connected to the machine part.

The flow controlling valve means may comprise a solenoid valve and a nonreturn valve.

A method and apparatus according to the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of an apparatus; and Figure 2 is a cross-sectional view of the heat exchanger on an enlarged scale.

The invention provides a method for cleaning machine parts of the kind referred to comprising the step of flushing them with a mixture of water and surfactant at elevated temperature and pressure.

The mixture is at a pressure in the range 20 to 2000 psi.

The mixture is at a temperature in the range 20 to 95 0C.

After such treatment, the machine parts are flushed with pressurised hot or cold moisture free air.

Examples of machine parts include the mixing heads of dispensing equipment which process and become contaminated by elastomeric materials such as polyurethane. Such machine parts have previously been cleaned by the use of solvents such as methylene chloride. Such solvents are quite expensive and environmentally unfriendly. The present invention utilises a relatively cheap and environmentally friendly medium in the cleaning process.

Referring now to the drawings, it will be seen that apparatus for cleaning a machine part 10 ofthe kind referred comprises: a pressure vessel 12 having a supply of pressurised air 14 and containing a mixture 16 of water and surfactant; a heat exchanger means 18 connected between pressure vessel 12 and the machine part 10 flow controlling valve means 20, 22 in the connection between the heat exchange means 18 and the machine part 10.

The supply of pressurised air 14 pressurises the mixture of water and surfactant 16 and the heat exchanger means 18 elevates the temperature of the pressurised mixture.

The pressure vessel 12 is connected to the heat exchanger means 18 via preheating means 26 for heating the pressurised mixture.

The pressure vessel 12 includes a heating element 28 for further heating of the pressurised mixture.

The heat exchanger means 18 is connected to the valve means 20, 22 by a pump 30, which further increases the pressure of the mixture.

The supply of pressurised air 14 is also connected via the heat exchanger 18 to the machine part 10 for flushing thereof following cleaning.

The flow controlling valve means comprises a solenoid valve 20 and nonreturn valve 22.

The operation of the apparatus will now be described in detail. The pressure vessel 12 is charged with a mixture 16 of water and surfactant and the mixture is pressurised by the supply of pressurised air 14 to a value in the range 20 to 150 psi.

The heating element 28 may be operated to preheat the mixture.

The pressure forces the mixture via valve 20 which is activated by a flow sensor 24 located downstream, to the pre-heating means 26 and then into the heat exchanger means 18, wherein the pressurised mixture is heated to a temperature in the range 20 to 95"C by a heating jacket 32 or heating element 34 (or a combination thereof). The precise temperature employed - together with the precise pressure employed - may be optimised to suit the particular application, e.g. the type of elastomer to be removed and the mixer size. The operation of the heat exchanger means 18 is controlled by a temperature probe 50 located at an optimal position in the internal circuit.

The pressurised and heated mixture is further forced by the pressure into the pump 30, which produces increased mixture pressures in the range 90 to 2000 psi. The operation of the pump 30 is controlled by the flow sensor 24 and the system includes a pressure relief bypass valve 36. The increased pressure of the mixture created by the pump 30 can enhance the cleaning process. However, the provision of the pump 30 should be considered as optional. If the pumping means 30 is not included, the circulation of the mixture of water and surfactant is driven entirely by the pressure created by the supply of pressurised air 14.

The subsequent passage of the pressurised and heated mixture into the machine part 10 is controlled by a solenoid valve 20 and a non-return valve 22. The solenoid valve 20 may be operated in a pulsed or full flow (open) manner. It is possible to substitute the solenoid valve 20 with another electronic valve, or with a pneumatic or a manual valve.

The combination of water and surfactant mixture at elevated temperature and pressure results in highly satisfactory cleaning of the machine part 10. The length of the flush cycle employed is dependent upon the machine part 10 being cleaned.

After cleaning in the above described manner it is advantageous to flush the machine part 10 with pressurised air in order to expel any water-surfactant mixture remaining. Advantageously the supply of pressurised air 14 used to pressurise the mixture 16 is also used for flushing purposes. The pressurised air may be cold or, preferably, hot and may be applied to the machine part 10 in pulses or continuously. The supply of pressurised air for flushing is controlled by a suitable valve system which may comprise manual, pneumatic or electronic valves. In Figure 1 the flushing air supply is controlled by an air valve 38 and is heated by the heat exchanger means 18 before being introduced to the machine part 10 via a solenoid valve 40 and a non-return valve 42.

Figure 2 shows the heat exchanger means 18 in more detail. The cold flushing air supply enters the heat exchanger means 18 at air inlet 44 and circulates around air coil 46 before exiting through an air outlet 48. The air is heated by heating jacket 32 or heating element 34 or a combination thereof. In similar manner the pressurised mixture 16 of water and surfactant enters at mixture inlet 52, circulates around mixture coil 54 and exits at mixture outlet 56.

The apparatus of Figure 1 also comprises pressure relief valve 58, pressure gauge 60, low level automatic warning system 62.

It will be appreciated that it is not intended to limit the invention to the above example only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof as defined by the appended claims.

Thus for example means may be provided to ensure that both flushing operations are carried out sequentially.

Again, for example, the entire process may be computer controlled.

Claims

1. A method for cleaning a machine part ofthe kind referred to comprising the step of flushing them with a mixture of water and surfactant at elevated temperature and pressure.

2. A method according to claim 1 in which the mixture is at a pressure in the range 20 to 2000 psi.

3. A method according to claim 1 or claim 2 in which the mixture is at a temperature in the range 20 to 95or.

4. A method according to claims 1 to 3 comprising the further step of flushing said machine part with pressurised air.

5. Apparatus for cleaning a machine part of the kind referred to comprising a pressure vessel adapted to contain a mixture of water and surfactant; means for supplying pressurised air to the pressure vessel and heat exchanger means connected between said pressure vessel and said machine part, the connection to said machine part having flow controlling valve means; wherein the supply of pressurised air pressurises the mixture of water and surfactant and the heat exchanger means elevates the temperature of said pressurised mixture for supply to the machine part.

6. Apparatus according to claim 5 in which the pressure vessel is connected to the heat exchanger means via pre-heating means for heating the pressurised mixture.

7. Apparatus according to claim 5 or claim 6 in which the pressure vessel includes a heating element.

8. Apparatus according to any of claims 4 to 7 in which the flow controlling valve means comprises a solenoid valve and a non-return valve.

8. Apparatus according to any one of claims 5 to 8 in which the heat exchanger means is connected to the valve means via pumping means, said pumping means increasing the pressure of the pressurised container.

9. Apparatus according to any one of claims 5 to 9 in which the supply of pressurised air is also connected to the machine part.

10. Apparatus according to any of claims 5 to 9 in which the flow controlling valve means comprises a solenoid valve and a non-return valve.

Amendments to the claims have been filed as follows 1. A method for cleaning machine parts of the kind referred to comprising the step of flushing them with a mixture of water and surfactant at elevated temperature and pressure and subsequently flushing them with pulses of pressurised air.

3. A method according to claim 1 or claim 2 in which the mixture is at a temperature in the range 20 to 95"C.

4. Apparatus for cleaning machine parts of the kind referred to comprising a pressure vessel adapted to contain a mixture of water and surfactant; means for supplying pressurised air to the pressure vessel and heat exchanger means connected between said pressure vessel and said machine part, the connection to said machine part having flow controlling valve means; wherein the supply of pressurised air pressurises the mixture of water and surfactant and the heat exchanger means elevates the temperature of said pressurised mixture for supply to the machine part; and means for flushing the parts with pulses of pulsed pressurised air.

5. Apparatus according to claim 4 in which the pressure vessel is connected to the heat exchanger means via pre-heating means for heating the pressurised mixture.

6. Apparatus according to claim 4 or claim 5 in which the pressure vessel includes a heating element.

7. Apparatus according to any one of claims 4 to 6 in which the heat exchanger means is connected to the valve means via pumping means, said pumping means increasing the pressure of the pressurised container.