GB2378037A

GB2378037A - Plasma cleaning of a machine or machine component

Info

Publication number: GB2378037A
Application number: GB0207456A
Authority: GB
Inventors: Christof Diener
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-03-29
Filing date: 2002-03-28
Publication date: 2003-01-29
Anticipated expiration: 2022-03-28
Also published as: GB0207456D0; FR2822732A1; DE10115394B4; GB2378037B; FR2822732B1; GB2378037A9; DE10115394A1

Abstract

A machine or machine component 1, having a hollow space 2 for a fluid or a granular product, and including movable machine elements, further includes a plasma cleaning arrangement comprising: means for supplying a process gas to the hollow space 8; and means for generating a plasma from the process gas, in the hollow space of the machine or machine component. The plasma may be generated by at least one electrode 5 fitted in or on the hollow space 2, or by other means such as microwave radiation or capacitive electrodes. The walls of the hollow space may act as a grounded return electrode 7. The invention allows cleaning of components and systems, including pumps, filters, catalytic converters, reactors, pipelines, injection moulds and mixers, even while in use. Deposits in the hollow space may be removed at any time or avoided from the outset.

Description

- 2378037

.. Machine or machine component with a hollow space, and a cleaning method for same 5 The invention concerns a machine or machine component (which term as used herein includes a process engineering unit) with a hollow space for either a fluid or a granular product, especially for accommodating machine elements that move with respect 10 to each other, and to a method of cleaning the said machine element or unit. Deposits and contamination can occur in the hollow space of such units because of the fluid flow or the granular product. In particular, the mode in which machine elements designed to work by 15 means of rotations and/or translational movements, such as pistons, valve actuators, paddles, mixing elements, etc., may be impaired. Various types of deposit may occur, according to the type of fluid or product.

During an engineering process, e.g. when separating or 20 etching material, residues are deposited in both the reaction space and machine components downstream of the reaction space, such as lines, pumps, catalytic converters and injection moulding equipment. According to the present description, the term "fluid" means a

25 liquid or gaseous substance, or a combination of both substances, such as a paste, or a viscous or fluid material (plastics, elastomers). The term "granular product" means powders, granules, etc. 30 German patent DEA-3725358 describes a coating installation with an integral plasma cleaning system, which can merely clean the reaction space of the coating installation whilst the coating process is interrupted. In this method of cleaning, a microwave 35 generated plasma is introduced into the reaction tube and the internal surfaces of the reaction space are

- 2 cleaned by dry etching. Only deposits in the reaction space can be removed. Other components of the coating installation must be dismantled for cleaning.

5 It is also known that process engineering units may be dismantled and affected components cleaned separately.

This method of working is very costly and labour intensive. 10 The function of this invention is to be capable of cleaning hollow areas of machine components and/or process engineering systems, especially moving machine elements within the component or system, at any time, even while a unit or machine is in operation, and hence IS without dismantling individual machine elements.

According to the invention, there is provided a machine or machine component of the type mentioned in the introduction, in which is embodied a plasma cleaning

20 installation, consisting of a process gas inlet to and an outlet from the hollow space, and means for generating a plasma in the hollow space, for example an electrode for plasma generation, fitted on or inside the hollow space.

The invention also provides a cleaning method for a hollow space fed by a fluid, in which a plasma cleaning installation embodied in the machine component or unit, fundamentally consisting of a process gas inlet to and 30 an outlet from the hollow space, and means (for example an electrode) for plasma generation, fitted on or inside the hollow space, is operated during the motion of the machine elements. This is beneficial for the removal of organic layers or contamination.

- 3 Microwave radiation can also be used for plasma generation. An electrode within the hollow space is not then required. Plasma can also be generated using capacitive or inductive methods.

The machine component may preferably comprise a vacuum pump. A plasma may be generated in the hollow space of the 10 machine component, or in the pumping space of the vacuum pump, in order that deposits or contaminants can be chemically or physically removed. There is no requirement to dismantle contaminated machine elements.

Long down-times and venting of hollow spaces can thus 15 be avoided. Suction-degrading filters can sometimes be dispensed with. Hence timewasting subsequent cleaning is not required. The plasma source can work both in standard or over-pressure mode, as well as in low pressure mode. A supplementary vacuum pump may be 20 required in the latter case. Plasma sources that may be considered are, for example, low frequency, high frequency, 50/60 Hz, microwave, corona and barrier sources. If a plasma is generated in the line or pump, this can be used to clean other components such as 25 valves, filters, sensors, catalytic converters and injection moulding equipment.

The term "process engineering unit", as used herein, includes mixers, injection moulding equipment, etc. If the walls of the hollow space and/or the vacuum pump are designed as a return electrode, only a single electrode may be embodied in the hollow space or the pumping space. It is preferable for the line forming 35 the return electrode to be grounded. If all the walls or the vacuum pump are designed as the return

- 4 electrode, a particularly good cleaning effect can be achieved. In a particularly advantageous method, the plasma 5 source can be operated during an engineering process.

Hollow spaces can thus be cleaned concurrently while a process takes place in the reaction space within a unit or machine, and this can dispense completely with down times of the unit or machine for cleaning purposes. If 10 the plasma source is always in operation during a process, deposits can be avoided from the outset, and chemical compounds emanating from the reaction space are broken down immediately (cracking). It is preferable for the chemical compounds to be broken down 15 into environmentally friendly components.

All recognised process gases may be considered for use as the process gas, in particular H202, 02, N2, N2O, air, CF4, noble gases, HCOOH, NH3, and mixtures of these.

A major advantage of the invention is that this cleaning method allows removal of organic material et al leaving practically no residue. It also kills off disease bearing agents.

Other features and benefits of the invention are brought out in the following description of an

engineered example of the invention, using the figure, which shows its fundamental features, and the claims.

30 The features described can be implemented alone, or in any combination, within the scope of the appended claims. Two preferred embodiments of the invention will now be 35 described with reference to the accompanying schematic

drawings, which show a vacuum pump and an injection moulding system respectively. In the drawings,: Fig. 1 is a schematic illustration of a vacuum pump connected to a vacuum unit, showing the 5 principle of the invention; and Fig. 2 is a schematic illustration of an injection moulding system operating according to the invention. These embodiments are by way of example only and should not be understood as restricting the invention in any way. The following key indicates the various parts shown in 15 the drawings.

1 Vacuum pump 2 Pump space 3 Feed 4 Vacuum unit 20 5 Electrode 6 DC or AC power source 7 Ground 8 Gas supply 9 Not used 25 10 Not used 11 Injection moulding unit 12 Device for producing a mouldable output product 13 Injection mould 14 Recipient 30 15 Process gas supply 16 Vacuum pump 17 Electrode 18 DC or AC power source 19 Ground 35 20 Seal 21 Contamination

- 6 22 Hollow space 23 Direction in which the container moves Fig.1 illustrates the principle of operation of a 5 vacuum pump 1, for example a dry sealing vacuum pump, lobe pump or turbo-pump, with a pumping space 2. The correspondingly shaped pistons (not shown in the figure) are rotated against the walls of the vacuum pump housing in the pumping space 2 to generate the 10 pumping effect. At the same time, a fluid is sucked by a known method via a feed line 3 from a vacuum unit 4 and expelled via an output flange (not shown in the figure). If this is a fluid used in an engineering system, it may contaminate the pistons and the housing 15 wall, for example in an engineering process such as Chemical Vapour Deposition (CVD). This can lead to deposits in the pump 2. For removal of the deposits, an electrode extending into the pump 2 is fitted, and this is connected to a DC or AC power source 6. In the 20 example shown, the feed 3 and the pump 2 are made from electrically conducting material. The pump 2 is grounded 7 and thus forms a second electrode. The feed line 3 is connected with a gas supply 8 for the process gas used for plasma generation.

Fig. 2 illustrates the construction of part of an injection moulding system with a device 12 for producing the mouldable output product and an injection mould 13. After extraction of the final or intermediate 30 product from the hollow spaces 22 in the injection mould 13, a container 14, capable of movement in the direction of the arrows 23, may be fitted over the injection mould 13, as shown in Fig. 2. The container 14 is coupled to the injection could 13 so as to form a 35 seal (seal 20), and hence the hollow spaces 22 in the injection would 13 can be evacuated. Contamination 21

- 7 in the hollow spaces 22 can be dissolved using a plasma treatment and then sucked out. Alternatively, the injection mould 12 can also be housed completely in a container. The container 14 has a gas supply 15 and a 5 connection to a vacuum pump 16. The plasma is generated using an electrode 17 (ground 19) and a DC or AC power source 18.

The invention thus provides a machine component (1) 10 and/or a process engineering system with an integral plasma cleaning installation and a cleaning method. A hollow space is employed, especially for housing machine elements fitted so as to be movable, and is fed with a fluid or accepts a granular product. Parts such 15 as pumps, filters, catalytic converters, reactors, pipelines, injection moulds and mixers etc. can repeatedly become contaminated by fluid residues during use. According to the invention the plasma generation installation consists of means (8) for supplying a 20 process gas and means for extracting the process gas from the hollow space (2), and an electrode fitted in the hollow space (2) for plasma generation. Deposits in the hollow space (2) can be removed at any time or avoided from the outset.

The plasma may also be generated without electrodes (e.g. using microwave radiation) in other forms of design. It can also be produced using capacitive electrodes. The plasma can be generated in the low 30 pressure area (low pressure plasma) or in the overpressure area (e.g. corona, barrier discharge, microwave discharge).

it.

Claims

- 8 CLAIMS

1. A machine or machine component, having a hollow space for a fluid or a granular product, and including 5 moveable machine elements, wherein the machine or machine component also comprises a plasma cleaning device, the said device including means for supplying a process gas to the hollow space, means for extracting the process gas from the hollow space, and 10 means for producing a plasma in the hollow space of the machine or machine component.

2. A machine or machine component as claimed in Claim 1,

wherein the means for producing a plasma comprises an 15 electrode fitted in or on the hollow space.

3. A machine component as in Claim 1, which is a vacuum pump. 20 4. A machine component as in Claim 1, which is an injection moulding unit.

5. A machine component as claimed in Claim 4, wherein the plasma cleaning installation is aligned on the 25 injection mould.

6. A method of cleaning method a hollow space of a machine or machine component which in use contains a fluid or a granular product, and which contains 30 moveable machine elements, which method comprises operating a plasma cleaning device, including means for supplying a process gas to the hollow space, means for extracting the process gas from the hollow space, and means for producing a plasma in the hollow 35 space of the machine or machine component, whilst the

9 - moving elements in the machine are in operation.

7. A method as claimed in Claim 6, wherein the means for producing a plasma comprises an electrode fitted in 5 or on the hollow space.

8. Machine component (1) and/or an engineering system (11) with a hollow space (2; 22) for a fluid or granular product, in which are fitted especially 10 machine elements capable of movement, characterized in that a plasma cleaning installation, consisting fundamentally of a process gas supply (8; 15) and an extraction system for the hollow space (2; 22), and an electrode (5; 17) fitted in or on the hollow space 15 (2; 22) for producing the plasma, in which is embodied the machine component (1) and/or the engineering system (11).

9. Cleaning method for a hollow space, for a fluid or a 20 granular product, in a machine component (1) and/or an engineering system (11), in which, especially in the hollow space (2j22), are fitted machine elements capable of movement, characterized in that a plasma cleaning installation embodied in the machine 25 component (1) and/or in the engineering system (11), fundamentally consisting of a process gas supply (8) and extraction system for the hollow space (2; 22), and an electrode fitted in the hollow space (2; 22) for producing the plasma, while the moving elements 30 in the machine are in operation.