EP0100171A2

EP0100171A2 - A cleaning and treatment process and apparatus

Info

Publication number: EP0100171A2
Application number: EP83303953A
Authority: EP
Inventors: Sydney Charles Corbett
Original assignee: Hoklykem Holdings Ltd
Current assignee: Hoklykem Holdings Ltd
Priority date: 1982-07-08
Filing date: 1983-07-07
Publication date: 1984-02-08
Also published as: EP0100171A3; GB2126930A; GB2126930B

Abstract

A treatment process, and apparatus for cleaning and treating articles, particularly applicable to the cleaning and treatment of brass stampings to remove contaminates such as grease and graphite therefrom comprises the steps of subjecting said articles to a washing treatment in washing apparatus (2) and subsequently subjecting the articles to a blasting process in a blast cleaning machine (8) in which the articles are subjected to abrasive particles projected at high speed.

Description

The present invention relates t_Q a cleaning and treatment process and an apparatus for carrying out such a process which has specific, but not exclusive, application to the cleaning and treatment of metal stampings.
Metal stampings, and in particular brass stampings, after removal from the die in which the articles have been stamped, are contaminated with grease and graphite with which the die is lubricated prior to the introduction of the metal from which the stamping are made.
After stamping of each article it is necessary for these contaminants to be removed therefrom, the contaminants possibly being ingrained in the surface of the article itself.
Two different methods of treatment have been used in the past, either:

I. a chemical process in which contaminated articles are subjected to a plurality of successive treatments to chemically remove the contaminants and so clean the surfaces of the articles, or
2. a mechanical abrasion process in which the article are "blasted" with abrasive particles to clean the surfaces thereof.

The chemical process for cleaning and treating the article surfaces has been found to be successful. However the cost of chemicals, and the problems and cost associated with the disposal of spent chemicals, which may be corrosive, can provide problems.
Two significant problems have also occurred when using the mechanical abrasive process. In use of blast cleaning machines the abrasive material becomes contaminated by the grease and graphite. Since the contaminants are lubricants and hence of a nature such that they are the complete opposite to the abrasive material, not only does the abrasive material soon become so contaminated as to be of little or no use, but the blast machine itself becomes contaminated with graphite and grease to an extent wherein the use of the machine can have an adverse effect by actually introducing contaminates into the articles to be cleaned.
It is one object of the present invention to provide a new or improved process for the treatment of parts to remove contaminants which overcomes or substantially reduces the problems associated with known processes.
According to one aspect of the present invention we provide a process for the cleaning and treatment of surface contaminated articles characterised in that said process comprises the steps of:

(a) subjecting said articles to a washing process to remove a substantial part of said surface contaminants;
(b) subsequently subjecting said washed articles to an abrasion process by blasting the surfaces of said articles with abrasive material in a blast cleaning machine.

Preferably said washing process comprises at least two stages, a first stage in which the articles are subjected to a liquid containing a contaminants solvent, and a second stage which comprises rinsing said articles.
Conveniently said second stage may be sub-divided into a first rinsing step and a second rinsing step, liquid used in the first rinsing step being kept separate from liquid used in the second rinsing step.
If it is desirable for the articles to be dried before subjecting them to abrasive treatment, a drying stage may be introduced in which case said second rinsing process may be carried out by a hot liquid to assist in drying said parts.
Conveniently means are provided for moving said articles between said stages of the cleaning processes and between said cleaning process and said abrasive treatment, said means comprising any suitable manually or automatically operated conveyor means.
Conveniently said abrasive material, comprises particles of a material the same as, or substantially the same as, that from which the articles themselves are made. Conveniently said articles are subjected to continuous movement during the abrasive treatment by said particles, which particles are preferably projected towards said articles at a high velocity.
Said process may be a continuous process or a batch feed system may be provided so that articles may be fed through the process in batches of a desired and predetermined volume or weight.
The process method is particularly suitable for the treatment of brass stampings.
It is another object of the present invention to provide a new or improved apparatus for the cleaning and treatment of articles.
According to another aspect of the present invention we provide apparatus for the cleaning and treatment of contaminated articles, characterised in that said apparatus comprises:

(a) washing means adapted to subject said articles to a liquid capable of removing a substantial part of surface contaminates from said articles;
(b) an abrasive cleaning means adapted to receive articles from said washing means and subject said articles to a blasting process by projecting abrasive material at high speed towards said articles;
(c) conveyor means for transferring said articles from the washing means to the abrasive cleaning means.

Preferably said washing part of the apparatus subjects said articles to a plurality of separate liquids in succession and conveniently the apparatus further comprises drying means whereby said articles are dried before transfer to abrasive treatment means.
Preferably said abrasive treatment means comprises a blast cleaning machine and said abrasive material comprises particles of material the same as or substantially the same as that from which the articles themselves are made.
Conveniently said apparatus includes means for feeding said articles to said cleaning apparatus.
The combination of said washing process and said blasting process produces an efficient process for the treatment of contaminated articles. It has been found that in the case of brass stampings for example, the washing station may comprise a hot alkali washing stage and rinsing with water which in itself is insufficient to produce the quality of surface required on the fininshed article, but after the articles have passed through the blast cleaning machine, the surfaces of the article have reached a very satisfactory standard of cleanliness and finish.
The removal of some of the surface contaminants by the washing process has been found sufficient to enable long and satisfactory operation of the blast cleaning machine without occurrence of the aforementioned problems.
The invention will now be described in more detail by way of example only with reference to the accompanying drawings wherein:-

FIGURE I is a side elevation of one embodiment of apparatus of the present invention;
FIGURE 2 is a plan view of the apparatus shown in Figure I;
FIGURE 3 is a side elevational view of the three stage washing apparatus shown in Figures I and 2;
FIGURE 4 is a side elevation of a container forming part of the washing apparatus;
FIGURE 5 is an end elevation of the container shown in Figure 4 forming part of the washing apparatus;
FIGURE 6 is a partly broken away view of one of the blast cleaning machines shown in Figures I and 2.

Referring now to Figures I and 2 the apparatus comprises a loading hopper and first transfer means indicated at I into which articles to he cleaned and treated are placed, the articles being fed into a three-stage washing apparatus indicated at 2, the articles being automatically and continuously fed from one stage to the next in the manner as will be described later in more detail with reference to Figures 2 to 5.
After termination of the washing stage of the process the articles pass into a combined swarf and liquid separator and transfer means 3 into a driving oven 4.
When the articles have been dried sufficiently they pass from the drying oven 4 via an elavating conveyor 5 into a second hopper 6.
The second hopper 6 feeds a measured batch feeding system 7 adapted to feed alternately to either one of a pair of identical abrasive blast cleaning machines 8 both of which after treatment of the articles discharge onto a discharge conveyor 9.
The washing part of the apparatus will now be described in detail with additional reference to Figures 3 to 5.
Referring to Figure 3 of the drawings, a spray washing apparatus for the articles is generally indicated at I and comprises three containers 11, 12, 13 which respectively provide a hot alkali washing stage, a cold water rinsing stage and a hot water rinsing stage for workpieces to be treated. Each of the containers 11, 12, 13 is substantially identical and Figures 4 and 5 show a typical container in more detail. However, in general, it is to be noted that the machine has a frame including roller tracks to be described, on which the containers are mounted coaxially about a common generally horizontal rotational axis 14. Each container 11, 12, 13 tapers from a large intake end 15 to a small outlet end 16, which is received within the large intake end 15 of the next adjacent container. As will subsequently be described, feed means are provided inside each of the containers to feed articles along from the intake end to the outlet end, from which they subsequently fall into the intake end of the next adjacent container. It will be seen that the length and the taper of the containers is such that they can be interfitted in the manner described.
Referring to Figures 4 and 5 of the drawings, a typical container which will be given reference numeral 11, is shown. The container is of a tapering shape and is made up of a plurality of wall panels 17, 18, 19 for example, which are of truncated triangular shape. In the example shown, eight such wall panels are provided and together form a container of regular octagonal crosssection taken in any plane perpendicular to the axis of the container. Alternatively the container could be truly frusto-conical.
Each container is supported by two pairs of rotating rollers 29, 30, rotated by shafts 31, 32 respectively. Each container has a pair of external parallel, axially spaced-apart, coaxial annular tracks 33, 34, which run on the rollers 31, 32 to provide the rotary movement of the containers.
A generally spiral or helical feed means of the type known as an Archimedes scroll is provided inside each of the containers. This feed means causes articles within the container to move along from the intake end 15 to the outlet end 16 as the container rotates about its axis 14.
Although it would be possible to provide a continuous scroll which is welded to the interior of the container throughout its length, it has been found that the scroll 20 can be provided in the form of generally rectangular metal strips 21 each strip spanning one of the wall panels 17, 18, 19 and the strips being closely overlapped in generally parallel relationship at their ends. In this way, small openings 22 are provided between the strips 21, to enable washing liquid to flow back down the container under gravity, in a direction opposed to the direction of travel of the workpieces under the feeding action of the scroll 20.
Drainage of washing liquid may be improved, for example where heavy spraying is to take place, either by using perforated metal for the strips 2l or by providing the strips 21 with slots.
The use of separate individual strips 21 to form the scroll also simplifies greatly its design, construction and securing in position.
Towards the intake end 15 of the container, the strips are abutted so . that the openings 22 are not provided. In this way, the end portion of the scroll 20 at the lowermost part of the container is less capable of allowing the washing liquid to drain away throughout most of its rotational cycle. The liquid can of course drain to some extent either over the scroll or through perforations or slots in the scroll, where these are provided. When the end of the scroll coincides with the lowest part of the container during its rotation, there is free outflow for the washing liquid.
Thus, the intake end 15 of the container affords a reservoir for the washing liquid, into which the workpieces are initially deposited either from a feeder or from the outlet end of the preceding container. The articles therefore tend to fall into a reservoir of washing liquid and are then transported by the scroll along the container, through a countercurrent of treatment liquid, to the spray zone.
A plurality of spray heads 23 are provided within the container at a position spaced from the intake end. It is convenient to mount the spray heads on spray pipes which are introduced through the intake end of the container between that intake end and the outlet end of the preceding container.
The first container 13 into which the articles are delivered from the first hopper I will have a bed to the spray heads associated therewith an alkali solution to dissolve the grease and remove some of the graphite contaminating the articles.
The articles are then in a manner as afore described moved in a continuous manner to a second container 12 where they will be rinsed in cold water to remove the alkali solution therefrom and moved onto the third container I where they will be subjected to a second rinse in hot water to increase the temperature of the articles to assist in drying of the articles in the drying oven 4.
The length of time to which the articles are subjected to the alkali solution and rinsing steps may be varied in accordance with the amount of contamination on the articles.
At the intake end 15 of each container which is supplied with a washing liquid , there is a drainage trough 24 disposed so as to catch the liquid outflow, which falls from the intake end intermittently, when the end of the scroll coincides with the lowermost part of the container during rotation. The trough has an inclined undersurface 25 so as to feed the liquid transversely of the axis 14 to a filter box 26. The filter box is fitted with a fine wire mesh or similar screen 27 which catches fairly large particles of swarf or other material which may be caught up in the liquid stream. A settlement tank 28 is disposed below the screen 27 in the filter box and relatively finer particles settle out at the bottom of the tank 28. The washing liquid can be discarded or, more usually, will be recycled to the spray heads 23, either by direct pumping from the settlement tank or by initially being fed into a holding tank (not shown), from which it is pumped to the spray heads 23.
lt will be seen that, because each washing stage is carried out in a separate container, there is little or no contamination of the washing liquids with washing liquid from the preceding stage. To reduce the possibility of contamination, the articles are fed for some distance beyond the spray heads 23 so as to permit the washing liquid to drain off them, before reaching the outlet end 16 of the container and being fed into the next adjacent container. Additionally, a flexible baffle plate (not shown) may be mounted behind the spray heads to screen the outlet end of the container.
The washing apparatus described has various advantages, stemming largely from the tapering shape of the containers used for the washing stages. These containers could be fabricated as frusto-conical sheet metal structures but the octagonal cross-section described above is preferred because the articles are then subjected to a more vigorous tumbling action because of the sudden changes in inclination of the surfaces on which they are resting as the container rotates. The tumbling action is more vigorous than would be the case with a smooth frusto-conical wall.
By the use of a container which tapers along its length, a continuous drainage of the washing liquid from the spray jets can be permitted without the need for the container to be mounted on an inclined axis. Furthermore, the shape of the container enables the containers to be interfitted one into another as shown in Figure I so that each container can feed articles directly from its own outlet end 16 into the intake end l5 of the next adjacent container without the need for successive containers to increase in overall size. The use of separate containers for the stages, in addition to reducing the risk of contamination of washing liquid, enables the apparatus to be very versatile because each container can be arranged to rotate independently of the others.
It is unnecessary for alt the transit times through the containers to be equal in any continuous process. The apparatus is so constructed that the process will be carried out continuously so that it is merely necessary to adjust the number of articles fed per unit time to the first stage container to a value which is consistent with satisfactory washing through the line.
It is intended that, where articles to be treated include quantities of long swarf or other relatively large pieces of extraneous material, this would pass through the process line without removal. Only very small particles would be carried back by the washing liquids in the various stages and filtered out in the filter boxes 26. At the end of the process line, there is provided a swarf and liquid separator 3 which is in the form of a container of either tapering or cylindrical form which is constructed by means of for example channel or angle section elements bolted together with elongate slots between them. The panels of the final container are arranged in a many sided polygonal form and the rapid rotation of this container tends to break up and force the swarf through the slots, while feeding the articles to the drying oven. A swarf removing conveyor or collector can be provided below the container to receive material passing through the slots.
The swarf and liquid separator 3 also serves to remove excess liquid trapped within cup-shaped workpieces by causing them to tumble vigorously. In certain cases, the elongate slots might be unnecessary and the container would be made of perforated material.
The drying unit 4 comprises an oven for drying the articles and may promote tumbling of the workpieces. A feed scroll conveys the workpieces through the drying unit 4 which is parallel-sided and enclosed in an insulated housing through which heated air is blown to dry the workpieces.
After the articles have been dried in the drying unit 4 they are moved by an elevating conveyor 5 into the second storage hopper 6. The second storage hopper 6 as at its outlet a feed conveyor which feeds the articles to a batching unit 7 which collects the articles to form a batch of a predetermined size and feeds the batch into whichever of the abrasive blast cleaning machines 8 is available. The pair of abrasive blasting machines 8 are identical and one of which will be described in more detail with reference to Figure 6.
After going through the cleaning stages and being dried in the drying oven 4 the articles are delivered by the elevating conveyor 5 to hopper 6 and batch feeder 7 to one of the abrasive blast cleaning machines 8.
The abrasive blast cleaning machine as shown in Figure 6 comprises a moving bed 40 which carries the articles indicated at 41. The bed 40 comprises a perforated rubber belt 42 driven by chains round a plurality of guide and driving sprockets two of such sprockets being shown at 43 and 44. The arrangements of the guide and driving sprockets and the rubber belt 40 is such that a permanently formed dip is created in which the articles 41 are positioned and continuously tumbled during the blast process.
Abrasive material which may be any suitable material for example in the case of the articles to be treated being brass stampings, brass swarf has been found to be particularly effective, is fed from a screw conveyor 45 to trunking 56 and a high speed rotating impeller 57 which projects the swarf at high speed onto the articles 41. Swarf is then collected in connecting zone 58 and moved via conveyor screw 59 and elevating conveyor 60 to return to the top of the blast machine and screw conveyor 55.
Whereas the specific embodiment of the apparatus of the present invention described herein has incorporated two blast cleaning machines it is envisaged that a single blast cleaning machine may be used. A single blast cleaning machine is likely to be used particularly in a continuous flow system.
The process,and apparatus for carrying out the process, of the present invention has been found to provide a high standard of finish in particular on brass stampings. The process dispenses with the need for extensive chemicals and the difficulties of disposing corrosive chemicals and the washing process permits of delivery of articles to the blast machines in a condition in which the finish on the articles may be further improved without undue contamination of either the blast cleaning machine itself,or the abrasive material used therein, thus permitting effecient operation of the blast cleaning machines.

Claims

l. A process for the cleaning and treatment of surface contaminated articles characterised in that said process comprises the steps of:
(a) subjecting said articles to a washing process (2) to remove a substantial part of said surface contaminants;

(b) subsequently subjecting said washed articles to an abrasion process by blasting the surfaces of the said articles with abrasive material in a blast cleaning machine (8).
2. A process as claimed in Claim I characterised in that said washing step comprises two stages:
(a) a first stage in which the articles are subjected to a liquid containing a contaminant solvent;

(b) a second stage comprising rinsing said articles in water.
3. A process as claimed in Claim I or 2 characterised in that said process comprises the further step of drying (4) said articles after said washing process and prior to said abrasion process.
4. A process for the cleaning and treatment of metal stampings characterised in that said process comprises the steps of:
(a) subjecting said metal stampings to a washing process (2) to remove a substantial part of contaminants therefrom, said washing process comprising:
(i) subjecting said metal stampings to a liquid containing a contaminant solvent;

(ii) rinsing said metal stampings to remove said solvent;

(b) subjecting said washed metal stampings to an abrasion process comprising the step of blasting surfaces of the metal stampings with abrasive material in a blast cleaning machine (8).
5. A process as claimed in Claim 5 characterised in that said articles comprise brass stampings.
6. A process as claimed in Claim 5 characterised in that said contaminant solvent comprises an alkali solution and said abrasion process comprises the step of blasting surfaces of said brass stampings with particles of brass.
7. Apparatus for the cleaning and treatment of contaminated articles, characterised in that said apparatus comprises washing means (2) and an abrasive cleaning means (8) adapted to carry out the process as claimed in any one of Claims I to 6.
8. Apparatus for the cleaning and treatment of contaminated articles, characterised in that said apparatus comprises:
(a) washing means (2) adapted to subject said articles to a liquid capable of removing a substantial part of surface contaminates from said articles;

(b) an abrasive cleaning means (8) adapted to receive articles from said washing means and subject said articles to a blasting process by projecting abrasive material at high speed towards said articles;

(c) conveyor means (3,5) for transferring said articles from the washing means (2) to the abrasive cleaning means (8).
9. Apparatus as claimed in Claim 8 characterised in that said apparatus further comprises drying means (4) adapted to dry said articles after said washing process (2) and prior to entry into said abrasive cleaning means (8).
10. Apparatus for the cleaning and treatment of brass stampings characterised in that said apparatus comprises:
(a) washing means comprising two or more separate washing containers (111, 12, 13) each adapted to provide a separate washing treatment and subject said brass stampings to separate washing liquids, one of said washing liquids comprising a contaminant solvent;

(b) abrasive cleaning means comprising a blast machine (8) adapted to project brass particles onto the surfaces of the brass stampings at high velocity;

(c) conveying means (3,5) for conveying the brass stampings from the washing means to the brass cleaning machine.