GB2113719A

GB2113719A - Solvent recovery and regeneration in washing operation

Info

Publication number: GB2113719A
Application number: GB08301194A
Authority: GB
Inventors: Guido Zucchini
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-01-26
Filing date: 1983-01-17
Publication date: 1983-08-10
Also published as: FR2520268B1; DE3300666C3; GB8301194D0; DE3300666A1; FR2520268A1; GB2113719B; DE3300666C2

Abstract

In washing metal and non-metal parts such as miscellaneous small items and components for the mechanical and electronics industries in a closed, impervious chamber with the use of solvents the continuous or discontinuous recovery of the solvent used for the washing operation, with continuous or discontinuous distillation, for regenerating the solvent is combined with the drying of the washed pieces with the recovery of the solvent vapor generated by a flow of air which, in a closed cycle circuit, is made to circulate inside the chamber in which the pieces are washed. Means for contacting the parts located in baskets moving in a closed path within the chamber with a pressurized jet of solvent located above the solvent level in the chamber is also disclosed.

Description

SPECIFICATION Process for washing metal and non-metal parts such as miscellaneous small items and components for the mechanical and electronics industries, and a machine for implementing the said process The invention relates to a process and to a machine for the implementation thereof, for washing metal and non-metal parts and components, especially studied for washing the mechanical parts of machines and motors, and electronic components etcetera.

Two types of processes are used at the present time for washing the mechanical parts of machines or pieces made of metal and small metallic items, and these can be classified as follows: - cold processes, where the pieces placed in a washing tank, normally open at the top, are sprayed with various detergents and/or solvents, or kerosine, and are then rinsed with running water; - hot processes, where the pieces placed in a washing tank are sprayed with a liquid, composed of water and detergent, brought to a temperature suited to the type of dirt to be removed from the pieces being washed and to the detergent utilized.

Both of the said processes envisage piece treatment operations during which the washing liquid is pressure sprayed onto the pieces to be washed and, upon completion of the washing cycle, the recovery of the liquid in a specially provided tank for it to be used again once it has been filtered.

The washed pieces are left inside the washing tank until they have dripped completely, after which they are taken to be dried, generally with jets of air.

With the modi operandi as outlined above, the main problem comes from the fact that both during the washing operation and that for the drying of the pieces, there is an accumulation of gases and vapors that penetrate into the work area atmosphere (or else are channelled externally). The said gases and vapors are in no way treated for the recovery of polluting substances and thus those who have to work in the area concerned operate in unhealthy surroundings. Furthermore, the loss of solvents and detergents has negative repercussions on costs for the treatment of the pieces being washed.

Another problem comes from the fact that in order to prevent a noticeable loss of detergents and solvents at the time the pieces are being dried, the dripping time needs to be considerable.

In hot processes, the said time can be less long (compared to cold processes) because of the fact that the piece heated during the washing operation by the hot liquid used encourages, for heat exchange reasons, the evaporation of the water and of the solvents.

The dripping time becomes a considerable pause time for washing machines, or else it requires the washed pieces to be taken out of the washing tank and placed in a dripping tank.

The main object of the invention is to overcome the aforementioned difficulties and, in particular, to exclude, in processes for washing metal pieces, and also metal and non-metal material small items and components, any loss of solvent and/or detergents during the washing and drying operations, and to reduce to a minimum the times required for the latter mentioned operation.

Another object of the invention is to make provision for there to be a regenerating operation for the solvent utilized in the washing cycle, through the distillation of the solvent, and to make use of the vapors derived from the distillation of an eventual further treatment operation of the pieces being washed, using the perfectly cleansed solvent.

These objects are all attained by the process forming the subject of the invention which essentially comprises the following operations: a) the washing of the pieces, in a closed impervious chamber, with the use of pure state solvents or solvents to which an additive has been added, with the immersion of the pieces in the said solvents and/or with the soaking of the pieces by pressurized jets of solvent; b) the continuous or discontinuous recovery of the solvent used for washing, with the regeneration thereof by means of continuous or discontinuous distillation; c) the drying of the washed pieces with a closed circuit forced circulation flow of hot air through the chamber in which the pieces are washed, and with the recovery, through condensation, of the solvent vapors generated by the said flow.

In this way, no polluting substance is discharged externally and the possibility exists of reducing losses of solvent to a minimum, or even of doing away with them completely. Furthermore, a reduction is achieved, to a notable extent, in the drying time for the washed pieces since, on account of the forced circulation of heated air inside the washing tank, the rapid vaporizing of the solvent is achieved.

Once the washing operation has ended, the pieces are, in one preferred operational sequence, treated with solvent vapor taken, by means of distillation, from the regeneration circuit of the solvent utilized for the washing operation.

The use of regenerated solvent vapor in the final stage of the washing operation makes it possible, in practice, to subject the washed pieces to being soaked in solvent, thereby improving the washing result and eliminating any residual traces of grease, crust or similar.

So that maximum productivity be achieved, the machine that can be employed for implementing the above described process is provided, inside the washing chamber, with an element that rotates, or is at any rate movable, inside which one or more pins or rods are provided for supporting one or-more baskets in which the pieces to be washed are contained.

The said element is so supported that, during the movement thereof, the baskets be carried, one or more times and in succession, into immersion in a bath of solvent that partially fills the washing chamber, in the region of at least one nozzle that delivers at least one pressurized jet of solvent towards the said basket, and in the region of the door that provides access to the inside of the washing chamber.

Thus, for one washing cycle, an operational stage is evolved in which one part of the pieces is immersed in the bath of solvent and another part is hit by pressurized jets of solvent that assist, thanks to the mechanical action they exert, in washing areas to which access is difficult.

When the washing operation has ended, the pieces can easily be discharged by removing the baskets from the support pins or rods. For this reason, in one preferred embodiment, the said pins or rods are cantilevered from the movable element inside the washing chamber and the said baskets can be freely threaded onto and subsequently withdrawn from the said pins or rods.

In order to render more clear the ideas behind the process forming the subject of the invention, the operations comprised therein and the characteristics of the machine for the implementation thereof will now be described, with the aid of the accompanying drawings, in which: - Fig. 1 shows, diagrammatically, one possible embodiment for a machine suitable for implementing the process in question; - Fig. 2 shows, diagrammatically in a front view with some parts in sectional form, a first embodiment for the washing chamber; - Fig. 3 shows, diagrammatically in a front view with some parts in sectional form, a second embodiment for the washing chamber, where the element that supports the baskets is in the form of a rocker arm;; - Fig. 4 shows, again diagrammatically in a front view, a third possible embodiment for the washing chamber, where the element that supports the baskets is a continuous conveyor; Fig. 5 shows, in a diagrammatic perspective view, one possible type of basket that can be mounted on the pins or rods connected to the movable element inside the washing chamber.

Shown at 1 in Fig. 1 is the washing chamber provided with a platform 2, for the pieces to rest on, that can be fixed or rotatable around a shaft set crosswise. Movement can be given to the platform 2 by the jets of solvent that hit the pieces to be washed or through the use of geared motor means connected mechanically to the said platform.

The charging of the pieces to be washed into the washing chamber 1 is, in the case described, effected from the top and thus the chamber 1 is provided with a suitable hermetically sealed door.

The washing chamber 1 is provided with a number of sprayer nozzles 3 by means of which the solvent, taken from a tank 4 by means of a pump 5, can be pressure sprayed onto the pieces to be washed in such a way as to combine with the cleansing effect due to the characteristics of the solvent, a useful mechanical action for reaching hidden parts, cavities, and blind and through holes, etcetera.

Via a discharge pipe 6, the washing chamber 1 is connected to a filter 7 that is able to withhold the dust removed from the pieces being washed.

The filter outlet is connected both to the tank 4 and to a fan 8, the output of which is connected to a condenser 9 which can be, for example, a cooling plant.

As the solvent is gradually discharged from the washing chamber 1, it is thus sent back, filtered, to the tank 4, while the solvent vapor exiting from the filter 7 and passing across the fan 8, reaches the condenser 9. The latter is connected: through a pipe 10 to a heat exchanger 11; through a pipe 12 to a filter 13, in direct communication with the outside atmosphere; and through a pipe 14 to another pipe 1 5 running out of a distillation group 16.

The output of the heat exchanger 11 is connected, via a pipe 17, to the washing chamber 1 and jointly with the filter 7, the fan 8 and the condenser 9, as well as the washing chamber 1, it constitutes the circuit for the drying of the washed pieces.

The presence of the filter 13 (that is in direct communication with the outside) makes it possible to avoid pressure from building up inside the machine during the washing operation. The said filter can be made of activated carbon or some other suitable material and the direct connection of the filter to the condenser 9 has the effect that during the drying cycle, on account of the vacuum that forms in the pipe 12 (due to the forced circulation of air inside the condenser 9) the incoming air, passing counter-current across the filter, returns to the condenser 9 at least part of the solvent absorbed, thereby enabling it to be recovered.

The distillation group 1 6 is connected, by means of the pipe 1 5, to the washing chamber 1, and by means of a pipe 1 8, to the delivery side of the pump 5.

The solvent taken from the tank 4 can be sent to the distillation group 16 and from this, via the pipe 14, the condenser 9 and the separator 1 9 (connected to the condenser 9 by means of a pipe 20) flow back, cleansed, into the tank 4, through the pipe 21.

A valve 22 controls the way in which the solvent vapor leaves the distillation group 1 6 in such a way as to either send it towards the washing chamber 1 or towards the condenser 9, as will be seen better below.

A further valve 24 controls the sendiny of the solvent on the part of the pump 5 directly into the chamber 1 or to the nozzles 3, and to the distillation group 1 6.

The foregoing description has been given purely on general lines since the process according to the invention can also be implemented by means of plants that differ from the one described herein.

For example, two washing chambers could be provided with the discharge thereof connected to the filter 7 and the inlet connected both to the heat exchanger 11 and to the distillation group 16 in such a way as to have, during the drying operation of the pieces in one washing chamber, the washing of the pieces in the other chamber.

In accordance with the above description and with the process forming the subject of the invention, the treatment operations on the pieces to be washed follow in succession as outlined below.

It should be borne in mind that, in the case of the immersion washing of pieces resting on the platform 2, a valve 23 for closing the discharge pipe 6 needs to be provided.

The solvent is taken, by means of the pump 5, from the tank 4 and is carried to the washing chamber 1 whence, when discharged through the pipe 6, it returns to the tank 4 passing across the filter 7.

As already stated, any solvent vapor generated in this operation passes, via the fan 8, into the condenser 9 where the solvent, brought back to the liquid state, returns to the tank 4 via the separator 19.

Once the washing operation has been concluded, the fan 8 and the heat exchanger 11 are started up. In this way the forced circulation of hot air is commenced inside the circuit constituted by the washing chamber 1 , the filter 7, the fan 8, the condenser 9 and the heat exchanger 11.

The flow of air causes the evaporation of the solvent from the washed pieces which is then left inside the condenser 9 from where the recovered solvent passes into the separator 19 and is then returned to the tank 4.

As can be seen, both during the washing operation and during the drying operation, there is no loss at all of solvent vapor or any freeing or purging of saturated solvent vapor into the outside atmosphere; and this is in conformity with the objects the process in question sets out to achieve.

Should it be wished to give the piece washing operation a better finish, once the operation has come to an end, that is to say when the solvent taken from the tank 4 has been completely discharged from the washing chamber 1, solvent is sent from the tank 4 to the distillation group 1 6 and from this superheated solvent vapor is discharged into the inside of the washing chamber 1. For this, the valve 22 has to close the pipe 14 leaving free the passage in the pipe 1 5. The solvent vapor entering the washing chamber 1 condenses as it makes contact with the colder atmosphere and, in particular, with the washed pieces, soaking the latter afresh.

The continuance of this operation results, as an effect of the heat exchange between the superheated solvent vapor and the washed pieces, in a gradual revaporization of the solvent which is then completely recovered during the subsequent drying cycle.

The distillation group 1 6 can also be utilized continuously to distill the solvent used for washing, or in a discontinuous fashion to purify the solvent after a certain number of operational cycles.

The chamber 1 can also be of a different type from that described in this text.

With reference to Fig. 2, shown globally at 40 is an element that rotates inside the chamber 1 around a horizontal shaft. In the case described, the element 40 is provided with three "spokes" 50, angularly equidistant one from the other, to the free extremities of which are fixed corresponding rods 60, one parallel to the other.

The element 40 is located in the proximity of the wall of the chamber 1 opposite that on which is situated the door 70 for access to the inside of the said washing chamber 1. On the accompanying drawings, the said door is represented only by a broken line. The element 40 is supported by the frame of the machine and it can be connected mechanically to a drive group 80 by which it is made to rotate unidirectionally in a continuous or intermittent fashion, inside the chamber 1.

At 90 is shown a pipe connected to the solvent tank. In the case described, there are in communication with the said pipe, several nozzles 100 oriented towards the inside of the washing chamber 1 in such a way as to send pressurized jets of solvent in the direction of the baskets, shown at 110, in which the pieces to be cleaned are contained. As illustrated in Fig. 5, the baskets 110 are virtually of reticular structure and are provided, on two opposite sides, with two holes 120 that are coaxial one with the other and are of an area greater than that of the rods 60 so that it be possible to freely thread them into and withdraw them from the said rods.

The rods 60 are provided, at the free extremity, with a head 130 whose area is greater than that of the said rods 60 but less than that of the holes 120; to the said head is entrusted the task of preventing the accidental withdrawal of the baskets 110 from the rods 60 during the working cycles.

With reference to the foregoing description, on account of the rotation of the element 40, during a washing cycle the baskets 1 10 are carried in succession into complete immersion in a bath of solvent contained in the lower part of the chamber 1 and, subsequently, into the region of the nozzles 100 from which the pressurized solvent is hurled towards the pieces to be washed, thus rendering easier the cleaning of parts with cavities, blind holes and, generally speaking, parts to which access is difficult. Following the washing operation, a drying cycle takes place in accordance with the description given above.

In the example given in Fig. 3, where for elements and devices corresponding to those illustrated in Fig. 2 the same reference numbers have been maintained, the element 40 is in the form of a rocker arm and the drive group 80 can be operated in a way whereby the element 40 is made to oscillate around its own axis.

According to this particular solution, while a basket 110 is immersed in the solvent contained in the bottom part of the chamber 1, the pieces contained in the other basket are subjected to the action of jets of solvent delivered by the nozzles 100 directed thereto. In the case described, the washing chamber 1 is provided with two doors 70 in the region of which arrive the two baskets 1 10.

According to the solution illustrated in Fig. 4, the element for supporting the rods 60 is formed by a continuous conveyor 1 50 mounted around transmission pulleys 1 60 supported by the frame of the machine, one of which is mechanically connected to the drive group 80.

Claims

1 ) Process for washing metal and non-metal parts such as miscellaneous small items and components for the mechanical and electronics industries which essentially comprises the following operations: a) the washing of the pieces, in a closed impervious chamber, with the use of pure state solvents or solvents to which an additive has been added, with the immersion of the pieces in the said solvents and/or with the soaking of the pieces by pressurized jets of solvent; b) the continuous or discontinuous recovery of the solvent used for washing, with the regeneration thereof by means of continuous or discontinuous distillation; c) the drying of the washed pieces with a closed circuit forced circulation flow of hot air through the chamber in which the pieces are washed, and with the recovery, through condensation, of the solvent vapors generated by the said flow.

2. Process according to Claim 1 wherein, once the washing operation has ended, the pieces are treated with solvent vapor taken, by means of distillation, from the regeneration circuit of the solvent utilized for the washing operation.

3. Process according to Claim 1 wherein, during the operation of drying the washed pieces, the flow of air leaving the washing chamber is made to pass through at least one condenserseparator element in which the solvent vapor is brought to the liquid state and then, through a heat exchanger, for it to be heated to a temperature sufficient to cause the vaporization of the solvent inside the washing chamber.

4. Machine for implementing the process according to Claims 1, 2 or 3, wherein there is an element that rotates, or is at any rate movable along a closed directrix inside the washing chamber, the said element being provided with at least one rod or pin cantilevered thereto, onto which can be hung at least one basket in which the pieces to be washed are contained; provision being made, furthermore, inside the said chamber for a pipe in communication with the solvent tank and provided with at least one nozzle for delivering a pressurized jet of solvent towards at least one of the baskets in which the pieces to be washed are contained, located above the level of the solvent contained inside the washing chamber and passing in the vicinity of the said nozzle during the movement cycle of the said movable element inside the washing chamber; the said washing chamber being provided with at least one access door of an area and outline greater than the area and the transverse outline of a basket in which the pieces to be washed are contained.

5. Process for washing metal and non-metal parts, substantially as hereinbefore described with reference to the accompanying drawings.

6. A machine for carrying out the process claimed in any one of claims 1 to 3 and 5, substantiaily as hereinbefore described with reference to the accompanying drawings.