NO169702B - PROCEDURE AND APPARATUS FOR MIXING A NUMBER OF SEPARATELY STORED MATERIALS - Google Patents

Description

The present invention is concerned with blower cleaning devices, and particularly relates to wet blower cleaning devices.

More specifically, the present invention relates to a method for mixing a number of separately stored materials, at least one of which is a particulate material or a combination of a particulate material and a liquid, and the materials are taken from the bottom of their respective containers and led into a flow of pressure fluid at the same time that the pressure fluid is introduced into the upper part of one of the containers, over at least one of the materials in relation to the outflow from the respective container.

Furthermore, the invention relates to an apparatus for carrying out the above-mentioned method, comprising a first container which is arranged to contain particulate material or a combination of a particulate material and a liquid and which comprises an inlet and a bottom outlet, a second container with an inlet and a bottom outlet for holding material to be mixed with the contents of the first container, a supply conduit through which a pressurized carrier fluid can be fed from a source and with which the containers are adapted to communicate, and a conduit for conducting pressurized fluid from the source to the upper part of one of the containers, above its contents in relation to the outflow from the outlet of the container.

In wet-blast cleaning devices, the abrasive material is usually mixed into a liquid stream under pressure or into a liquid stream with mixed gas, which in the following for practical reasons is simply referred to as pressurized fluid flow, and is directed via a controllable nozzle towards the surface or object to be treated. When using such devices, it is common to add a dry abrasive material to a gas stream and then liquid is added to moisten the abrasive material before it is ejected from the nozzle outlet to reduce dust formation at the workplace.

Usually, this liquid is delivered in the abrasive material and the pressure-fluid flow via a separate pump, which makes the blower's price higher than desirable, makes the blower cleaner more susceptible to breakdowns, and requires better technical knowledge on the part of the operator. It is also a disadvantage that pressure variations in the mixed fluid necessitate either manual regulation of the output pressure from the pump, or the connection of pressure balance control devices between the fluid supply and the pump.

As a result of this, the control of the device is made difficult, and especially with regard to the outflow of abrasive material and liquid, firstly with the consequence that the device's efficiency will vary, and secondly, the device's price is further increased as a result of the need for organs to control the pressure balance , and which in no case produces any instantaneous pump regulation when the incoming fluid pressure varies. All of this has an adverse effect on the device's effect.

When it comes to examples of devices that can be used to mix and then spray a homogeneous/heterogeneous mixture of different materials (air-liquid-solid particles), then reference should be made to FR patent publication 1.080.033 (wet blast cleaning device), US -patent document 2,942,860 (concrete sprayer), and CH patent document 202,922 (apparatus for spray painting). But these devices also suffer from the disadvantages mentioned above, and later in this description these patent publications will be reviewed in more detail in comparison with the blower cleaning device according to the present invention.

It is an object of the present invention to produce a method and an apparatus for mixing a number of separately stored materials, for wet-blow cleaning purposes, and where one can eliminate or mitigate the aforementioned disadvantages regarding price, the varying control, and degree of efficiency, and where there is only a need for a single source of pressurized fluid.

Furthermore, the present invention aims to produce an apparatus which enables the ratio between the sprayed materials to be freely and continuously regulated during the blower's operation, and which can be used for dry blower cleaning, and possibly for other spraying purposes than blower cleaning.

The method according to the present invention is characterized by the fact that the pressure in the containers and the pressure in the pressure fluid flow are balanced by creating a connection between the containers so that either the pressure fluid or one material under pressure affects the material in the other container to produce a simultaneous outflow and discharge of the materials from the respective containers into the flowing fluid, and the outflow of the materials from the containers into the flowing fluid is regulated independently of each other by means of valves.

In a preferred embodiment of the method according to the invention, and when one of the materials is a liquid, the temperature is kept above the ambient temperature.

The device according to the invention is characterized by the fact that the containers can be shut off and a connection has been created between the containers to approximately balance the fluid pressure system between the containers themselves and between the containers and the delivery line, and flow control valves are arranged between the bottom outlet of the containers and the supply line so that the outflow rate of the materials from the containers and into the line can be controlled independently of each other.

According to a preferred embodiment of the invention, the containers are arranged so that one is arranged inside the other, and furthermore the first and second container can be separated by a porous wall.

Thus, according to the invention, the outer container can comprise the first container which is arranged to accommodate a mixture of

a particulate material and a liquid, while the inner container comprises the second container which is arranged to contain a liquid which can be refilled by advancing the liquid through the porous wall from the first container.

Another preferred embodiment of the apparatus according to the invention is characterized by the fact that jet means are arranged in the containers to create a peripherally directed liquid jet to swirl the particulate material so that it can be more easily introduced into the first container.

Another preferred embodiment of the device according to the invention is characterized by the fact that the supply line ends in a lance which comprises a rigid tube with a straight bore with a length of at least 100 mm and the ratio between the diameters of the supply line and the lance is 1.5:1, 0-10:1.

The two containers are preferably arranged coaxially and concentrically, and according to an example, the inner container can contain the liquid/abrasive agent while an outer and enclosing container contains the liquid. In addition, it is an advantage to valve control the connection between each container and the supply line.

The pressure fluid is preferably delivered inside the inner container, as the above-mentioned connection between the inner container and the outer container balances the fluid pressure system.

At least one of the containers should be equipped with a quick pressure acting fluid outlet which is normally kept closed. The liquid used is preferably water with or without additives which may include rust inhibitors, while the pressure fluid used is preferably air.

Preferably, the inner container is first filled with water and then with abrasive material such as e.g. sand to ensure effective mixing and prevent clogging of the container outlet.

With the present invention, a pumpless device suitable for wet-blower cleaning has therefore been produced, and since the carrier fluid under pressure is also supplied directly to the liquid/abrasive material and the separate liquid, an immediate and equal regulation of the pressure carrier fluid is achieved at any occurring pressure variation in the pressure fluid source.

With regard to the aforementioned patent publications which are representative of the state of the art, it should be pointed out that the blast cleaning device referred to in FR patent publication 1,080,033 relates to a wet blast cleaning device used for cleaning ships. In contrast to the solution according to the present invention, however, this blower cleaning device only comprises a single chamber where sand and water are to be mixed together. The water is pumped into the bottom of the chamber through a line and drawn off through another line to a nozzle for delivering sand/water to the treatment site. However, most of the sand material is led into the blowing stream through another pipe. In the solution according to the present invention, however, the abrasive or the abrasive mixture is stored in separate containers before they are mixed together and drawn into the outgoing air stream. With this solution, the air is thus the main propellant, in contrast to the known solutions where the water in the chamber is used. The advantage of this is that much less water can be used to produce a higher blowing pressure, and consequently better results are achieved with the present blowing cleaning apparatus.

The device referred to in US patent 2,942,860 relates to a combined concrete sprayer/sandblaster and a mixing device where a chamber includes an upper part for mixing added cement or raw materials, while the bottom part is used to supply the blaster. Unlike the present invention, however, the contents of the two chambers are not simultaneously delivered to a carrier fluid. This sandblasting apparatus also differs from the present invention in the manner in which the water is mixed into the blowing stream. According to the known solution, the water is supplied exclusively to the blowing nozzle, while the present invention involves the liquid being mixed with the particulate abrasive material under pressure in one of the chambers and led into the carrier fluid. The advantage of this is that the air is not present when the materials are mixed together, and consequently the abrasive cleaning of the treated surface becomes even more effective.

In the above-mentioned CH patent document 202,922, there is mention of a spray painting apparatus where two liquids are stored separately and which are pumped to a nozzle where they are mixed together immediately before spraying. This apparatus differs from the present invention primarily in that no form of control can be exercised with the flow rate of the two liquids. Thus, it is only possible to mix equal volume parts of the two liquids, whereas according to the present invention, both the volumes and the outflow rates of each of the blowing materials can be precisely controlled, and thus the outflow of any of the materials can be immediately shut off.

The device according to the present invention can be used in dry conditions, and furthermore the device can be used for purposes other than blower cleaning. These alternative applications will later be investigated in more detail.

In what follows, an embodiment of the present invention will now be described, with reference to the accompanying drawings, in which: Fig. 1 shows a partial view of an apparatus for wet-blower cleaning according to the present invention.

Fig. 2 shows a corresponding plan section.

The apparatus comprises two coaxial and concentric containers or chambers 10 and 11. The inner chamber 10 serves to store the grinding material such as e.g. may be sand as the sand may be moist. According to the present invention, it is not necessary, as is common with wet-blast cleaning devices where sand is used as abrasive material, to use dry sand which is often delivered in bags to the device. Accordingly, the present invention provides a wet-blast cleaning apparatus where it is possible to recycle wet sand. In use, the inner chamber 10 naturally also contains water, and it should be noted that the water is always introduced first into the inner chamber 10, followed by sand (or other solid abrasive material) to ensure that there is an effective mixing of the sand and water and that the outlet 12 from the inner chamber is not blocked. The introduction of the sand into the water in the chamber 10 causes the sand to sink down through the water, and it is thereby immediately moistened. The introduction of compressed air into the inner chamber 10, as described below, causes a swirling action in the inner chamber 10 to complete the mixing. The outlet 12 is arranged at the bottom of the chamber 10, while the inlet to the inner chamber 10 is arranged at the top of the chamber.

During use, the outer chamber 11 contains additional water for addition to the sand/water mixture which is ejected from the inner chamber 10, as will be described below.

There is arranged at least one opening (or hole) 14 which forms a connection between the outer chamber 11 and the inner chamber 10, the hole 14 being arranged at the upper end of both chambers 10,11.

The inlet 13 to the inner chamber 10 is controlled by an air shut-off valve, e.g. a poppet valve, 15, and the valve 15 is closed when compressed air is introduced. For the apparatus, compressed air is used as a drive or carrier fluid, as the air is led from a source of compressed air, for example from a main supply of compressed air (not shown), and to a supply line system which is generally indicated at 16.

The compressed air is delivered from a source (not shown), possibly an air compressor to the line system 16 at the main inlet 17 and is controlled via a valve 18. The compressed air is delivered to the valve 15 via a line 19, and the air thus flows from the inner chamber 10 into the outer chamber 11 via hole 14.

Compressed air is also supplied via a line 20, and valve controlled as indicated at 21, to a blow hose for abrasive with a nozzle (not shown) which is connected to the line 20 by means of a bayonet coupling as indicated at 38. The nozzle on the blow hose for the abrasive is equipped with a dead man's handle so that the blowing operation with the abrasive material can be controlled by the operator, as the release of the handle will close the nozzle and interrupt the blowing operation with the abrasive material.

The blowing nozzle is preferably of the lance type and not of the usual venturi nozzle since it has been shown that the abrasive material has a tendency to deposit and clog a venturi nozzle when the device is used. The lance produces a compressed air outflow which has a thinner jet than the corresponding one for the supply line 20 so that the fluid flow under pressure is concentrated through the nozzle so that it can be appropriately set by the operator. It has been found that the lance works effectively when the diameter ratio between the tube 20 and the lance is in the range 1.5:1 - 10:1, a ratio that applies when the lance has a length of at least 100 mm. Typically, the diameter of the lance bore is in the order of 15 mm for a line 20 with a diameter of 4 5 mm for delivery of compressed air at 10 m<3>/minute at 7.031 kp/cm<2> (100 psi). The length of the lance is usually 450 mm so that the operator can keep a distance from the blast and get a secure grip on the lance.

The chambers 10 and 11 communicate with the line 20 via the lines 22 and 23, respectively, and the flow through each of these is controlled by the valve 24,25. Thus, the lines 22, 23 form a connection between the bottom of the chambers 10 and 11 and the line 20.

At the top of the outer chamber 11, a quick-acting pressure outlet line 26 is arranged which is controlled by a valve 27.

Water is supplied to the inner and outer chambers from e.g. a main water supply (not shown) via a line 28 where a one-way valve 29 and an open/close valve 30 are connected. The water is delivered directly to the chamber 11 via the line 28 which is connected to a line 31 for supplying water to the interior chamber 10, this line being controlled as indicated at 32.

A water level control or an overflow pipe 33 communicates with the inner chamber 10, the pipe 33 also being valve controlled as indicated by d 34.

The various valves are indicated as manually controlled valves, but it should be understood that these valves can be controlled automatically in a known manner.

To make the device ready for use, the valves 18, 21, 24, 25, 27, 30 and 34 are closed. Then the valves 30 and 32 are opened so that water can flow into the inner and outer chambers 10,11. A given amount of abrasive material, for example sand (moist or dry), is then fed through the inlet 13, which is open since the valve 15 is not affected by air pressure that can close the inlet. Water is continuously fed into the chambers 10 and 11 and will flow out of the pipe 33 when the required total volume of sand and water has been supplied to the inner chamber 10. At this stage the valve 32 is closed and then the valve 34. When sufficient has been supplied water in the chamber 11, the valve 30 is also closed.

The valve 17 is then opened so that the valve 15 is moved to the closed position and so that compressed air is introduced to the inner chamber, as well as to the outer chamber 11 via the connection hole 14.

Now the valve 21 is opened so that compressed air can flow through the line to the hose and the nozzle (not shown). Then the valves 24 and 25 are opened sufficiently so that the water/sand mixture from the chamber 10 as well as further water from the chamber 11 can flow into and be carried along by the air flow for delivery in the hose and out of the nozzle at the same time as this is directed towards the surface or another object to be blast cleaned.

The sand/water mixture and the extra water are subjected to the same air pressure in the upper part of the chambers 10 and 11 as that used to lead these out of their respective chambers.

Thus, a variation in the air pressure from the main source will automatically and instantly affect both the carrier air and the air in the chambers 10 and 11.

The valve 24 can be closed at any stage and it can be fed

water only from the chamber 11 into the air stream to rinse the work area. Optionally, the valves 24 and 25 can be closed so that only air is advanced through the hose and nozzle for blowing or drying purposes.

The supply pressure of the air can be varied up or down during operation

to achieve different working speeds or different types or degrees of finishing on the work surface. In such cases, a pressure gauge can be connected to the air inlet line 17 so that the operator can assess the working pressure more accurately.

The normal operating sequence for shutting down the apparatus primarily involves closing the valve 24 to prevent further discharge of abrasive material. When all abrasive material has been cleaned out of the hose, the valve 25 can be closed to prevent further water from being allowed into the line. After all the water has been removed from the hose, the valves 21 and 18 are closed. The valve 27 can then be opened to cause a slow drop in the air pressure in the containers 10 and 11, which in turn enables the air shut-off valve 15 to open.

If for some reason during normal operation there is a need for an emergency stop, this can be carried out manually or started automatically (by e.g. releasing the deadman's handle), by opening the valve 27, preferably with a simultaneous closing of the valve 18.

Organs are arranged to effect a rapid filling in the chamber 10 with substances which in themselves do not flow easily (e.g. moist sand or a suspension). Such devices include a water jet device 35 which is arranged inside and close to the wall of the filling funnel 36 at the top of the device. The jet member 35 is directed circumferentially so that, if necessary, it swirls the water around the funnel area and enables the material to be introduced into the chamber 10 through the open inlet 13. A valve 37 controls the flow of water to the jet member 35.

It should be noted that additives can either be introduced into the water in the chamber 10 or alternatively into the water in the chamber 11, and such an additive can, for example, be rust-inhibiting if an object or metal surface is treated, or it can include an anti-freeze agent for processing by low temperatures. The additive can optionally be added in powder or granular form mixed with the abrasive material. Since the total material volume in both chambers is known at the start of the operating sequence, pre-measured doses of additives can be added to one or the other chamber so that the correct dilution of the additives is obtained.

The wet abrasive blast cleaning apparatus described above can be used in dry conditions and in such a case the dry abrasive or other abrasive materials can simply be stored in the chamber 10 and the water supply system shut off and the sand or other abrasive materials fed through the line 20 through the line 22 via the open valve 24, the sand being subjected to internal air pressure that corresponds to the advance air pressure as described above.

The device can also be used for ice blowing, and in this case the inner chamber contains ice particles and water, while the outer chamber 11 contains water. It should be noted that the ice particles produced from water can be prevented from coagulating (freezing together) by introducing suitable additives into the water before freezing. Suitable additives can be, for example, polyphosphates.

The apparatus described above can either be used under moist or dry conditions, and it can be used for washing down by using only water from chamber 10 or even from chambers 10 and 11.

With the device, faster cleaning is achieved than with known wet-blower cleaning devices (under otherwise similar operating conditions). It can work up to 20% faster or even faster under given circumstances. The reason for this is that each abrasive particle wetted under pressure is contained in a water film so that its effective weight is increased when it leaves the blast nozzle. Thus, the particle's momentum is greater and can exert more work when it hits the surface of the workpiece.

The device is not subject to throttling like the known devices which are often blocked in the outlet for grinding material from the pressure chamber. In practice, such blockages in the known devices are usually released by immediately turning off the main air supply, i.e. by closing the valve 21.

The device is relatively cheap to manufacture compared to known devices.

Use of the device according to the invention involves less wastage of abrasive material at the workplace since the used abrasive material can be recycled in a moist state, i.e. that it is unnecessary to dry the abrasive material.

The device can be used in areas with high humidity since contaminating moisture does not adversely affect the device.

The device is spark-free and free of static electricity. It is also pumpless, as can be seen from the above, and since it does not include a pump, there is obviously no need to arrange a pump-driving generator.

The device contains no mechanically working parts, and due to its simple construction, all device parts can be easily maintained, replaced and renewed in a short time.

Furthermore, the device is safe to use and can therefore be used by a relatively unskilled worker.

When the device is used for wet blast cleaning, much less airborne dust is formed than with comparable known devices, and consequently much less fallout in a given area around the workplace, and this makes the device more environmentally friendly.

Finally, the device can be used with a large number of readily available wet and dry abrasive materials, and is assumed to consume much less abrasive material than with other wet-blast cleaning systems (in the order of magnitude of about 20% less) during use, and the device involves less cleaning at the workplace than during use that the conventional wet-blow cleaners.

The device according to the present invention is very flexible and can i.a. used as follows: 1. Wet and dry blast cleaning of stones, bricks, terracotta, steel, iron and all other hard or semi-hard surfaces. 2. Removal of paint or other coatings from such surfaces, either in one operation or layer by layer.

3. Washing down such surfaces.

4. Removal of contaminants from surfaces, e.g. radioactive contamination or biological contamination (possibly using chemical additives in water to improve the effect of the treatment), removal of oil or grease from surfaces (possibly using hot water, or solutions instead of water so that the removal is accelerated).

5. Removal of graffiti from stones and other surfaces.

6. Surface structuring either for an aesthetic appearance or as a pre-treatment for covering or bonding to the surface, highlighting the structure on wooden surfaces, matting glass to make it compact, rubbing or matting plastic material and all other surfaces. 7. Engraving of glass, stone, plastic and other surfaces using suitable masks if necessary. 8. Mixing materials, diluting solutions, spraying materials, mixing substances in one or more forms (such as solids in powder, granular or fibrous form, or semi-solid materials, or liquids) with themselves or with each other, and spraying or blowing the resulting mixtures. For example, the mixing and application of plasters, slurries, coatings, paints, adhesives, de-icing agents (e.g. mixing salt with sand or gravel etc. that are sprayed on roads where there is a risk of frost, or de-icing compounds on aircraft), mixing of plant seeds in culture medium and application of such by spraying, mixing and spraying of fertilizers and weed killers on agricultural land, mixing or coating textile fibers with binding agents and applying these in, e.g., connective tissue production, impregnation of surfaces with another substance, variegated coloring of surfaces such as floors, walls, bricks by using different colored materials in the different chambers or of different densities in one chamber.

The above apparatus can be designed with modifications. For example, according to the invention, a porous wall can be installed between the chambers 10 and 11 so that e.g. a liquid can be fed from the chamber 11 into the chamber 10. During ice blowing, e.g. ice and water are introduced into the chamber 10 while water is introduced into the chamber 11. If the amount of water in the chamber 10 drops too much during the blowing operation, water can seep through from the chamber 11 to the chamber 10 and consequently prevent clumping of the ice in the chamber 10.

In another embodiment, an outer chamber is used for the abrasive material and the liquid and an inner chamber for the liquid material. In this case, the inner chamber may have a small volume in relation to the outer chamber and a porous wall is used to separate the chambers so that the liquid can flow from it. outer chamber and into the inner chamber so that this is filled with liquid before and during blowing and thereby avoids the need for special pipeline arrangements and other filling devices. Some of the abrasive material may also pass through the wall and into the inner chamber, but this does not interfere with the mixing and blowing process. However, this is preferably prevented by using a wall with pore sizes so that the abrasive material cannot pass through the wall. In this embodiment, the inner chamber can be effectively reduced to a porous tube which is located inside the outer chamber and which communicates with it above the level of abrasive material in the chamber, liquid can be withdrawn from the liquid/abrasive material through the conduit and carried forward separately in the pressure fluid from the abrasive/liquid material.

The apparatus can comprise more than two chambers, provided that the chambers communicate with each other so that the air pressure in the chambers is equal to the pressure in the carrier fluid.

The chambers can be placed inside each other and be coaxial and concentric as in the apparatus described above or they can be arranged next to each other either parallel to each other or coaxially after each other.

The chambers can also be separated from each other and there can be two or more chambers provided that there is a connection between the chambers to ensure that the fluid pressure inside all chambers is the same, as the pressure corresponds to and varies with

the pressure in the carrier fluid.

Claims (8)

1. Method for mixing a number of separately stored materials, at least one of which is a particulate material or a combination of a particulate material and a liquid, and the materials are taken from the bottom of their respective containers (10,11) and led into a flow (20) of pressure fluid at the same time that the pressure fluid is introduced into the upper part of one of the containers (10,11), above at least one of the materials in relation to the outflow from the respective container, characterized in that the pressure in the containers (10,11) and the pressure in the pressure fluid flow is balanced by creating a connection (14) between the containers (10,11) so that either the pressure fluid or one material under pressure affects the material in the other container (11) to produce a simultaneous outflow and release of the materials from the respective containers (10,11) into the flowing fluid (20), and the outflow of the materials from the containers (10,11) into the flowing fluid is regulated independently of each other re by means of valves (24,25). 2. Method in accordance with claim 1 and where one of the materials is a liquid, characterized in that the temperature of the liquid is kept above the ambient temperature. 3. Apparatus for carrying out the method according to claim 1, comprising a first container (10) which is arranged to contain particulate material or a combination of a particulate material and a liquid and which comprises an inlet (13) and a bottom outlet (12) , a second container (11) with an inlet (28) and a bottom outlet (23) for holding material to be mixed with the contents of the first container (10), a supply line (20) through which a carrier fluid under pressure can be fed from a source and with which the containers (10,11) are arranged to communicate, and a line (19) to conduct pressure fluid from the source and to the upper part of one of the containers (10), over its contents in relation to the outlet the flow from the outlet (12) of the container (10), characterized in that the containers (10,11) can be shut off, and a connection (14) has been created between the containers to approximately balance the fluid pressure system between the containers themselves (10,11) and between the containers and the feed line (20), and it is anor dnet flow control valves (24,25) between the bottom outlet (12,23) of the containers (10,11) and the supply line (20) so that the outflow rate of the materials from the containers (10,12) and into the line (20) can be controlled independently of each other . 4. Apparatus in accordance with claim 3, characterized in that the containers (10,11) are arranged so that one is arranged inside the other. 5. Apparatus in accordance with claim 4, characterized in that the first and second containers (10,11) are separated by a porous wall (10). 6. Apparatus according to claim 5, characterized in that the outer container (11) comprises the first container which is arranged to accommodate a mixture of a particulate material and a liquid, and the inner container (10) comprises the second container which is arranged to accommodate a liquid which can be refilled by advancing the liquid through the porous wall (10) from the first container. 7. Apparatus in accordance with claim 3, characterized in that jet means (35) are arranged in the containers (10,11) to create a peripherally directed liquid jet to swirl the particulate material so that it can be more easily introduced into the first container. 8. Apparatus in accordance with claim 3, characterized in that the supply line (20) ends in a lance which comprises a rigid tube with a straight bore with a length of at least 100 mm and the ratio between the diameters of the supply line and the lance is 1.5:1, 0-10:1.