EP3517244A1

EP3517244A1 - Abrasive blasting cabinet

Info

Publication number: EP3517244A1
Application number: EP18153639.2A
Authority: EP
Inventors: Seppo Koivuniemi
Original assignee: Finnblast Oy
Current assignee: Finnblast Oy
Priority date: 2018-01-26
Filing date: 2018-01-26
Publication date: 2019-07-31

Abstract

An abrasive blasting cabinet comprises a cabinet housing (1) and a transparent plate (6) attached to an opening (6a) in the cabinet housing (1). Inside the cabinet in front of the plate, apart from the plate, there is a protective net (7) of the plate. The plate and protective net and battens (8) attached between them form a case-like structure, which has one or more openings (9), which are connected to the outside (1a) of the cabinet housing (1). The connection from the case-like structure through the opening to the outside of the cabinet is realized by means of a channel (10), through which air coming into the case-like structure (9a) between the protective net (7) and the plate (6) is led to flow completely or partly in the direction of the plate (6) surface.

Description

The invention relates to an abrasive blasting cabinet, which comprises a cabinet housing and a transparent plate attached to an opening in the cabinet housing, in front of which transparent plate there is inside the cabinet apart from the plate a protective net of the plate, which plate and protective net and battens attached between them form a case-like structure, and that a case-like structure formed in this way has one or more openings, which are connected to the outside of the cabinet housing.
Abrasive blasting is generally used for cleaning surfaces e.g. in preparation for painting. In abrasive blasting grains are blasted at a high velocity toward the surface to be cleaned. The grains hitting the surface at a high velocity detach impurities from the surface, such as for example rust and mill scale from the surface of steel. The grains to be blasted can for example be sand or some other granular material suitable for the purpose. Pressurized air is used in abrasive blasting for transporting the grains from a container via a hose to the blasting nozzle. The mixture of pressurized air and blasting grains bursts from the nozzle at a high velocity, as much as over 200 m/s. The grains bursting inside the cabinet and the detached impurities cause rapid deterioration and dirtying of the structures inside the cabinet.
Abrasive blasting of objects is generally done in a closed abrasive blasting cabinet, which has hand openings for holding onto the blasting nozzles and a window, through which the user can see the object to be blasted, the blasting spray and nozzle. Lighting inside the cabinet is often arranged so that the lamp is outside the cabinet and a transparent glass protects the lamp. The abrasive blasting cabinet apparatus comprises a blasting hose, along which the mixture of pressurized air and grains enters the nozzle. The grains exit the nozzle at a high velocity. Additionally, the apparatus comprises a grain recycling apparatus and devices needed for ventilating the cabinet. Abrasive blasting is also done in large blasting rooms, where the user completely enters the room to perform the blasting job.
Especially in hand blasting, visibility in the cabinet is important for the quality of the cleaned surface and the productivity. When the visibility is good, the user sees which spots on the object have been blasted and which surfaces still need blasting. The blasting grains exiting the blasting nozzle at a high velocity and the dirt and dust detaching from the surface to be cleaned however impair visibility. The velocity of the blasting grains after they have hit the surface to be cleaned can still be over 100 m/s. Grains hitting the window wear down the glass and the glass gets a matt surface on the inside due to the blasting grains hitting it. After a while of use, the window is so worn and has such a matt surface that the user can no longer see inside the cabinet. In addition to the wear, dust attaching to the window impairs the visibility. The same is true for the glass protecting the lamp.
Various solutions have been developed for improving the visibility in an abrasive blasting cabinet. One solution is to make the glass of the monitoring window easy to replace or to place an easily replaceable protective film in front of the glass. Publication US 4098033 presents as a solution a protective film, which is rolled below the window from one roller to another as it is worn out. Disadvantages with this solution are that the visibility remains good only for a little while, that dust attaches to the protective film and that the consumption of protective film is great.
Publication DE 4123 018 presents a moveable protective net in front of the window. The idea is that during the blasting job, the protective net is in front of the window, and when the blasting is stopped, the protective net can be turned away from the window, whereby the blasting result can be reviewed better. This solution also has problems. The protective net protects the window to some extent but grain particles of different sizes, which wear down the window, constantly fly through the protective net to the window. The protective net slows down the wearing of the window but does not eliminate it. In addition to the wearing of the window, another disadvantage is that dust generated in the abrasive blasting sticks to the protective net the same way as to the window.
Publication US 5 177 911 presents as a solution that an elongated pipe is installed in the abrasive blasting cabinet, one end of which pipe has a monitoring glass and the other end of which pipe is open. The open end of the pipe-like piece is close to the object to be blasted. Air is blown into the pipe-like piece, and the air flow exiting the open end prevents dust from entering the pipe-like piece. The object is looked at through this elongated pipe during the blasting. This solution is applicable only in cases where the object to be blasted and the area to be blasted is small, for example in the magnitude of 10 cm x 10 cm, and the blasting grains have a small size and a small specific gravity. If the object to be blasted is larger in size, for example about 1 m x 1 m, it is difficult for the user to see the object to be blasted and to clean it, because the field of vision is limited due to the small window and pipe-like piece.
If the blasting grains are large and their specific gravity is high, the air flow in the pipe-like piece cannot prevent large and heavy grains from hitting the glass, whereby the glass starts to wear and become opaque. Large and heavy grains have such a high kinetic energy at high velocities that the air flow cannot stop them before they hit the glass. The second end of the pipe-like piece is open, whereby large and heavy objects can fly unhindered to the glass. For example, grains with a diameter of over 0.5 mm can be considered as large grains and for example steel grains as heavy grains.
Publication JP 2013180376 presents an air curtain as a protective device for the glass of the monitoring window. In this solution air is blown onto the surface of the monitoring window's glass. An air curtain does not protect the glass from particles with a size of 0.1-0.7 mm generally used in abrasive blasting, the kinetic energy of which particles is so great that the air curtain cannot impact their trajectory.
Published application DE 4325608 presents a small sand blasting cabinet. In the presented solution an underpressure is generated in the sand blasting cabinet with a suction device. Replacement air is sucked both from openings in the edges of the monitoring glass in the sand blasting cabinet and from holes in the bottom part of the sand blasting cabinet. The generated air flow is used for trying to prevent the glass of the monitoring window from being exposed to sand blasting residues.
Patent GB990257 presents a sand blasting cabinet, the glass of the monitoring window of which has a layered structure. It contains several glass layers and a protective net. The layers form one airtight set, which is bound together with a sealing ring, with which the glass is attached to the upper part of the sand blasting cabinet.
An object of the invention is to present an abrasive blasting cabinet, which eliminates aforesaid disadvantages in the prior art and improves visibility during blasting work regardless of the size of the object or the quality of the blasting grains or the amount of dust generated in the blasting.
The objects of the invention are obtained with an abrasive blasting cabinet, which is characterized by what is presented in the independent claim. Some advantageous embodiments of the invention are presented in the dependent claims.
The abrasive blasting cabinet comprises a cabinet housing and a transparent plate attached to an opening in the cabinet housing, in front of which transparent plate there is inside the cabinet apart from the plate a protective net of the plate, which plate and protective net and battens attached between them form a case-like structure. The formed case-like structure has one or more openings, which are connected to the outside of the cabinet housing. The connection from the case-like structure through the opening to the outside of the cabinet is realized by means of a channel, through which air coming into the case-like structure between the protective net and the plate is led to flow completely or partly in the direction of the plate surface. The transparent plate protected with a protective net can be the transparent plate of the monitoring window of the abrasive blasting cabinet or for example the transparent plate protecting a lamp outside the abrasive blasting cabinet.
In one advantageous embodiment of the abrasive blasting cabinet according to the invention the protective net is shaped so that it forms a case-like structure with the plate without separate battens.
In another advantageous embodiment of the abrasive blasting cabinet according to the invention an underpressure can be arranged inside the cabinet, due to which underpressure air flows through the channel via an opening into the case-like structure and out of the case-like structure through the protective net into the cabinet.
In a third advantageous embodiment of the abrasive blasting cabinet according to the invention an excess pressure can be arranged inside the channel, due to which air flows through the channel via an opening into the case-like structure and out of the case-like structure through the protective net into the cabinet.
In still another advantageous embodiment of the abrasive blasting cabinet according to the invention the channel has one or more air flow guide vanes.
In still another advantageous embodiment of the abrasive blasting cabinet according to the invention the protective net is a cross-stitched steel wire net.
In still another advantageous embodiment of the abrasive blasting cabinet according to the invention there is outside the plate in its immediate vicinity a lamp for lighting the inside of the cabinet.
In still another advantageous embodiment of the abrasive blasting cabinet according to the invention the blasting cabinet is to its size bigger than 0.5 m x 0.5 m x 0.5 m (length x width x height) and smaller than 6 m x 10 m x 10 m (length x width x height).
The structures in sand blasting cabinets can have different variations. Typically, an abrasive blasting cabinet is a closed case-like structure. The cabinet has at least one door or hatch that can be opened, through which the object to be blasted is brought into the cabinet. The front side of the cabinet has a monitoring window and hand openings. The hands are pushed into the cabinet through the hand openings, which have protective gloves. The user holds onto the blasting nozzle with his hand. Through the monitoring window the user looks at the object to be blasted and the blasting process and simultaneously controls the movement of the blasting nozzle with his hands. The bottom part of the blasting cabinet has a suction opening and a suction hose connected thereto. A powerful underpressure is present at the suction opening, whereby air flows from inside the cabinet to the suction opening and onwards to the suction hose connected to the suction opening and takes with it dust and grains from inside the cabinet. The top part of the cabinet has an opening, from which replacement air enters the cabinet.
The abrasive blasting cabinet can have one or more openings, over which a transparent plate has been attached. As a protection of the plate installed over the opening there is on the inside of the cabinet a protective net, which is roughly the size of the opening and is somewhat apart from the glass. A necessary amount of battens have been attached to the protective net, by means of which the net is sealed to the glass so, that a case-like space is formed between the net and the glass. On the other hand, the protective net can be shaped so that it forms a case-like structure with the protective glass. The case-like structure has an opening, which is connected to the outside of the cabinet housing, for example with a channel or the like. Through the opening or along the channel, air is led to the case-like space between the glass and the net and from there onwards through the net into the cabinet.
The flow of air from outside the cabinet through the opening and along the channel into the case-like structure between the net and the plate and onwards through the net into the cabinet can be achieved for example by means of underpressure present in the cabinet or by blowing air into the channel with a blower or compressor outside the cabinet.
A suction hose is connected to the suction opening in the bottom part of the cabinet and its second end is attached to a cyclone separator or for example a filter. Along the suction hose the grains and dust pass with the air to the cyclone separator, where usable grains and fine dust are separated from each other. Usable, cleaned grains pour into a grain silo or pressure vessel placed beneath the cyclone separator and the fine dust goes into the cyclone separator along with the air flow.
The grain silo contains blasting grains and in the bottom part of the grain silo there is an opening and a regulating valve meant for regulating the pouring of grains. Through the regulating valve blasting grains pour into a pipe system, where a powerful flow of pressurized air is present. The pressurized air takes the blasting grains along a blasting hose into the nozzle, from which the grain/pressurized air mixture exits at a high velocity inside the cabinet.
The cyclone separator is connected with a channel to a filter. A blower placed after the filter sucks dust-bearing air from the cyclone separator into the filter. From the filter clean air is sucked to the blower and onwards the air is led out from the removal opening of the blower. Part of the exiting air can be led along a channel back into the abrasive blasting cabinet.
In order to light up the inside of the abrasive blasting cabinet, there can be an opening in the roof of the cabinet, which opening is covered with a transparent plate. Outside the cabinet, close to the plate, there can be a lamp, from which light radiates into the cabinet. The protection of the plate protecting the lamp can be done in a corresponding manner to the protection of the plate of the monitoring window. Inside the cabinet, apart from the plate protecting the lamp, there can be a net, the battens connected to which form a case-like structure together with the plate. The case-like structure has an opening, through which air flows in between the plate protecting the lamp and the net. Air flows from inside the case-like structure through the net into the cabinet.
An advantage of the invention is that the transparent plate does not wear or become matt, and that dust cannot accumulate on the surface of the plate, because air flows in the direction of the surface of the window. Visibility into the cabinet thus remains good during the blasting.
In the following, the invention will be described in more detail with reference to the appended drawings.

Figure 1 shows as an example an abrasive blasting cabinet according to the invention,
Figure 2 shows a cross-section of the abrasive blasting cabinet presented in Figure 1 by the transparent plate of the monitoring window and the protective net protecting the plate and
Figure 3 shows a cross-section of an advantageous embodiment of the abrasive blasting cabinet by the transparent plate of the monitoring window and the protective net protecting the plate.

Figure 1 shows an abrasive blasting cabinet according to the invention, which has a protective net 7 for protecting the transparent plate 6 from wear caused by the abrasive blasting. Figure 2 shows a cross-section of the abrasive blasting cabinet presented in Figure 1 by the transparent plate of the monitoring window and the protective net protecting the plate. In the following both figures are described simultaneously.
The abrasive blasting cabinet is formed from a sealed housing 1, which is formed as a sealed case structure. The housing separates the outside 1a and inside 2 of the cabinet. A space, where the abrasive blasting occurs, is formed inside the housing. The object 3 to be blasted is brought into the cabinet through a door or hatch that can be opened. The user pushes his hands into the cabinet through a hand opening or hand openings 4. In the cabinet housing 1 there is an opening 6a, over which a transparent plate 6 is placed, which can be for example glass or plastic. The opening 6a in the housing and the transparent plate 6 over it form a monitoring window, through which the user can monitor what happens inside the abrasive blasting cabinet. The opening and the transparent plate over it can also be used for lighting the inside of the cabinet by placing a lamp outside the cabinet close to the transparent plate. The user holds in his hand a blasting nozzle 5 and looks into the cabinet through the transparent plate 6 of the monitoring window and the protective net 7 protecting it and guides the blasting spray 8 toward the object 3 to be blasted.
The protective net 7 is encased tightly against the plate 6 with battens 8 attached to the protective net. Thus, a case-like structure 9a is formed from the protective net 7, the battens and the plate 6. The case-like structure has an opening 9, from which air flows into the case-like structure between the plate 6 and the protective net 7. The opening is in contact with the outside of the housing 1 for example by means of a channel 10. The first end of the channel is attached to the opening 9 and the second end of the channel opens up outside 1a the cabinet housing 1. Clean air flows into the channel and into the case-like structure from outside the blasting cabinet. The channel 10 can have air flow guide vanes 11, which guide the air flow or part of it substantially in the direction of the surface of the transparent plate 6.
In addition to the monitoring window the housing can have one or more other openings. Such openings covered with a transparent plate can be used for lighting the inside 2 of the cabinet. For example, in the top part or roof of the cabinet housing there can be an opening 6a and a transparent plate over it. As a protection of the plate inside the cabinet there is a case-like structure 9a equipped with a protective net 7, inside which case-like structure the airflow is led. The lamp is placed outside the housing close to the plate.
Air can enter the inside 2 of the cabinet also through a separate replacement air opening 13. There can be one replacement air opening 13 in the cabinet, or more, or none.
In the bottom part of the cabinet there is a suction opening 14, to which a suction hose 15 is attached. An underpressure caused by a fan 16 is present in the suction opening and air flows from the inside 2 of the cabinet to the suction hose 15.
Air and blasting grains and dust generated in the cabinet flow in the suction hose 15 to the cyclone separator 17. In the cyclone separator dust and other fine matter is separated from healthy, usable grains. Grains 18 suited for further use pours into the grain silo 19 through the valve 20.
A pressurized air pipe system 22 is connected to the grain silo. Through a valve 21 beneath the grain silo the blasting grains pour into a blasting hose 23. A pressurized air flow present in the blasting hose 23 brings the grains into the blasting nozzle 5 and onwards inside 2 the cabinet and to the object 3 to be blasted.
From the cyclone separator 17 fine matter flows along with the air via a channel 24 to the filter 26. The filter 26 has a filter element 26a, through which air can pass but which separates fine dust 25 from the air flow, which dust finally pours to the bottom of the filter. Clean air 27 exits the filter via a fan 16.
Part of the exiting air can be recycled back into the abrasive blasting cabinet. Thus, there is an air lock 28 in the apparatus, which is used for regulating the amount of exiting air flow 27 in relation to the amount of air being returned to the blasting cabinet 1. Returning air is led into the blasting cabinet 2 inside the channel 29. The second end of the channel 29 can be connected to the channel 10 leading to the protective net 7.
The protective net 7 can to its structure be for example a cross-stitched steel wire net or the like. The wires can for example be round steel wires 7a. The material of the wires is advantageously hard and durable. The openings 7b in the protective net are dimensioned so that the largest blasting grains cannot fit through the openings 7b in the protective net. The thickness of the wire is typically in the range of 0.1-1.0 mm. The diameter of the holes can also typically be in the range of 0.1-1.0 mm. The share of the opening from the total area of the protective net is typically 40-60 %. The shape of the protective net can be plane, convex or have a V-shaped cross-section. Substantial for the invention is that the protective net and the thereto attached battens form a case-like structure with the transparent plate, which structure has an opening for air flow.
Figure 3 shows as an example a part of an advantageous embodiment of the abrasive blasting cabinet according to the invention. The figure shows a cross-section of the abrasive blasting cabinet in the same point as Figure 2. The embodiment shown in Figure 3 differs from the above-described abrasive blasting cabinet in that a flow channel 29 is attached to the air channel 10a, by means of a blower connected to which flow channel an excess pressure is achieved in the air channel 10a (blower not shown in the figure).
The abrasive blasting cabinet functions in the following manner: When the abrasive blasting is turned on, the grain valve beneath the grain silo is open and pressurized air pushes the grain/air mixture in the blasting hose towards the nozzle. The grain/air mixture exits the nozzle at a high velocity inside the blasting cabinet and the grains hit the surface to be cleaned. As they hit the surface the grains detach impurities from the object to be blasted, such as rust or mill scale. The impurities detach from the object and spread as dust inside the cabinet.
Part of the grains and dust bounces towards the transparent plate of the monitoring window and towards the plate protecting the lamp and the protective nets in front of them. The mesh size of the protective net is adapted to be so small that the largest grains do not fit through the mesh. Thus, the large grains can be mechanically prevented from flying to the plate.
Small grains and fine dust can fit to pass through the mesh towards the transparent plate. The air flow coming from the other side of the protective net, in the opposite direction, prevents dust and small grain particles from passing to the other side of the protective net toward the plate. The flow velocity of the air passing into the cabinet through the protective net is dimensioned so that small grains and fine dust cannot pass through the net but pass along with the air flow back into the cabinet, and do not fly towards the plate.
The air flow coming between the net and the transparent plate or part of it is directed to flow in the direction of the surface of the plate to be protected, so that dust cannot accumulate on the surface of the plate, which would work to impair visibility.
Air thus flows into the cabinet through the net in front of the plate. The cabinet can also have a second or several openings, through which replacement air flows into the cabinet.The same kind of transparent plate and protective net in front of it, the battens of which form a case-like structure together with the plate, can be placed for example in front of a lamp outside the cabinet or there can be more than one monitoring window in the cabinet.
The air flow coming between the net and plate can be caused solely by the underpressure present in the cabinet. The air flow into the case-like structure can also be produced with a separate blower or by means of pressurized air.
Substantial for the protective effect of the protective net is that the mesh size of the protective net is adapted according to the grain size of the blasting grains and that the flow velocity of the air entering the cabinet through the protective net is adapted to be such that dust and grain particles flying towards the net cannot due to air flowing in the opposite direction pass through the net and onwards to hit the plate. When grain hits are not directed at the plate, its surface is not worn or scratched.
The structure according to the invention is suitable for use in blasting cabinets both for very small grains and large grains. The invention is also suitable for use in blasting cabinets of different sizes and objects to be blasted of different sizes over a very wide size range. The invention and its advantages are not limited only to blasting small objects, but the invention can be used both for blasting small and large objects. The size of the transparent plate of the monitoring window and the protective net protecting it can be dimensioned without particular limitations. The amount of air flowing through the protective net is also dimensioned to suit each structure.
The protective effect of the case-like structure equipped with air flow according to the invention is good. In the abrasive blasting cabinet according to the invention the protective net mechanically stops grain particles with a larger size than the mesh size of the protective net and the air flow stops grains and dust with a smaller size than the mesh size of the protective net. The protective net is made from a thin wire, whereby you can see through it. Due to the combined protective effect of the protective net and the air flow the transparent plate does not wear and remains clear and the visibility to the object to be blasted inside the cabinet is good through the whole blasting process.
Some embodiments of the abrasive blasting cabinet according to the invention have been described above. The details of the realization of the invention can vary within the limits set by the claims.

Claims

An abrasive blasting cabinet, which comprises a cabinet housing (1) and a transparent plate (6) attached to an opening (6a) in the cabinet housing (1), in front of which transparent plate there is inside the cabinet apart from the plate (6) a protective net (7) of the plate (6), which plate (6) and protective net (7) and battens (8) attached between them form a case-like structure, and that a case-like structure (9a) formed in this way has one or more openings (9), which are connected to the outside (1a) of the cabinet housing (1), characterized in that a connection from the case-like structure (9a) through the opening (9) to the outside (1a) of the cabinet is realized by means of a channel (10), through which air entering the case-like structure (9a) between the protective net (7) and the plate (6) is led to flow completely or partly in the direction of the surface of the plate (6).
The blasting cabinet according to claim 1, characterized in that the protective net (7) is shaped so that it forms a case-like structure (9a) with the plate (6) without separate battens (8).
The blasting cabinet according to claim 1 or 2, characterized in that an underpressure can be arranged inside (2) the cabinet, due to which underpressure air flows through the channel (10a) via an opening (9) into the case-like structure (9a) and out of the case-like structure (9a) through the protective net (7) into (2) the cabinet.
The blasting cabinet according to claim 1 or 2, characterized in that an excess pressure can be arranged inside the channel (10a), due to which air flows through the channel (10a) via an opening (9) into the case-like structure (9a) and out of the case-like structure (9a) through the protective net (7) into (2) the cabinet.
The blasting cabinet according to any of the claims 1-4, characterized in that there are one or more air flow guide vanes (11) in the channel (10a).
The blasting cabinet according to any of the claims 1-5, characterized in that the protective net (7) is a cross-stitched steel wire net.
The blasting cabinet according to any of the claims 1-6, characterized in that there is a lamp for lighting the inside of the cabinet outside the plate (6) in its immediate vicinity.
The blasting cabinet according to any of the claims 1-7, characterized in that the size of the blasting cabinet is larger than 0.5 m x 0.5 m x 0.5 m (length x width x height) and smaller than 6 m x 10 m x 10 m (length x width x height).