FI20170063A1 - A tight blast/suction head for a sandblasting device - Google Patents

Abstract

This publication discloses a blow suction capsule for a grinding blasting device comprising a capsular sheath (7), a blow nozzle (6), a suction opening and a suction hose (9) attached thereto, an air-impermeable seal (20) which is outside the canister. a distance from the wall of the capsule, and an air duct (18). The air duct (18) conducts air from outside the canister inside the canister through a gap between the seal (20) and the shell (7) of the canister, and further through a gap (26) between the lower edge (7a) of the capsule and the surface (8) to be blasted. By means of the construction, a dense blowing suction head is provided, from which the blasting groove does not fly out but air will flow freely into the blowing suction head. Thereby, a blowing suction capsule is provided which effectively sucks away the grits from the surface being blasted, without blasting grits and dust spreading in the environment. At the same time, the pressure loss caused by the blowing suction head in the air flow is reduced, so the energy consumption of the apparatus is reduced and its movement on the surface to be blasted is easy.

Description

Dense blowing suction head for sand blasting unit

The present invention relates to an apparatus according to claim 1 for the suction housing of a sandblasting device.

Sandblasting is commonly used to clean surfaces, eg for painting. Sandblasting (or more commonly known as grain blasting because sand is only one of the grains used in blasting) blows the blasting blast at a high speed to the surface to be cleaned. At high speed, the impact granule removes impurities, such as rust and rolling grit from the steel surface.

Blowing uses compressed air to transport the granule from the tank through a hose to the blowing nozzle. The mixture of compressed air and blasting granulate discharges from the nozzle at high speeds up to 150 m / s.

The high speed blasting nozzle exiting the nozzle and the dirt and dust from the surface to be cleaned are widely distributed in the environment. The velocity of the blasting granule after it has struck the surface to be cleaned and predominantly sideways from it may, for example, still be 50 to 80 m / s m / s. Various solutions have been developed to limit the spread of dust and granules in the environment. In general, different sized enclosures have been used in which sandblasting occurs. The enclosure is placed tightly against the surface to be cleaned and the mixture of suction blower and dust is sucked out inside the enclosure. For suction, a suction hose is connected to the opening in the housing and connected to the suction apparatus.

The blasting nozzle discharging from the nozzle into the housing causes problems with the housing structure. Firstly, the blowing grain causes wear to the housing because of the high speed of the grain. Secondly, the housing should be sealed to prevent the bladder from escaping from the housing, but at the same time be able to draw in air from inside the housing to suck up the compressed air and blowing collar inside the housing and transport it back to the blowing equipment.

The sealing problem is most commonly solved by sealing the housing between the housing and the inflatable surface by a brush or a bristle element that prevents the granule from flying out but allows air into the housing between the bristles.

JP 11207624 discloses a sand blasting apparatus wherein the blasting takes place inside the housing and the blasting horn is sucked back into the blasting apparatus. The case has a brush that seals the case against the surface to be cleaned. The air inside the housing is sucked through the brush.

EP 0160353 discloses a blowing suction housing for a sand blasting apparatus wherein the brush is resiliently attached to the suction housing. The flexible joint allows the brush to move flexibly if the surface to be sealed varies in smoothness. Likewise, if the blower suction head is moved manually, the brush will adjust to the distance variations.

Both of these solutions have a number of problems. First, the sealing brush is exposed to heavy wear. Within the blowing head, the granules bounce back and forth and wear bristles. Already after a moment the use of the inside of the brushes wear and sealing deteriorates. Secondly, because of the strong vacuum in the blower housing, the vacuum and the air flowing through the bristles bend the bristles inward, thereby opening a free opening between the inflatable surface and the bristles. From this opening, the blasting granules fly out and the seal is no longer working. The strong vacuum inside the housing also causes the blowing suction head to be difficult to move because the vacuum draws against the inflatable surface of the housing.

US 5,709,590 discloses a blow-in suction head having a vacuum valve that can maintain a vacuum of the desired size, no matter how tightly the bristles or the like sealing member is against the inflatable surface. This solution makes moving the blower suction head easier because the vacuum inside the housing can be adjusted. But in the same way, air flows through the bristles as well as bending the bristles inward, opening a free entrance to the granules.

US 4,045,915 and UK 7444466 disclose support wheels mounted on a blow nozzle for solving the problem of sealing and moving the blower suction head. The support wheels keep the distance between the housing and the surface to be cleaned constant so that the distance of the bristles or other seal to the surface to be cleaned remains constant. These solutions have brushes or other sealing element flexibly attached to the housing, which improves the sealing problem. In this solution, a high vacuum is still needed inside the enclosure in order to obtain an air flow rate high enough to transport the granules away from the blow-in suction head. Similarly, air flows partly through the bristles and partly under the bristles, bending them inward. This opens an opening from which the granules can fly straight out.

US 5,833,521 discloses a structure in which the compressed air suction head is blown inside a blow suction head sealing problem. In this solution, the compressed air forms an air curtain through which the blowing granules cannot escape. The disadvantages of this design are the high consumption of compressed air and the fact that the structure is not tight. Because the blowing granules move within the blowing suction head up to 80 m / s, a thin compressed air curtain is not enough to hold them inside the housing. This is particularly emphasized by the metal blasting granules which have a high density and thus high kinetic energy. Heavy granules fly easily through the compressed air curtain.

US 6,273,154 discloses two sealing rings and two separate suction passages to improve sealing of the blow-in suction head. One duct system draws air from inside the suction blower housing and the other suction duct is arranged to suck air between the seals. In this solution, the sealing of the blow-in suction head is better than in those with simple sealing. Basic sealing problems do not disappear with double sealing. Air is sucked through and under the seals to open a direct connection to the outside of the blower suction housing. From this opening the granules fly out at high speed. Another disadvantage is that larger suction channels require more efficient suction equipment to maintain sufficient vacuum and air flow to transport the blasting granules back to the blowing equipment.

UK 1,102,688 also discloses two seals around the housing. The downside to this solution is that it only works on vertical surfaces. If the surface to be blown is horizontal, the amount of air required is large to suck the blowing granules back into the blowing equipment. This solution also has the problem that when air flows through the seals inwardly, a free opening is opened between the seals and the surface to be cleaned, from which the blowing granules can fly directly out.

GB 2 276 342 A discloses a solution having a seal around the blowing head and additionally having a hole or holes in the rear of the blowing head which allow air to be drawn into the blowing head. The sucked in air assists in transporting the granule away from the blowing head via a separate suction passage. This solution reduces the vacuum created inside the blowing head and at the same time increases the amount of air used to transport the granulate. The air flowing inside the blowing head has not been used to improve the sealing of the housing or to prevent the granules from flying out. Conversely, when air is introduced into the blowing head via a separate passage, the vacuum inside the blowing head is reduced, thereby allowing the granules to exit, for example, under the seal. Therefore, the sealing of this blowing head is poor.

GB 1518 785 discloses a blowing device for vertical walls and a blowing head therein. This blowing head has a seal sealing against the surface and the top of the blowing head also has a brushed seal. Air is drawn through the brush into the channel formed between the seal and the brush. The purpose of the seal is to keep the granules inside the blowing head and also to prevent the flow of air through the brush into the blowing area. The air sucked into the space between the seal and the brush continues to flow along the duct to the top of the blower head body. This has increased the amount of air used to transport the granulate. This solution has only one seal at the bottom and sides of the blower head, so it has a poor seal. Again, this solution does not use air flow to improve sealing, nor does air flow prevent the granules from escaping.

The object of the invention is to provide a solution which eliminates the aforementioned sealing problems and other drawbacks and the blow-in suction housing is always tight regardless of the position, flatness or properties of the blown material.

This is accomplished in accordance with the invention by preventing the granules from escaping by mechanical barriers and at the same time utilizing the air entering the blowing head to significantly slow down the velocity of the expelling granules so that eventually the incoming air returns the aspirated granules back into the blowing head. This is done so that the flow rate of air flowing into the blowing head is high enough. The air flowing into the blower suction housing is directed to a duct or slot where the granules tend to exit and the direction of the replacement air is opposite to the direction of flight of the outgoing particles. This is achieved by the structure according to the invention, which at the same time is dense and open.

The structure comprises the following main components:

a blow-in suction housing that is open from one outlet to the other end is fitted with a blow nozzle with hoses and a suction port and a suction hose attached thereto. A seal is attached to the open end of the housing, which is placed near the inflatable surface. The seal is disengaged from the housing shell so that a conduit is formed between the seal and the housing, through which air can flow into the housing.

along the suction hose, the mixture of air, blowing granule and dust in the blowing suction housing is sucked into the blowing equipment as a seal of the housing is an air-impermeable flexible seal, for example, rubber attached to the blowing suction head. The seal is disengaged from the housing casing and this gap forms part of the air flow passage. The seal is pressed against the inflatable surface so that there is no gap between the seal and the surface. Instead, the lower edge of the housing is higher than the lower edge of the seal.

a gap is formed between the inflatable surface and the underside of the housing, where the blowing granules tend to exit. Through this slot, a flow of replacement air is provided inside the blower suction head. This slot may be short or longer and may be shaped in a flow-friendly manner.

- an air duct runs between the gasket and the casing casing, through which the externally aspirated replacement air passes freely through the gap between the casing lower edge and the inflatable surface into the inflow suction head.

the air channel has bends and mechanical disadvantages that prevent the granules from flying outward inside the air channel.

The structure works as follows:

When grain blasting is on, the nozzle becomes a high-velocity mixture of granule air inside the blower suction housing and the granules hit the surface to be cleaned. For example, the granules may have a speed of 150 m / s when exiting the nozzle. The output speed depends on e.g. the nozzle design, the blowing pressure used, and the mass flow rate of the blowing granules. When the granules hit the inflatable surface, they mainly bounce sideways. In this case their speed drops considerably, but the speed can still be e.g. 50 - 70 m / s. A small part of the granules flies outwardly from the slot below the bottom of the housing in the direction of the blown surface and strikes a flexible seal. At the same time, air is drawn from inside the housing and replacement air enters through the air passage between the housing shell and the seal to the gap between the bottom and the surface and further into the housing. The gap between the lower edge of the housing shell and the inflatable surface is dimensioned to provide an air flow rate in the gap of about 40 to 50 m / s or more. For example, the gap may be 10-20 mm in size. As the granules fly outwardly through the gap, their velocity is greatly reduced by the effect of air flowing in the opposite direction. The flight speed of the granules in the gap is reduced by 40 to 70% depending on the size and specific gravity of the granule. For example, if the alumina grain is 0.2 mm in size and its flight velocity inside the gap is 50 m / s, its velocity has decreased to 28 m / s as it exits the gap and hits the seal. When the granule that expels from the gap hits the gasket, its flight speed stops completely or at least continues to slow down significantly. At this point, most of the granules return with the airflow back into the housing.

From the housing, they are further transported by the air stream along the suction hose to the blowing equipment. A small part of the granules still bounce outwardly in the air channel. The air passage between the housing jacket and the seal has mechanical drawbacks and bends so that the outward movement of the granules is stopped when they are hit. In the air duct, the air velocity is dimensioned such that the granules exit with the air flow back to the blower suction housing and from there through the suction hose to the blowing equipment.

Outside the seal, for example, a brush may be provided as an additional seal through which replacement air is sucked into the flow duct.

Thus, a large amount of replacement air flows into the blower suction housing via a separate, open duct. The introduction of replacement air into the blower suction head via a separate duct does not bend the gasket inward, thereby opening the gap between the gasket and the inflatable surface, but the gasket remains tight at all times. This separate replacement air duct is arranged so that the air flowing therein prevents the granules from flying out of the blowing head.

The air velocity in the gap between the lower edge of the housing and the inflatable surface is dimensioned such that the resting granules on the surface to be cleaned start to move with the air stream. The granules resting on the surface are thus sucked into the blower suction housing and cannot get outside the blower suction housing as the housing is moved over the granules. This arrangement prevents dust, blasting grains or other contaminants on the blown surface.

Further, the blow-in suction housing according to the invention has the advantage that the vacuum inside the housing is considerably lower than with previously known solutions. This makes moving the housing easier.

More specifically, the blow-in suction housing of the invention is characterized by what is stated in the characterizing part of claim 1.

The invention will now be described in more detail with reference to the accompanying drawings. Fig. 1 shows a grain blasting apparatus having a blowing suction housing according to the invention. Figure 2 is a cross-sectional view of the blow-in suction housing showing the seal and air duct according to the invention. Figure 3 illustrates another embodiment of a blower suction head seal and air flow passages.

The blasting apparatus comprises a pressure vessel (1) containing a blasting blade (2). The blowing grain is generally 0.1 to 0.7mm in size. Below the pressure vessel, a grit valve (3) to regulate the amount of grain to be blown. Compressed air is supplied to the system via the pneumatic valve (4) and the piping connected to it. The blowing granules flowing from the pressure vessel (1) through the grit valve (3) are mixed with the compressed air flow below the grit valve (3), and through the blowing hose (5) the compressed air-grit mixture enters the blowing nozzle (6). At the blowing nozzle, a mixture of compressed air and blowing granules (16) exits at high speed into the blowing suction housing (15). Finally, the blasting granules strike the inflatable surface (8) and clean it by removing impurities from the surface. When the blow granules hit the inflatable surface (8), their direction of travel is changed to that of the inflatable surface (29), whereby they strike the casing (7) of the blow suction housing, in particular its lower part and seal (20).

A suction hose (9) is connected to the casing (7) of the blow-in suction housing with a vacuum created by the vacuum (14). Due to negative pressure, air flows from the blower suction box to the suction hose. Blowing granules and impurities removed from the surface (8) to the cyclone (10) run in the suction tube. In the cyclone, dust and other fines are separated. The reusable granule flows back into the pressure vessel (1) and the finely divided material passes through the channel (11) into the filter (12). The filter separates dust and other impurities from the air flow. Dust (13) is collected at the bottom of the filter. Clean air exits the filter through the vacuum cleaner (14).

The blow-in suction housing (7) may be a cylindrical rotary body or may be, for example, rectangular in shape.

At the top of the blowing suction housing (15) is a blowing nozzle (6), within which a grain jet (16) flies towards the inflatable surface (8).

A seal (20) is attached around the casing (7) of the blow-in suction housing, the lower edge of which is lower than the bottom (7a) of the blow-in suction box. The seal is disengaged from the housing shell (7) so that an air flow passage (18) is formed between the seal and the housing. A gap (26) is formed between the bottom edge (7a) of the housing and the inflatable surface (8), along which air from the flow passage (18) flows into the housing (15).

The seal (20) may be rigidly attached to the sheath (7) but may be resiliently secured to springs or rubber elements such that the springs or similar elastic members press against the inflatable surface (8).

Air flows through the channel (18) into the slot (26) and further into the housing (15). The air channel (18) is formed by a gap between the seal (20) and the casing (7) of the blow-in suction housing. The gasket (20) is shaped such that air flows from above the gasket (20) and further down from the space between the gasket (20) and the housing (7) and from the gap (26) between the lower edge (7a) and the inflatable surface (8) 15).

The flow channel (18) may be short or long. A separate duct structure (17) may be mounted thereon to form an air flow duct (17a). Air is led through the duct (17a) to the duct (18). Air flows in from the outside through the orifice (21) of the duct structure (17). The air channels (17a) and (18) have a bend or bends (23) in the direction of flow of air, whereby the granules flying from the inside of the blow-in suction head collide with the bends of the channels and the wall. In collisions, the outward movement of the granules is reduced or stopped completely. The air flow in the passages (17a) and (18) then returns the grain particles back into the blowing suction chamber (15). The channels also have projections (24) which contribute to preventing the grain particles from flying out of the straight line. In addition, duct walls have recesses (25) that stop the grain particles flying into them.

Loud noise is generated in grain blasting because air and grain jet (16) discharge from the blowing nozzle (6) at high speed, for example at 150 m / s. The interior of the air channels (17a) and (18) may be coated with sound-absorbing material (27). This will significantly reduce noise levels in the environment. In addition, the noise level outside the housing can be reduced by, for example, installing an air-permeable brush-like seal (30) outside the mouth (21).

The gasket (20) is made of a resilient material, e.g. rubber, whereby the gasket presses tight against the surface (8) to be cleaned, even when the surface (8) is uneven. Since the vacuum in the suction blowing chamber is low due to the open air channels (7a), (18) and (17a), the seal (20) remains permanently attached to the surface to be cleaned (8). It does not bend under vacuum so that a free opening is formed between the surface (8) and the seal (20), from which the granules can fly directly out.

The seal (20) is usually an air-impermeable, wear-resistant material. The gasket (20) is secured by means of rods (19) or similar means to the air channel (17) or to the housing casing (7).

The gap (26) between the lower edge (7a) and the surface (8) of the blower suction housing through which air flows into the housing is dimensioned such that the air flow in the gap is so rapid that the grain particles resting on the surface (8) set off according to the flow of air. Typically, the air flow rate in the gap (26) is in the order of 40-50 m / s. At this rate, the airflow enters the grain and dust particles on the inflatable surface (8) into the blower suction housing (15), from where they continue to enter the suction hose (9) with the airflow.

Figure 3 shows another embodiment of the gap (26) between the lower edge of the housing and the inflatable surface. In this embodiment, the slot (26) is made longer. In this way, the distance that the outgoing granules have to travel in the opposite direction of the air flow can be increased. Longer distance more effectively reduces the outward velocity of the granules and thus improves the air tightness of the blow-in suction head. In the embodiment of Figure 3, the bottom edge (7b) of the housing is shaped to be flow-friendly to reduce the pressure loss caused by the flow.

Figure 3 also shows a ridged seal (30) arranged outside the duct system which reduces the noise level outside the blowing head.

The structure according to the invention is suitable for both small and large nozzles (6) or more nozzles. The diameter of the blowing head according to the invention may vary according to the particular application. For example, the gasket (20) may have a diameter of 100 mm or large blowing suction heads, for example, 250 mm. The seal of the blow-in suction housing according to the invention is also good when the flow of grain from the nozzle to the blow-in suction box is high. The structure according to the invention can be moved over the surface (8) faster than known structures without leaving blast grains on the surface to be blown. The force required to move the blow-in suction housing is less than the force required to move known structures because of the lower vacuum inside the housing.

Only one embodiment of the invention according to the claim has been described above. The details of the implementation of the invention may vary within the scope of the claim.

Claims (9)

The claims A blow-in suction housing comprising an open-end housing-like casing (7), a blow nozzle (6), a suction opening in the casing (7) and a suction hose (9) attached to the casing (7), a body (7). ) and the flow channel formed between the seal (20) and the gap (26) formed between the lower edge (7a) of the housing and the inflatable surface (8), characterized in that the air flow channel (18) and the slot (26) the direction of air flow therein is opposite to the direction of flight of the particles (29) which swell sideways from the inflatable surface. The blower suction housing according to claim 1, characterized in that the air flow velocity in the duct 18 and the slot 26 is arranged so high, typically 40-50 m / s, that the outwardly flying particle velocity is reduced to zero and finally the outwardly moving particle motion . Blower suction housing according to Claims 1 and 2, characterized in that a duct (17a) is attached to the casing casing on the flow channel (18) through which air flows from the outside (21) to the flow channel (18). Blower suction housing according to claims 1-3, characterized in that the flow channel (18) or channel (17a) has one or more bends. Blower suction housing according to Claims 1 to 3, characterized in that the flow channel (18) or channel (17a) has one or more projections (23) inside the channels. Blower suction housing according to claims 1-3, characterized in that one or more recesses (24) are provided inside the flow channel (18) or channel (17a). Blower suction housing according to claims 1 to 3, characterized in that the inner surface of the flow channel (18) or channel (17a) is partially or completely coated with a sound-absorbing coating (27). Blower suction housing according to Claim 1, characterized in that the opening (26) from the flow passage (18) is dimensioned so that the flow of air acting in the slot activates particles (28) resting on the surface (8) and introduces them into the housing (8). 15). A blow-in suction housing according to claims 1-8, characterized in that the seal (20) is a resilient material. Blower suction housing according to claims 1 to 9, characterized in that the channel (17) and the gasket (20) are fixed by a flexible connection (22) to the suction suction 15 in the blower housing (7).