ABRASIVE BLASTING APPARATUS

Abstract: An apparatus for cleaning a surface (0) by means of an abrasive in a transporting air current at high velocity, which apparatus substantially consists of a nozzle (1) for placing on the surface (0) provided with a feed line (3) to be connected onto a pressure source (4), which line (3) has an inlet opening (9) for the abrasive, and a discharge line (6) connected to a vacuum source and leading to a dust collector (8) wherein a dust/abrasive separator (7) is accomodated in the discharge line (6) and connected via a closable port mechanism (13) with a storage tank (10) for the reclaimed abrasive connected to the inlet opening (9), and further said dust/abrasive separator being a container having baffle means arranged therein, whereby the discharge line leading to the dust collector runs out beneath the lowest of the baffle means in order to separate the dust from the grit more efficiently.

Description: The invention relates to an apparatus for cleaning a surface by means of an abrasive material in a transporting air flow at high velocity, said apparatus comprising a nozzle for placing on said surface, provided with a feed line to be connected onto a pressure source, said line having an inlet opening for said abrasive, and a discharge line connected to a vacuum source and leading to a dust collector, wherein a dust/abrasive separator is accommodated in said discharge line and connected via an intermediate pressure tank with a storage tank for the separated abrasive connected to said inlet opening, wherein one way valve means are arranged between said seperator and pressure tank, said pressure tank and storage tank respectively. Apparatus of the type described in the preamble, for example disclosed in US-A-2597434, are often used for abrasive cleaning of arched surfaces, for example ship hulls, car body work, where a large removal capacity is required. The object of the invention is to improve the working of such a device, said device being characterized in that both said pressure tank and the storage tank are connected via a controlled bleed conduit into the dust collector. It is noticed that owing to the bleed of lines the pressure tank and storage tank can be vented rather fast, whereby the dust in the air to be removed from said tanks is directly collected in the dust collector. An especially robust, disturbance-free apparatus is hereby obtained. In accordance with an embodiment of the invention the dust/abrasive separator is a container having baffle means arranged therein, whereby the discharge line leading to the dust collector runs out eneath the lowest of the baffle means. The discharge line preferably protrudes into the container and is provided with an upward facing screening plate above its intake opening. Finally, the lowest of the baffle means is preferrably formed wholly or partially as a screening sieve. The invention is further elucidated in the figure of the description of an embodiment following below. The annexed figure 1 shows in schematic form an embodiment of the the apparatus according to the invention. Indicated in the figure with the numberal 1 is the blast nozzle which has to be moved manually or in another manner over a surface 0 for blasting. Blast nozzle 1 consists here of a housing provided with a brush 2 resting on surface 0, and is connected on the housing to a feed line 3 which is supplied by a pressure source 4 with compressed air. Housing 1 is in addition provided with a connecting stump 5 onto which is connected a flexible suction hose 6 which leads via a dust separator 7 to be further explained below to a dust collector also to be described hereinafter. The conduit 3 is provided with an inlet opening 9 on which is arranged a storage hopper 10 for the abrasive material, for example grit of any random type. This hopper 10 is formed with a dosage mechanism 11 which can be adjusted manually or otherwise. This mechanism is provided with a handle 12 for this purpose. Located between dust separator 7 and storage tank 10 is a port mechanism 13 consisting of a pressure tank 14 communicating with dust separator 7 via passage opening 15, and communicating with storage tank 10 via passage opening 16. Each of the openings 15 and 16 can be closed by means of a valve 17 and 18 respectively counter to the action of gravity. Both the pressure tank 13 and storage tank 10 are connected via a rapid bleed conduit 19 to an inlet opening 20 of the dust collector 8. Arranged between each tank and the conduit 19 are shut-off valves 21 and 22 respectively which are controlled by a line 23 which transmits a signal from a handle 24 at the blast nozzle. Line 23 is also connected via a branch line 25 to a control unit 26 which is accommodated in the pressure feed conduit 3 as shut-off valve as well as ensuring the connection with the pressure source 4 to pressure tank 13 and storage hopper 10 via conduits 27 and 28 respectively. The dust collector 8 consists of a housing 29 of sufficiently large volume in which is suspended a dust filter 30. Suspended inside dust filter 30 is a fan motor 31 which can draw off the air present in container 29. The conduit 6′ leads to a position in housing 29 outside the dust filter 30 as do the return pipes 19 of pressure tank 13 and storage tank 10. Located at the bottom of housing 29 is a drawer 32 for collecting the separated dust. The dust separator 7 consists of a housing 33 of likewise suitable volume, into the upper portion of which conduit 6 runs out. Arranged directly opposite the debouchment 34 is a resilient reflecting plate 35 of, for example, rubber. Fitted zig-zag-wise above one another beneath reflecting plate 35 are baffle plates 36 as well as a screening sieve plate 37. Placed underneath screening sieve plate 37 is a discharge stump 38 which has an inlet 39 protected by an overhanging plate portion 40. The above described apparatus operates as follows. The starting point is the position that the control unit 26 places the conduit 3 in communication with the pressure source 4 so that a determined volume flow of air at a determined pressure is created in conduit 3. The abrasive medium runs out of the storage tank 10 in doses via opening 11 into conduit 3 and arrives with the air current at the blast nozzle 1. As a result of the blasting nozzle present in housing 1 the air current with the abrading medium reaches a determined speed and is impelled against the surface 0 and creates as a result a determined abrading action which will clean the surface 0. In the housing 1 a vacuum is generated which discharges the quantity of air with grit and dust via stump 5 and conduit 6. This mixture is carried at a determined speed into the dust separator 7, whereby the grit and dust are impelled against the plate 35 which because of its elastic function prevents excessive wear of the inner wall of the tank. The impact action that is nevertheless present causes a separation between dust and grit particles which then sink downward over the baffle plates 36 in zig-zag fashion whereby the screen 37 sieves out the grit particles as a result of their higher specific weight to the lower part of tank 7. The dust particles are discharged at low speed with the air via pipe 6′ to the dust collector 8. The intake opening 39 is protected by the guard 38 against the downward falling grit so that carrying away of the grit with the discharge air flow via pipe 6′ occurs hardly or not at all. In dust collector 8 the dust will sink downward into the tray 32, while the air is filtered via filter 30 and discharged by fan 31. The dust can be disposed of regularly via the removable drawer 32. The reclaimed grit particles in tank 7 can fall via opening 15 into pressure tank 13 since the valve 17 is located in the lowest position under the influence of gravity. Assumed here is that initially atmospheric pressure prevails in tank 13 and that subsequently the vacuum from pipe 6′ is present in this tank. After a time the conduit 27, under the control of control unit 26, is placed under pressure from the pressure source 4, whereupon tank 13 receives this pressure, which immediately pushes valve 17 upward so that opening 15 is closed off. Because of the pressure in conduit 3 the pressure from pressure source 10 already prevails in storage tank 10 so that valve 18 keeps the opening 16 closed in the operating position. This pressure is applied more rapidly to hopper 10 via conduit 28 which is placed in direct communication with pressure source 4 by control unit 26. The reclaimed grit remains for the time being in pressure tank 13. As soon as an operative reverses the switch 24 at the blast nozzle the control unit 26 is regulated such that conduit 3 is closed off from pressure source 4 and blast nozzle 1 is rendered inoperative. In this situation the valves 21 and 22 in the bleed conduit 19 are also opened and the pressure present in tanks 10 and 13 is immediately decreased. the respective valves 17 and 18 consequently drop downward under the influence of gravity and open the passage openings 15 and 16, as a result of which the grit can drop into the storage tank 10. When pressure is once again fed into conduit 3 the control unit 26 is regulated such that conduits 27 and 28 are again placed under pressure and therefore also the tanks 10 and 13, which results in valves 17 and 19 returning to the closed position. It will be apparent from the above that opening and closing of valves 17 and 18 takes place each time the blast nozzle 1 is turned on and off respectively, which will occur regularly. This ensures that the storage tank 10 always remains provided with sufficient grit material, this material being carried in a cycle via dust separator 7. Loss of grit material is consequently reduced to a minimum and only as a result of wear and the resulting dust forming will the grit material diminish. This grit that has been reduced to dust is carried away normally with the other dust to the dust collector 8. The invention is not restricted to the above described embodiment. So for example the system of valves 17 and 18 can be replaced by any other random valve, for instance electro-magnetic or pneumatic types. The dust collector 8 can of course take any random suitable form.

Claims: Apparatus for cleaning a surface by means of an abrasive material in a transporting air flow at high velocity, said apparatus comprising a nozzle (1) for placing on said surface, provided with a feed line (3) to be connected onto a pressure source (4), said line having an inlet opening (9) for said abrasive, and a discharge line (6') connected to a vacuum source and leading to a dust collector (8), wherein a dust/abrasive separator (7) is accommodated in said discharge line and connected via an intermediate pressure tank (14) with a storage tank (10) for the separated abrasive connected to said inlet opening (9), wherein one way valve means (17, 18) are arranged between said separator (7) and pressure tank (14), said pressure tank and storage tank (10) respectively, characterized in that both said pressure tank (14) and the storage tank (10) are connected via a controlled bleed conduit (19) into the dust collector (8). Apparatus as claimed in claim 1, characterized in that the dust/abrasive separator (7) having the form of a container is provided with baffle means (36, 37) arranged therein, said discharge line (6') leading to the dust collector (8) runs out beneath the lowest of said baffle means (37). Apparatus as claimed in claim 2, characterized in that a part of the discharge line (6') protruding into the container (33) is provided with an upward facing screening plate (37) above its intake opening. Apparatus as claimed in claims 2 and 3, characterized in that said lowest of the baffle means is formed wholly or partially as a screening sieve. Apparatus as claimed in any of the foregoing claims, characterized in that both the air tank and storage tank are connected through a feed conduit (27 and 28), said controlled bleed conduit (19) having a greater flow capacity than said feed conduits.

Inventors: VAN LEEUWEN, JACOB KAREL LODEWIJK
Applicants: LTC INTERNATIONAL B.V.
Application year: 1987
Main classification: B24C3
IPC codes: B24C3, B24C9