Non-contact particle accelerator for blasting applications

Abstract

A blast chamber having a plurality of blast assemblies, with each blast assembly comprised of a clocking mechanism having a particular geometric shape, a rotor assembly, and a power source. Each rotor assembly is capable of rotating about a center line axis and has a plurality of spaced-apart rotors. At least one rotor includes a generally central opening. The blast chamber further includes a grit intake source for introducing grit into each clocking mechanism and a power source to impart a rotational force to the each rotor assembly. The blast chamber also includes a blast area adjacent to each blast assembly. Grit is gravity fed from the grit intake source and into the clocking mechanism and directed via the particular geometric shape of the clocking mechanism while the rotors are rotating. The grit is then directionally hurled according to the shape of the clocking mechanism through the at least one central opening of the rotating rotors and out through the space between the individual rotors and at the adjacent blast area, which contains a steel plate or other metal in which blasting is desired. An optional shroud may cover a portion of each rotating assembly to divert incidental grit.

Description

TECHNICAL FIELD

[0001] The present invention is generally directed to a non-contact particle accelerator for use in blasting applications in order to prep metal surfaces prior to painting or coating.

BACKGROUND OF THE INVENTION

[0002] Blasters are used to prep plate and shaped steel prior to painting or coating the steel. Blasters utilize steel grit that is forcibly directed at steel to achieve a “white metal” surface prior to painting or coating the steel. White metal surfaces are highly preferred by coating suppliers because white metal surfaces remove scale on the surface of the steel and provide a “grippable” surface to which paints and other coatings can readily adhere. By prepping steel to a white metal surface, paints and/or coatings can adhere to the steel surface for a long time. This technique is heavily used in marine applications and structures that have high impact regions (such as an aircraft carrier deck) where the painted or coated surfaces are vulnerable to high wear and are expensive to replace.

[0003] Conventional blasters typically use a paddle arrangement in which a wheel configuration having paddles or rotors forcibly blast or propel steel grit onto a targeted steel surface. Because the grit can directly strike the paddles or rotors, and the grit is designed to be highly abrasive in order to achieve a white metal surface on the surface to which the grit is directed, abrasion of the paddles is extremely high. In such applications, wear of the paddles and related components may occur in as little as 8-10 hours after commencement of the grit blasting and require replacement. The cost to replace the paddles can be in the thousands of dollars. Thus, down time and extremely high replacement costs plague the current known blast systems.

[0004] Because of the extreme replacement cost with direct grit blasting, the industry has been often forced to run two passes at the surface to which blasting is directed. The first pass includes forcibly blasting steel shot peen that creates a peened surface. Steel shot is rounder than the angular grit shot. The shot peening creates less wear on blasting components such that the replaceable wear is at 40-50 hours of application, as compared to the grit blasting wear of 8-10 hours. However, shot peening creates a cratered but relatively smooth surface that is not conducive to paint or coating adherence. As such, blasting applications traditionally apply a two part blasting process: a first shot peening pass to removed most of the scale or other material, and then a second grit pass to create the final surface. The two pass process is expensive because it is time-consuming and requires more labor, equipment, and supplies, and wear of the blasting parts is less than every 40-50 hours.

SUMMARY OF THE INVENTION

[0005] The present invention is directed to a new apparatus and process for blasting steel to a white metal surface prior to the application of paints/coatings with vastly reduced wear over conventional blasters and eliminates the need for multiple blasting passes during the blasting process. The blast apparatus or assembly essentially operates as a particle (grit) accelerator with little to no contact with wear surface. In one embodiment, the blast assembly includes a plurality of spaced-apart rotors capable of rotating about a centerline axis of a shaft, where at least one of the rotors has a generally central opening axially-aligned of the shaft. The assembly further includes a clocking mechanism having a particular geometric shape for accelerating and directing the grit or shot into the at least one generally central opening and out through at least one space between the rotors. The assembly also includes a power source that provides a rotating force to the rotor assembly and a grit intake device that directs grit to the clocking mechanism. Preferably, the assembly also includes a shroud for diverting incidental grit or shot.

[0006] The present invention is further directed to a new blast chamber containing a plurality of blaster assemblies with the rotor assemblies from which grit is hurled toward an adjacent blast area that can receive a steel plate or other metal sheet in which a surface of the plate is to be prepped. The blast chamber may include a grit intake chamber and grit collector system that is capable to recycling the used grit and redirecting the grit back into the grit intake chamber.

[0007] The present invention further includes a method of obtaining a white metal surface on a steel plate to which paint/coating is to be applied. The method includes applying grit to a metal surface via a blaster that pulls in grit through a grit intake source into a clocking mechanism that directs grit into a rotor assembly or a plurality of rotor assemblies, where each rotor assembly has a plurality of space-apart rotors. Each or most of the rotors include a generally central opening through which a portion of the clocking mechanism extends. Grit is directed from the clocking mechanism and hurled substantially parallel to the rotors and within the space between the rotors along boundary layers of the rotor surfaces in an angular acceleration path onto the surface of the metal. The grit is directed in a particular path such that it is designed to not contact the surfaces of the rotors and makes incidental contact with a shroud, if present, to significantly reduce wear on the rotors and other working components.

[0008] These and other features and benefits will be discussed in further detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Like reference numerals are used to designate like parts through the several views of the drawings, wherein:

[0010] FIG. 1 is a schematic diagram of the blasting assembly of the present invention illustrating the grit intake source, clocking mechanism, power source, rotor assembly, and optional shroud, in which the rotor assembly is directed at a targeted surface;

[0011] FIG. 2 is a schematic section view of the rotor, shroud, and clocking mechanism of the blasting assembly of FIG. 1 directed at a steel plate surface;

[0012] FIG. 3 is an enlarged schematic view showing the flow path of grit accelerated and directed by the geometric shape of the clocking mechanism and hurled into the rotor assembly through openings in the individual rotors and being hurled into the space between the individual rotor blades along boundary layers adjacent surfaces of the rotors;

[0013] FIG. 4 is a section view taken substantially along lines 4--4 of FIG. 3 and better illustrates the angular acceleration path of the grit directed from the clocking mechanism, along the boundary layers adjacent the rotor surfaces and onto a targeted surface;

[0014] FIG. 5 is a front view of a single blaster assembly including a rotor assembly, shroud, grit carburetor, clocking mechanism, and motor;

[0015] FIG. 6 is a right side perspective view of FIG. 5;

[0016] FIG. 7 is a left side perspective view of FIG. 5 better illustrating one embodiment of the power source imparting a rotating force to the rotor assembly;

[0017] FIG. 8 is an exploded perspective view of the individual rotors, power source, shroud, clocking mechanism; grit, and grit carburetor;

[0018] FIG. 9 is a perspective view of the clocking mechanism;

[0019] FIG. 10 is a section view taken substantially along lines 10--10 of FIG. 8;

[0020] FIG. 11 is a schematic diagram illustrating the blasting apparatus of a blast chamber along with grit collection apparatus;

[0021] FIG. 12 is a perspective view illustrating several blasting assemblies fixedly connected to a frame positioned adjacent a blast area;

[0022] FIG. 13 is a perspective view like FIG. 12 better illustrating additional frame structure of the blast chamber and a grit intake chamber;

[0023] FIG. 14 is a view like FIG. 13 and better illustrating additional frame structure and exterior;

[0024] FIG. 15 is a top view of FIG. 13 and better illustrating the grit intake chamber with a device to assist direct grit into the grit carburetors at each blast assembly;

[0025] FIG. 16 is a side elevation view of the blast chamber of FIG. 14 shown less a portion of the frame exterior;

[0026] FIG. 17 is a perspective view of a piece of sheet steel with scale about to enter the blast area of the blast chamber of the present invention and with a “white metal surface” on at least one side of the steel sheet after the blasting process;

[0027] FIG. 18 is a perspective view of a grit collector of the blaster that is part of the bottom of the blast chamber;

[0028] FIG. 19 is a side view of an alternate embodiment rotor blade and shaft; and

[0029] FIG. 20 is an end view of the rotor blade of FIG. 19.

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] The present invention is directed to apparatus and a method for blasting metal surfaces in order to remove scale and other material and to provide a white metal surface on the desired surface of the metal, such as steel, prior to coating or painting. The present invention is an improvement of the prior art because the key components of the blasting apparatus or assembly are designed to last many times longer than the prior art because the grit path is not designed to touch the surfaces of the system and reduced dust, as discussed in more detail below.

[0031] FIG. 1 is a schematic diagram of the basic blaster apparatus or assembly 10, which includes a grit intake source 12, a rotor assembly 14, a power source 16, a clocking mechanism 18, and an optional shroud 20. Grit 22 enters the grit intake source and is directed into the rotor assembly 14 in order to hurl (or blast) grit 22 onto a targeted metal surface 24.

[0032] Now referring to FIGS. 2-8, which better structurally illustrate the features of the blaster assembly 10 of the present invention, the rotor assembly 14 comprises a plurality of individual spaced apart rotors 26 (or blades) that are capable of rotating about a centerline axis 28 when a rotating force is applied directly or indirectly from the power source 16. Each rotor, which according to a first embodiment is a smooth disk, includes a generally central opening 30 in which grit 22 is introduced into the rotor assembly. Grit enters a grit intake source, such as a grit carburetor as shown, and is directed into the central openings of the individual rotors by the clocking mechanism 18. The clocking mechanism is axially aligned with the central openings 30 of the rotors 26. Grit is directed by the clocking mechanism into the central openings of the rotating rotor assembly. Because the grit enters the rotating rotor assembly, the grit is hurled outwardly of the rotor assembly within the space between the individual rotors along an angular acceleration path to the targeted surface.

[0033] Referring particularly to FIGS. 3 and 4, the present invention is based upon boundary layer principles where grit is gravity fed into the grit intake source, and directed into the clocking mechanism 18. The clocking mechanism 18 extends into a least one central opening 30 of an individual rotor 26 of the rotor assembly which is rotating at a relative high rate of speed, such as approximately 6000 rpm. The grit is directed into the space between the rotors as illustrated in FIG. 3 and is angularly hurled outward from the clocking mechanism via the space between the rotors along boundary layers 40 that are adjacent rotor surfaces 42. The hurled grit is directed at the targeted surface to which the white metal surface is desired.

[0034] Now referring particularly to FIGS. 5-8, the rotor assembly may be like that disclosed and claimed in my co-pending patent application Ser. No. 10/285,116, filed Oct. 30, 2002, and entitled “Mixer”. A shaft 32 to which at least one outer rotor 26 is connected is directly or indirectly connected to the power source 16, such as a motor with a belt and sieve configuration (FIG. 7), in order to impart a rotating force to shaft 32 such that rotor assembly 14 rotates about central axis 28. The shaft may be connected to only one end of the rotor assembly, or may extend axially through the central openings of the individual rotors. The clocking mechanism 18 may be adjacent and parallel to the shaft 32, such as illustrated in FIG. 8. A plurality of spacers 34 (two per rotor are shown for illustrative purposes) between each rotor keep the individual rotors spaced apart as well as to provide a connecting means for each rotor to the overall assembly.

[0035] Referring also to FIGS. 9 and 10, the clocking mechanism essentially directs the grit 22 into an area dictated by the particular geometric shape of the clocking mechanism. In preferred form, the clocking mechanism may be like a piece of angle iron having a substantially ninety degree angle when viewed in cross section of the clocking mechanism (FIG. 10). The effective grit flow within the central opening 30 is reduced to a quarter circle 36 (although other geometric configurations may be used such as, but not limited to, octagonal, hemispherical, semi-circular, and triangular) in order to accelerate grit into the rotor assembly Grit 22 is then hurled from the rotor assembly through the space between the individual rotors is accelerated along a boundary layer 40 between rotor surfaces 42.

[0036] From the time that the grit exits the clocking mechanism and enters into the rotor assembly, the grit is not directed at any of the rotor assembly surfaces, and, thus, wear of the surfaces is greatly reduced over the prior art. However, there may be some incidental contact on to the spacers upon occasion. As such, the spacers 34 may preferably be made of a hard steel with a hard anneal bushing and/or covered with a gum rubber for increased life.

[0037] The shroud 20 may be added about a portion of each rotor assembly to divert incidental grit or shot. Although the shroud is optional to the integrity of the blasting assembly of the present invention, it is preferably added to the assembly to not only divert incidental grit but protects equipment from the contact with incidental grit and aids in the reduction of dust.

[0038] The power source is preferably a motor sized to impart rotational force to the shaft that rotates the rotor assembly. As such, the size of the motor is a function of the size and operational requirements of the rotor assembly. However, to achieve the 6000 rpm for a blaster assembly such as illustrated and having a rotor diameter of 18″ to 36″, a 15 hp induction motor may be used.

[0039] The invention further includes a complete blaster chamber 50 as schematically illustrated in FIG. 11. In addition to the blast assembly 10, as discussed above, the used grit is collected and recycled back to the grit source in order to minimize grit cost. As the blasting process may use two tons of grit a minute, recycling of grit can be a great cost reduction as well as dust reducer. In this embodiment, an auger 44 or other device may be employed that can drive the grit from the chamber grit intake source 47 into the individual blast assembly grit intake source 12 and into the individual clocking mechanisms 18 prior to entry into the rotor assembly. A steel plate 46, of which surface 24 is being prepped in the blasting process, is brought into close proximity to outer edges 48 of the individual rotors 26. Grit that has already hit the surface 24 drops to the bottom of a blast chamber 50. At the bottom of the blast chamber 50 is a collection bin or bucket 52. Another auger 54 may be employed to drive the grit to a grit return path 56 that will eventually take the grit to the grit intake source 12. In this way, grit is recycled to be used over a long period of time.

[0040] Referring now to FIGS. 12-16, the blast chamber 50 includes a plurality of blast assemblies 10, which are placed in a configuration to ensure the entire surface 24 of the steel plate 46 has grit directed to it. For example, a typical steel plate having dimensions of 10′6″×1-½″×40′ might require eight blasting assemblies arranged into four rows and two columns all with the shrouds 20 open in the same plane P as best illustrated in the FIG. 12. The steel plate 46 would enter a blast area 58, where the surface 24 of steel plate 46 would be adjacent and exposed to the open shroud rotors in plane P.

[0041] FIGS. 13 and 14 better illustrate frame enclosure 49 that houses the blast chamber 50. The chamber grit intake source 47 is shown at the top of the blast chamber 50 having an optional grit driver, such as an auger 44 which is illustrated in hidden lines in FIG. 13. Grit collection bin 52 (which may be like that illustrated in FIG. 18) may be positioned at the bottom of the blast chamber 50. Chamber exteriors members 51 (such as steel plate) may be used to cover the chamber for safety reasons as well as dust and noise reduction.

[0042] FIGS. 15 and 16 illustrate the grit intake source as viewed from the top of the blast chamber (FIG. 15) and how the grit is channeled or otherwise directed to the individual grit carburetors and clocking mechanisms of each blast assembly 10 (FIG. 16).

[0043] FIG. 17 best illustrates how a typical steel plate 46 is fed into an opening 57 of the blast chamber 50 and exits the blast chamber in its desired prepped (“white metal”) form. Power rollers or chains (not illustrated) may be used to move the steel plate 46 through the blast area 58 of blast chamber 50. The rate of movement will be determined by the size of the steel plate, and the amount of “scale” that must be removed in the blasting process. The configuration as shown in FIG. 17 is designed to remove scale on a plate having dimensions of 10′6″×40′ at a linear rate of ¾″ to 2″ per second. Sensors (not shown) may be used to determine when a plate is in the blast area and to signal to the power source to stop until the a new plate has entered the blast area for blasting, which reduces power consumption and overall operating costs. Because the present blasting process does not require the two step shot peening first pass and grit second pass of the prior art, the process increases productivity and reduces in half the amount of time it takes to conventionally obtain a white metal surface on a similar size steel plate.

[0044] Although not illustrated in FIGS. 13-14, the frame structure may hold another set of blast assemblies all with the clocking mechanisms and rotor assemblies directed at the blast area 58 in order to blast both sides of the steel plate at the same time. Thus, for the blast chamber illustrated in the example of FIG. 13, there would be a total of 16 blast assemblies with 8 to each side of the blast area.

[0045] Individual rotors may take on various forms, such as those discussed in my aforementioned co-pending patent application Ser. No. 10/285,116, and which is incorporated herein by reference. Moreover, the rotors may be “auger-like” in form, such as the rotor 26′ illustrated in FIGS. 19 and 20. In that embodiment, a single auger-like rotor may be used with out the central opening. The clocking mechanism will direct the grit in the space about the auger-like rotor and onto the adjacent steel surface (not shown).

[0046] The present invention includes a process for obtaining a white metal surface that includes the blaster assemblies, and, preferably, the blast chamber, described above.

[0047] Advantages of the present invention include greatly increasing the lifespan of blasting apparatus due to a lack of grit contact on wear surfaces; reduction in material costs due to the systems grit recycling capabilities, reduction of grit dust given the generally self contained nature of the blast chamber, and reduction of costly two-pass processing to achieve a white metal surface. The illustrated embodiments are only examples of the present invention and, therefore, are non-limitive. It is to be understood that many changes in the particular structure, materials, and features of the invention may be made without departing from the spirit and scope of the invention. Therefore, it is the Applicant's intention that his patent rights not be limited by the particular embodiments illustrated and described herein, but rather by the following claims interpreted according to accepted doctrines of claim interpretation, including the Doctrine of Equivalents and Reversal of Parts.

Claims

1. A blast assembly comprising:

a rotor assembly capable of rotation about a centerline axis; said rotor assembly including a at least one rotor having a boundary of space about the at least one rotor;

a power source capable of imparting a rotational force to the rotor assembly;

a grit intake device providing grit to a clocking mechanism having a particular geometric shape in order to directionally hurl grit within the space about the at least one rotor.

2. A blast assembly comprising:

a rotor assembly capable of rotation about a centerline axis; said rotor assembly including a plurality of spaced-apart rotors wherein at least one rotor contains a generally central opening;

a power source capable of imparting a rotational force to the rotor assembly;

a grit intake device providing grit to a clocking mechanism, which is axially-aligned with the at least one generally central opening; said clocking mechanism having a particular geometric shape in order to directionally hurl grit out of the generally central opening and through the space between at least two adjacent individual rotors.

3. The blast assembly according to claim 1 further comprising a shroud that surrounds a portion of the rotor assembly.

4. The blast assembly according to claim 2 further comprising a shroud that surrounds a portion of the rotor assembly.

5. The blast assembly according to claim 1 wherein the rotor is in the shape of modified auger.

6. The blast assembly according to claim 2 wherein each rotor is a generally smooth surfaced disk.

7. The blast apparatus according to claim 2 wherein there are four rotors.

8. The blast apparatus according to claim 3 wherein the shroud is positioned to leave an opening to one longitudinal side of the rotor assembly.

9. The blast apparatus according to claim 1 wherein the clocking mechanism's geometric shape substantially forms a ninety degree angle as viewed in lateral cross section of the clocking device.

10. The blast apparatus according to claim 2 wherein the clocking mechanism's geometric shape substantially forms a ninety-degree angle as viewed in lateral cross section of the clocking device.

11. A blast chamber comprising:

a frame;

a plurality of rotor assemblies positioned within the frame, each said rotor assembly having at least one rotor capable of rotation about a centerline axis, and a clocking mechanism that is co-axially aligned with the centerline axis in order to directionally accelerate and hurl material into a space about the at least one rotor and out of the rotor assembly in a particular accelerated path;

a grit intake source that feeds grit into each clocking mechanism; and

a blast area having at least an inlet of a size to receive a metal surface for blasting within the frame and adjacent the rotor assemblies such that the output of each rotor assembly is directed at the blast area.

12. The blast chamber according to claim 11 wherein each rotor assembly has a plurality of spaced apart rotors with a generally central opening in at least one rotor, and wherein the clocking mechanism accelerates and hurls material into the at least one generally central opening and out through the space between at least two of the rotors.

13. The blast chamber according to claim 11 further comprising a grit collection system, said grit collection system includes a grit collection bin at the base of the blast area in which to collect fallen grit, said grit collection system further includes a conduit in which to funnel grit back to the grit intake source.

14. The blast chamber according to claim 11, wherein the chamber is substantially enclosed.

15. The blast chamber according to claim 11 wherein a shroud covers a portion of each rotor assembly.

16. The blast chamber according to claim 11 wherein there are eight rotor assemblies.

17. The blast chamber according to claim 11 wherein the grit collection bin is a substantially v-shaped trough.

18. The blast chamber according to claim 11 wherein the grit intake source further includes an auger in which to direct the grit from the grit intake source to each rotor assembly's clocking mechanism.

19. A method for obtaining a white metal surface on a piece of sheet metal, the process comprising:

providing a blast assembly consisting of a rotor assembly capable of rotating about a center axis and having a plurality of spaced-apart rotors with at least one generally central opening, and a clocking mechanism having a particular geometric shape;

providing a power source to impart a rotational force to the rotor assembly;

providing a metal surface to which a white metal surface is desired to be positioned adjacent the opening of the shroud;

providing grit through a grit intake source to be fed into the clocking mechanism;

directing the grit through the geometric shape of the clocking mechanism and hurling it into the generally central opening of the spaced apart rotors and outward of the rotor assembly between at least one space between individual spaced-apart rotors.

20. The method according to claim 19 wherein the metal surface is fed into the area adjacent the opening of the shroud at a linear rate of ¾ inch to 2 inches per second.

21. The method according to claim 19 wherein the grit enters the grit intake source at a rate of 2 tons a minute.

22. The method according to claim 19 wherein the a plurality of blast assemblies are placed in a configuration to simultaneously blast the adjacent metal surface all at the same time.

23. The method according to claim 19 wherein at least a portion of the rotor assembly is shrouded.