Patent Application
20100173569
The present invention relates to a system for containing particulate matter released during the blasting of surfaces with a particulate stream.
The bombardment of metal surfaces with abrasive materials is finding an increasing number of technical applications in recent years. Techniques such as grit blasting, shot blasting, sand blasting, shot peening and micro abrasion fall under this category of surface treatment technique. In each of these techniques, generally, an abrasive material, shot or grit, is mixed with a fluid and delivered at high velocity to impinge the surface to be treated. The technique used to deliver the abrasive material can be classified as wet or dry depending on the choice of fluid medium used to deliver the abrasive to the surface, usually water and air respectively.
Applications of these technologies include metal cutting, cold working metallic surfaces to induce desirable strain characteristics and the pre-treatment of surfaces to induce desirable texture (surface roughness) for the purposes of enhanced adhesion of further coating materials. (See Solomon et al., Welding research, October 2003: p. 278-287; Momber et al., Tribology International, 2002. 35: p. 271-281; Arola et al., J. Biomed. Mat. Res., 2000. 53(5): p. 536-546; and Arola and Hall, Machining science and technology, 2004. 8(2): p. 171-192.).
The result of accelerating powder particles and blasting them onto a substrate results in large amounts of powder being suspended in the air and ultimately escaping the blasting chamber. Disclosed herein is a system for containment of particulate matter that results from a blasting procedure.
One embodiment provides a deposition system comprising:
a blasting device comprising at least one fluid jet nozzle for delivering a stream of particles under pressure toward a substrate positioned on a supporting platform;
a plastic, flexible container having openings penetrated by the at least one fluid jet nozzle and supporting platform, the openings being sealably attached to the blasting device to isolate the interior of the container and the device from the outer environment;
wherein upon delivery of the stream of particles, the system prevents escape of particulate matter into the outer environment.
Various embodiments of the invention will be understood from the following description, the appended claims and the accompanying drawings, in which:
Grit blasting finds various applications industries, such as the automotive, aerospace, construction, medical, and other industries that involve surface texturing or smoothing. An example of abrasive blasting in the medical industry is found in the grit blasting of titanium implants with alumina or silica to achieve an optimum level of surface roughness that will subsequently maximize the adhesion of plasma sprayed hydroxyapatite (HA) coatings on the surface of the implants. HA-coated implants are desirable because of the biomimetic properties of the apatite layer but an optimum bonding strength between the titanium surface and the apatite layer is also necessary.
The recent significant interest in surface modification technology as it relates to biomedical devices is fueled by the success of the Drug Eluting Stent (DES), among other drug eluting medical devices. The drugs are typically coated onto the device in conjunction with a carrier, such as a polymer matrix, that adheres to the device and consequently, secures therapeutic agents to the device.
As discussed above, a typical blasting device involves accelerating a stream of particles toward a surface via pressurized liquid or gas, causing large amounts of particulate material to escape the blasting chamber. As a result, blasting devices are typically housed in a separate room, an external building, or even outdoors, where contamination does not present a problem.
Although there are a few reports involving grit blasting of drugs onto substrate surfaces, there are currently no commercially available devices that provide therapeutic drugs deposited onto medical devices via grit blasting. From a safety standpoint, grit blasting would be an undesirable method for drug deposition as it would result in the release of particulate drug matter throughout the room or building housing the blasting equipment. The operator of the grit blasting equipment would be placed at risk of significant levels of exposure to the airborne drug.
Accordingly, disclosed herein is a deposition system having a containment of particulate material resulting from blasting processes. In one embodiment, the system comprises:
a blasting device comprising at least one fluid jet nozzle for delivering a stream of particles under pressure onto a substrate positioned on a supporting platform;
a plastic, flexible container having openings penetrated by the at least one fluid jet nozzle and supporting platform, the openings being sealably attached to the blasting device to isolate the interior of the container and the device from the outer environment;
wherein upon delivery of the stream of particles, the system prevents escape of particulate matter into the outer environment.
The jet nozzle 10 can be connected to the blasting device 4 (e.g., the hopper) by a hosing (not shown). The hosing material typically has high abrasive resistance to the particles that are transported to the blast zone. In one embodiment, the hosing comprises a rubber.
System 2 further comprises a container 6 having openings that allow the penetration of jet nozzle 10 and platform 12 into the interior of the container. The container 6 can have a sleeve 23 (or collar) that envelops or circles the processing head 8 to facilitate a seal between the container 6 and device 4. The container 6 is sealably attached to the blasting device so as to isolate the container interior and the device 4 from the outer environment. In
Container 6 is prepared from a plastic material with sufficient flexibility to wrap around the nozzle 10 and platform 12. Moreover, container 6 has the durability and strength to withstand the conditions of the blaster, e.g., the force of the particulate stream. In one embodiment, the at least one fluid jet operates at a pressure ranging from 0.5 to 100 bar, such as a pressure ranging from 1 to 30 bar, a pressure ranging from 1 to 10 bar, or a pressure ranging from 3 to 10 bar.
In other embodiments, the container does not contain a sleeve or collar but has a sufficient amount of flexible material to wrap around the processing head 8 or other components of the device 4.
In one embodiment, the container 6 is made from an anti-static material.
In one embodiment, the container 6 is made from a clear or translucent material sufficient to allow a user to view the components within the container, e.g., nozzle 10, platform 12, and the substrate.
In one embodiment, container 6 is made from polyurethane, such as anti-static polyurethane.
Due to its flexibility, container 6 may collapse and interfere with the blasting process. In one embodiment, the container 6 is attached to a rigid framework 18, which may be located inside or outside the container 6. Framework 18 secures the container at attachment components 20, thereby maintaining a space within the interior. In one embodiment, framework 18 is slightly larger than the interior space of container 6. Although shown as a cube, the framework 18 can be of any shape so long as it can prevent collapse of the container. Attachment components 20 can be selected from clips, adhesives, snap-fit or push-fit assemblies, etc.
In the embodiment of
In another embodiment, the walls of the container can be supported by encasing the bag in a rigid chamber. The rigid chamber can be a plastic material (clear, translucent, or opaque) or can be a metal chamber.
In one embodiment, container 6 further comprises at least one additional opening sealably attached to and surrounding an exhaust pipe 26. Airborne particulate matter within container 6 can be extracted through pipe 26 either via an external vacuum or blower (not shown), or under the operating conditions of the blasting device. After removal of the airborne particles, the bag can be detached from the device and resealed with minimal release of particulate material into the outer environment.
In one embodiment, the container is disposable. Upon removal of airborne particulate matter and detachment of the container from the blasting device, the container can be resealed and disposed, thereby ensuring that the particulate matter resulting from the blasting process remains contained. A disposable bag eliminates or substantially reduces the amount of cleaning that necessarily follows a blasting operation.
It is understood that the container is sealably attached to prevent escape of particles/powder. In another embodiment, the container 6 is sealably attached to the device 4 in a gas tight manner. The particle stream can be released from nozzle 10 using an inert gas (He, N2, Ar, Kr, etc.) as a fluid carrier to achieve an inert atmosphere within the interior of container 6. In another embodiment, container 6 further comprises at least one additional opening sealably attached to and surrounding a gas inlet 24. An inert gas can be introduced through inlet 24 to allow the blasting process to be performed in an inert environment.
In one embodiment, the container 6 has a resealable opening 28 allowing access to the container from outside the system. This allows the operator to manipulate the nozzle 10, platform 12, and other components within the system even after securing the sealable attachments 22. For example, opening 28 can be sealed and unsealed via a zipper, as shown in
In one embodiment, the blasting device is selected from wet blasters, abrasive water jet peening machines, and wet shot peening machine, where water is typically used as a fluid carrier. In another embodiment, the blasting device is selected from dry shot peening machines, dry blasters, wheel abraders, grit blasters), sand blasters(s), and micro-blasters, where a gas (air, He, N2, Ar, Kr, etc.) is the fluid carrier.
In one embodiment, the blasting device can be incorporated as a stand alone unit or can be incorporated into a manufacturing line. The equipment can be used in a point of use setting whereby it would constitute an aseptic surgery based machine that a surgeon could use in an operating room for custom/prescriptive surface modification prior to implantation of the device in the patient.
In one embodiment, the stream of particles includes particles having a modus hardness ranging from 0.1 to 10, such as a modus hardness ranging from 1 to 10, or a modus hardness ranging from 5 to 10. In another embodiment, the stream of particles has a particle size ranging from 0.1 μm to 10000 μm, such as a particle size ranging from 1 μm to 5000 μm, or a particle size ranging from 10 μm to 1000 μm.
The stream of particles can be selected from abrasive materials including, but not limited to, shot or grit made from silica, alumina, zirconia, barium titanate, calcium titanate, sodium titanate, titanium oxide, glass, biocompatible glass, diamond, silicon carbide, calcium phosphate, calcium carbonate, metallic powders, carbon fiber composites, polymeric composites, titanium, stainless steel, hardened steel, carbon steel chromium alloys or any combination thereof.
In other embodiments, blasting equipment can be used in conjunction with controlled motion such as CNC or robotic control.
In one embodiment, the substrate is a metal, such as those metals chosen from pure metals, metal alloys, intermetals comprising single or multiple phases, intermetals comprising amorphous phases, intermetals comprising single crystal phases, and intermetals comprising polycrystalline phases. Exemplary metals include titanium, titanium alloys (e.g., NiTi or nitinol), ferrous alloys, stainless steel and stainless steel alloys, carbon steel, carbon steel alloys, aluminum, aluminum alloys, nickel, nickel alloys, nickel titanium alloys, tantalum, tantalum alloys, niobium, niobium alloys, chromium, chromium alloys, cobalt, cobalt alloys, precious metals, and precious metal alloys. In one embodiment, the metal is titanium.
In one embodiment the stream of particles includes an abrasive material (e.g., alumina, silica, etc.) and hydroxyapatite. This mixed media can be delivered to a titanium surface using a standard grit blasting machine operating in the pressure range of 0.5 Bar to 20 Bar, such as a pressure range of 2 to 10 bar, or a pressure range of 4 Bar to 6 Bar. The distance between the nozzle and the surface can be in the range of 0.1 mm to 100 mm, such as a range of 0.1 mm to 50 mm, or a range of 0.1 mm to 20 mm. The angle of the nozzle to the surface can range from 10 degrees to 90 degrees, such as a range of 30 degrees to 90 degrees, or a range of 70 to 90 degrees.
One of ordinary skill in the art can appreciate the influence of machine parameters including jet velocity, operating pressure, venturi configuration, angle of incidence and surface to nozzle distances.
In one embodiment, the system provides at least one of the following features:
In one embodiment, the container is a clear, anti-static polyurethane bag. The bag has sleeves that extend from openings, where the sleeves can be sealed against the device via o-rings. The interior of the bag can be substantially cubic as shown in
The blasting operation is typically operated under pressures of 40 to 120 psi, or even higher. The particles of the particle stream released from the fluid jet typically range from 2 to 100 microns in diameter.
Other details of grit blasting operations are disclosed in U.S. Publication No. 2008/0274671, the disclosure of which is incorporated herein by reference. U.S. Publication No. 2008/0274671, discloses the use of grit blasting for adhering dopants, such as therapeutic agents, onto metal surfaces. This method eliminates the use of polymer coatings as a material for affixing the therapeutic agents as polymer materials may not be sufficiently bio-inert. In one embodiment, a hydroxyapatite can be blasted onto the metal surface along with a therapeutic agent.
