Centrifugal Finisher With Fixed Outer Vessel and Rotatable Inner Vessel

The present invention relates to an apparatus for finishing the surface of an object by contact with abrasive pieces caused by centrifugal and rotational forces.

Surface finishing a product can be an essential step in its manufacture as a final commercial product. In some instances, it is essential to finish the product to a smooth surface without deforming the characteristics of the material to its end purpose. Some finishing machinery use the centrifugal force imparted by a rotating vessel to finish products. Some of these machines subject objects to both centrifugal and rotational forces using a complicated set of gears. These types of machines are limited to a particular ratio of revolutional speed to rotational speed. Also, these machines are complicated and require many moving parts. They are quite noisy. Other types of machines create centrifugal forces by revolving a vessel around a shaft and creating rotational forces using a belt wrapped around the shaft and the exterior of the vessel. The speed of the belt is related to the speed of the shaft. Overheating is common in these types of machines.

One successful machine using both centrifugal and rotational forces in a simple design without a system of gears and which can be operated at very high speeds is disclosed in U.S. Pat. No. 5,355,638 to Hoffman, the disclosure which is hereby incorporated by reference in its entirety.

As disclosed in that '638 patent, the centrifugal finisher (or polisher) has an outer vessel that is rotatable, and at least one inner vessel that is revolved about the axis of the rotatable outer vessel and rotated about its own axis. A traction surface exists between the inner surface of the outer vessel and the outer surface of the inner vessel. The traction surface allows the outer vessel to restrain the inner vessel while the inner vessel experiences centrifugal forces. This machine simultaneously causes the rotational movement of the inner vessel to transfer momentum from the outer vessel to the inner vessel because the outer vessel is rotated at a different speed and possibly a different direction than the rotational movement thus causing the revolution of the inner vessel.

This invention discloses an apparatus where a center drive can be used for rotating the outer vessel and the inner vessel. One drawback of this type of machine is its size limitation because the outer vessel must be designed to rotate. For large objects, this becomes impractical and expensive. Additionally, the invention disclosed in the '638 patent has inner and outer vessels engaging each other causing an inability to control rotation of the inner vessel unless you rotate the outer vessel. Also, a traction surface is necessary, and as is explained in detail in the '638 patent, requires a band of resilient material having a high coefficient of friction. The traction surface maximizes pressure between the inner vessel and outer vessel walls to create the drive relationship. Also, the operation of the whole unit is constrained by the total RPM the unit can operate, and especially the outer vessel which can be difficult to manage when greater diameters are required.

It would be advantageous if a centrifugal finisher could be designed that overcomes the disadvantages of the finisher disclosed in the '638 patent. It would be advantageous if a traction surface was not necessary. If the outer vessel did not rotate and could be fixed, then much larger objects could be finished without requiring massive amounts of energy and force applied to the unit. Additionally, it would be advantageous if the inner vessel could be removed so that other vessels of various diameters could be inserted within the unit without necessarily having to change the outer vessel. In the '638 patent, the inner vessels are mounted on respective bearing supports that are mounted on arms connected to a centrally driven hub.

The centrifugal finisher of the present invention now allows an object or plurality of objects to be finished by contact with abrasive pieces caused by centrifugal and rotational forces using a fixed, non-rotatable outer vessel having an inner surface and a central axis. In accordance with the present invention, at least one inner vessel is positioned inside the outer vessel and contains an object to be finished. The inner vessel has an outer surface. At least one intermediate roller is positioned between the inner surface of the outer vessel and the outer surface of an inner vessel and engages the surfaces of respective outer and inner vessels. A drive mechanism then rotates each of the inner vessels around the central axis of the outer vessel by causing rotation of the inner vessels and engaging each of the inner vessels with at least one intermediate roller rotating along the inner surface of the outer vessel. The drive mechanism can include a mechanism for biasing the inner vessel against the intermediate roller as the intermediate roller engages the inner surface of the outer vessel and the outer surface of the inner vessel.

In one aspect of the present invention, two intermediate rollers engage an inner vessel and provide two contact points against the inner surface of the outer vessel. In accordance with another aspect of the present invention, the intermediate roller comprises a vertically oriented spool roller having opposing ends of a first larger diameter for engaging the inner surface of the outer vessel and a smaller diameter medial portion that engages the outer surface of the inner vessel. The rotation between the smaller diameter medial portion and the larger diameter end portions characterizes how the inner vessel rotates.

The drive mechanism can include a rotor arm supported for rotation at the central axis of the outer vessel. The rotor arm has an end and a drive roller mounted on the end of the rotor arm for engaging the outer surface of the inner vessel and biasing the inner vessel against the intermediate roller. A central support can be positioned at the central axis of the inner vessel. A plurality of rotor arms can be mounted on the central support. Each rotor arm can have at each end a drive roller that engages a respective inner vessel. In yet another embodiment, drive roller can act initially to position the inner vessel against the intermediate roller. The intermediate roller can be driven around the outer vessel by suitable drive means. When the centrifugal force reaches a level that the inner vessel maintains contact with the intermediate roller, the positioning is no longer required.

In still another aspect of the present invention, the centrifugal finisher of the present invention can include at least one support member mounted for movement about the inner surface of the outer vessel on which the vertically oriented spool roller is rotatably mounted. An inner vessel support is mounted on the support member in a position radially inward toward the central axis of the outer vessel for rotatably supporting the inner vessel in which an object to be polished is inserted. The support member can also include a guide wheel for engaging and rolling along the outer surface of the outer vessel to aide in stabilizing the support member as it moves along the surface of the outer vessel. Thus, when the drive mechanism exerts a biasing force against the inner vessel, it engages the spool roller, and the support member then is moved about the inner surface of the outer vessel.

The support member in the illustrated embodiment includes two intermediate rollers rotatably mounted on the support member. This provides two contact points. The inner surface of the outer vessel also can include guide channels, and the spool roller ends having the larger diameter can be configured for engaging the guide channels of the outer vessel.

This invention and its mode of operation will be more clearly understood from the following detailed description when read with the appended drawings in which:

FIG. 1 is a general environmental view showing the centrifugal finisher according to the present invention connected to an external controller;

FIG. 2 is a close-up of the centrifugal finisher of FIG. 1 showing in greater detail some of the internal parts;

FIG. 3 is a schematic isometric view showing the inner vessel engaged with intermediate rollers;

FIG. 4 is a schematic top plan view showing the outer vessel, inner vessels and support members and intermediate rollers;

FIG. 5 is a schematic isometric view showing the relationship among the inner vessel, intermediate rollers, drive mechanism and outer vessel;

FIG. 6 is another schematic isometric view showing the relationship among the inner vessel, intermediate rollers, and drive mechanism;

FIG. 7 is a side elevation view in partial section showing the support member that mounts the intermediate rollers;

FIG. 8 is a top plan view of the centrifugal finisher of the present invention;

FIG. 9 is a side elevation view of the centrifugal finisher of the present invention;

FIG. 10 is a top plan view of the centrifugal finisher of the present invention with parts broken away to show details about the drive mechanism, the inner vessel, the outer vessel and the intermediate rollers;

FIG. 11 is another side elevation view showing details of the support member, center drive shaft and related components;

FIGS. 12a through 12c show profilometer scans of unpolished and polished nose cone pieces using a silicone carbide solution and colloidal silica;

FIGS. 13a and 13b show an atomic force microscope image of an unpolished sapphire nose cone surface;

FIGS. 14a and 14b show an atomic force microscope image of a sapphire nose cone piece polished in colloidal silica;

FIGS. 15a through 15c show an atomic force microscope two dimensional scan of unpolished sapphire and polished sapphire in colloidal silica;

FIGS. 16a through 16c show digital instrument AFM images of unpolished arced surface and a surface that has been polished by the apparatus of the present invention, and another surface polished by another method;

FIGS. 17a through 17c show atomic force line plots of a nose cone surface polished for fifty hours in colloidal silica;

FIG. 18 shows a typical AFM of rough unpolished sapphire surface;

FIG. 19 shows a typical AFM scan of polished sapphire surface that has been polished using the present invention;

FIGS. 20a and 20b show a 3D profile of new drills before and after polishing in accordance with the present invention;

FIGS. 21a and 21b show a surface profile of new drills before and after polishing in accordance with the present invention;

FIGS. 22a and 22b show a 3D profile of new drills before and after polishing in accordance with the present invention;

FIGS. 23a and 23b show a surface profile of new drills before and after polishing;

FIGS. 24a and 24b show a 3D profile of used drills before and after polishing in accordance with the present invention;

FIGS. 25a and 25b show a surface profile of used drills before and after polishing;

FIGS. 26a and 26b show a surface profile of used drills before and after polishing;

FIGS. 27a and 27b show a 3D profile of used drills before and after finishing;

FIG. 28 shows a 3D representation of a cutter surface before polishing with the present invention;

FIG. 29 shows a representation of a 3D surface of a cutter after polishing in accordance with the present invention;

FIG. 30 shows a 3D plot of a cutting tool before polishing in accordance with the present invention;

FIG. 31 shows a 3D plot of a cutting tool after polishing in accordance with the present invention;

FIG. 32a is a section analysis of a line plot cutter surface after polishing in accordance with the present invention while FIG. 32b is a spectrum of the section analysis;

FIG. 33a and FIG. 33b show a line plot and spectrum of a cutter surface before polishing; and

FIGS. 34a and 34b show a line plot and spectrum of a cutter surface after polishing.

The present invention now allows the use of a centrifugal finisher or polisher that has an outer vessel that is fixed and nonrotatable. The present invention allows a much greater diameter outer vessel to be used and accordingly much larger objects can now be polished or finished. The outer vessel is fixed and nonrotatable and has an inner surface and a central axis. At least one inner vessel (in the illustrated embodiment three inner vessels) are positioned inside the outer vessel and contain at least an object to be finished. Each inner vessel has an outer surface. An intermediate roller (in the illustrated embodiment two intermediate rollers) are positioned between the inner surface of the outer vessel and the outer surface of each of the inner vessels and engages the surfaces of respective outer and inner vessels. A drive mechanism includes a rotor arm having a roller at its end, which biases the inner vessel against the intermediate rollers and forces the inner vessel around the central axis of the outer vessel. The rotation of the inner vessel is caused by its which is in engagement with the intermediate roller that rotates along the inner surface of the outer vessel.

The present invention now allows greater control over the finishing process and also allows larger objects to be polished. The final product after finishing is a superior product with enhanced properties. A listing of various objects that can be finished using the present invention can include but are not limited to:

nose cones on weapons to allow transmission of infra-red guidance signals; domes and windows; gem stones; orifices for air and liquid metering; nozzles for printing heads; pen tips; guide wires; windows for high temperature or corrosive environment; probes for measuring instruments; magnetic tapes; cleaning blades; pistons; ball check valves for precision metering pumps and dispensers; water jet cutting orifices and nozzles; fiber optic connectors; fiber optic lens; optical fiber slicing tips; gauge contact points; chemical and medical valves; stylus tips; apertures for particle counting; restrictors; torch tips; air bearings; aircraft instrumentation; medical implant devices; gyroscopes; laser optics--mirrors and lenses for guidance and focusing and crystals for laser generation; substrates for epitaxial deposition of semiconductor electronics; IR transmitting sensor windows used on aircrafts; quartz crystals in watches; telescopic mirrors.

The above-identified list is not inclusive of the varied and different objects that can be finished using the present invention.

Referring now to the drawings and more particularly to FIGS. 1 through 11, there is illustrated at 200 the centrifugal finisher of the present invention that finishes at least one object to high standards. The centrifugal finisher 200 includes a rectangular configured frame indicated generally at 204 having four support legs 208 and a number of supporting cross members 212. The support legs 208 and cross members 212 can be formed from extruded, rectangular configured stock made from aluminum, steel or other materials that exhibit strength and can resist stress. The frame is supported on a platform 216 that also supports the drive motor 220 used with the present invention.

As shown in FIGS. 2, 8, 9 and 10, the outer vessel 224 is supported within the rectangular configured frame 204 by opposing angle struts 228 and brackets 232 that are connected to the struts 228 and frame 204 by fasteners such as bolts 236, which are connected to the outer vessel 224. In the illustrated embodiment the outer vessel 224 is formed from a large cast piece or could be formed from other rigid material. Although the illustrated embodiment shows the outer vessel held within the rectangular configured frame 204, for much larger outer vessels used for polishing large objects, the outer vessel could be formed from concrete which could be placed in a large hole or rested on a large support surface. For very large objects to be finished such as jet turbine blades and other similar objects, the concrete could rest within a large hole for aesthetic purposes.

As shown in greater detail in FIGS. 7 and 11, the outer vessel includes an upper and lower member 240, 240' each having a guide rail 244 which is used to guide the intermediate rollers 250 that engage the inner vessel 254, shaped similar to a barrel in which the objects to be polished are inserted. Each inner vessel 254 engages two intermediate rollers 250 that are supported by respective upper and lower bearing housings 258, 258' mounted on a support member 262 that is adapted to move along the inner surface of the outer vessel. The support member 262 includes an upper and lower roller support plate 264, 264' which mount the bearing housings 258, 258'. Wheel supports are mounted to the overhanging ends of the support plates 264, 264' and include a wheel 274 held by a bearing housing 278 so that the wheel is positioned on the outer surface of the outer vessel. This forms a structure similar to an overhead crane, but in a vertical orientation so that the entire support member 262 is supported on the outer vessel and can roll along the outer vessel.

As illustrated in FIG. 11 the intermediate roller includes two opposing ends 282, 282' having a greater diameter so that the medial portion 286 that engages the inner vessel 254 is of a reduced diameter. The opposing ends 282, 282' of the intermediate roller 250 include a guide groove 290 that engages the formed guide rail of the outer vessel. Thus, the entire structure of the support member 262 is held in place by the outer wheel 274 engaging the outer surface of the outer vessel 224 and the guide groove 290 positioned on the end portions 282, 282' of the intermediate roller engaging the guide rail that is positioned along the inner surface of the outer vessel.

FIG. 3 illustrates the relationship between the two intermediate rollers 250 and the inner vessel 254. The intermediate rollers 250 are held on the respective upper and lower bearing housings 258, 258' and the inner vessel 254 has an outer surface that engages the small diameter medial portion 286 of each intermediate rollers. In FIG. 3, a milling cutter 300 is held within the inner vessel 254, which typically also contains an abrasive media such compressed felt chunks having a particulate abrasive coating material such as described in U.S. Pat. No. 5,140,783, having a common inventor, and which is incorporated herein by reference in its entirety. FIG. 7 shows the relationship between the medial portion of the intermediate roller and the inner vessel.

As shown in FIGS. 1, 8, and 9, a diagonally extending drive support 304 extends diagonally across the rectangular configured frame 204 and includes diagonally extending upper and lower support members 308, 308'. Support members 308, 308' are fixed by diagonal cross pieces 312 and appropriate fasteners 316 such as bolts. As best shown in FIG. 11, a central drive shaft 320 extends vertically along the central axis defined by the outer vessel from the lower diagonal support 308 to the upper diagonal support 308 and is supported on a bearing housing 324 fixed by fasteners 328 to the diagonal support members. The drive motor 220 has an output shaft 332 that connects into a gear drive 336 that in turn has an output shaft 340 that connects to the vertical drive shaft 320. The drive shaft 320 has a medial portion that includes upper and lower rotor arm supports 344, 344'. Each rotor arm support has three rotor arms 348 extending outward from the rotor arm support, forming an iscoseles triangle configuration as shown in FIG. 10. Each end of the rotor arm 348 includes a drive roller 352. As shown in FIGS. 8 and 10, the rotor arms 348 and drive rollers 352 are biased against respective inner vessel 254 (FIGS. 6 and 8) and through rotation of the central drive shaft 320 moves and rotates 254 the inner vessel against the intermediate rollers so that the intermediate rollers rotate and move along the inside surface of the outer vessel while the inner vessel rotates against the medial portion of the intermediate rollers.

For some very large outer vessels used for finishing very large objects, it may be desirable to drive the intermediate rollers by driving the support members instead of by the rotor arm. The rotor arm and drive wheel can be used for initially holding and positioning the inner vessels against the intermediate rollers when enough speed and resultant centrifugal force have been achieved. The inner vessels remain against the intermediate rollers without the need of the positioning aid, i.e., the rotor arm.

Each inner vessel is rotatably supported on the support member 262 resting on an inner vessel support 356 that is formed as a cone 360 with a blunt point for receiving a notch 364 located the flat bottom surface of the inner vessel. It is evident that the inner vessel can be easily removed from the support member 262 and reinserted. The two intermediate rollers 250 and the drive roller 352 form a support cradle 368 in which the inner vessel can be inserted onto the inner vessel support 356. The drive roller 352 biases the inner vessel 254 against the intermediate rollers 250, which engage the inner surface of the outer vessel. It is evident that the ratio between the enlarged end portions of the intermediate rollers and their medial portions as well as the diameter of the inner vessel controls the rotation of the inner vessel.

In operation, an operator works a digital computer as shown at 372 in FIG. 1, which controls the drive motor 220 and drive shaft rotation. Depending on the object to be finished, the drive shaft 320 rotates a predetermined number of revolutions per minute (RPM). The shaft 320 causes the drive roller to engage the inner vessel which is pushed against the medial portion of the intermediate roller so that the intermediate rollers rotate and move along the inner surface of the outer vessel and, in turn, rotate the inner vessel. The object then is polished. A traction surface is not necessary as noted in the incorporated by reference '638 patent and much greater control can be exerted over the finishing process to obtain much better results as well as any desired surface hardening characteristics without damaging the object to be finished.

FIGS. 12 through 34 show various test results using unpolished and polished materials. Some of the polished materials were finished using a colloidal and other prior art techniques. The tests prior art and are compared with results obtained with the apparatus and method of the present invention. FIGS. 12 through 19 show various results obtained with measurements on sapphire (ceramics) and more particularly the testing of sapphire optical lenses of missile cones (one of the most important components of a missile). The test results were conducted by Materials Modification, Inc. (MMI), a U.S. Federal Government (Department of Defense, NASA, Department of Commerce and the National Science Foundation) funded testing institute. MMI extensively tested the sapphire optical lens of missile cones and the process used in accordance with present invention represented on improvement. For example, the customary time to polish a sapphire optical lens of a missile cone was reduced for one piece from twenty hours manual skilled labor to twenty pieces per twenty hours with superior results on a fully automated basis. A high level of skilled labor is required to transform a machine condition sapphire to optical clarity (same classification as a contact lens). The method and apparatus of the present invention now allows increased optical clarity and increased strength in the optical lens of missile cones. The high quality of finishing in accordance with the present invention removes any minute deformities which prevents fracturing thereby increasing overall strength.

FIGS. 12a to 12c illustrate profilomitor scans of nose cone pieces. An unpolished piece is shown in FIG. 12a. A nose cone piece is polished for ten hours in a silicon carbide solution is shown in FIG. 12b. A nose cone piece is polished in colloidal silica for ten hours is shown in FIG. 12c.

FIGS. 13a and 13b shows the topometrix atomic force microscope image of unpolished sapphire nose cone surface.

FIGS. 14a and 14b show a topometrix atomic force microscope image of a sapphire nose cone piece polished for thirty hours in a colloidal silica.

FIGS. 15a shows a topometrix atomic force microscope in two dimensional scans of unpolished sapphire disks. FIG. 15b is a polished sapphire disk polished for thirty hours in a colloidal silica. FIG. 15c shows a sapphire disk polished for sixty hours in colloidal silica. The vertical scale in the chart is progressively smaller for the scans of FIGS. 15a through 15c to bring out the smaller features as finish improved. The peak to valley distance has been reduced from 600 nm to 110 nm overall.

FIG. 16a illustrates a digital instrument AFM image of unpolished arced surface. FIG. 16b illustrates the surface that is polished for twenty-five hours in accordance with the present invention. FIG. 16c illustrates a piece polished to optical clarity by Insaco Corporation.

FIG. 17a through 17c illustrate a topometrix atomic force microscope line parts of nose cones surface polished for fifty hours in a colloidal silica.

FIG. 18 illustrates a typical AFM of rough unpolished sapphire surface.

FIG. 19 shows a polished sapphire surface using the apparatus and method of the present invention.

FIGS. 20 through 34 represent the results on surface roughness values and measurements on drills.

Four measurements were done on each cutting tool, and on either side of the cutting edge and the average values are reported in the table below. The 3D and the surface profile plots in are representative i.e., two of the four measurements made per drill. The measurements were done using the Zygo New View 200 surface structure analyzer.

FIGS. 20a and 20b show a 3D profile of a new TiN coated drill both before and after polishing using the apparatus and method of the present invention.

FIGS. 21a and 21b show the surface profile of a new drill, both before (FIG. 21a) and after (FIG. 21b) polishing.

FIGS. 22a and 22b show the before and after polishing and show a 3D profile of new drills.

FIGS. 23a and 23b show the same coated drill before and after polishing and shows the surface profile.

FIGS. 24a and 24b show the 3D profile and surface profile of used drills both before and after polishing.

FIG. 28 shows a 3D cutter surface before polishing.

FIG. 29 shows the 3D cutter surface after polishing in accordance with the present invention.

FIG. 30 shows a 3D plot of a cutting tool before polishing while FIG. I shows the plot of a cutting tool after polishing.

FIGS. 32a and 32b show a line plot cutter surface after polishing with the section analysis shown in FIG. 32a and a spectrum shown in FIG. 32b.

FIGS. 33a and 33b show a line plot cutter surface before polishing with the section analysis in FIG. 33a and a spectrum in FIG. 33b.

FIGS. 34a and 34b show a line plot cutter surface after polishing with the section analysis in FIG. 34a and a spectrum in FIG. 34b.

The apparatus and method of the present invention now allows for greater control over surface finishing and polishing by having a structure where an outer vessel does not have to be rotated. A traction surface is not required and less energy is required for the polishing operation as compared to prior art devices where a traction force is required. The present invention allows more efficient polishing without a necessary traction surface Extensive sound deadening is also not necessary.

What has been described is merely illustrative of the present invention. Other applications other than the disclosed apparatus and method are contemplated as being within the knowledge of one skilled in the art and may be utilized without departing from the spirit and scope of the present invention.