Random Walk Polishing Machine

Abstract

A polishing machine for fine polishing and abrading work configured to employ a random walk theory algorithm to generate the movement pattern of the polishing or abrading element.

Description

RELATED APPLICATIONS

Pursuant to 37 C.F.R. 1.53(b), this is a Continuation in Part application to application Ser. No. 15/471,962 filed Mar. 28, 2017.

BACKGROUND OF THE INVENTION

The present invention relates to apparatuses and methods for abrading or polishing a surface of a workpiece. The abrading or polishing of the surface of a workpiece is a technique that has many different applications in a variety of technical fields, including the production of semi-conductor devices, optical fiber connectors, mirrors, prisms, lenses and other optical components. It is desirable in these fields, and others, to employ a fine polishing or abrading process that results in a particular and specific surface profile and a particular and specific surface finish, i.e., smoothness. This is typically accomplished by means of a tool that is moved across the workpiece while the workpiece is held stationary. Several apparatuses and processes have been developed to accomplish the fine movement of a polishing tool in this manner. For example, U.S. Pat. No. 4,128,968, discloses a polishing apparatus and system whereby two polishing pads are maintained in contact with the surface of the workpiece and are relatively rotated and moved in a spiraling path around the surface of the workpiece. Another technique is disclosed in PCT No. WO97/00155, which uses a tool that has a flexible working surface so that the effective area of contact with the workpiece can be controlled. In these and other prior art techniques, the tool is usually spun around an axis normal to the workpiece or parallel to the surface of the workpiece. Since regular tool paths across the same portion of the workpiece invariably create grooves and ridges in the surface of the workpiece, prior art designs have included apparatuses and methods whereby the abrading tool employs a non-closed orbits movement or a figure-eight movement. This is designed to avoid repeated polishing paths over the same area. This is obtained in the case of FIG. 8 movements imposing a lateral displacement of the abrasive platform after cycles of number 8 figure.

However, polishing and abrading machines that employ these movement techniques are expensive to manufacture as the tools, the tool mounting, and the associated machinery all require a high level of mechanical precision.

What is needed therefore are abrading and polishing machines and methods suitable for use over a wide variety of materials, that is relatively easy to operate, that utilizes tool movements designed to ensure that the polished surface is free of grooves or ridges, specifically movements that avoid closed loops, Lissajous figures or path repetition, and that is easy and inexpensive to manufacture.

GENERAL DESCRIPTION

According to the present invention there is provided a novel automated polishing apparatus and method configured to move the polishing/abrading tool over the workpiece surface in a pattern that replicates on a macroscopic scale the random motion seen in the Brownian motion of microscopic particles. The apparatus employing such movements can be manufactured in a variety of ways, but always based on the same principle of random walk. Such a method of employing a random walk movement of an abrasive platform under or over the pieces to be lapped, abrading or polished being suitable for curved surfaces, plane surfaces, for optical connections, and other precise optical parts including mirrors, prisms, and lenses. Brownian motion is the random motion of particles suspended in a fluid (liquid or gas) resulting from their collision with the fast moving atoms or molecule in the gas or liquid. This phenomenon has been shown to result in a movement that over time reproduces statistically a normal distribution with a perfectly symmetrical around the center polishing or abrading configuration. Further, for polishing convex surfaces, as, for example, those found in optical fiber connectors, the result is that the apex eccentricity equals to zero, which is a desired characteristic in polishing and abrading such objects.

An apparatus is provided whereby a workpiece to be polished and/or abraded is secured to the apparatus and brought into contact to the polishing platform. The polishing platform is then displaced pursuant to the movement generated by two independently driven motors operating at separate frequencies and that are configured such that the two independent frequencies result in a movement pathway that is not repeated. Any groove or ridge in the surface of the workpiece created by the movement of the polishing tool over a particular path is removed or smoothed by the movement of the polishing tool in another direction. Further, this random movement will result in no apex eccentricity of a surface being polished. As a result, for convex surfaces, a smooth surface with no apex eccentricity can be achieved. As a result, when an optical surface is polished in this manner, namely by this “random walk movement” of the polisher, it will possess a higher quality and smoother polished surface than one polished in the manner of currently available and known polishing machines that employ a FIG. 8 polishing pattern and/or orbital polishing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood with reference to the accompanying drawing wherein like reference numerals refer to like components throughout the several views.

FIG. 1 is a perspective view of an embodiment of the invention.

FIG. 2 is a exploded view of an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in general to a random movement abrading system for lapping surfaces of a workpiece.

FIG. 1 shows an embodiment of the invention wherein a polishing unit (200) which comprises a polisher housing (220) that is generally cylindrical in shape and which further comprises a base (130) and case (120), and an upper plate (90). A cushion (140) is provided upon which the base (130) rests. The cushion (140) preferably is formed of rubber. A plane platform (60) is disposed along the top of the upper plate (90) and a pad (70), preferably formed of a hard rubber, is disposed along the top of the plane platform (60).

Disposed within the housing (220), is a motor assembly (230) comprising a lower motor (210) secured to the Base (130). A lower eccentric ball bearing (40) is disposed on top of the lower motor (210) along the same vertical axis of the lower motor (210). The motor assembly (230) also comprises a second, upper motor (205) with a upper eccentric ball bearing (30) that is disposed on top of the upper motor (205) and along the same vertical axis as the upper motor (205). The upper motor (205) is coupled to the lower motor (210) by being attached to the lower eccentric ball bearing (40) by means of a lower flange (50) and an upper flange (55). The motor assembly (230) is positioned within the housing so that the upper eccentric ball bearing (30) is in secured contact with the underside of the plane platform (60).

FIG. 2 further illustrates the composition—and operation—of the motor assembly. As seen in FIG. 2, the lower eccentric ball bearing (40) is disposed on top of the lower motor (210). The lower flange (50) is configured to secure the lower motor and lower eccentric ball bearing to ensure that they both remain disposed within the same vertical axis as the upper motor (205) and to affect the coupling of the lower motor (210) to the upper motor (205). The lower flange (50) is further configured with an opening of sufficient size to allow the lower eccentric ball bearing (40) to pass through the lower flange (50) to the upper flange (55). As shown in FIG. 2, the upper flange (55) is secured to the lower flange (50) and is configured with an opening to allow the lower eccentric ball bearing (40) to pass through the upper flange (55) and to be secured by it such the lower eccentric ball bearing will be disposed on the upper motor (205). The upper flange (55) is further configured to secure the base of the upper motor (205).

Referring to FIG. 1, a sanding disc (80) is secured to the top surface of a rubber pad (70) that stays over a platform, which in this embodiment is plane and circular, but, it is understood that other embodiments of the platform within the scope of the invention may not necessarily be plane and circular. A circular abrading template (150) is provided that is removably secured to the upper plate (90) and comprises embedded supports (170) disposed along the surface of the template (150). The embedded supports are configured to allow insertion and retention of a workpiece and further configured to allow the surface of the workpiece to be in contact with the sanding disc (80) when the abrading template (150) is secured to the upper plate (90).

The random walk motion of the sanding disc (80) is accomplished by the combination of the oscillatory motions created by the two motors when operated simultaneously. This is accomplished by virtue of the two motors (lower motor (210) and upper motor (205)) being independently driven making each to rotate about their respective axis. As shown in FIG. 2, the lower eccentric ball bearing (40), is acted on by the lower motor (210) and then imparts its movement to the upper motor (205) by virtue of it being secured to the upper motor (205) by the upper flange (55) and lower flange (50).

The independent drive of each motor means that each motor can be driven—and in a preferred embodiment and method they each will be driven—with different frequencies, non-multiple frequencies and non-fixed phase frequencies. These frequencies will not only be different but will also form a frequency pair which has no correlation among themselves. This manner of driving the motors when combined with the manner in which the motors and the corresponding lower eccentric ball bearing (40) and upper eccentric ball bearing (30) are coupled, described above, will compel the sanding disk (80) to vibrate in a random manner, or more particularly in a manner replicating a random walk motion or Brownian motion with no closed loops, Lissajous figures and no resulting path repetition on the polishing platform.

A shown in FIG. 1, a blocking ring (211) secured to the housing (220) provides further support for the motor assembly (230). As shown in FIG. 1, the lower motor (210) is powered by a lower power unit (300) and the upper motor (205) is powered by a separate upper power unit (400). As described above, in a preferred method, each power unit will apply power to its respective motor at a different frequency and phase, both of which would be uncorrelated among and between themselves. The resulting oscillatory motions of the motors are transmitted through the motor assembly (230) to create the random movement of the abrading disc (80) described above.

In the embodiment shown in FIG. 1, the abrading template (150) is configured to accept and retain optical connectors. In this configuration, a preferred method may include fastening weights (180) to the connectors to aid in securing the workpiece (160) to holes in the abrading template (170) as well as aiding in maintain proper contact pressure of the workpiece (160) against the abrading disc (80). It is also contemplated and understood that in this embodiment, the holes of the abrading template (170) can be configured to accept a variety of workpieces, including, for example, jewelry, optical devices, lenses and various metallurgical samples.

The above-described embodiments relate also to methods for performing a surface treatment on a workpiece. The method for performing such a surface treatment would comprise, in a preferred method, generating a series of random paths which visit all points of a surface area and moving the surface treatment device along the series of random paths such that the surface treatment device passes over all points of the workpiece. Alternatively, the described invention may encompass an apparatus whereby a machine employs a processing unit to execute a previously embedded sequence of steps corresponding to a positive and negative sequence of numbers whose algebraic sum is zero, chosen among many sequences of randomly generated numbers. This and other similar methods are thus described.

Although the present invention has been described herein above with reference to specific embodiments, it will be apparent to a skilled person in the art that the present invention is not limited to the specific embodiments and modifications can be made within the spirit and scope of the invention.

Claims

1. A machine for polishing a workpiece comprising: a supporting surface for securing and supporting the workpiece; a polishing surface for polishing the workpiece secured to the top of the supporting surface; a mounting arrangement for supporting said supporting surface and said polishing surface with said mounting arrangement configured in a generally cylindrical shape and comprising a base, a casing and an upper plate; a movement arrangement for moving said polishing surface with respect to said supporting surface and across said workpiece with said movement arrangement housed within the said casing of said mounting arrangement and comprising a first oscillatory motor secured to said casing; a first eccentric ball bearing disposed on top of the first oscillatory motor and further disposed below and in contact with a second oscillatory motor disposed above the first oscillatory motor; a second eccentric ball bearing disposed on top of the second oscillatory motor; with said mounting arrangement further configured such that the second eccentric ball bearing is in contact with the bottom of the supporting surface; a first power source to operate the first oscillatory motor and a second power source to the second oscillatory motor, whereby said polishing surface moves across said workpiece in a number of random polishing paths generated by the combined operation of the first oscillatory motor operating at a first frequency and the second oscillatory motor operating at a second frequency.

2. The machine for polishing a workpiece of claim 1 wherein the first frequency of the first oscillatory motor and the second frequency of the second oscillatory motor are uncorrelated both between and among them.

3. The machine for polishing a workpiece of claim 1 wherein the first oscillatory motor is coupled to the second oscillatory motor by means of at least one flange configured to secure the base of the second oscillatory motor and further configured to secure the first eccentric ball bearing to the second oscillatory motor.

4. The machine for polishing a workpiece of claim 1 wherein the movement arrangement is secured within the case of the mounting arrangement by means of a blocking ring.

5. The machine for polishing a workpiece of claim 1 wherein the supporting surface is comprised of hard rubber.

6. The machine for polishing a workpiece of claim 1 wherein the polishing surface comprises removable sanding pads.

7. The machine for polishing a workpiece of claim 1 wherein the supporting surface comprises embedded supports for supporting the workpiece.

8. The machine for polishing a workpiece of claim 1 wherein said polishing surface has either a plane or curved shape and said polishing surface executes random-walk movements across said workpiece wherein said random-walk movements do not replicate a planetary movement, figure-eight pattern or any other Lissajous figures.