US3545138A - Metal polishing apparatus - Google Patents

Description

Dec. 8, 1970 F. Housi'oN 3,545,133

METAL POLISHING APPARATUS. 1

Filed June 17 1968 I NVENTOR Z;%W, ZW

United States Patent 3,545,138 METAL POLISHING APPARATUS Russell F. Houston, Hamilton, Ohio, assignor to The Mosler Safe Company, Hamilton, Ohio, a corporation of New York Filed June 17, 1968, Ser. No. 737,431

Int. Cl. B24b 7/00 US. Cl. 51-59 8 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for finishing a metal surface so as to obtain a metallic satin grain finish consisting of numerous parallel striations. This finish is achieved by grinding the metal surface with a coarse grain abrasive so as to achieve a striated surface having numerous parallel short bright striations. The surface is then polished by a unique reciprocating band polisher in which the abrasive band is backed by a resilient element and is regularly indexed during the polishing operation. This polishing then converts the short bright striations produced during grinding to long dull or satin striations having a wood grain type of appearance.

This invention relates to the finishing of metal surfaces and more particularly, to an apparatus for achieving a satin or dull wood grain type of finish on a metal surface without the application of any paint or decorative material to the surface of the metal.

'In many applications metal surfaces must be finished or polished in such a manner that the surface is decorative but still gives the impression of being an exposed unpainted, unplated, or artificially colored metal surface. One such application is that of metal safes, vaults, and safety deposit boxes where the exposed metal surface conveys the impression of impenetrability. Because of this impression, banks and savings institutions often insist that the exterior of vaults, safes and safety boxes be decorative but still have the appearance of an exposed metal surface.

Another criteria of any metal surface finish applied to the exterior of bank vaults or safes is that the finish be capable of duplication or refinishing in the field since no finish will remain perfect forever.

One finish which has satisfied all of these criteriabeauty, metallic appearance, and capability of duplication in the field-has been a decorative striated grain finish. This finish is now commonly applied to the exposed surfaces of vault doors, safes or safety deposit boxes by first grinding the surface and then manually hand-polishing it with an abrasive belt.

Grinding of the surface is accomplished with a coarse abrasive belt grinder, as for example an abrasive belt having an aluminum oxide abrasive of a grit size from a number 60 to 120. At the end of this grinding operation, the surface has a rough ground surface appearance, i.e., the appearance of short bright parallel striations in the surface of the metal. Traditionally, this surface is then finished by hand-rubbing it with a polishing emery cloth wrapped around a cylindrical rubber tube. At the end of the polishing operation, the surface has asatin or dull type of wood grain finish consisting of numerous parallel long striations. Because the polishing is done manually in the factory, it may be easily repaired in the field by duplicating the polishing operation there.

The only disadvantage of this finishing technique is that it is extremely expensive to apply because of all of the manual labor involved. It is also difficult to maintain uniformity because of operator fatigue, differences in strength of different operators, and dilferences in pressure applied in a single stroke. Furthermore, the

Patented Dec. 8, 1970 length of a stroke is limited to the reach of an operators arms so that awkward setups are required on long parts.

It has been a primary objective of this invention to determine some apparatus for mechanically duplicating the grained finish which has heretofore only been produceable manually.

This invention is predicated upon the discovery that an attractive grained finish may be mechanically produced if the metal is first ground with a rough abrasive and then polished by reciprocating a narrow section of abrasive cloth over the ground surface and indexing the cloth regularly so that the section of cloth which is engaged with the workpiece surface remains in contact with the surface such a short time that it cannot become loaded with workpiece chips.

We have found that conventional sanding machines Will not give the desired efiect but will produce a surface finish that closely resembles a ground finish, i.e., numerous short bright striations in the workpiece rather than a long striation, dull or satin type grained structure. We have further found that the desired finish may be produced on a reciprocating sander type of machine if the machine is modified so that a rubber or resilient roller serves as the backing for the abrasive material and the emery cloth or abrasive material is regularly indexed so that a new section of emery cloth is regularly moved beneath the roller.

This machine has the advantage of eliminating a great deal of handwork which has heretofore been required to produce a highly decorative grained finish on metal. Additionally, it produces a superior finish in that the finish is more uniform than has heretofore been capable of production on a manual basis. -It also eliminates the necessity for awkward fixtures to enable manual operators to have access to large surfaces. And most importantly, it is capable of manual repair and duplication in the field.

These and other objects and advantages of this invention will be more readily apparent from the following description of the drawings in which:

FIG. 1 is a diagrammatic illustration of a reciprocating sanding machine equipped with the invention of this application,

FIG. 2 is an enlarged front elevational view of the reciprocating head of the machine,

FIG. 3 is a cross sectional view through the reciprocating heat taken on line 33 of FIG. 2, and

FIG. 4 is an end elevational view of the ratcheting mechanism of the reciprocating head.

Referring to FIG. 1, there is illustrated a reciprocating sander type of machine 10 commonly used in the woodworking industry but modified with a unique reciprocating head 12 to enable the machine to be used in the practice of this invention. This machine comprises a fixed frame 11, a vertically adjustable table 13, and a transversely movable feed slide .14. Workpieces 15 to be finished on the machine are clamped on the slide 14 by conventional C clamps, magnetic clamps, or any other conventional form of clamping mechanism.

In the practice of this invention, workpieces 15 are first ground to prepare the top surface 16 to receive the grain finish imparted by the machine 10. This grinding operation is preferably performed on a conventional belt grinder such as a Hammond Flat Finishing Machine manufactured by Hammond Machinery Builders, Inc., of Kalamazoo, Mich. An aluminum oxide abrasive belt of from 60 to 120 grit size is preferably used for this grinding operation and produces a surface having a smoothness which measures approximately 70 to millionths of an inch root means square. The abrasive material may vary, and the grit or grain size may vary slightly from this range, depending upon the composition of the metal, its surface treatment and hardness, and the exact grain structure desired in the finished product. Additionally, if the surface is rough or imperfect, the surface may first be ground in a rough grind operation to remove surface imperfections. This pre-grind operation may be accomplished with any type of grinder and a rough abrasive of from 36 to 60 grit size. Ordinarily, the rough grind will producev a surface having a measured smoothness of approximately 300 to 350 millionths of an inch root mean square.

Throughout this application, abrasives are described in terms of their composition and grit size. As is conventional in the abrasive industry, grit size refers to the mesh of a screen through which the abrasive grains will pass before being stopped in the next smaller mesh screen. For example, a sixty (60) grit size abrasive is one in which the grains of abrasive material pass through a 60 mesh (openings per square inch) screen before being stopped in the next smaller standard mesh screen.

Finish polishing or so-called strip scouring of the workpiece is then performed in the belt sanding machine 10. One suitable machine useful in the practice of this invention is a Curtis Belt Sander manufactured by the Curtis Machine Company of Niagara Falls, N.Y. This sander comprises a vertically movable table 13 having a transversely movable feed slide 14 mounted thereon. An overhead beam 17 of the frame supports the reciprocal sanding head 12, the reciprocation of which is controlled by two motors 18 and 19 located at opposite ends of the beam and operative to drive an endless cable 20 in reciprocation. When the head .12 is clamped to this cable, it is caused to reciprocate with the cable over an inverted T-shaped beam 21. As the head is reciprocated, the feed slide 14 moves the workpiece rearwardly into and beneath the beam 17 so that the complete top surface 16 of the workpiece is exposed to the bottom surface of an abrasive belt 22.

The conventional reciprocating head 12 comprises a central body or casting 24 having front and rear caps 25, 26 bolted thereto. This body 24 and the caps 25, 26 support a pair of upper front rollers 27, 28, a pair of upper rear rollers 29--29, a pair of lower front rollers 30, 31, and a pair of lower rear rollers 32-32. All of these rollers are rotatably supported upon stub shafts 35 mounted within the body 24 and are rollable over horizontal flanges 36, 37 of the beam 21. To prevent lateral movement of the body relative to the rail, front and rear rollers 33, 34 are engageable with and movable over vertical edges 38, 39 of the flanges 36, 37 of the rail 21.

The reciprocating sanding machine heretofore described is conventional in the woodworking art and has therefore not been described in detail herein. To practice the invention of this application, the head '12 has, however, been modified by the addition of a unique abrasive belt support 40 as described more fully hereinafter.

The support 40 comprises a supporting plate 42 which depends from a T-shaped slide 43. The slide 43 is adjustably mounted within a T-shaped slideway 44 in a bottom depending section 45 of the body 24 and may be locked therein by a set screw (not shown).

Four vertical studs 47 extend through unthreaded apertures in the four corners of the plate 42 and are threaded into apertures in a base plate 48. A pair of washers 49, 50 and a compression spring 51 are mounted over each of the studs 47 above the upper plate 42. These washers 49, 50 are biased apart by the compression spring 51 and, upon proper adjustment, function to maintain the depending base plate 48 in a horizontal plane.

A ball bearing 55 is mounted between the plates 42, 48 and is supported in a recess 52 in the bottom of the plate 42 and a recess 53 in the top of the plate 48. This ball bearing 55 holds these plates 42, 48 in spaced relationship while still permitting the lower plate 48 to rock about the bearing against the bias of the springs 51.

A semi-cylindrical roll 56 of neoprene rubber is secured to the bottom of the base plate 48. This roll preferably has a hardness of approximately 90 durometer and serves as a resilient backing for the abrasive belt 22.

Base plate 48 has four lateral braces 57-57, 58--58 extending upwardly and outwardly from the four corners thereof. These braces are all bolted to the front and rear side edges of the base plate 48 by screws 59. Two of these braces 58-58 rotatably support a storage roll 60 of the abrasive belt 22 while the two others 5757 rotatably support a takeup roll 6.1 therebetween.

As may be seen most clearly in FIGS. 2 and 4, a generally L-shaped outboard brace 65 is bolted to the outer end of one brace 57. One leg 66 of this brace 65 has a ratchet supporting bracket 67 fixedly secured thereto and a threaded stop 69 is adjustably mounted in the other leg 68.

To effect rotation of the takeup roll 61, a conventional ratchet 70 of the type which may be purchased in any hardware store as a part of a set of socket wrenches is rotatably mounted between a setscrew 71 and the front side wall 72 of the brace 57. The setscrew 71 is adjustable within a threaded aperture 73 in the bracket 67 and may be locked in an adjusted position by a lock nut 74. As may be seen most clearly in FIG. 4, the takeup roll 61 has a journal pin press fit into one end. This journal pin 80 extends into an aperture 81 of the brace 57 and rotatably supports the roller 61.

The journal pin 80 has a square aperture 82 machined in one end and adapted to receive the square-ended drive shaft 83 of the ratchet 70. This driving relationship between the ratchet shaft 83 and the journal pin 80 enables oscillatory arcuate movement of the ratchet 70 to impart rotational movement to the takeup roll or drum 61.

A pair of ratchet actuating arms 86, 87 are bolted to the handle '88 of the ratchet 70 and support a dowel pin 89 therebetween. This dowel pin 89 is engageable with a cam stop 90 (FIG. 1) attached to the frame 17 of the machine so as to effect oscillatory movement of the outer end 88 of the ratchet 70 upon engagement of the pin 89 with the cam stop 90. To bias the ratchet in a clockwise direction as viewed in FIG. 2, a tension spring 85 is at tached at one and 84 to the arm 86 and at the opposite end to leg '68 of the outboard brace 65.

In operation, a workpiece is first prepared for polishing or for application of a striated grain finish by grinding the surface 16 with a belt grinder. The belt should have an abrasive of from 60 to 120 grit size. Depending upon the condition of the surface and imperfections therein, a rough grind or pre-grind operation may be required to remove recesses, holes, etc., from the surface of the workpiece. Ordinarily, this pre-grind operation is accomplished with an aluminum oxide abrasive having an abrasive grain size of from 36 to 60 grit and produces a surface finish in the general range of 300- to 350 root mean square.

After the grinding operation is completed, the surface 16 has a rough striated finish consisting of numerous parallel short bright marks. The roughness of the surface should be between 60 and 80 millionths of an inch root mean square as measured by a conventional surface roughness measuring instrument.

After grinding, the workpiece is clamped to the top surface of the table 13 with the previously ground surface 16 in the uppermost position and in a horizontal plane. The table 13 is then moved upwardly until the top surface of the workpiece 16 is engaged with the abrasive belt 22 which extends from the storage roll, over one end of the base plate 48, beneath the contact roll 56, over the opposite end 97 of the base plate and into engagement with the takeup roll 61. The end of the belt 22 may be secured to the takeup roll in any way desired, as for example by fitting the end of the belt into a radial slot of the roll or by taping the belt to the peripheral surface of the roll. The workpiece surface is moved upwardly into engagement with the belt 22 until the band of contact A between the top surface 16 of the workpiece and the abrasive belt is approximately one-half inch in width.

The abrasive belt 22 is either an aluminum oxide abrassive or a silicon carbide abrasive belt having a cloth or paper backing. The abrasive has a grain size of from approximately '80 to 120 grit. In one preferred embodiment, the surface is just polished with a belt 22 having a grain size of 80 grit and is then finish polished with a belt 22 having an abrasive grain size of 120 grit. After both polishing operations, the completed surface has a surface smoothness of approximately 40 to 60 millionths of an inch, root mean square.

After mounting of the workpiece on the table 13, the head 12 of the machine is then reciprocated by the drive motors 18 and 19 of the machine while simultaneously the feed slide 14 of the table 13 is fed inwardly so as to expose the complete surface 16 of the workpiece to the belt 22 of abrasive material.

Referring to FIG. 1, it will be seen that as the head 12 reaches the leftward extent of its travel and passes off of the left edge of the workpiece, its direction of movement is reversed and it returns to the right until it passes off of the right edge of the workpiece. The dowel pin *89 attached to the upper end of the ratchet arm 88 then engages the cam stop 90 causing the upper end of the ratchet arm to be moved to the left so as to rotate the takeup roll 61 and pull a new section of belt 22 into the operating band A. The linear travel of the belt 22 over the roll 56 is preferably one-half inch, the same as the width of the band A so that a new section of abrasive is moved into the band A after the band has moved completely across the width of the workpiece twice, once as the head moves leftward and once as it moves rightward.

After indexing movement of the ratchet 70in a counterclockwise direction as viewed in FIG. 2, the head 12 reverses its movement and moves to the left while the outer end of the ratchet arm moves in a clockwise direction into engagement with the end 98 of the adjustable stop screw 69. The screw should be positioned so that the ratchet effects approximately one-half inch of travel of the band 22 each time the ratchet arm engages the cam stop 90.

In making only two passes over the top surface of the workpiece before the belt is indexed, the operative band A of abrasive belt engaged with the workpiece does not have sufiicient exposure to the workpiece surface for the abrasive grains to become broken and smooth or for the abrasive belt to become loaded with chips or swarf. Consequently, the abrasive belt 22 imparts a dull satin finish of from 40 to 60 millionths of an inch root mean square smoothness to the workpiece. This finish is characterized by long parallel striations or lines which give the appearance of a grain type of finish. This is a highly desirable finish because of its decorative characteristics and its repairability in the event that it becomes scarred or damaged in the field. If it is damaged, it may be repaired by a workman rubbing a rubber cylinder covere by an abrasive belt over the damaged surface. After a few passes of the belt over the surface, the damaged surface will once again perfectly match the surrounding area.

While I have described only a single preferred embodiment of my invention, those persons skilled in the arts to which this invention pertains will readily appreciate numerous changes and modifications which may be made without departing from the spirit of my invention. Therefore, I do not intend to be limited except by the scope of the following appended claims.

Having described my invention I claim:

1. Apparatus for polishing a flat surface of a metal article to obtain a grain type of finish consisting of numerous long parallel striations, said apparatus comprising:

means for supporting said article,

a polishing head including a long narrow resilient pad mounted on the bottom of said polishing head, the narrow dimension of said pad extending transversely to said head, means for supporting a long wide strip of abrasive material on said head, which strip passes beneath said resilient pad, said strip of material having abrasive of between and grit size secured thereto,

means for effecting relative longitudinal reciprocating movement between said polishing head and said workpiece while a narrow section of said abrasive strip of material on said head is engaged with said flat surface of said article, that section of said strip which is engaged with said surface being backed by said resilient pad, and

means for repeatedly and regularly indexing said strip on said head so as to place an unused section of said strip in engagement with said surface before a portion in engagement with said surface can become loaded with chips.

2. Apparatus for polishing a fiat surface of a metal article to obtain a wood grain type of finish consisting of numerous long parallel striations, said apparatus comprising:

means for supporting said article,

a polishing head including a long narrow resilient pad mounted on the bottom of said polishing head, means for supporting a long wide strip of abrasive material which passes beneath said resilient pad,

means for effecting relative longitudinal reciprocating movement between said polishing head and said article while a section of said abrasive strip of material on said head is engaged with said fiat surface of said article, that section of said strip which is engaged with said surface being backed by said resilient pad, and

means for repeatedly and regularly indexing said strip on said head during reciprocation of said head so as to place an unused section of said strip in engagement with said surface before a portion in engagement with said surface can become loaded with chips.

3. The apparatus of claim 2 wherein said indexing means includes a ratcheting mechanism.

4. Apparatus for polishing a flat surface of a metal article to obtain a wood grain type of finish consisting of numerous long parallel striations, said apparatus comprising:

a frame including an overhead beam,

a polishing head mounted for longitudinal reciprocating movement upon said beam, said polishing head including a long narrow resilient pad mounted on its bottom side, the narrow dimensions of said pad extending transversely to said head, a storage roll rotatably mounted upon one side of said head and a takeup roll rotatably mounted on the opposite side of said head, a long wide band of abrasive material etxending from said said storage roll beneath said resilient pad and over to said takeup roll,

means including a table for supporting a metal article having a flat upper surface beneath said polishing head,

means for effecting relative longitudinal reciprocating movement between said polishing head and said article while that section of said abrasive band beneath said resilient pad is engaged with the top surface of said article, and

means for intermittently and regularly indexing said band of abrasive on said head during reciprocation of said head so as to place an unused section of said band in engagement with said surface before a portion in engagement with said surface can become loaded with chips.

5. The apparatus of claim 4 wherein said indexing means includes a ratcheting mechanism operative to pcriodically index said takeup roll.

6. The apparatus of claim 5 wherein said ratcheting mechanism is engageable with a stop at one end of the reciprocating movement of said polishing head over said beam.

7. The apparatus of claim 2 wherein said apparatus pivotal support, said head including resilient means for comprises a frame including an overhead beam for supbiasing said body to a position in which the bottom surporting said polishing head for longitudinal reciprocating face of said resilient pad is located in a horizontal plane. movement over said article supporting means, said article supporting means including a table having a flat upper 5 References Cited h 1 b d h 11 UNITED STATES PATENTS sai po1s mg ea mcu inga o y avingagenera y flat bottom surface, said head including a storage g u roll rotatably mounted upon one side of said body 6 8 4 6 4 9/ 928 Yummer and a takeup roll longitudinally spaced from said 10 A coung 5 T storage roll and rotatably mounted on the opposite 16 OX 9 side of Said body and 2,284,556 5/1942 Brackett 51-59 3,416,261 12/1968 Sherman et al. 51--60 a long strip of abrasive material extending from said storage roll longitudinally beneath said resilient pad LESTER M SWINGLE Primary Examiner and over to said takeup roll. 15

8. The apparatus of claim 7 wherein said body is US. Cl. X.R.

mounted for universal pivotal movement about a central 5l36l Patent No.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Inventor(s) R. F. HOuStOn Dated December 8, 1970 It is certified that error appears in the above-identified patent 2, line 47,

the

2, line 70, the

4, line .42,

the

5, line 56,

I Attesting Officer the word

word

word

word

and that said Letters Patent are hereby corrected as shown below:

"heat" should be head "means" should be mea'n "and" (before the figure 84) should "covere" should be covered :sxawanm swan W9 87! m1. mum, mnion or Paton

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