US3510993A - Segmental grinding wheel - Google Patents

Description

May 12, 1970 A. M. COCK 3,510,993

SEGMENTAL GRINDING WHEEL Filed Nov. 14. 1967 E E. 3 ARN OLD 'FIX 'EZ QK United States Patent 3,510,993 SEGMENTAL GRINDING WHEEL Arnold M. Cook, Holden, Mass., asslgnpr to Norton Company, Worcester, Mass., a corporation of Massachusetts Filed Nov. 14, 1967, Ser. No. 682,933

. Int. Cl. B24d 7/08 Us. or. 51-209 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The field of the invention is abrading and the invention is particularly concerned with rigid rotary cylinder tools having detachable segments.

The prior art uses, raw materials, standards, shapes and methods of making bonded abrasive products are disclosed in Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd edition, volume I, particularly pages 25- 28, 31, 30 and volume 4, particularly pages 293 and 301.

Bonded abrasive segments are commercially available in a wide choice of abrasive materials, bonds and shapes. According. to the prior art methods of mounting, each of the segments is held in a chuck which requires periodic adjustment since the segments must resist grinding and centrifugal forces. The prior art methods of chucking the segments have inherent limitations wherein:

(a) The chuck designs and clamping systems determine the shapes of the segments and result in shapes which are costly and difficult to make;

(b) The change or adjustment of an individual segment requires shutting down the machine, and since each segment is individually clamped, a considerable amount of time is required for these adjustments during the life of a given set of segments;

(c) The surfaces of the segments held by the clamps are not useful for grinding and in most cases the unusable length of stub represents a 25% loss of the available bonded abrasive;

(d) The chucks require constant maintenance; and

(e) The clamping and support of the segments in a chuck is inadequate and results in chatter or nonuniform application of the bonded abrasive product to the work.

SUMMARY OF THE INVENTION Having in mind the limitations of the prior art, it is an object of the present invention to provide a system of segment mountings which is superior to that now used on surface grinding machines.

It is an object of the present invention to provide for the use of bonded abrasive segments having a cross sectional geometry which is the most efiicient to make and 'use.

3,510,993 Patented May 12, 1970 "Ice A further object of the invention is to provide an assembly of bonded abrasive segments having a reduced weight.

Still another object of the invention is to reduce the amount of dressing required in repositioning the assembly of bonded abrasive segments.

A further object of the invention is the improvement of safety conditions resulting from the use of steel bands surrounding the periphery of the segment assembly.

A further object of the invention is the provision of economical packaging, handling and storage resulting from the use of simple rectangular shapes.

Still another object of the invention is the mounting of varied and dissimilar shapes which are accommodated by changing the geometry of the spacers to accommodate the shapes.

Another object of the invention is to assemble the segments under compression which provides for the most efiicient use of the inherent strength characteristics of the segments.

Upon further study of the specification, drawings and claims, other objects and advantages of the present invention will become apparent.

According to the present invention, an improved rigid rotary cylinder tool having detachable bonded abrasive segments is provided for use on surface grinding machines. According to a particular embodiment, the tool comprises a circular mounting ring which is adapted to 'be secured to the driving member of a grinding machine and a plurality of bonded abrasive segments of simple cross-sectional geometry with intermediate spacers of a rigid easily abraded material, such as, phenol formaldehyde resin or other plastic material. A number of steel bands are used to clamp the segments and spacers in a circular pattern.

BRIEF DESCRIPTION OF THE DRAWING The invention will now be described more in detail with reference to the drawing, wherein:

FIG. 1 is a view of the assembled grinding tool;

FIG. 2 is a cross-section, on a line 11-11 of FIG- URE 1;

FIG. 3 is a cross-section on the line III-III of FIG- URE 1; and

FIG. 4 is a fragmentary cross-sectional view of a modified form of the grinding tool.

Although the grinding and/or polishing tool of the present invention is operable in any plane of rotation, it is designed primarily for rotation on a vertical axis for applications involving the grinding of an upwardly facing flat surface, such as on a sheet of plate glass, a block of stone or a metal surface mounted on a suitable table.

With particular reference to FIGURE 1, bonded abrasive segments 4 are shown secured by spacers 5 to mounting ring 2 which in turn is secured to disc or driving member 1 of a grinding machine. In a particular embodiment, the grinding tool has a 25 inch diameter with 16 bonded abrasive segments and 16 spacers. Metal bands 7 are stretched tightly around the outer periphery of the assemblage to engage the segments tightly against the spacers and counteract the effects of centrifugal force.

As particularly shown in FIG. 2, spacers 5 have threaded inserts 6 for mounting on bolts carried in suitable apertures on the ring 2 and the spacers have recesses for accepting and positioning the bands 7.

In FIG. 3, the disc or driving member 1 is shown with a shoulder near its periphery adapted to receive the mounting ring 2 which is flat on the side next to the disc 1 but is recessed at 3 on its opposite side against which is mounted the series of abrasive segments 4 with spacers between adjacent edges of the segments. Each spacer is anchored at one end to ring 2 in the recess 3 of the mounting ring, while the mounting ring is in turn secured to the disc 1.

During use the free ends of the spacers wear down together with the working ends of the abrasive segments, and after the assembly has been worn down to near the level of the first metal band 7, the latter is removed and the same operation is continued and repeated until the last metal band has been reached. The ring 2 and the remains of the abrasive segments and spacer assembly are then disconnected from the disc 1 and a new assembly of a ring with new abrasive segments and spacers is substituted therefor.

There is shown in FIG. 4, a modified form of the grinding tool wherein each abrasive segment 4 has an insert 6a molded therein for attaching it to the ring 2 provided with co-operating bolting means therefor. In this instance, the spacers 5 are not bolted to the ring 2.

It will be noted that the bolts 8 holding either the spacers on ring 2 as shown in FIG. 2, or the bolts 8a holding the bonded segments to ring 2 as shown in FIG. 4, have freedom to move somewhat with respect to ring 2 so that the assembly can be drawn tightly together without any of the bolts engaging against the walls of their respective apertures in ring 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The mounting ring 2 is preferably constructed of steel and a plurality of these rings are made available for mounting the segments for a particular grinding machine. The mounting ring 2 has means for attaching the ends of the spacers 5 or abrasive segments 4. In a particular embodiment, a cap screw 8 or 8a is inserted through an elongated hole in the mounting ring 2 and is threaded into a threaded insert 6 or 6a contained within the spacer 5 or segment 4.

The cross-sectional size and shape of the spacers is determined by the diameter of the bonded abrasive tool assembly and the size and number of segments in the set. The length of the spacers is the same for all which may be slightly shorter than the length of each segment. The cross-sectional shape of the spacer is such that it fills the space between each segment and provides surfaces on which the segments bear uniformly while assembled. The spacer may have lips or flanges that extend from the flat surfaces to embrace and support the corners of the segments. These lips or flanges also facilitate the alignment of the segments during assembly and clamping. The outer flanges also prevent the steel bands from coming into contact with the abrasive, and at the same time transfers the forces exerted by the bands directly to the segments. Grooves 9 are provided in the outer surfaces to assure proper spacing of the bands.

The spacers are preferably composed of a thermosetting material such as phenol formaldehyde resin, epoxy resin or hard rubber. The resins used may contain fillers of inert material such as carbon black and in a particular embodiment the filler may be graphite which provides a lubricant to enhance the grinding action. Other materials such as Wood or relatively softer metals may also be used the only requirements being that they shall be hard and rigid, have good compressive strength, have resistance to moisture and chemical compounds used in grinding, have possible lubricating qualities to enhance the grinding action, have the ability to wear away with the segments without imposing a deleterious effect on the work or grinding action and are low cost.

The present invention may be used with any segment having the usual cross-sectional shape for surface grinding. In the preferred embodiment used for illustrating the present invention, the shape used is rectangular. The proportions of the rectangle should be approximately 2 to 1 in order to provide good stability and at the same time to keep the interconnections between segments and spacers to a minimum. A preferred length of the segment,-e.g. the dimension perpendicular to the grinding surface, is 6 /2 inches which gives approximately 6 inches of usable abrasive. Three sizes of segments which are found to have particular utility according to the present invention are 1%" x 4" x 6 /2"; 3" x 6 x 6 /2" and 4" x 8" at 6 /2". The standard aluminum oxide, silicon carbide and diamond abrasive grains are bonded by the standard ceramic, resin and metal bonds. In an embodiment where these segments are secured to the mounting ring, it is possible to secure a threaded insert in the end of the segment withvresin during the molding process and in the case of ceramic bonded segments, a threaded insert can be secured in a recess in the end of the segment with lead.

Steel bands are suggested for securing the segments in place. The standard strapping type of steel band sold under the trademark Signode is suitable for the present invention, but other standard banding materials are also useful. With segments having a length of 6 /2", it is pre-' ferred that 4 steel bands be used and be placed strategically along the length of the segments. The width and thickness of the bands is determined by the strength requirements of the assembly. The first band is preferably placed near the mounting surface and the other three bands are uniformly spaced along the length of the spacer means. The purpose of the spacing of the bands is to exert uniform pressure along the length of the segment. As the segments wear down and the grinding surface approaches a band, the machine is stopped and the band nearest to the surface is cut and removed. This procedure is repeated until the segments are used up to the last band. At this point, the entire mounting plate is removed from the machine and replaced by a new assembly.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and accordingly, it is apparent that many modifications thereof may occur to those skilled in the art, which will fall within the scope of the appended claims.

I claim:

1. A segmental grinding tool comprising a mounting ring having means for attachment to the driving member of a grinding machine and an outer fiat side, a plurality of abrasive segments extending generally perpendicularly from said outer fiat side of the ring, said segments having side edges, a plurality of rigid spacers between said side edges of the abrasive segments to space the segments from one another, said spacers having outwardly facing sides situated beyond the abrasive segments, said segments and spacers defining a circular series of assembled abrasive segments with intermediate spacers and having end faces which are the only portions thereof engaging the mounting ring, a series of spaced apart tightly stretched bands surrounding and securing said assembled abrasive segments and spacers in compression, said bands being substantially out of engagement with the abrasive segments and in contact with outwardly facing sides of the spacers, and means including members extending beyond the outer flat side and into a plurality of the end faces for attaching said assembly to said ring with only the end faces engaging the ring. 1

2. The grinding tool of claim 1, wherein each ,of said segments has means in the end face for securing the seg ment to said mounting ring. i

3. The grinding tool of claim 1, wherein each of said spacers has means in the end face for securing said spacer to said mounting ring.

4. The grinding tool of claim 1, wherein said outwardly facing sides of the spacers are provided with a series of circumferential recesses adapted toreceive bands. 7 i

:5. The grindingtool of claim 1, wherein said bands are steel, said spacers being formed of molded phenol 5 6 formaldehyde resin, and said segments are substantially 1,892,434 12/ 1932. Larsson 51209 rectangular bonded abrasive segments. 1 23 314 9 /1933 Koss 51 20 6. The grinding tool of claim 5, wherein said molded 1 996 980 4/1935 Skmings 51 209 phenol formaldehyde resin contains a grinding aid in the form of a filler material. 5

References Cited UNITED STATES PATENTS 1,642,096 9/1927 Vance 51-209 1,868,492 7/1932 Bucheister 51-209 10 2,092,978 9/ 1937 Larsson 51209 3,171,237 3/1965 Howard 51-209 ROBERT C. RIORDON, Primary Examiner D. G. KELLY, Assistant Examiner

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