US3144739A

US3144739A - Grinding wheel

Info

Publication number: US3144739A
Application number: US170940A
Authority: US
Inventors: William J Brutvan; Carl F Foster
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-02-05
Filing date: 1962-02-05
Publication date: 1964-08-18
Anticipated expiration: 1981-08-18

Description

Aug. 18, 1964 w, J. BRUTVAN ETAL 3,144,739

GRINDING WHEEL Filed Feb. 5, 1962 2 She ets-Sheet 1 INVENTORS WILLIAM J. BRUTVAN 8 BY CARL F. FOSTER ATTORNEYS 8, 1964 w. J. BRUTVAN ETAL 3,144,739

GRINDING WHEEL Filed Feb. 5, 1962 2 Sheets-Sheet 2 FIG. 6

AREA 8 INVENTORS WILLIAM J. BRUTVAN a BY CARL F. FOSTER ATTORNEYS United States Patent Ohio Filed Feb. 5, 1962, Ser. No. 170,940 8 Claims. (631. 51-2065) This invention relates to an interlocking grinding wheel, and more specifically to a grinding wheel comprising a plurality of grinding segments, secured to a shaft with a hub. Each of the segments forming the wheel is either of the same or of a different grade of grit, depending on the particular surface finish required. Still more specifically, this invention relates to a grinding wheel having means of supplying a coolant or fluid from the center of the Wheel to the outer grinding edge for direct cooling. The size and direction of the channels and passageways located in the hub, shaft, and between the interlocking segments of the wheel provide a means of controlling the amount of fluid to be supplied over the cutting surface in each case.

Grinding and grinding wheels, as distinguished from polishing, lapping, etc., consist broadly of an abrasive wheel mounted on a suitable machine rotating at high speeds, so as to act as a cutting edge at the surface of a workpiece. Grinding wheels or stone grits may be used on any metal or non-metal for purposes of finishing the surface as long as the surface is sufficiently hard to resist the amount of compression ordinarily encountered during a cutting or grinding operation.

Most of the grinding wheels used for cutting comprise different grades of grit which are characterized by their particular structure and strength. The strength of the grinding wheel will depend, for the most part, on the grain size of the abrasive, e.g. aluminum oxide, silicates, or silicon carbide, etc., and on the bonding material used to form the grit. The reason for this is because the grain size of the abrasive, together with the bonding material, determines the porosity of the grit, which, in turn, suggests the relative strength. It is the porosity, then, which is a means of indicating the effectiveness of a grit to resist the stress normally encountered in a cutting operation, and which may be responsible for the rapid breaking or wearing down of the wheel.

In the manufacture of grinding wheels, each is made from difierent sizes of abrasive materials and is distinguished from natural abrasives, such as corundum or diamond, in that it is known as coarse, medium, or fine. The different grain sizes are bonded together by bonding materials, such as resins, rubbers, or silicates, to form the grinding wheel, each wheel being of a different grade, known commercially as a very soft to a very hard grinding wheel. The particular grinding wheel to be used on a specific job will depend upon the finish required. Thus, for example, the coarse or medium-sized-grain grinding wheels are used for rough and semi-finishing operations, whereas the fine wheels are used for finishing.

In preparing for a particular grinding or surface finishing operation, then, it is important to determine the hardness or grade of wheel to be used in conjunction with the speed and the type of surface to be finished. During grinding, the wheels are operated at 6,500 surface feet per minute (s.f.p.rn.) but faster speeds, i.e. 9,500 s.f.p.m., may be used with rough-finishing wheels where it is known that this particular wheel meets the specifications required for operating at these speeds.

To improve the grinding procedures further, coolants are applied over the workpiece at the point of contact with the grinding wheel. Most of these coolants contain water, e.g. water and oil emulsions, which helps to dissipate the heat caused by the grinding. More important,

the use of coolants regulates the amount of heat on the workpiece and thus prevents hot spots, which cause burning, from occurring. In addition to the water-containing coolants, grinding oils are used in many operations and have some advantage over water. Oils, for example, are used in combination with finer grits, which helps to produce a finer finish. There are many ways of applying the coolants to the grinding Wheel.

In accordance with the teachings of this invention, however, the coolant, e.g. water, is fed aXially through the center of the wheel and flows radially through the channels provided to its periphery and over the cutting edge. By having the coolant flow evenly over the cutting edge of wheel, the small particles of metal being cut from the workpiece are washed away, thus avoiding any buildup of metal particles on the surface of the porous grit and at the same time providing a smoother finish. By having an even and continuous flow of coolant directly over the cutting surface, overheating or hot spots will be avoided and the possibility of breaking the grit will be minimized. It has been found, also, that by having the coolant flow from an internal source directly over the cutting edge of the wheel, that deeper or heavier cuts can be taken without impairing substantially the effectiveness of the grinding wheel. Usually in taking deep cuts, the particles of metal enter the pores of the grit or plaster over the grit so as to make it ineffective. This is avoided by having a continuous flow of the fluid over the cutting edge.

Accordingly, it has been discovered that grinding or finishing metal surfaces can be improved by using a wheel comprising a shaft, a hub, and a plurality of grits, each separately secured around the periphery of the hub which is attached to the spindle or shaft, the hub, shaft, and grits having means of forcing a coolant centrifugally through the channels and passageways to the outer cutting edge of the grit. The segments of grit, which comprise the wheel, may be of the same grade or of a different grade, depending upon the particular grinding operation desired. By using a plurality of different grits, provided with channels for direct cooling, the life of the wheel is increased and a more precise grinding is obtained.

In a normal grinding operation, it is estimated that a wheel running at 6,500 s.f.p,rn. is moving at approximately 74 mph when it hits the metal and begins to take a chip into the surface. Because of the amount of energy needed to deform the metal, both the metal and the grit become very hot. Thus, the purpose of the coolant is to chill this cutting surface, while at the same time washing away the particles of metal being cut from the metal. It is indicated that temperatures as high as 2,000 F. may result because of the friction between the metal and the grit. In addition to these temperatures, the pressure exerted on the small areas being cut away from the metal also are very high. It is these high temperatures and pressures which cause the grit to react with the metal giving a plaster effect to the grit, which results in an ineffective cutting edge.

Thus, with a thorough understanding of what takes place during grinding, it is possible to select the grade and type of grinding wheel that should be used with any particular type of metal, and thus possibly eliminate most of the wear ordinarily encountered in grinding. For example, where a grinding wheel has become glazed or plastered over, it can be assumed that this is due largely to the abrasive becoming plastic in nature and, consequently, wearing down to the point where it becomes smooth and thus ceases to be an effective abrader. This may be avoided by selecting the right grit for that particular metal. In addition to wear, fractures of the grit may be caused by the stress imparted to the wheel upon coming into contact with the metal surface. The high temperatures generated by the grinding action, however,

are responsible for most of the wear and ineffective grinding. Accordingly, the ability of the grit to conduct heat, e.g. as high as 2,000 E, which is built up at the interface between the workpiece and the grinding wheel will be related to the ability of the grit to withstand wear. By having a direct and continuous amount of coolant passing over the cutting edge of the grit during the grinding, the temperatures at the cutting surface will be lowered, and more important will be held uniform throughout the cutting operation. The uniformity and lowering of the temperatures by the coolant will, in the long run, improve and increase the life of the grinding Wheel.

By using an internal supply of coolant flowing directly over the cutting edges comprised of different grades of grit, maximum cutting and finishing are obtained without any substantial amount of wear. Thus, for example, a wheel containing different grades of grinding segments, will provide a means of grinding whereby a high cutting efiiciency is obtained along with a low cutting efficiency, and a good finished appearance. As indicated above, the strength and grade of a particular grinding wheel depend on the grain size and the bonding material used in preparing the wheel. By alternately having segments of fine and coarse grades of grit in the same wheel, the removal of stock by the fine grit will be slower than the adjacent coarser grit but will help to avoid any plastering effect that could result by having the particles of cut-away metal fill the interstices of the coarse grit. The alternate fine grit supplies extra coolant which has an opportunity to wash away the particles of metal cut by the coarse grit, before plastering can take place.

Accordingly, it is an object of this invention to provide a grinding wheel comprising a shaft, a hub, and a plurality of grinding segments.

It is another object of this invention to provide a grinding wheel comprising a plurality of grinding segments secured around the periphery of a spindle or shaft by means of a hub, the construction of the wheel being such that each of the segments can be replaced easily without the necessity of disassembling the entire wheel.

It is another object of this invention to provide a grinding wheel comprising a plurality of grinding segments, each of the segments having channels located between their adjoining ends so as to provide a means of supplying a coolant to the outer working edge or periphery of the grinding wheel.

It is another object of this invention to provide a grinding wheel containing a plurality of interlocking grinding segments, each of a different grade, and internally supplied with a cooling fluid.

It is another object of this invention to provide a grinding wheel having a plurality of interlocking grinding segments, each of the segments being of a different or the same grade of grit, and being supplied internally with a coolant which is forced through to the outer cutting edge of the wheel by centrifugal force.

It is still another object of this invention to provide a grinding wheel whereby the fluid is spread continuously and evenly over the cutting edge by adjusting the size and direction of the grooves, channels, and passageways which are in communication with the internal supply of coolant.

It is still another object of this invention to provide a segmented grinding wheel comprising a plurality of grinding grits mounted on a shaft by means of a plurality of dovetail keys located around the periphery of a hub; the hub including substantial axial passageways whereby a cooling fluid is forced centrifugally through the shaft and hub toward the radial channels between the segments and outwardly to the cutting edge of the wheel.

It is a still further object of this invention to provide a grinding wheel whereby the wheel comprises a shaft, a hub, and a plurality of grinding segments, each of the segments provided with a means of feeding a lubricant or coolant evenly and continuously over the cutting edge 4 of the wheel, and each of the segments being removable without disassembling the entire wheel.

It is a still further object of this invention to provide a grinding wheel whereby the temperature at the interface of the workpiece and the grinding wheel is lowered and held constant by a lubricant or coolant flowing directly over the cutting edge; the coolant being supplied internally from the shaft of the wheel and radially between the segments of grit to the outer cutting edge.

It is a still further object of this invention to provide a segmented grinding wheel containing a shaft, a hub, and a plurality of grits with internally supplied cooling means which minimizes the cutting temperature and prevents particles of metal from plastering over the cutting edge. The lowering and equalizing of the cutting temperature by the continuous and direct flow of the coolant prevents the cutting surface of the grit from going into solution with the surface of the metal.

These and other objects of the invention will become apparent from a further and more detailed description of the invention.

The invention is illustrated in the accompanying drawings, as follows:

FIG. 1 is a side elevation view of the grinding wheel with a partial sectional view of the wheel;

FIG. 2 is a transverse sectional view of the grinding wheel on the line 2-2 of FIG. 1;

FIG. 3 is an enlarged detail view in cross section from area A of FIG. 1;

FIG. 4 is an elevation view of FIG. 3;

FIG. 5 is an enlarged detail view from area B of FIG. 6;

FIG. 6 is a front elevation view of the grinding wheel;

FIG. 7 is a perspective view of a segment of the grit;

FIG. 8 is a fragmentary side elevation View of a modified grinding wheel with a partial section of the grit;

FIG. 9 is a fragmentary elevation similar to FIG. 1, showing a modified form of keying grits to the wheel;

FIG. 10 is a section on line 10-10 of FIG. 9; and

FIG. 11 is a fragmentary section similar to FIG. 10 showing a further modification.

Referring more specifically to the drawings:

FIG. 2 shows a segmented grinding wheel 5 mounted on a tapered shaft or spindle 1. The taper of the spindle may range from 2 to 10 degrees with a cap screw 2 at the tapered end. The size of this cap screw permits it to extend into a threaded hollow pipe 3 to provide an axial passageway for the cooling fluid. The fiuid is forced centrifugally past the screw toward the channels in the grinding segments. The open end of the hollow pipe 3 is connected to a slip coupling 25 which is supplied with a coolant, e.g. water or oil.

Mounted on the spindle is the flanged hub 4 of the wheel 5, which has a bore tapered to coincide with the taper of the spindle. The spindle is bolted with a cap screw 2 which abuts against the back of the hub thus securing the hub 4 to the spindle 1. By tightening the screw, the hub is secured firmly to the spindle which is connected to a source of power and driven at any desired speed. The larger end of the tapered bore is recessed at 7 with the opposite end being internally threaded to cooperate with the threaded pipe member 3, the diameter of the pipe 3 being approximately the same as the driving end of the spindle 1A. Around the periphery of the tapered end of the hub and adjacent the threaded pipe are located a plurality of substantially axial passageways 8 and 811. Each of these axial passageways is in communication with the fluid reservoirs 9 and with the radial channels 10 located between the segments of grit which interlock to form the wheel. A lubricant or coolant is forced through the threaded hollow pipe 3, past the screw and through the passageways 8 to the reservoirs 9, where it is then forced slowly through the channels 10 between the grits, outwardly to the groove 16 and over the outer cutting surface of the wheel. The sizes of the passageways 8 and 8a, the channels 10, and the grooves 16 will depend for the most part on the type of fluid being used. In instances were viscous oils are used, the sizes of the grooves, channels, and passages Will be larger in comparison to their sizes when the fluid is water. The viscosity of the fluid together with the speed at which the wheel is to be operated will determine the optimum sizes of these openings. By adjusting the sizes of the grooves, channels, and passages to correspond with the speed and viscosity of the fluid, the amount of fluid caused to come to the outer periphery of the grit by the centrifugal force can be controlled to meet any desired needs. The contour of the channels also will help to break or restrict the flow of fluid as it passes to the outer surface. Thus, for example, channels that follow a zigzag contour will slow down the flow in comparison to straight line channels. The contour or restrictions of the channels will help to control the amount of fluid passing to the outer cutting surface.

The grinding segments of the wheel take the form of a disk 11, illustrated in FIG. 1, which comprises a plurality of grit segments 13 attached to the hub 4 by means of a plurality of ribs or dovetail keys 12, which extend from the hub and are shaped to fit into and lock each segment to the hub. Each of the grit segments 13, as illustrated in FIG. 7, has a dovetail cutaway 14 corresponding to the size and shape of the rib or key 12 on the hub. The cutaway sections in each segment of grit 13 are designed so that they can be slipped on and off from the keys without removing the remaining grits. The width of the rib or key at the base is substantially less than at the top, thus preventing the segments from being thrown outwardly by the centrifugal force normally encountered at operating speeds.

The non-circular or interlocking ends of each segment 13 may be zigzag as at 15 or any other shape which corresponds to the shape of the next adjacent segment so as to provide a continuous circular disk or wheel of grit as illustrated in FIG. 1. The channels extend from the outer surface 17 of the interlocking segments radially through the center of the joining ends, communicating with the fluid channels 8a in the hub. Fluids, e.g. lubrieating oil, water, or mixtures thereof, which are supplied through the hollow pipe 3 will be sucked through the passageways 8 and 8a to the channels 10 and out over the surface 17 of the grinding wheel by centrifugal force. Axial grooves 16 which are perpendicular to the channels 10 on the outer periphery of the grit 17 allow the fluid to be fed evenly over the surface at a constant rate without substantial loss due to the circular rotation of the wheel. Here again the size of this groove may vary and will depend on the viscosity of the fluid and the speed at which the wheel is to be operated. The zigzags a illustrated on FIG. 8 are reduced to provide for the use of coolants having higher viscosities.

FIG. 3 is an enlarged sectional view of a channel formed by segments of grit 13 cooperating or interlocking to complete the grinding wheel as illustrated in FIG. 1. When all the segments of grit 13 are placed about the hub 4 and secured thereto by equally spaced ribs or keys 12, a continuous wheel of grit is obtained as illustrated in FIG. 1. The segments of grit are prevented from sliding axially off the ribs by placing mounting

plates

18 and 19 adjacent to the sides of the disk.

The hub 4 is flanged to hold the mounting plate 19 against the side of the disk as the nut 2 is tightened. The mounting

plates

18 and 19 may have a cutaway similar to that of the rib or key and are slipped over them as the wheel is assembled on the spindle. The mounting rim 20 with O-rings 21 and washer 22 are secured against the side of the wheel and hub by a nut 23. The pipe 3 extends into slip coupling 25 which has a source of fluid supplied through pipe 26. As the fluid is fed into the coupling, the centrifugal force causes it to flow axially through the pipe 3 past the nut 2 to passageways 8 and 8a 6 and radially through channels 10 to the outer cutting edge or periphery.

As an alternative to the above, the segments of grit can be secured to the spindle or shaft by replacing the dovetail keys or ribs on the hub with holding sections or studs 27 held in place by pins or bolts 28. The sections or studs 27 are designed or shaped to fit into a corresponding cutaway section in the segments of grit as illustrated in FIG. 9.

As shown in FIG. 10, a pin or bolt 28 passing through the mounting plates 19 and through the stud 27 secures the individual segments of grit to the plates which are in turn secured around the periphery of the hub 4 which is bolted to the shaft. As another alternative one of the mounting plates 18 may have a depression 29 with a complementary projection of stud 27a on the other plate 19 in order to hold the interlocked segments of grit against the centrifugal force, as illustrated in FIG. 11. These methods of holding the segments to the wheel have a particular advantage in that each of the segments can be replaced simply by removing the individual studs, without the need for disassembling the entire wheel.

According to the invention described, a cooled, interlocked grinding wheel comprising a shaft, a hub, and a plurality of interlocked sections, e.g. four, with a system for direct cooling, provides a better grinding and finishing surface with a minimum amount of wear. The reasons for these improvements, while not completely understood, are believed to be due to the use of various grades of grit on the same wheel with a means of supplying a direct and specific amount of coolant evenly over the cutting surface. Moreover, the manner in which the segments are secured to the wheel facilitates the ease with which they can be replaced.

In grinding or finishing metal surfaces, the energy required to deform or cut away the metal is converted to heat, with temperatures up to about 2,000 F. These high temperatures are controlled immediately by the direct cooling action of the fluid flowing from the center of the wheel out over the cutting edge. When the wheel strikes the metal surface, even with cutting depths less than five percent of the diameter of the grit, the total force on the wheel may range from about 2 or 3 pounds for a period of less than 10- seconds. At these pressures and temperatures, it is possible for adhesion to take place between the metal and the abrasive Which causes particles of the grit to be pulled from the abrasive surface. It has been discovered, however, that this problem can be overcome or minimized by using different but selected grades of grit in the same wheel. Thus, as an example, alternate segments of grit ranging from fine to coarse with direct cooling will give better grinding results and avoid most of these cutting problems. The direct cooling supplied internally from the wheel, as distinguished from external cooling, permits an even flow of the liquid over the cutting surfaces and also washes away most of the waste chips which otherwise would become impregnated or plastered over the grit. Moreover, by having the coolant supplied directly to the cutting edge, an even and continuous flow of the fluid is obtained which equalizes the temperature over the entire cutting surface and thus eliminates hot spots or burning. Each of the segments of grit, joined or interlocked at their jagged edges to form a continuous grinding wheel should be selected according to the specific grinding or finishing operation desired.

The axial grooves which are located around the periphery of the cutting edge and communicate with the radial flow of fluid coming from between the segments, disperse the fluid over the surface and help to prevent the fluid from being thrown from the wheel. A continuous supply of fluid to these grooves will insure an even and continuous flow of the liquid over the entire cutting surface. Without these axial grooves, there would be a tendency for some of the fluid to be thrown from the wheel without completely covering the edge because of the concentration 7 of fluid at that one point. Like the sizes of the channels and passageways, the sizes of the grooves are regulated so that the correct amount of fluid is spread over the entire cutting edge.

When the wheel is in motion, the interlocking sections of grit cooperate with the holding sections and keys to hold the grits firmly to the wheel. The means by which the grits are secured to the Wheel enables the changing of these grits at any point during a grinding operation, without breaking down and reassembling the whole wheel.

While the above invention has been described with reference to specific illustrations, it is to be understood that the invention is not intended to be limited thereto, except as recited hereinafter in the appended claims.

The invention claimed is:

1. A grinding wheel comprising a plurality of interlocking segments of grit, each of said segments being secured to a supporting shaft extending through said wheel by means of a hub thereby forming a wheel having a pcripheral surface thereon with a width equal to the width of one of said segments, substantially radial zig-zagged channels in said segments intermediate the opposite sides thereof to the peripheral surface thereof, and a source of coolant fluid connected to said radial channels.

2. The grinding wheel of claim 1 in which there are a multiplicity of grooves in the peripheral surface connected to said radial channels to provide an even distribution of coolant fluid over the peripheral surface of the grinding wheel.

3. The grinding wheel of claim 1 in which the radial channels are between the interlocked segments of grit.

4. The grinding wheel of claim 1 in which flow restrictors are placed in the radial channels to control the amount of coolant fluid passing therethrough based upon its viscosity and the peripheral speed of the grinding wheel.

5. The grinding wheel of claim 1 in which at least some of the interlocked segments of grit are of a different coarseness in order to provide improved grinding and reduced plastering of metal.

6. The grinding wheel of claim 1 in which the interlocked segments of grit are secured to the wheel by means of a plurality of dovetail keys.

7. The grinding wheel of claim 1 further characterized by a shaft, a pair of mounting plates with securing means therefor to hold the interlocked segments of grit therebetween, said mounting plates and said interlocked segments of grit having a depression on one of said members and a complementary projection on the other in order to hold said interlocked segments of grit against centrifugal forces.

8. A grinding wheel having a hub and a shaft and comprising a multiplicity of radially interlocked segments of grit, each segment being of a different grade of grit and being secured to said shaft through said hub, and substantially radial zag-zagged grooves between said interlocking segments of grit intermediate the sides thereof for passage of coolant fluid therethrough, and a coolant fluid passageway to said radial grooves from said hub and shaft.

References Cited in the file of this patent UNITED STATES PATENTS 796,466 Stolzenberg Aug. 8, 1905 933,603 Wagg Sept. 7, 1909 985,116 Nichols Feb. 21, 1911 1,469,985 Bath Oct. 9, 1923 2,078,452 Larsson Apr. 27, 1937 2,887,276 Minarik -1 May 19, 1959 2,929,568 Vawter Mar. 22, 1960