MXPA99002291A

MXPA99002291A - Grinding wheel

Info

Publication number: MXPA99002291A
Application number: MXPA/A/1999/002291A
Authority: MX
Inventors: L Holden Robert; P Mc Namara John
Original assignee: Norton Company
Priority date: 1996-09-10
Filing date: 1999-03-09
Publication date: 1999-09-01

Abstract

A molded bonded abrasive grinding wheel adapted for relatively rough grinding operations is provided with a plurality of protuberances spaced in a predetermined pattern along the peripheral surface thereof and extending substantially orthogonally therefrom to define a textured grinding face. The protuberances are molded integrally with the grinding wheel and are perfomed by placing a perforated, or textured annular insert in a grinding wheel mold during molding wherein the insert is molded in-situ about the peripheral surface of the grinding wheel. The insert is removed from the peripheral surface after molding or during grinding to expose the protuberances defined by the perforations of the insert.

Description

GRINDING WHEEL BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This invention relates to grinding wheels and, more particularly, to a molded grinding wheel with a textured grinding face for ease of use in coarse grinding or conditioning operations. 2. BACKGROUND INFORMATION The technique of the grinding wheels is highly developed and includes a wide scale of wheel constructions and wheel manufacturing procedures adapted to optimize specific grinding operations and / or applications. A specific operation that has been given consideration is known as conditioning. The conditioning is generally the removal of surface defects from billets, lupins, ingots and steel plates before further processing. The types of defects include cracks, creases, scales, crusts, cracks, scum plasters and burned steel. Conditioning operations are generally characterized as "coarse grinding" operations and use relatively large contact pressures between the wheel and the work piece. Typically, the grinding wheels optimized for these conditioning operations are commonly known as conditioning wheels, and are manufactured from relatively heavy duty abrasive particles such as aluminum oxide, alumina zirconia, silicon carbide, or combinations thereof, of relatively large size (normally corresponding to a normal "grit size" in the industry from 4 to 46). Moreover, the particles used for these wheels tend to be relatively hard or durable to provide resistance to the above-mentioned relatively high grinding pressures. These particles are generally maintained in a three-dimensional matrix of organic binders, such as those provided, for example, by resinoids or phenolic resin binder material. Examples of conventional conditioning wheels are known as "BZZ conditioning wheels" available from Norton Company of orcester, Massachusetts. As discussed hereinabove, the durability of the abrasive used in the conditioning wheels serves to withstand the relatively high pressures associated with the conditioning operation. The coarse grinding face provided by the relatively large grit size, moreover, serves to effectively reduce the contact surface area between the wheel and the work piece to provide a relatively high pressure per unit area of contact between them. . In this way, the contact pressure exerted between the exposed cutting edges of the abrasive and the work piece is relatively high to facilitate coarse grinding or conditioning operation while minimizing the undesirable effects of excessive wheel pressure such as uneven wear. of the wheel or breaking of the wheel, as will be described hereinafter. Conditioning wheels, like most other types of grinding wheels, have generally been manufactured by hot or cold pressing molding operations. Disadvantageously, however, this manufacturing method tends to produce wheels that exit the mold having substantially uniform peripheral grinding faces in which relatively few, if any, of the cutting edges of the abrasive are exposed. Thus, in the event that such uniform surfaces are brought into contact with a work site in a conditioning application, the increased contact area provided by the same could tend to reduce the contact pressure per unit area. To compensate for this condition, an additional wheel pressure would generally be required to provide sufficient contact pressure between the wheel and the work piece to carbonize or break the binders of the grinding face and expose the cutting edges of the abrasive. Disadvantageously, however, this increased pressure of the wheel tends to generate rubbing that can lead to the breaking of the wheel or alternatively, falling out of balance and causing vibration during the operation. To overcome these disadvantages, more conventional packaging wheels are subjected to an additional post-molding operation commonly known as "finishing". The finish generally includes applying a sharp implement, such as crushing finish, ammunition liner, or conical cutter, to the uniform face of the wheel during the rotation of the wheel to remove the outer layer of the binder material therefrom. This serves to expose the relatively run texture defined by the abrasive particles to facilitate the conditioning operations. Once the abrasive particles have been exposed, the grinding wheel will wear out during subsequent grinding operations in a conventional manner, thereby exposing new abrasive particles continuously in the binder matrix. Although this finishing operation can serve to alleviate the problem generated by the molding process, it is not without disadvantage. In particular, this additional operation disadvantageously contributes to the manufacturing cost, as well as the length of time or main time required to manufacture the wheel.

Thus, there is a need for an improved grinding wheel that overcomes the disadvantages of the prior art.

BRIEF DESCRIPTION OF THE INVENTION According to one embodiment of this invention, a molded grinding wheel includes abrasive particles adhered to a substantially curved peripheral surface and a plurality of surface irregularities spaced in a predetermined pattern along the substantially curved peripheral surface to define a textured grinding face. . According to a second aspect of the present invention, an insert is adapted to be used in conjunction with a grinding wheel having a mold cavity defined by at least one curved surface. The insert includes at least one coating measured and formed for arrangement in superimposed and concentric relation to the curved surface (at least one) of the grinding wheel mold. The coating (at least one) has a plurality of discontinuities disposed therein and is adapted to be selectively molded in-situ with a grinding wheel in the grinding wheel mold, and removed from the grinding wheel, wherein the plurality discontinuities define surface irregularities on a peripheral surface of the grinding wheel. In a third aspect of the present invention, a method for forming a grinding wheel includes the steps of molding the grinding wheel to form a substantially curved peripheral surface and arranging a plurality of surface irregularities in a predetermined pattern along the peripheral surface. substantially curved to define a textured grinding face. In a fourth aspect of the present invention, a grinding wheel consists of a plurality of protuberances disposed on a peripheral surface thereof providing at least one liner having a plurality of depressions disposed therein, molding the liner (at least one ) in-situ around the peripheral surface and removing the coating (at least one) from the peripheral surface after molding. The foregoing and other features and advantages of this invention will be more readily apparent from a reading of the following detailed description of various aspects of the invention taken in conjunction with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a sculler wheel of the invention of the subject. Figure 2 is a cross section taken along the line 2-2 of Figure 1. Figure 3 is a perspective view of a component used to manufacture the grinding wheel of Figure 1. and Figure 4 is a viewed in perspective, with portions in imaginary line, of the grinding wheel of figure 1, during a step in the manufacture thereof.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Briefly described, as shown in Fig. 1, an embossed grinding wheel 10, molded, adapted for relatively coarse grinding operations, is provided with a plurality of surface irregularities such as protrusions 20 spaced in a predetermined pattern along the length of the peripheral surface thereof and extending substantially orthogonally or radially therein to define a textured grinding face 18. The protuberances 20 are integrally molded with the grinding wheel and are formed by placing a ringed insert 22 having a plurality of discontinuities, such as perforations 24, in a grinding wheel mold during molding of the wheel wherein the insert is molded in-situ around the peripheral surface of the grinding wheel. The insert is removed from the peripheral surface after molding to expose protuberances 20 defined by perforations 24. For additional objects, through this description, the term "axial" when used in connection with an element described herein, it should refer to a direction substantially parallel to the axis of a circular dimension thereof. The term "orthogonal" when used in connection with an element described herein, should refer to a direction substantially perpendicular to a tenant of a curved surface at a point of intersection of the element with the curved surface. Referring now to the drawings in detail, as shown in Figure 1, the grinding wheel 10 of the present invention is of conventional construction, generally disc-shaped, having a generally cylindrical internal surface or hole 12, flat side surfaces 14 and 16 (Figure 2) and a substantially cylindrical outer surface or grinding face 18. The dimensions of the grinding wheel, including the diameters of the inner surface 12 and the outer surface 18 as shown in a and b respectively, as well as the thickness of the The wheel as shown in the figure in t (FIG. 2), are predetermined in a conventional manner, based in part on the particular grinding application for which the wheel 10 is to be used. The grinding wheel can be made of a conventional bonded abrasive material such as, for example, the type mentioned hereinabove. In a preferred embodiment, the grinding wheel 10 is "a conditioning wheel" as generally described here before. The outer surface 18 has a diameter preferably within a range of 35 cm to 91 cm. The thickness _t (Figure 2) is preferably within a range of about 3 cm to 15 cm. The grinding wheel 10 also preferably consists of abrasive particles having a grit size within a scale of 4 to 46, or an average diameter within a range of .65 cm to .05 cm. The abrasive is preferably kept inside cold or hot pressed phenolic resin or resinoid binders. As shown in Figures 1 and 2, the outer surface 18 is provided with a series of surface irregularities as protuberances 20 which, as shown, extend orthogonally or radially outwardly thereof. The protuberances 20 are spaced at predetermined intervals from each other around the outer surface 18 and serve to give the outer surface a relatively rough or "buttoned" texture as shown. Referring now to Figure 3, a mold liner, insert or ring 22 is provided to facilitate the molding of the protuberances 20. The mold band liner 22 consists of a generally cylindrical net of predetermined diameter and width or a size that nominally defines the outer surface 18 of the wheel 10 as will be discussed hereafter. The liner 10 is preferably provided with at least one axially extending or cutting contour 23, as shown in the phantom, to facilitate the removal of the insert from the wheel 10 as will be discussed hereafter. Discontinuities of openings or perforations 24 are spaced at predetermined intervals through the liner 22. The perforations serve to define protuberances 20 in a way that will be discussed in greater detail hereinafter. The liner 22 is adapted to slidably engage in a super imposed and concentric manner with a cylindrical outer surface of the cavity of a conventional grinding wheel mold (not shown). In this way, the liner 22 serves as a pattern for the outer surface 18, which includes the integral protuberances 20, of a grinding wheel 10 molded therein, as will be discussed in greater detail hereinafter with respect to the operation and manufacture of the present invention. The liner 22 is preferably made of a material capable of resisting deformation due to the heat and pressure generated during hot press molding operations commonly used to make the grinding wheels. further, the material is preferably relatively flexible to facilitate the removal of the wheel 10, as will be discussed hereafter. In a preferred embodiment, the liner is thus made of a relatively light gauge steel or aluminum, or of a paper product such as ordinary gray cardboard or cardboard. In an alternate embodiment (not shown), the liner may consist of an inflatable bag made of a suitable material such as heat-resistant polymer. Such a bag may include a plurality of discrete inflatable portions disposed on the generally cylindrical surface of the mold cavity as discussed hereinabove. It can therefore be inflated during molding to define the textured face 18 of the wheel and subsequently deflated to facilitate the removal of the wheel from the mold in the manner discussed here above. Having been fully described a preferred embodiment of the invention, the following is a description of the manufacture and operation thereof. As discussed here above, the liner 22 is placed in concentric and over-imposed orientation with the cylindrical outer surface of the cavity of a conventional grinding wheel mold (not shown). A grinding wheel 10 is then molded in a generally conventional manner. Briefly described, a grinding wheel mixture, such as the mixture of phenolic resin and abrasive particles described above, is deposited within the mold and subsequently pressed either hot or cold. A post-bake operation can be provided, in which the wheel is held for a predetermined period at typical elevated cure temperatures. During these molding operations, the grinding wheel mixture will enter and fill the openings 24 of the liner 22, to effectively form a grinding wheel 10 having a liner 22 molded in place with the peripheral surface thereof. Once the molding process is complete, the grinding wheel 10 and the liner 2 are preferably removed from the mold as a single wheel / liner assembly 26, in which the liner 22 is arranged in concentric relation, superimposed with the wheel , as shown partially in imaginary line, in Figure 4. As also shown, when so arranged, the wheel 10 and the liner 22 cooperate to provide the assembly 26 with a substantially uniform, cylindrical outer surface 28 which serves to facilitate the removal of the wheel / liner assembly from the mold without disadvantageously damaging either the wheel or the mold. In this aspect, the cylindrical outer surface 28 allows the removal of the wheel / liner assembly 26 by simply sliding the wheel / liner assembly in an axial direction away from the mold. One skilled in the art will recognize that a cast wheel having an irregular or textured circumferential grinding face completely defined by a wall of the mold cavity will generally not be removable from the mold simply by axial movement. Rather, irregularities in the grinding face, such as protuberances of the type described hereinabove, would tend to engage the corresponding depressions within the mold cavity and thereby prevent such axial movement relative to the mold. Such a wheel would not be removable from the mold without damaging the mold and / or the wheel. To avoid this problem, a fragmented mold with discrete multiple sections can be used to mold wheels of the invention without using a perforated liner. Other types of molds can be used. Such molds must be adapted to allow the removal of the textured side walls of the mold without altering the grinding face of the wheel. Once it is removed from the mold, the liner 22 is removed from the wheel 10. This can be achieved by properly engaging the liner close to the stroke or cut 23 such as on a tongue 30., and detaching the liner from the outer surface 18 of the wheel 10 as shown in Figure 4 and continuing until the liner is completely removed from the wheel. Once the liners have been removed as such, the grinding wheel 10 can then be used in grinding operations without further finishing operations. In fact, the textured grinding face defined by the irregularities of the surface or pre-bushes 20 serves to effectively reduce the contact area between the wheel and the work piece. This lower contact area serves to increase the contact pressure per unit area between the wheel and the workpiece to facilitate the carbonization or decomposition of the binders of the grinding face to expose the cutting edges of the abrasive as discussed here above. Once the cutting edges are exposed, the grinding wheel will wear out during subsequent grinding operations in a conventional manner, thereby continuously exposing new abrasive particles in the adhesive matrix as also discussed here above. In an alternative embodiment, the liner can be manufactured from ordinary cardboard or cardboard material as discussed here above, either with or without tab 30. This material is advantageously flexible to facilitate fabrication and insertion into the mold cavity of wheel, while also tending to become relatively brittle when subjected to the elevated temperatures of typical post-bake operations. Accordingly, such liner 22 can be left in situ, in concentric orientation around the wheel 10 until the wheel is used for grinding, whereby the grinding operation itself will tend to disintegrate the liner to remove it from the wheel 10. Such an ordinary gray cartonboard or cardboard liner can thus advantageously allow the elimination of the aforementioned liner removal step in order to further reduce the manufacturing costs of the wheel 10 of the subject invention. In a further alternative embodiment, the inflatable bag liner discussed hereinabove can be used to provide the textured face. In this mode, the step of removing the lining of the wheel can be done simply by deflating the bag. Moreover, the bag can be secured to the mold so that deflation can be achieved while the wheel is arranged within the mold to facilitate the removal of the wheel from the mold. The use of the liner 22 thus allows a grinding wheel to be molded with an irregular exterior surface to eliminate the need for subsequent "finishing" operations of the type mentioned hereinbefore, while allowing the use of substantially conventional molding techniques and molds. and relatively cheap. The elimination of these operations serves to advantageously reduce the costs of manufacturing grinding wheels such as "conditioning wheels". Moreover, the elimination of the need for finishing serves to substantially reduce the length of time or main time required to manufacture such grinding wheels. This reduced main time can advantageously serve to reduce inventory costs for both the wheel manufacturer and the wheel buyers. The reduced main time also tends to allow the wheel manufacturer to provide an improved service to customers, allowing orders for relatively large or customary amounts of wheels to be fulfilled relatively quickly. The discontinuities of the insert 22 and irregularities of the surface of the wheel 10 have been shown and described herein as generally concave depressions 24 and generally convex protuberances 20, respectively. However, those skilled in the art should recognize that the discontinuities of the insert 22 may generally consist of convex protuberances of the type shown and described herein above with respect to the wheel 10., and that irregularities of the surface of the wheel 10 may generally consist of concave depressions of the type shown and described hereinabove with respect to the insert 22, without departing from the spirit and scope of the present invention. Moreover, those skilled in the art should recognize that the discontinuities of the insert 22 can be of any configuration, such as a series of channels, grooves or other concave or convex structures sufficient to provide a grinding wheel with a substantially textured grinding face, without depart from the spirit and scope of the present invention. Although the present invention has been described herein with respect to a grinding wheel having a substantially cylindrical grinding face, the invention can be practiced with grinding wheels having a grinding face of any other substantially curved geometry, including but not limited to substantially frustoconical, dome-shaped, bowl-shaped, or other concave or convex geometries, without departing from the spirit and scope of the present invention. Although the present invention is described herein with respect to wrapping wheels, one skilled in the art should understand that any type of grinding wheel can be provided with a textured grinding face as set forth herein without departing from the spirit and scope of the invention. the present invention. The aforementioned description is designed primarily for illustration purposes. Although the invention has been shown and described with respect to an illustrative embodiment thereof, those skilled in the art should understand that the foregoing and various other changes, omissions and additions in the form and detail thereof can be made to the same. without departing from the spirit and scope of the invention.

Claims

NOVELTY OF THE INVENTION CLAIMS

1. - A molded conditioning wheel (10) adapted for coarse grinding operations consisting of: adhered abrasive particles; a peripheral surface (18) substantially curved; and a plurality of surface irregularities (20) spaced in a predetermined pattern along the substantially curved peripheral surface (18) to define a textured grinding face.

2. The molded conditioning wheel (10) as set forth in claim 1, further characterized in that the plurality of surface irregularities (20) consists of protuberances extending substantially orthogonally from the peripherally (18) substantially curved face.

3. The molded conditioning wheel (10) as set forth in claim 1, further characterized in that the grinding wheel (10) consists of abrasive particles dispersed in a phenolic resin binder material.

4. - The molded conditioning wheel (10) as set forth in claim 1, further characterized in that the plurality of surface irregularities (20) are formed by selectively placing at least one liner (22) in a grinding wheel mold having a cavity defined by at least one curved surface wherein the liner (22) is disposed within the cavity during the molding of the grinding wheel (10), and removing the liner (22) from the peripheral surface (18) substantially curved afterwards of the molding.

5. - The molded conditioning wheel as set forth in claim 4, further characterized in that the liner (22) consists of a ring having a plurality of perforations.

6. A grinding wheel mold, having a mold cavity defined by at least one curved surface, and at least one lining (22); further characterized in that the liner (22) is measured and formed for disposition in a substantially over imposed and concentric relationship with the curved surface of the mold cavity; the liner (22) has a plurality of convex or concave discontinuities (24) disposed therein; and the plurality of discontinuities (24) of the liner (22) define reciprocal surface irregularities (20) on a substantially curved peripheral surface (18) of a grinding wheel made in the grinding wheel mold.

7. The liner (22) according to claim 6, further characterized in that the liner (22) is adapted to be removed from the mold unitarily with the grinding wheel (10).

8. - A method for forming a molded conditioning wheel (10) adapted for coarse grinding operations, consisting of the steps of: molding abrasive particles arranged in a binder material to form a peripheral surface (18) substantially curved; and arranging a plurality of convex or concave surface irregularities (20) in a predetermined pattern along the substantially curved peripheral surface (18) to define a textured grinding face.

9. The method according to claim 8, further characterized in that the step of arranging a plurality of surface irregularities (20) additionally consists of molding the surface irregularities (20) integrally with the grinding wheel (10).

10. The method according to claim 9, further characterized in that the plurality of surface irregularities (20) comprises a plurality of protuberances.

11. The method according to claim 9, further characterized in that the step of arranging a plurality of surface irregularities (20) additionally consists of the steps of selectively: placing at least one liner (22) for in situ molding around the peripheral surface (18) substantially curved within a grinding wheel mold by arranging the liner (22) around an internal curved surface of the grinding wheel mold during the molding of the grinding wheel (10), and removing the lining (22) of the substantially curved peripheral surface (18) of the grinding wheel (10) after molding.

12. - The method according to claim 11, further characterized in that the liner (22) contains a perforated ring.