US3526998A - Grinding wheel guard for abrading machines - Google Patents

Description

- Sept. 8,1970 'L R ETAL 3,526,998

Original Fi led Jan. 5. 1967 GRINDING WHEEL GUARD FOR ABRADING MACHINES 2 Sheets-Sheet l I ENTORS WILLIAM R AKER .E/CHARD A. AHLIN NBS Sept. 8,-1970 w. R. BAckER ET AL I GRIND-INC} WHEEL GUARD FOR ABRADING MACHI Original Filed Jan. 5; 1967 2 Sheets-Sheet 2 W LLIAM R -R RICH/LfiDfi- AISLIN ATTORNEY Us. or 51-269 United States Patent 3,526,998 GRINDING WHEEL GUARD FOR ABRADING MACHINES William R. Backer and Richard A. Dahlin, Holden, Mass., asslgnors to Norton Company, Worcester, Mass., a corporation of Massachusetts Continuation of application Ser. No. 606,799, Jan.'- 3, 1967. This application June 24, 1969, Ser. No. 835,928

Int. Cl. B24b 55/04 8 Claims ABSTRACT OF THE DISCLOSURE On an abrading machine including a large hollow base and a grinding wheel rotatably mounted upon a support either fixedly or slidably mounted upon the hollow base, an improved grinding wheel guard comprising a peripheral portion substantially coextensive with the half por-. tion of the circumference of the enclosed grinding wheel most remote from the hollow base except immediately adjacent to the line of contact with a workpiece relieved to permit engagement of the grinding wheel with the workpiece; spaced side portions of the grinding wheel operatively engaging the peripheral portion and together with the peripheral portion forming a substantially enlarged chamber on the side of the grinding wheel most remote from the hollow base of a size suflicient to receive and contain a major portion of the volume of the grinding wheel in the event of grinding wheel failure and including an inner surface portion immediately adjacent to the line of contact with a workpiece to be ground so disposed fragments of a broken grinding wheel driven into the chamber are deflected into the hollow base; and a lip portion at the end of the peripheral portion closest to the line of contact between the grinding wheel and a workpiece to be ground extended toward the circumferential surface of the grinding wheel to further assure deflection of the fragments of a broken grinding into the hollow base.

CONTINUATION OF PRIOR APPLICATION This application is a continuation of copending application Ser. No. 606,799, filed Jan. 3, 1967 now Pat. No. 3,375,677.

CROSS-REFERENCE TO A RELATED APPLICATION Reference is made to the copending application Ser. No. 606,800 of Kallander, the disclosure of which is incorporated herein, filed I an. 3, 1967 and entitled Grinding Wheel Guard and Safety Shutter for Abrading Machines, now U.S. Pat. No. 3,452,489, issued July 1, 1969.

BACKGROUND OF THE INVENTION The field of the invention is abrading machines and particularly accessories therefor.

Grinding wheels up to several feet in diameter and several inches thick are used on various types of abrading or grinding machines for removing stock from and finishing workpieces of metal and other materials, and their most eflicient operation may require rotation of these grinding wheels at speeds sufficient to produce surface speeds as high as 16,000 surface feet per minute at the circumference of such grinding wheels. Since a grinding wheel rotating at the required speed develops a substantial quantity of kinetic energy released with fragments of the grinding wheel if it is broken while it is rotating at its operating speed, it has long been customary to enclose such grinding wheels in fixed guards commonly including spaced side portions adjacent to opposite sides of the grinding wheel and a peripheral portion con- 3,526,998 Patented Sept. 8, 1970 centric of the grinding Wheel enclosing its entire periphery except for an area immediately adjacent to the line of contact with a workpiece to be ground, in order to provide as much protection as possible for the operator, usually stationed in front of the grinding machine in line with the grinding wheel. However, it has been noted that a grinding wheel guard with a peripheral portion concentric of the grinding wheel may serve as a conduit to direct wheel fragments through the opening in the guard in the direction of the operator.

Wheel guards representative of this particular peripheral configuration are shown and described in US. Pat. Nos. 953,496 of Stone and 1,351,908 of Howe.

US. Pat. Nos. 1,208,186 of Middleton and 2,745,230 of Krogsgaard disclose grinding wheel guard configurations arranged as illustrated in each of these patents to facilitate the colection and disposal of dust and larger particles produced during normal grinding operations. The Howe patent also discloses a shutter arranged to be moved by fragments of a grinding wheel to close the opening in the wheel guard required for the engagement of the enclosed grinding wheel with a workpiece, in order to confine within the grinding wheel guard itself the relatively large wheel fragments released at high velocities when a grinding wheel is broken in use.

SUMMARY In contrast to the fixed guards for large grinding wheels rotated at relatively high speeds which enclose most of the periphery and most of both side faces of the grinding wheel, already well known in the art, the instant invention provides a grinding wheel guard composed of fixedly positioned interconnected portions arranged and particularly adapted for use in association with the hollow base of a grinding machine on which the grinding wheel enclosed by such a guard is rotatably mounted, which guard consists of spaced side portions and an interconnecting peripheral portion enclosing most of the half of the circumference of the grinding wheel most remote from the hollow base of the grinding machine and defining a chamber above the grinding wheel large enough to receive a major portion of the volume of the grinding wheel and including a portion of its inner surface so disposed as to deflect wheel fragments driven into this chamber into the hollow base of th egrinding machine, and a lip at the edge of this portion of the inner surface of the chamber extending toward the grinding wheel.

Noting that a grinding wheel is normally reduced substantially in diameter due to wear in use and to the truing operations necessary to maintain the grinding surface in proper condition, the instant invention also provides means for positioning the lip portion, projecting from the edge of the wheel fragment deflecting inner surface portion and, closely adjacent to the circumference of the grinding wheel as the diameter of the grinding wheel is reduced in use.

It is, therefore, an object of the present invention to provide a grinding wheel guard open on substantially the entire half of the circumference of an enclosed grinding wheel closest to the hollow base of a grinding machine on which it is rotatably supported.

Another object of the present invention is the provision of a grinding wheel guard for use in association with a grinding wheel rotatably mounted upon a grinding machine including a hollow base, shaped to provide a chamber relatively remote from the hollow base of a size sufficient to receive and contain more than half the volume of the grinding wheel with which it is associated and including a surface and a lip portion projecting from the edge thereof so disposed as to deflect wheel fragments driven into the chamber into the hollow base.

Still another object of the present invention is the provision of means for changing the position of the lip portion included in the grinding wheel guard comprising the instant invention periodically as the grinding wheel with which this guard is associated is reduced in diameter so as to locate this lip portion in close proximity to the circumference of the grinding wheel.

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

FIG. 1 is a side view of a grinding wheel guard embodying the instant invention shown in operative relation to a typical abrading or grinding machine the related components of which are represented in phantom lines;

FIG. 2 is a side view of the same wheel guard configuration shown in operative relation to a typical grinding wheel operatively associated with and partially enclosed thereby; and

FIG. 3 is a side view of the upper front portion of the grinding wheel guard showing a modified embodiment of means for adjusting the position of the lip portion relative to the circumference of the grinding wheel.

Referring now particularly to the showing in FIG. 1,

the base 2 is representative of the hollow cast or fabricated base, commonly incorporated in an abrading or grinding machine, including an internal compartment 22 accessible through an opening 21 through a substantially horizontal portion of the upper surface of the base and beneath the grinding wheel rotatably mounted on such a machine so that a cooling fluid delivered to the workpiece during a grinding operation can be drained through the opening 21 into the chamber 22 within the hollow base 2. In practice, the large opening 21 may be covered by a perforate cover of relatively light construction arranged to exclude relatively large foreign objects such as tools from the chamber 22 within the hollow base. However, the relatively large fragments of a grinding wheel which fails in use would be deflected toward and deposited in the chamber 22 with sufficient force to carry away such a cover located in the opening 21. Thus, the chamber 22 and opening 21 useful as a coolant tank, Whether covered as described or not, also form an open receptacle located and supported apart from, but arranged to cooperate with, the grinding wheel guard described below.

The showing of a typical grinding machine in FIG. 1 also includes representations of a wheel slide base 24 and a wheel slide 25 arranged to support grinding wheel 7 on a suitable spindle, and a representation of a workpiece 9 supported for engagement with the periphery of the grinding wheel 7 by a footstock assembly 27 and a headstock assembly not illustrated both mounted upon a work table 8 slidably mounted upon the base 2.

The grinding wheel guard illustrated in FIGS. 1 and 2 consists of a housing generally designated by reference numeral 2 including a pair of generally parallel spaced side portions 3 respectively adjacent the opposite side faces of the grinding wheel and a peripheral portion 5 including an adjustable portion thereof described further below and enclosing slightly more than half of the circumference of the grinding wheel 7.

From consideration of the various features of the grinding wheel guard described and illustrated herein, it will be apparent its successful performance, in the event of a grinding wheel failure, depends upon maintaining contiguous the respective lengthwise edges of the peripheral portion 5 thereof and the respective adjacent edges of the side portions 3 thereof under the forces exerted by fragments of the grinding wheel 7 rotating Within the housing 1, whether the side portions are permanently or releasably interconnected with the peripheral portion.

One of the side portions may be hinged as by hinge assemblies 4 for access to the grinding wheel 7 for the purpose of changing the grinding wheel vfrom time to time.

The means of supporting the housing 1 upon the wheel slide 25 is not illustrated in the drawings, since details of this attachment means form no part of the instant invention. Such attachment means may comprise threaded bolts, welded joints, or the like, effective to secure the housing 1 to the wheel side 25, both during normal grinding operations and in the event of grinding wheel failure. For one example of such attachment means see the showing of bolts 26 in FIG. 2 of Backer Patent No. 3,129,538.

The outer peripheral portion 5 of the housing 1 c0- extensive lengthwise thereof with the are A carries a pivot pin 10 forming a pivotal support for an adjustable section thereof comprising a hood 6 with spaced parallel sides 6 overlying the respective side portions 3 of the housing 1 and provided with arcuate slots 11 through which are passed clamping bolts 12 threadably engaging the respective side portions 3 to hold the hood 6 in a predetermined fixed position. The lower front edge of the hood 6 has a rearwardly directed lip portion 13 extending transversely thereof and disposed closely adjacent to the circumference of the grinding wheel 7 as shown in FIGS. 1 and 2.

It should be noted that the portion of the housing 1 enclosing most of the half of the circumference of the grinding wheel 7 most remote from the base 2 is so shaped by the spacing of the side portions 3 and the location of the peripheral portion 5 relative to the circumference of the grinding wheel as to form a chamber within the housing 1 and outside the space normally occupied by the grinding wheel 7 with a volume suflicient to receive and contain a major portion of the volume of a grinding wheel 7 broken in use.

Moreover, it should be noted that the portion of the housing 1 immediately adjoining the portion coextensive with are B of the peripheral opening through the housing 1 through which a workpiece 9 is presented for line contact with the circumference of the grinding wheel 7 comprises a surface coextensive with the arc D so disposed in relation to the remainder of the inner surface of the housing 1 and the associated grinding wheel 7 that fragments of a grinding wheel driven into the chamber described above when a grinding wheel 7 is fractured in use is deflected substantially vertically downwardly and rearwardly past the portion of the peripheral opening through the housing 1 coextensive with the arc B through the portion of the peripheral opening through the housing *1 coextensive with the arc C, and thence through the opening 21 into the chamber 22 within the hollow base 2.

FIG. 3 illustrates an alternative embodiment of the housing 1 in which the entire peripheral portion 5 including the surface disposed at the angle necessary to deflect fragments of a broken grinding wheel 7 into the base 2 is a fixed structure which does not include an adjustable hood 6. In this embodiment, the adjustment of the lip portion 13' is provided by incorporating it in a U-shaped member 14 having a pair of parallel sides overlying the side portion 3 of the housing 1 and provided with slots 17 engaged by a pair of locking bolts 16 threadably engaging the side portions 3.

DlSrRIPTION OF THE PREFERRED EMBODIMENT A grinding wheel 7 used with the present invention is mounted upon a suitable wheel spindle supported in a Wheel slide 25 mounted upon the base 2 of the grinding machine in the manner well known in the art.

After the grinding wheel 7 is mounted and the housing 1 is closed by pivoting the side portion 3 supported on hinges 4 into the position shown in FIGS. 1 and 2, the hood 6 is rotated about the pivot 10 to position the lip portion 13 colse to but out of engagement with the circumference of the grinding wheel, and the grinding wheel is rotated in the usual direction, indicated by arrow E in FIG. 2, at the proper operating speed to perform grinding operations on successive workpieces 9. As the grind ing wheel 7 is reduced in diameter in use the hood 6 is periodically readjusted to maintain the lip portion 13 closely adjacent to the circumference of the grinding wheel 7.

In case of the accidental destruction of the grinding wheel while it is rotating within the grinding wheel guard embodying the instant invention, the broken fragments of the wheel move radially away from the center of the grinding wheel either directly into the chamber 22 within the base 2 or into engagement with the inner surface of the peripheral portion 5 of the housing 1 whence they are driven into the enlarged chamber within the side of the housing most remote from the base and finally into engagement with the angularly offset deflecting surface inside the hood 6 and the rearwardly extending lip portion 13 by means of which they are deflected, downwardly and rearwardly into the chamber 22 within the base 2.

In grinding wheel breaking tests grinding wheel guards of conventional design including a peripheral portion closely adjacent to and concentric of most of the circumference of a full sized grinding wheel and a spaced pair of side portions interconnected by this peripheral portion were compared with grinding wheel guards incorporating the several features of the instand invention. In the first instance, when both full sized and fully worn grinding wheels rotating at predetermined speeds exceeding their normal operating speeds were broken within grinding wheel guards of the conventional design, by the application of an abnormal high stress, wheel fragments totaling about 25% of the total weight of the grinding wheel were thrown from the front of the guard in the direction of the station normally occupied by the grinding machine operator. In the second instance when both full sized I and fully worn grinding wheels rotating at corresponding predetermined speeds exceeding their normal operating speeds were broken within grinding wheel guards incorporating the instant invention, by the application of an abnormal high stress, wheel fragments amounting to substantially less than 5% of the total weight of the grinding wheel were discharged from the guard in the direction of the station normally occupied by the grinding machine operator under the least favorable test conditions, and for most test conditions wheel fragments totaling less than 1% of the total weight of the grinding wheel were discharged from the guard in the direction of the station normally occupied by the grinding machine operator.

Thus, the instant invention provides a grinding wheel guard configuration especially adapted to enclose a grinding wheel mounted upon a grinding machine having a large hollow base, which substantially reduces the hazard to the grinding machine operator in the event of failure of the grinding wheel while it is rotating at its normal operating speed.

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 desired to comprehend such modifications within this invention as may fall withing the scope of the appended claims.

What is claimed is:

1. A grinding wheel guard fixedly disposedin operative relation to a given grinding wheel rotating about a predetermined axis of rotation and supported for operative engagement with a workpiece along a given predetermined line of contact extending transversely of the circumferential surface of the given rotating grinding wheel, said grinding wheel guard including,

first and second side portions, impervious to the passage of grinding wheel fragments therethorugh, respectively spaced from the opposite side faces of the given grinding wheel, and

a co-acting elongated peripheral portion, impervious to the passsages of grinding wheel fragments therethrough, having first and second longitudinal edge portions operatively interconnecting said first and said second side portions along predetermined edge portions thereof and of predetermined limited length extending peripherally of the given rotating grinding wheel around most of the half of the circumferential surface of the given rotating grinding wheel approaching the given predetermined line of contact, from a first end of said peripheral portion disposed closely adjacent the given predetermined line of contact to a second end of said peripheral portion located substantially diametrically of the given rotating grinding wheel from said first end of said peripheral portion, said first and said second side portions and said peripheral portion together defining a chamber having a substantially elongated continuous peripheral opening therethrough consisting of a first opening portion of relatively smaller peripheral extent adjacent said first end of said peripheral portion spanning and symmetrical about the given liue of contact with a workpiece and a second opening portion of relatively larger peripheral extent adjacent said second end of said peripheral portion, and said peripheral portion having an inner surface radially more remote from the given axis of rotation between said first and said second ends of said peripheral portion than at said first and said second ends of said peripheral portion, and also having a predetermined portion peripherally of said inner surface adjacent said first end of said peripheral portion disposed progressively closer to the circumferential surface of the given grinding wheel toward said first end of said peripheral portion and angularly so disposed relative to the respective extremities of said second opening portion, that grinding wheel fragments released into said chamber in the event of fracture of the given rotating grinding wheel are so constrained by said peripheral portion and thence by said predetermined portion of said inner surface of said peripheral portion as to be deflected on rebound therefrom chordwise of the space occupied by the given grinding wheel prior to its fracture past said first opening portion and out of said grinding wheel guard through said second opening portion between its respective extremities, whereby such grinding wheel fragments may be collected safely in a receptacle suitable for this purpose located and supported separately from said grinding wheel guard. 2. A grinding wheel guard as described in claim 1, wherein,

said peripheral portion includes at its first end adjacent said predetermined portion of said inner surface a lip portion extending transversely of said peripheral portion between said first and said second side portions and also extending toward the given rotating grinding wheel and closely adjacent to the circumferential surface of the given rotating grinding wheel. 3. A grinding wheel guard as described in claim 2, wherein,

said peripheral portion includes a relatively fixed portion operatively interconnecting said first and said second side portions and a relatively movable portion adjustably connected to said relatively fixed portion and having first and second side extensions respectively adjustably fixedly secured to said first and saidsecond side portions in a predetermined complementary positions relative thereto. said relatively movable portion comprising an adjustable hood including both said predetermined portion of said inner surface and said lip portion. 4. A'grinding wheel guard as described in claim 2, wherein,

said peripheral portion includes a relatively fixed portion operatively interconnecting said first and said second side portions and a relatively movable portion adjustably fixedly secured to said relatively fixed portion at said first end of said peripheral portion,

the inner surface of said relatively fixed portion including said predetermined portion of said inner surface, and

said relatively movable portion comprising said lip portion.

5. The combination of a grinding wheel and a grinding Wheel guard fixedly disposed in operative relation to said grinding wheel.

said grinding wheel being supported for driven rotation in a predetermined direction about a predetermined axis of rotation and for operative engagement with a workpiece along a given predetermined line of contact extending transversely of the circumferential surface of said grinding Wheel, and said grinding wheel guard comprising,

first and second side portions impervious to the passage of grinding wheel fragments therethrough, respectively spaced from the opposite side faces of said grinding wheel, and

a co-acting elongated peripheral portion, impervious to the passage of grinding Wheel fragments therethrough, having first and second longitudinal edge portions operatively interconnecting said first and said second side portions along predetermined edge portions thereof and of predetermined limited length extending peripherally of said grinding wheel around most of the half of the circumferential surface of said grinding wheel rotatable about said predetermined axis of rotation in said predetermined direction toward said predetermined line of contact, from a first end of said peripheral portion disposed closely adjacent said predetermined line of contact to a second end of said peripheral portion located substantially diametrically of said grinding wheel from said first end of said peripheral portion,

said first and said second side portions and said peripheral portion together defining a chamber having a substantially elongated continuous peripheral opening therethrough consisting of a first opening portion of relatively smaller peripheral extent adjacent said first and of said peripheral portion spanning and symmetrical about said predetermined line of contact and a second opening portion of relatively larger peripheral extent adjacent said second end of said peripheral portion,

said peripheral portion having an inner surface radially more remote from the given axis of rotation between said first and said second ends of said peripheral portion than at said first and said second ends of said peripheral portion, and also having a predetermined portion peripherally of said inner surface adjacent said first end of said peripheral portion disposed progressively closer to the circumferential surface of the given grinding wheel toward said first end of said peripheral portion and angularly so disposed relative to the respective extremities of said second opening portion, that grinding wheel fragments released into said chamber in the event of fracture of the given rotating grinding wheel are so constrained by said peripheral portion and thence by said predetermined portion of said inner surface of said peripheral portion as to be deflected on rebound therefrom chordwise of the space occupied by the given grinding wheel prior to its fracture past said first opening portion and out of said grinding wheel guard through said second opening portion between its respective extremities, whereby such grinding wheel fragments may be collected safely in a receptacle suitable for this purpose located and supported separately from said grinding wheel guard. 6. The combination of a grinding wheel and a grinding wheel guard as described in claim 5, wherein,

said peripheral portion includes at its first end adjacent said predetermined portion of said inner surface a lip portion extending transversely of said peripheral portion between said first and second side portions and also extending toward said grinding wheel and closely adjacent to the circumferential surface of said grinding wheel. 7. The combination of a grinding wheel and a grinding Wheel guard as described in claim 6, wherein,

said peripheral portion includes a relatively fixed portion operatively interconnecting said first and said second side portions and a relatively movable portion adjustably connected to said relatively fixed portion and having first and second side extensions respectively adjustably fixedly secured to said first and said second side portions in predetermined complementary positions relatively thereto, said relatively movable portion comprising an adjustable hood including both said predetermined portion of said inner surface and said lip portion. 8. The combination of a grinding wheel and a grinding wheel guard as described in claim 6, wherein,

said peripheral portion includes a relatively fixed portion operatively interconnecting said first and said second side portions and a relatively movable portion adjustably fixedly secured to said relatively fixed portion at said first end of said peripheral portion, the inner surface of said relatively fixed portion including said predetermined portion of said inner surface, and said relatively movable portion comprising said lip portion.

References Cited UNITED STATES PATENTS 3,129,538 4/1964 Backer 51269 X 469,310 2/1892 Wilson 51269 1,351,908 9/1920 Howe 51269 2,745,230 5/1956 Krogsgaard 51269 1,208,186 12/1916 Middleton 51269 JAMES L. JONES, Jr., Primary Examiner

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