Dust Collector For Grinding Tool

Abstract

The disclosure is directed to an improved dust collector for a manually operable grinder comprising a hood overlying the top of a cupstone grinding wheel and having a depending skirt to form a dust-collecting chamber and at least one passage through the back wall of the cupstone wheel for connecting its hollow center to the dust-collecting chamber. With the added passages in the back wall of the cupstone wheel the edge of the depending skirt of the hood may be located at a height so as not to interfere with the use of the lower peripheral edge of the wheel.

Description

The present invention relates to hand grinding tools and more particularly to an improved dust collector for a manually operated grinder.

Manually operating grinding tools have been in common use for a long period of time to "snag" rough castings by grinding off the flashings and sprues remaining on the casting after removal from the mold. The most common type of grinder for this purpose comprises a cupstone grinding wheel rotatably mounted on a frame and driven by a suitable motor. The cupstone grinding wheel has continuous back and sidewalls to form an inverted cup, usually of frustoconical shape, but sometimes in the form of a right cylinder. The outer rim of the continuous sidewall has a flat annular grinding surface which surrounds an opening at the center. Radially extending handles project from the frame to manually guide the implement when its flat annular grinding surface engages the surface of the part being ground. Also, the angular edge between the sidewall and annular grinding surface of the cupstone is used by the operator to undercut projections on the part or casting being ground, and the tool is many times held at an angle to the surface to obtain a grinding effect only at the outer peripheral edge of the wheel.

Operation of the grinding implement produces dust which constitutes a health hazard. It has heretofore been proposed to provide a dust-collecting shield or hood around the periphery of the wheel in which a partial vacuum is maintained to draw off the dust in the stream of air flowing into the hood. Such hoods have a skirt which extends downwardly to a position closely adjacent the work to increase the velocity of the air flowing into the hood and thereby insure the collection of all dust generated by the wheel. However, the location of the lower edge of the skirt of such dust-collecting hoods interferes with the use of the angular edge of the cupstone wheel and the tilting of the implement as practiced by many operators. To overcome this difficulty it also has been proposed to use a dust-collecting hood or shield that extends to a position adjacent the annular grinding surface around the greater part of its circumference, but eliminating the hood from a small sector of the wheel to adapt the edge at that portion to be used without interference from the hood. Grinding tools with such dust-collecting hoods have been found awkward to use and have not been favorably accepted by the trade.

One of the objects of the present invention is to provide an improved dust-collecting arrangement for a grinding wheel of the type indicated which is more efficient in operation in removing dust produced by the grinding operation and one which facilitates manipulation by the operator.

Another object is to provide an improved dust collector for a cupstone grinding wheel which does not interfere with the use of the peripheral edge of the wheel.

Still another object is to provide an improved dust collector for a cupstone grinding wheel which is of simple and compact construction, economical to manufacture and one which is reliable in operation.

These and other objects will become more apparent from the following description and drawing in which like reference characters denote like parts throughout the several views. It is to be expressly understood, however, that the drawing is for the purpose of illustration only and is not a definition of the elements of the invention, reference being had for this purpose to the appended claims.

In the drawing:

FIG. 1 is a side elevational view of a conventional cupstone grinding tool incorporating the novel dust-collecting arrangement of the present invention and showing the implement tilted to adapt the peripheral edge of the wheel to be used in a conventional way;

FIG. 2 is an enlarged side elevational view of the implement partly in section to show the dust-collecting hood and openings in the backwall of the cupstone wheel for directing streams of air into the dust-collecting chamber;

FIG. 3 is a bottom plan view of the grinding implement illustrated in FIGS. 1 and 2 to show the arrangement of the holes in the backwall of the cupstone wheel for directing dust into the collection chamber; and

FIG. 4 is a side elevational view partly in section of a grinding implement having a cupstone grinding wheel of right cylindrical form.

Referring now to the drawing, the novel features of the present invention are shown applied to a manually operated grinding tool comprising a frame 10 in which a depending shaft 11 is rotatably mounted and which, in turn, mounts a cupstone grinding wheel 12 at its lower end. The frame 10 encloses a driving motor 13 which may be of any suitable type. In the illustrated embodiment, the motor 13 is illustrated as an air-driven turbine wheel connected to the upper end of shaft 11 and supplied with air under pressure through an air connection 14 and a nozzle 15 constituting one of the handles for holding the implement. However, it will be understood that the motor 13 may be electrically or hydraulically operated. A similar handle 16 projects radially from the casing 10 to adapt the implement to be held by the operator in his two hands.

The cupstone grinding wheel 12 shown in FIGS. 1 to 3 has a frustoconical shape and comprises a continuous backwall 17 and peripheral sidewall 18 and forming a hollow center 19. The backwall 17 has a reinforcing plate 20 formed as an integral part of the wall and a central insert 21 having a tapped bushing 22 for receiving the lower threaded end 23 of the shaft 11. Shaft 11 has a stepped shoulder 24 against which the reinforcing plate 20 engages to limit the relative movement of the cupstone wheel along the shaft 11. The outer end of the sidewall 18 provides a flat annular grinding surface 25 and the junction of this surface with the conical sidewall forms an annular peripheral cutting edge 26. As thus far described, the grinding implement is identical with those in common use.

In accordance with the present invention, an improved dust-collecting arrangement is provided which insures the removal of ground dust to eliminate any health hazard but does not interfere with the operation of the implement. As shown most clearly in FIG. 2, the dust collector comprises a hood 30 having a flat backwall 31 which abuts and is attached to the bottom of the frame 10 by means of screws 32. The hood 30 has a depending skirt 33 of the same general frustoconical shape as the shape of the cupstone wheel 12, but of slightly greater diameter, so that the lower edge portion 33a of the skirt 33 overlies the upper peripheral edge of the reinforcing plate 20 of the wheel 12 only, to provide an annular space 34 therebetween. The hood 30 and plate 20 of the cupstone wheel 12 form a dust-collecting chamber 35 therebetween which is partially evacuated through a flexible suction line 36 to produce a flow of air through the annular space 34. In addition, the backwall 17 of the cupstone wheel 12 has a series of holes 40 extending therethrough and through the reinforcing plate 20 to provide additional passages through which air-laden dust may flow into the dust-collecting chamber 35. By providing the additional passages 40 through the backwall 17 of wheel 12 for dust-laden air, the lower edge portion 33a of the skirt 33 of the hood 30 may be located a sufficient distance above the edge 26 of the cupstone wheel 12 to permit the edge to be used to undercut projections or grind a flat surface 41 on the casting 42, or to adapt the conical side 43 of the wheel to engage an edge 44 of the casting and to adapt the implement as a whole to be tilted to the position shown in FIG. 1.

In operation the grinding implement is used in the usual way by placing the flat annular surface 25 against a flat surface 41 of a part to be ground, or by tilting the implement in the manner illustrated in FIG. 1 to use the laterally projecting edge 26 or inclined side 43 of the wheel for grinding. Any dust produced by such grinding is drawn into the annular curtain of air flowing up the side of the wheel into the annular passage 34, or is caught in a stream of air flowing along the bottom surface 25 and into the open center 19 of the cupstone 12 and then through the passages 40 into the dust-collecting chamber 35. In both cases the dust is withdrawn through the suction line 36 to a collection unit where the dust is separated from the air. It has been found in practice that the central passages 40 in the backwall 17 of the grinding wheel 12 so supplement the removal of dust through the annular passage 34 adjacent the top of the wheel as to produce as good or even better dust removal than the prior constructions having hoods extending to a position adjacent the bottom of the wheel.

FIG. 4 illustrates a modified construction of cupstone wheel 12a in the form of a right cylinder. The wheel 12a in FIG. 4 has a continuous backwall 17a and sidewall 18a to form the open center 19a. The backwall 17a is also provided with the spaced passages 40a the same as in the frustoconical wheel illustrated in FIGS. 1 and 2. However, the outer periphery of the sidewall 18a constitutes a cylindrical surface, instead of a frustoconical surface, but the skirt 33a depending from the hood 30a need only extend down a short distance below the top of the backwall 17a to insure adequate dust removal, due to the additional passages 40a in the backwall of the wheel.

It will now be observed that the present invention provides an improved dust-collecting arrangement for a manually operated cupstone grinding implement which is more facile and efficient in operation. It will also be observed that the present invention provides an improved dust-collecting arrangement for a cupstone wheel which does not interfere with the use of the edge of the tool during operation. It will still further be observed that the present invention provides an improved dust collector for a cupstone grinding wheel which is of extremely simple and compact construction, adapted for economical manufacture, and one which is reliable in operation.

While two embodiments of the invention are herein illustrated and described, it will be understood that further modifications may be made in the construction and arrangement of elements without departure from the spirit or scope of the invention. For example, the top of the reinforcing plate of the rotating cupstone may have vanes formed thereon to augment the vacuum-producing means and increase the velocity of air flow to the dust-collecting chamber. Therefore, without limitation in this respect, the invention is defined by the following claims:

Claims

I claim:

1. A grinding tool having a cup-shaped grinding stone with a continuous back and sidewalls to form a hollow center, a motor connected to rotate the cupstone wheel, a hood overlying the backwall of the cupstone wheel in spaced relation thereto to form a chamber therebetween, said hood having a depending skirt overlying the outer periphery of the backwall of the cupstone wheel in spaced relation thereto to form an annular passage therebetween, the backwall of the cupstone wheel having a plurality of unobstructed openings therein between its hollow center and the chamber, and means for producing a partial vacuum in the chamber to cause dust produced by the cupstone wheel to flow into the dust-collecting chamber through the annular passage around the periphery of the cupstone and the openings from the hollow center.

2. A grinding tool in accordance with claim 1 comprising a frame, a motor mounted on the frame and having a shaft with a threaded end, the cupstone wheel having a tapped fitting, the hood being supported on the frame in spaced relation to the backwall of the cupstone and having a depending skirt overlying the upper periphery of the cupstone in spaced relation thereto, and the means for producing a partial vacuum comprising a suction line and a source of partial vacuum.

3. A grinding tool in accordance with claim 1 in which the cupstone has an outer periphery in the form of a truncated cone, and the skirt of the hood depending to overly the top of the sidewall of the cupstone for a short distance only so that the angular corner at the bottom of the cupstone projects outwardly beyond the skirt whereby to prevent the depending skirt from interfering with the use of the corner edge of the stone.

4. A grinding tool in accordance with claim 1 in which the cupstone has an outer periphery in the form of a right cylinder, the depending skirt of the hood overlapping the top of the sidewall of the cupstone for a short distance only so that the angular corner at the bottom of the cupstone can be tilted to engage the surface of a workpiece without interference by the depending skirt of the hood.

5. A grinding tool comprising, in combination, a frustoconical grinding wheel having relatively small diameter and a relatively large diameter end surfaces, a motor connected to rotate said wheel, a hood positioned adjacent to said small diameter surface to form a chamber therebetween, said hood having a depending skirt extending a short distance only along the conical surface of said wheel and spaced therefrom to form an annular passage, and means for producing a partial vacuum in said chamber to cause dust produced by the grinding action of said wheel to flow through said annular passage into said chamber.

6. A grinding tool according to claim 5 wherein the diameter of said large diameter surface is greater than the diameter of the lower periphery of said skirt to prevent said hood from interfering with usage of the peripheral portions of said wheel near said large diameter surface.

7. A grinding tool comprising, in combination, a frustoconical cupstone grinding wheel having a continuous back and sidewalls cooperating to define a central cavity therein, a motor connected to rotate said wheel, a hood positioned adjacent to said backwall to form a chamber therebetween, said hood having a depending skirt that extends a short distance only along the conical surface of said grinding wheel, a plurality of passages extending through said backwall from said cavity to said chamber and means for producing a partial vacuum in said chamber to cause dust produced by the grinding action of said wheel to flow through said passages into said chamber.

8. A grinding wheel according to claim 7 wherein the maximum diameter of said wheel is greater than the maximum diameter of said skirt to prevent said hood from interfering with usage of the larger diameter portions of the conical surface of said wheel.