US2763972A

US2763972A - Means for dust extraction and ventilation of grinding wheels

Info

Publication number: US2763972A
Application number: US342043A
Authority: US
Inventors: White William Holloran
Original assignee: British Cast Iron Research Association
Current assignee: British Cast Iron Research Association
Priority date: 1952-03-19
Filing date: 1953-03-13
Publication date: 1956-09-25
Anticipated expiration: 1973-09-25

Description

Sept. 25, 1956 w. H. WHITE 2,763,972 MEANS FOR DUST EXTRACTION AND VENTILATION OF GRINDING WHEELS Filed March 13, 1953 3 Sheets-Sheet l INVE N TOR Wm M Houamq/v Wwrr Z; ATTORNEY Sept. 25, 1956 w. H. WHITE 2,763,972

MEANS FOR DUST EXTRACTION AND VENTILATION OF GRINDING WHEELS Filed March 1;, 1955 3 Sheets-Sheet INVENTOI? W/L L m /7 Ha LO RA N WH/TE i ATTORNE v 5M 1956 w. H. WHITE {763,972

MEANS FOR DUST EXTRACTION AND VENTILATION OF GRINDING WHEELS Filed March 13, 1953 3 Sheets-Sheet 3 IIVI/ENTOR WALL/AM? Mama/WW www.13-

@Lii ATTORNE v United States Patent MEANS FOR DUST EXTRACTION AND VENTI- LATION F GRINDING WHEELS 'William Holloran White, Redditch, Birmingham, England, assignor to The British Cast Iron Research Association, Alvechurch, Birmingham, England "This invention relates to improved grinders and more particularly to means for dust control in such machines.

In existing systems of dust control the greater portion of the grinding wheel is enclosed, where the grinder is of the pedestal type, partly in a cowl and partly in a collecting box upon which the cowl is mounted and through which the dust-laden air is drawn bv an extraction fan. Even when large volumes of air are rapidly drawn through the box or cowl in this way, however, the efficiency of dust extraction is not satisfactory, since the system fails to control the dust-laden air-streams generated by the revolution of the wheel and discharged at high velocity from the space between the top of the wheel and the cowl, and particularly the dust-laden air stream which moves with high velocity over the top of the work and up the operators body into his breathing zone.

The improved system of the present invention comprises dust controlling and collecting means enclosing the grinding wheel, except for a suflicient working surface, to a maximum of the wear down mark on the wheel. Surrounding the exposed portion of the wheel, i. e. across the top close to the wheel where it emerges from the cowl and vertically on each side close to the sides of the wheel,

;there are provided slot openings to a plurality of ducts through which high-velocity, low-volume streams of air are drawn by means of a fan or fans connected to or :situated in the ducts. In this way the exposed portion of 1the wheel is enclosed between curtains of rapidly moving air which are not penetrated by (i. e. are clear of) the currents of dust-laden air from the wheel and the grinding action. if desired, means may be provided whereby the direction in which the slot openings face can be varied, e. g. by rotation of appropriate portions of the ducts through a small angle, to suit the work in hand.

An independent extraction duct may withdrawn dustladen air from in front of the work rest, the duct being for example expanded into a hopper placed immediately in front of the work rest. This duct may, if desired, be carried through the lower portion of the collecting box, whilst remaining independent thereof.

An important feature of the invention is the provision of means, such as generally described hereinabove, for creating a curtain or curtains of moving air between the wheel and the breathing zone of the operator, the speed of the moving air being sufficient to intercept any dust clouds moving in the direction of the breathing zone. It will be apparent that this can effectively be achieved by creating a more or less horizontal curtain of moving air at a level somewhat above the level at which the wheel emerges from its cover (and hence well below the breathing Zone). The creation of a pair of vertical curtains, one on each side of the wheel, is of advantage in conjunction with the horizontal curtain.

The uppermost duct which produces the horizontal curtain of air above the wheel may be divided to form two or more divergent sub-branches, with slots facing inwardly, which, with a breast-piece connecting their If desired, the breast-piece an inwardly facing slot. 7

drawn through the collecting two ends form a triangle. may also be provided with Optionally air may be box and hood.

It is of advantage that the collecting box should be of large volume and in the preferred form of the inventic-n it is large enough to contain one or more grinding wheels and the driving mechanism suitably mounted and enclosed. It may indeed be a large chamber through a slot or slots in the front wall of which suficient working surface of the grinding wheel or wheels protrude, suitable work rests being provided. In .such a construction the upper part of the chamber takes the place of the cowl or cowls. The large volume ensures that the air in the chamber or collecting box shall be relatively quiescent so that the dust can settle. An outlet pipe at the back of the chamber or box may be connected to a chimney and/or may contain an exhaust fan.

In all forms of the invention the work rest is preferably slotted or perforated, and may be seated on a suitable extension of the collecting box.

Some embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 shows in perspective a pedestal grinder provided with means for creating curtains of high-velocity air between the grinding wheel and the operator.

Fig. 2 shows a variant in which a breast piece is provided.

Fig. 3 shows in perspective a two-wheel grinding unit provided with means for creating air curtains as in Figures l and 2, but housed in a large collecting box or chamber.

Fig. 1 shows a grinding wheel 1 partly enclosed in a cowl 2 over a collecting box 3 through which passes a lower exhaust duct 4, ending in a hopper 5 extending the full width of the collecting box 3 and from the front of the latter to the work-rest 6. An upper exhaust duct 7 is provided with two side-branches, 8, 9, having

vertical slots

10, 11. The upper duct 7 also serves a pair of horizontal sub-branches 12, 13, provided with slotsl4, 15. As shown diagrammatically,

ducts

4 and 7 are both connected to the intake of a single exhaust fan indicated at F.

In Fig. 2, in which corresponding parts bear the same numbers as in Fig. 1, the upper duct serves two

subbranches

16, 17, provided with

slots

18, 19 on their inner faces, and joined at their ends by a breast piece 20, some 8 inches in front of the grinding surface of the wheel 1. The breast piece 20 will usually be concave when viewed from the operators position. In the particular arrangement shown, each of

ducts

4 and 7 is connected to a separate exhaust fan F.

In each case it is convenient to have

flexible connecting tubes

21, 22 to connect the

vertical pieces

8, 9 to the branch pipes of the duct 7; this permits of the adjustment of the sub-branches (12, 13 in Fig. l; 16, 17 in Fig. 2) to any desired angle with the horizontal.

Fig. 3 shows a pair of

grinding wheels

31, 31, mounted on a countershaft 32 rotated by an electric motor 33. The whole, exceptfor a suflicient portion of the wheels for working purposes, is enclosed in a large exhaust chamber 34 provided with an exit pipe 35 which contains an exhaust fan 36 (or is connected to a suitable chimney) for the maintenance of reduced pressure in the chamber 34. The work rests 37, 37 are supported on

extensions

38, 38 of the exhaust chamber 34 which encloses lower portions of the

wheels

31, 31, without, however, approaching them closely. Close to each wheel where it emerges from the chamber 34 is an air-extracting duct 39 provided with a fan 40 and opening into the chamber 34. The rear opening of the duct 39 directs a high-velocl 3 ity, low-volume stream of air towards the periphery of the when 31 within the crnainiber 34. The "front portion of duct 39 lying outside the chamber '34 carries a slotshaped nozzle 41 rather longerthan the thickness of the wheel 31, and is provided with two branches '43 disposed yertically'on either side of the wheel 31. These branches "43 have slot-shaped lengthwise openings 44 which create side curtains of high-velocity, low-volume air-streams, whilst a similar horizontal air-stream created by nozzle 41 completes the protection of the operator.

If desired, ducts with funnel inlets, situated similarly to duct lin Figs. 1 and 2, may be added to the unit shown in Fig. 3. Such ducts may be provided with exhaust fans and/ or maylead into the exhaust chamber 34. 'A'fsingleexhaust chamber of sudicient'sizecan serve for any desired number of grinding uni-ts. It may be external to the grinding room itself, with one wall in cornmonprovided with panelswhich can be replaced with 2-'wheel grinding units as required. Each unit may have its owndriving' motor, or may be driven by belting from a common shaft within the chamber.

In all forms'of the invention described a high-velocity air curtain is created between the dust'generation point and'the breathing levelof the operator, and ihthe form of the invention illustratedin Fig. 2 the body of the operator, pressed againstthe breast-piece Zih'effectively seals off the dust-contaminated area.

In operation the heavy dustis thrown by the'a'cticn of thewhe'el and the peripheral air streams into the collectingbbx'where the velocityfd'ecreases and allows the dust to settlejby"'gravitat-ion, and the light air-borne dust is ollected'by the system of extraction air curtains. As is evident, the separate air-exhausting system which 'provides these air curtains is isolated on the low pressure side from thesp'ace within the enclosing means (e. g. cowl) by which the wheel is surrounded.

I claim:

' 1. In combination a grinding wheel housed, except for a sufiicien-t working portion, in a relatively large chamber, means for maintaining the air in the chamber at less than atmospheric pressure, a work rest, means for withdrawing dust-laden air from the vicinity of the work rest, and a plurality 'of air-extracting duets with slot-shaped intake openings so disposed as to create curtains of high-velocity, lowvolume air currents above and on each side of the exposed portion of the wheel, the said'ducts being arranged to discharge the dust-laden air into the said chamber.- I V p Incombination a grinding wheel housed, except for a'sufficientworking portion, in a relatively large chamber, means for maintaining the air in the chamber at less than atmospheric pressure, a work rest, means for withdrawing:dust-laden air from the vicinity of the work rest, and a plurality ofYair-extracting ducts with slotshape'd intake openings so disposed as to' create curtains of"hi'gh-velocity, low-volume air currentsabove andon each side of the exposed portioniof the wheel, the said ducts being arranged to discharge the dust-laden air into the said chamber in-the-"dire'c'tion of the unexposed portion of the Wheel 7 3; In combination, a grinding wheebmounted upon a collecting box' and otherwise surrounded,;'except' for"a sufiic'ient working surface, by a cowl, a work res-t, means for withdrawingdust-laden air from the vicinity of the 'work rest through said cowl and aplurality of air-extract- 'ing ducts isolated from the space within'th'ecowl and each 'h-aving a"slot shaped intakeope'ning, at least one of said openings being disposed horizontally and sufficiently above/the pointwhere the wheel emerges from the cowl to be clear'of'the highvelo'city layer of air carried round the wheel while-at least two others of said openings are disposed vertically one on each side-of the exposed part of-the wheel periphery so as to create,-respectively,

at least one substantially horizontal curtain of high-veloc- .ity' low-volume air cu'rrent'at a short distance above the level at which the wheel emerges from its cover, and a "suistannany vertical similar "curtain 'on each side of the emergent wheel.

4. In combination a grinding wheel mounted upon a collecting box and otherwise surrounded, except for a sufficient working surface, b'ya cowl, a work rest, a high speed air stream generator, and a plurality 0f extraction ducts extending from the low pressure side of the said generator and each terminating in a slot-shaped opening located clearer the layer of high speed air-carried round by the wheel and so "disposed as to create at least one substantially horizontal curtain bf high-velocity, low volume 'air cur'rent at a short distance above the'level at which the wheel emerges from its cowl, and a substan- 'tially verti'cal'similar curtain on each side ofthe emergent wheel, the dust-laden air drawn through the ducts being discharged behind the emergent portion of the wheel.

5. A pedestal grinder comprising a casing, a grinding wheel'lbc ated in the top 'of' said casing, an opening in "the front wall 'of's'aid casing through which a portion of the periphery 'ofs'aid wheel protrudes, a'worlc rest locatedad jaeentthe' exposed portienof the wheel periphery, a high speed air flowgenerator isolated, on at least its low'pressur'e'side, from the space within the casing, and ducting leading from thesaid low pressure side of the generator to first elongated dust intakeepening'in'front of and below the work rest a second elongated dust intake OpeningeXtending parallel to thewhecl axis and located adjacent the point cfemergence of the wheel from the casing "but clear of'the layer of high velocity air carried round"by the'whcel, saidsecond intake opening serving to create'a hfgh'veiocity' low volume curtain of airbetween the operator and the'wheel.

6. in combination, a suitably mounted'grinding wheel sur'i'eun'ded, except "for a suihcient working surface, by apprepriate'enclosingmeans, an air-exhausting system 'Cbmprisihg-aduct on the lowpressure side of said system isolated from the space within said enclosing means, Said" duct having at least one elongated air intake opening disposed generally horizontally a short distance above the uppermost part'of said working surface of the wheel, and means for withdrawing air through said intake opening to establisha high-velocitylaw-volume curtain ofair ex- '-ternally-of said enc'losingrneans between the eperators rea'thi ngfzone and said 'whecl and clear of the layer-0f h'i'gh 'yelccity air' carried round by the wheel.

5 7&Thect3mbination set fcrth'in claim 6 wherein said air-exhaust" system"ttir'ther'includes ducts isolated from the spacawithin said enclosing means on either side of the' exposed partof the Wheel having elongated air intake openings disposed substantially vertically so as to create a substantially veitical'curtain of high-velocity low-volnine air-current oneach side of the exposed part of the wheel.

'j-8.--The *eoii1bi1iatibn set forth in claim 6 which further ihclud'esseparate means" for witl'idrawing dust-laden air from a location adjac'ent said working surface.

9. The combination set forth in claim 6 which further includes a 'w'orlc rest and separate means for withdrawing dust-laden air-frem thevicinity of said work rest, said "exhaust duiztcomprising a'pairof convergent elongated air' intakememb'ers extending from the position of the I =operators' body to a point above the point-ofemergence of the wheel f-rcm'its enclosing means.

10. The method of dust extractionfor grinders'which comprises the establishment, between the exposed port-ion-of 'the'wheel periphery and the breathing zone of the operator, of a fast-moving low-volume air curtain having a lateral spread suflicient to trap particles of dust moving upwards between the operatorsbody andthe wheel, and physically isolated throughout its low pressure circuit from the chamber within which the shielded. part of the wheel is located.

lIJ'The'methOd of dust extraction for grinders which i comprises establishing; in the space between the exposed portion-of the'wheel periphery and'the operatorsbe'dy,

at least three high-velocity low-volume air curtains, each moving from the operator towards the wheel and each physically isolated throughout the low pressure portion of the total flow circuit from the chamber in which the shielded part of the wheel is housed, one of said curtains being established in a plane tangential to the wheel periphery and transversely between the wheel and the breathing zone of the operator, While two other curtains are established in generally vertical planes one on each side of the exposed portion of the wheel and of a height, 10

at the intake aperture, approximately equal to the height of the exposed portion of the wheel above the work-rest.

References Cited in the file of this patent UNITED STATES PATENTS 673,047 Dennis et a1 Apr. 30, 1901 6 Middleton Apr. 11, 1905 Mueller May 20, 1913 Power July 8, 1919 Segui June 6, 1933 McElevey Dec. 17, 1940 Bagshaw Oct. 7, 1941 Walpole Apr. 13, 1943 Harrison Mar. 7, 1950 FOREIGN PATENTS Italy Oct. 29, 1936 Great Britain Aug. 1, 1940