US 2789404 A
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Description (OCR text may contain errors)
April 1 957 R. E. DOWNING ETAL 2,789,404
DUST COLLECTING Filed Jan. 11, 1955 'INVENTORS 81;.73mzzn I BY 4 ATTORNEY United States Patent DUST COLLECTING Robert Ernest Downing, Pool, Redruth, Cornwall, and
Eric Basil James, Camborne, Cornwall, England, assignors to Holman Brothers Limited, Cornwall, England, a British company Application January 11, 1955, Serial No. 481,247
4 Claims. (Cl. 51-273 This invention relates to dust extractors for use with grinding wheels. In the grinding and fettling of castings or other metal parts large volumes of airborne dust are released into the atmosphere unless special precautions are taken. It is now generally accepted that certain constituents of this dust and particularly the finer and lighter particles, are highly injurious to the operator or others exposed to the dust for long periods.
According to the present invention we provide a dust extractor for a grinding wheel comprising a duct adapted to be mounted adjacent to and to extend around a part of the circumference of a grinding wheel, and having an open end adapted to be directed towards and located adjacent to the working portion the wheel forwardly of that portion in the direction of rotation of the wheel, a closed end, and an outlet for coupling to suction means, the duct being adapted between the open end and the closed end to be in communication with the circumferential surface of the wheel.
In order that the present invention may be well understood we will now describe, by way of example only one embodiment thereof with reference to the accompanying drawings in which:
Figure 1 is a cross section of a grinding wheel guard fitted to such a wheel and incorporating a dust extractor, and,
Figure 2 is a diagrammatic view of a suction apparatus for coupling to the dust extractor.
Referring to Figure l, a grinding wheel 1 mounted upon a spindle 2 is shown with a part of its circumferential surface in contact with a work piece 3, the wheel being driven to rotate clockwise as viewed in Figure 1, i. e. in the direction of the arrow.
The grinding wheel is provided with a guard 4, which has side walls 5, carried by a casing which supports the spindle 2 in known manner, and a circumferential wall 6.
Extending around a part of the wall 6 is a duct 7 defined by said wall 6, an outer wall 8 and two side walls of which one 9, can be seen in Figure 1. The duct 7 has one end closed, as at 10 by the outer wall 8 and an open end 11 directed towards and adjacent to the working portion of the circumferential surface of the wheel and on the forward side of the working portion in the direction of rotation of the wheel.
The duct 7 is in communication with the circumferential surface of the wheel by means of slots 12, 13. These slots are set obliquely in the wall 6 so that particles which are thrown forwardly at the working portion of the wheel and which tend to follow the circumference thereof but to be thrown outwardly may pass into the duct. This action is assisted by lips 16, 17 on the trailing side of each slot and extending inwardly from the duct.
The duct 7 has a suction outlet 14 which is adapted to be coupled to suction means such as that to be described with reference to Figure 2.
The open end 11 is provided with a flange 15 extending inwardly from the outer wall 8 and obliquely towards the "ice wall 6 in the direction of rotation. This flange restricts the opening and increases the suction elfect at that point.
In operation heavier particles will be thrown forward in a direction tangential to the wheel at the point of contact with the work piece while finer and more dangerous particles will be'thrown forwardly but will tend to follow the surface of the wheel. These finer particles enter the open end 11 of the duct 7 assisted by the suction means, whilst other particles will pass between the 'surface of the wheel and the wall 6. These latter particles, tending to move away from the wheel pass into the duct 7 through the slots 12 and 13 which operate especially when wear reduces wheel diameter. The particles which enter the duct pass out through the suction outlet and may be disposed of in any desired manner.
It is to be understood that the above described embodiment may be modified without departing from the scope of the invention. Thus the duct 7 may extend the length of the wall 6 if desired and furthermore if desired a compressed air outlet may be disposed adjacent the closed end of the duct on the side remote from the duct, and be disposed to direct a stripping jet of compressed air in the direction opposite to the direction of rotation and between the circumferential surface of the wheel and the inner wall of the duct, to prevent the escape of any particles not picked up by the duct and to form a seal between the duct and the wheel. Where such a jet is provided a slot is preferably located adjacent the end wall of the duct.
Referring now to Figure 2 the suction means may be operated by exhaust from a grinding wheel driving motor or other available gas under pressure. In this embodiment the suction means are operated by a driving motor exhaust from which a forcing nozzle 20 extends into a chamber 21 to which is connected a suction inlet 22 of diameter E adapted for coupling to the suction outlet 14 of the dust extractor duct. Extending from chamber 21 is a Venturi outlet 23 in the form shown and open to atmosphere at 24. We have found that to obtain maximum vacuum consistent with minimum exhaust pressure on the machine the dimensions of the suction means parts should be as follows:
Area B=2A Length C=greater than 6 (diameter of area B) Length D=greater than 2/ 3C It is intended that the dust extractor described above should be adapted to operate automatically and continuously while the grinding wheel is in use, the use of the extractor not being left to the discretion of the operator.
To dispose of the dust extracted from the hood we prefer to interpose between the hood and eductor a dust collector comprising a small cyclone and terminal cloth filter. This device is under vacuum at all times when the grinder is in operation, thereby precluding the possibility of harmful dust particles escaping to the atmosphere from this source.
The invention claimed is:
1. A dust extractor for a grinding wheel comprising a duct including means defining a suction mouth directed towards and positioned closely in front of the working portion of the wheel, an arcuate inner wall extending around and close to a part of the circumference of the wheel from the suction mouth, means defining holes in the inner wall facing the circumference of the wheel, dust stripping plates at said holes projecting inwardly from said inner wall towards the wheel, and an outlet for said duct for connection to a source of suction.
2. A dust extractor as claimed in claim 1 in which the duct is closed in except for the suction mouth, the holes in the inner walls and the outlet connection.
3. A dust extractor as claimed in claim 1 in which the infi'erkwall aextende aronndazthecircumference' fiffhe fi'rheel beyond the end of the duct lemotehfrqm 1he,.suc tion mouth in the form of a guard for the wheel.
4. A dust extractor as claimed in claim 1 in which each ;du'stt-stxzipping'j=:p1ate' comprises: an intcg-Ealjptdjecling gpor- .tionmfiihe; inner-Walli situated at-ethe' reansedgeiofi cneeof flhcdzolesuin-the innerwall: and bent=inward1y .=:t0wards the wheel.
Refetences fiited: inlhe file .0152 this patent UNITED STA'EESPATENTS 3790,9 43 Weber Mayi30, 1905 '4 Hawes Q'Iune' 2,
,Plant May v17, 1 Morris June 30, Segui June 6, Bagshaw Oct. 7, Walpole Apr. 13, Reader May 8, Fisher, May 7,
FQREIGN PATENTS SWitzr-lafid 'N,ov.- ,15, Germany Aug. 3,