US2429742A

US2429742A - Treating surfaces of workpieces with abrasives

Info

Publication number: US2429742A
Application number: US558425A
Authority: US
Inventors: Kenneth H Barnes
Original assignee: Wheelabrator Corp
Current assignee: Wheelabrator Corp
Priority date: 1944-10-12
Filing date: 1944-10-12
Publication date: 1947-10-28
Anticipated expiration: 1964-10-28

Description

1947- K. H. BARNES 2,429,742 TREATING SURFACES 0F woaxPIEcBs IITH ABRASIVBS Filed Oct. 12, 1944 2 Shoots-Shoot. 1

Fl9.l

I INVENTOR.

Oct. 28, 1947. K. H. B-ARNES TREATING SURFACES OF 'ORKPIECBS WITH ABRASIVES med Oct. 12, 1944 2 Sheets-Sheet 2 FIO.

Y INVENTOR.

#aBmMM M /(M m ATTOQ I'Y Patented Oct. '28, 1947 TREATING SURFACES OF WORKPIECES WITH ABRASIVES I Kenneth H. Barnes, Mishawaka, Ind., assignor to American Wheelabrator & Equipment Corporation, a corporation of Delaware Application October 12, 1944, Serial No. 558,425 (01. 51-9) 2 Claims. 1 This invention relates to a method and device for the treatment of surfaces of work pieces.

The invention provides a method and device for treating a surface to produce a diffused smooth appearance, for removing impurities from a surface without injury to the surface or alteration of close surface tolerances, for applying a finish to machined surfaces to increase their lubricant. retaining ability, for increasing the fatigue life of the treated parts and many other purposes.

According to theinvention a mixture, emulsion colloid, or suspension of a finely divided abrasive and a liquid is prepared and is fed onto the blades of a centrifugal throwing wheel driven at high speed. The bladesof the throwing wheel break up the stream of the mixture, emulsion colloid, or suspension into small particles, each particle consisting of liquid with abrasive suspended therein. The broken-up particles are accelerated directly by the wheel and are projected at high velocity in a fan-shape blast without the aid of a carrying or enveloping airjet or liquid jet, and strike the surface of the work piece where they perform the desired surface treating action. The stream of particles discharged from the centrifugal throwing wheel covers a large area of impact. The surface treating action of the particles is substantially uniform throughout that area, insuring an even treatment of parts at all points within a large area without formation of spots or focuses as are commonly formed where air jets or liquid jets are employed for projecting abrasive.

Work pieces to be treated may either remain fixed within the projected stream of particles for a predetermined period of time, or may be moved through the stream by suitable means, such as a conveyer belt, a turntable, a chain; or the like,

Various kinds of abrasives and liquids may be employed. The abrasive may be organic matter, such as pulverized husks or shells, or may be inorganic matter, such as emery, pumice, marble dust, silicon carbide and similar material and may vary in fineness from relatively coarse particles to extremely fine powder of the order of 2500 mesh. The liquid may be water or a nonoxidizing or corrosion retarding liquid such as kerosene, light oils, carbon tetrachloride, trichlorethylene or other liquids. The selection of the liquids is determined according to the materials treated and the particular action desired. For example, it is often advantageous to employ a liquid which is a solvent of impurities to be removed from the surface of the material.

The invention produces economically and at a 7 high rate of production, surface conditions which are not obtainable in any other way. For example, a velvety-smooth surface of extremely fine and only microscopically perceptible grain may be produced on aluminum parts without change of very close tolerances of the treated work piece. Aircraft engine parts, such as pistons, may be cleaned economically according to this method without wear or change in the dimensions of the treated parts.

These and other features, advantages, and objects will appear more fully from the detailed description which follows, accompanied by drawings showing for the purpose of illustration, a machine for practicing this invention.

The invention also consists in certain new and original features of construction, combination of parts, and steps of procedure, as hereinafter set forth and claimed.

Although the novel features, which are believed to be characteristic of this invention, will be particularly pointed out in the claims appended hereto, the invention itself, its objects and advantages, and the manner in which it may be carried out may be better understood by referring to the following detailed description taken in connection with the accompanying drawings forming a part thereof in which- Fig. l is a front elevation, partly in section of a machine for practicing this invention;

Fig. 2 is the side elevation, partly in section,

of a centrifugal throwing wheel of the machine, shown in Fig. 1 and Fig. 3 is an elevation view of the rotor of the throwing wheel, shown in Fig. 2, a section being taken on line 3-3 of Fig. 2.

The machine, shown in Fig. 1, comprises a cabinet l0 resting on a suitable base I l. A chamber l2 on the top of the cabinet ID houses a centrifugal throwing wheel 13 accessible through a cover l4 hinged at IS. The bottom of the'cabinet Ill may befunnel-shaped as shown at l6 and opens into a tank l1.

The cabinet Ill contains suitable means for supporting work pieces, such as a turntabl l8 accessible through a door l9.

The turntable I 8 has a central shaft 20 driven by suitable means.

The tank I! contains a charge of a mixture 2| consisting of a liquid and a finely divided abrasive. The abrasive is maintained in suspension in the liquid by a paddle wheel 22 on a through a conduit 25 equipped with a valve 28 for controlling the amount of mixture fed to the wheel l3.

Details of the centrifugal throwing wheel l3 are shown in Figs. 2 and 3. The wheel comprises a rotor'2l built up of parallel face plates, 28 and 29, held together by connecting posts for spacers 30. The face plates have radially extending grooves 3! adapted to receiv throwing blades 32 held in place by set screws 33. The rotor 21 has a hub 34 mounted on a drive shaft 35 supported in a bearing 36. The drive shaft 35 is connected to a suitable source of motive power, such as an electric motor, capable of driving the wheel at high speeds.

The inner ends of the throwing blades 32 are tapered as at 31, and define a central space 38 into which a tubular discharge cage 39 extends. The discharge cage isrotatably supported on a bracket 40. The interior space of the cage 39 communicates with the pressure duct 25 which leads to a coupling 4| in the bracket 40. The control cage has a discharge port 42 in its periphery through which liquid and abrasiv mixture is discharged in a predetermined direction against the inner ends of the throwing blades 32.

The direction of discharge from the wheel may be controlled by adjustment of the clock-dial position of the discharge port 42 of the cage 39. The adjusting mechanism comprises a hand wheel 43 on a shaft 44. The shaft 44 is mounted in a bearing 45 and carries at its outer end a spur gear 46 meshing with a further gear 41 integral with the hollow discharge cage 39. A rotation of the hand wheel 43 causes a rotation of the discharge cage 39 relatively to the supporting bracket 40 and an adjustment of the direction in which liquid mixture is issued through the discharge port 42 against the inner ends of the blades 32 of the wheel I 3.

Driven at high speeds and supplied with a mixture of abrasive and liquid, the throwing wheel l3 discharges a fan-shaped blast 48 of particles ordroplets (see Fig. 1) against the turntable carrying the parts to be treated.

The operation of the device is as follows:

The tank I! of the machine is filled with a mixture of a suitable liquid and a finely divided abrasive. Parts to be treated are placed on the turntable l8. The centrifugal throwing wheel I3 is brought up to operating speed and liquid mixture is admitted to the wheel by opening the valve 26. The paddle wheel 22 agitates the abrasive and liquid mixture, so that the mixture maintains the character of a uniform suspension. 1

The turntable 18 moves the parts to be treated slowly through the fan-shaped blast 48 discharged from the centrifugal throwing wheel. The surface treatment may be interrupted simply 4 by turning on the supply of abrasive and liquid mixture at the supply valve 28, whereupon-the parts on the turntable may be removed.

The rotation of the turntable may also be interrupted at will in order to discharge mixture against the parts while the parts are at rest.

The surface of the treated parts is comparable, in appearance and in mechanical properties to a honed surface. Impurities are removed without change in the close tolerance of the treated parts. This is a particular feature in reconditioning ma.- chine or engine parts, such as parts of aircraft engines.

The method is very economical and requires only a fraction of the time required for conventional honing.

Another feature of the invention is the uniform action of the blast over a large area, as distinct from methods and machines operating on the air-jet or liquid-jet principle, where the jets usually leave an objectionable track pattern on the treated surfaces.

A further feature of the invention is the unusually favorable ratio of amount of mixture discharged per unit of power consumed. The power required for discharging a given amount of mixture according to this invention is only a very small fraction of the power required in methods employing an air blast for accelerating. the particles of the mixture.

A further feature of the invention is the elimination of objectionable moving air masses which tend to form a shielding film, or cushion, on the surface to be treated through which the abrasive and liquid particles have to be driven. The result is a more eflicient treatment of the surface for a given amount of mixture discharged thereagainst.

It has been found that treatment of machine parts according to the invention increases fatigue life of the part considerably. This is probably due to the elimination and rounding out of sharp marks and crevices which, although only of microscopic magnitude, are found in practically all machined parts.

Obviously the advantages of the invention are not limited to the specific examples given, nor is the method limited to the use of the particular machine hereinbefore described. Various modifications, additions, omissions and substitutions may be made by persons skilled in the art without departure from the spirit and the teaching of this invention.

What is claimed is:

1. The method of surface treating, utilizing a centrifugal throwing wheel, which comprises forming a slurry in which finely divided solid blast particles are suspended in a carrying liquid, directionally discharging under pressure a stream of said slurry at a substantial velocity onto the inner ends of substantially radial blades of the centrifugal throwing wheel adjacent its axis, rotating said wheel to accelerate centrifugally the slurry received by the blades and to throw it as a controlled directional stream of uniformly dispersed liquid and solid mixture.

2. In 'a system for directionally throwing a slurry in which solid particles are-homogeneously suspended in a carrying liquid, a blasting wheel for directionally projecting the slurry, said wheel comprising a central portion, means for rotating the wheel, a plurality of bl des extending from said central portion to the o ter'periphery of the wheel, a stationary closed chamber within said central portion, said chamber having a discharge REFERENCES 'crrEn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Beeg Feb. 11, 1896 Perkins Aug. 28, 1934 Fritsche June 19, 1935 Minich Apr. 20, 1937 Gartner Sept. 9, 1941 Wieland Jan. 9, 1945 Grochoil Dec. 10, 1940 Hitchcock Mar. 8, 1927 Burroughs June 15, 1937 Smith May 12, 1936 Tirrell Oct. 17, 1939