US3008274A - Blasting machine - Google Patents

Description

Nov. 14., 1961 w. WELTER 3,008,274

BLASTING MACHINE Filed March 18, 1959 5 Sheets-Sheet 1 INVENTOR Willy Welter ATTORNEY! Nov. 14, 1961 w. WELTER BLASTING MACHINE 5 Sheets-Sheet 2 Filed March 18, 1959 PIC-3.2

ATTORNEYJ' Nov. 14, 1961 w. WELTER 3,008,274

BLASTING MACHINE Filed March 18, 1959 5 Sheets-Sheet 3 InventQr Willy W'elter M,MP&

Nov. 14, 1961 w. WELTER BLASTING MACHINE 5 Sheets-Sheet 4 Filed March 18, 1959 Fig. 6

Inventor Willy- Welter fidhr, M,

ttorneys Nov. 14, 1961 w. WELTER BLASTING MACHINE 5 Sheets-Sheet 5 Filed March 18, 1959 Fig. 7

Inventor Willy Welter Altornevs United States Patent O 3,008,274 BLASTING MACHINE Willy Welter, Schaifhausen-Buchtalen, Switzerland, as-

signor, by mesne assignments, to Bell Intercontinental Corporation, South Bend, Ind., a corporation of Delaware Filed Mar. 18, 1959, Ser. No. 800,250

6 Claims. (Cl. 51-13) particularly to the treatment of parts formed of plastic material and the like. 7

Whereas machines have been previously designed for blasting plastic parts, they have heretofore operated according to conventional processes and usually employ bucket elevators or the like for conveying the blasting medium. Furthermore, centrifugal blasting machines designed for sand and metallic blasting media have been provided with pneumatic conveyor devices for the blasting medium. The blasting medium and are blown by a blower-impeller into a large apparatus separating the air from the blasting medium. The blasting medium is then conveyed mechanically by means of a trough to impeller blades fixed to the exterior side of a blower wheel. Such systems have not been practical for economical reasons.

More specifically the invention is directed to a centrifugal blasting ,machine for the surface treatment of articles by a blasting medium in which machine the blasting medium is projected by the centrifugal action of rotating impeller means onto the article disposed within a chamber and the spent blasting medium is returned to the impeller means.

According to the invention, the machine includes a closed circuit passageway for astream of air, means producing a stream of air in said passageway, a duct form ing part of said passageway and having the up stream end adapted to receive blasting medium supplied by a storage of spent medium in said chamber, said duct conveying the blasting medium in the stream of air to said impeller means, and means intermediate the down stream end of the duct and the impeller means for diverting the stream of air away from the impeller means and into the closed circuit passageway while permitting the conveyed blasting medium to pass to the impeller means for projection of said medium onto the article in the chamber in the absence of said air stream.

The means producing the stream of air preferably comprises a blower having its suction inlet connected to the down stream end of the duct.

According to an important feature'of the invention, the blower and the impeller means form a compound rotatable structure including impeller blades disposed between radial side walls and forming compartments receiving the blasting medium through a central opening in the side Wall, facing the down stream end of the duct, and suction producing channel means on the outer side of said side wall, said channel means having an entrance portion in communication with said central opening, and the air stream diverting means is associated with said entrance portion and said central opening.

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2 An embodiment of'this invention is represented in the drawing in which:

FIG. 1 is a' vertical section through one form of machine of the invention;

FIG. 2 is a vertical section taken substantially along the plane of section line 2-2- in FIG. 1;

FIG. 3 is an enlarged verticalsection taken substantially along the plane of section line 33 in' FIG. 2;

FIG. 4 is a front view of the machine;

FIG. 5 is a plan view of the machine;

FIG. 6'is an enlarged scale section of the blower fan impeller portion of the machine, and

FIG.,7 is a side view of the impeller. As shown in the drawing herewith, the machine may comprise a blasting chamber 1 in which an endless conveyor belt 2 is passed over three rollers 3, 4 and 5 and a pair of spaced apart guide pulleys 6. The parts to be blasted are placed in the pocket formed by the belt 2 passing under the pulleys 6-6 and are caused to rotate by movement of the belt 2 in the blasting chamber 1. The media blasting device portion of the machine is provided with two chambers, an impeller housing 11 opening directly into the blasting chamber 1 and a spiral housing 12. The air guided into the channel 21 passes into the chamber 12 of the'impeller-fan and is then'directed therefrom by means of the duct D to the return duct 30.

The rotor of a combination blower fan and impeller 10 driven by a motor 13 comprises an impeller 14 of which one wall 15' is continuous, while the wall 16 on the inlet side is provided with openings 17 directly adjacent the rear edge of the impeller blades 18'. An edge 19 extends at the opening 17 from the front of each blade 18 in the direction of rotation of the blade and forms a guiding ledge for the conveyance of the blasting media. Communicating with these openings 17 is a guiding channel 21 of a blower fan 20. In'the embodiment shown, the guiding channel is bounded by a stationary bafile section 22. In lieu thereof, it would also be practicable to employ a rotary guiding channel. The diameter of the blower fan 20 must in all events exceed that of the impeller 14. T

Together with the/air, the blasting medium is carried into the impeller 14from the suction tube 31 through the pipe bend 32 and through the stationary length of suction tube 33. The air is passed from the suction tube 33, through the inner portions of the impeller 14 and hence, after deflection by almost laterally into the guiding channel 21 of the blower fan 20. The comparatively heavy particles of the blasting medium cannot undergo this deflection and they are accordingly separated, accelerated in the impeller 14 and caused to impinge on the parts to be treated in the blasting chamber 1. From the blasting chamber 1, the blasting medium passes through bores in the conveyor belt 2 into the intermediary chamber 40 separated from the blasting medium tank 50 by means of a flap 42 biased by a counterweight 41. The pressure exerted by the weight of the medium collected inthe chamber 40 operates to open the flap 42 over its entire length so that the medium falls therethrough and forms a fine screen 43. This screen 43 is deliberately kept as fine as possible so that dust may be separated therefrom.

A separate fan has its intake connected to the opening 54 in one side wall of the machine and air is passed through the opening 53 at the top. of the machine, see particularly FIGS. 1 and 3, and through a slit 2 on one side wall of the machine as is shown in FIG. 1. Immediately below the slit 52 is a sight glass 51, the purpose of the slit 52 being to pass clean air continuously past this sight glass 51 'so that the same remains free and clear, without having dust and foreign particles settle thereon, so that the interior of the machine may be observed through the sight glass 51 at all times.

The interior of the machine is divided into the dust separating section 55 by means of a wall lllllbelow the blasting chamber 1, as shown in FIG. 11, this wall being sloped as shown so as to feed the'spefnt blasting media toward the weighted ilap 42. The wall 100 eittendsbetween opposed side walls of the machine and therefore forms a shelf therewithin which'is sloped toward the flap 42. As previously stated, the purpose of the flap 42 is to permit the accumulated blasting medium 40 to be returned to the blasting medilun tank 511* in the form of a veil-like sheet. The dust separating section 55 is separated from the blasting medium tank 50 by means of the sloping wall 101 which, like the 100, extendsbetween opposite side walls of the machine so that these two wallsltlt), and 101, together with they wall portion 102 of the machine, form the chamber or seotion55. The wall 101, however, terminates short of the wall 100 to provide a relatively narrow passageway 103 leading from the blasting medium tank 50 to the dust separating sec tion 55. Since the intake opening 54 of the secondary air fan is in direct communication with the dust separating section or chamber 55, and shoe the inlets '52 and S3 for this secondary air communicate exterionly of the dust separating section 55, the secondary air is directed in stream-like fashion through the relatively narrow passageway 103 which leads into the section 55. How: ever, since the veil-like sheet 43 of the spent blasting medium is disposed closely adjacent the passageway and extends subctan-tially completely across from one side wall of the machine to the other, this secondary is passed through this veil-like sheet and smaller particles, that is unusable blasting medium or foreign materials, are picked up by this stream of air and drawn into the dust separating section'SS. Preferably the intake 54 is provided with some sort of filtering medium and the majority, of the dust will'settle to the bottom of the chamber 55 in he area designated by the reference character 56 and may be subsequently removed in any desired; fashion. 7

Itwill be appreciated that the return duct 30 and the suction tube 31 are of relatively small dimensions as compared with the width of the machine so that although the blastof secondary air is blocked by the duct 30 in a localized area, as shown in FIG. 1, it will be appreciated that on either side of this duct, the passageway 103 is open.

the passage103 is effected. Naturally, the reason why the secondary air system is operated continuously is to prevent dust and smaller usable particles from being passed back into the chamber 50 since the veil-like sheet 43 will continue to flow so long as sufiicient material 4% is present, see particularly FIG. 1.

It will be appreciated that the system for conveying the blasting medium from the tank portion 50 to the blasting chamber 1 is of a closed system. As previously stated, the housing 12 is in direct communication with the pressure return duct 30 so that air circulated by the combination blower fan and impeller is constrained to follow a path of movement upwardly through the suction line 30 and thence out through the blower fan 20 into the housing 12 and then directly back into the pressure return duct 30, both the suction duct 31 and the pressure duct 30 having communication at their lower extremities directly with the blasting medium tank.

The suction pipebend 32 of the combination impeller and blower fan 10 rams an important feature of the machine. This member collects the blasting medium at the upper periphery 3 lthereof and produces the desired and prescribed jet configuration in the blasting chamber 1. The blasting medium particles enter the impeller 14 at a. locally limited point and leave it after passing through the impeller channel at a certain geometrically predetermmined point. With the number of revolutions constant and was certain diameter of the impeller, the jet angle position isaccurately determined.

The con eyor rollers 3, 4 and 5 of the belt 2 are equipped with half-round sections arranged parallel to the axes of the rollers so that the blasting medium passing through the, conveyor belt 2 may freely circulate in the supportiugarea of -the rollers 3, 4 and 5 without ac cumulatingther'eon. In prior machines with similar conveyor installations for the parts to be treated, the bear- In practice, the machine will be stopped for the purpose 7 of changing the charge while the dust separating fan remains in continuous operation. In order to change the charge, the door 61, seen particularly in FIGS. 1,

and 2, is opened and naturally this will provide an additional air intake for the second air fan, which will increase the velocity of the air. blast through the passage 103. This velocity increase of the secondary air, were.

cooperates with the upper extremity 105 of wall to form a passageway 60 which is opened to the atmosphere when door 61is opened. Since this passageway is closely adjacent the intake 54 for the secondary air fan, no increase in velocity of the stream of passing through ings of the conveyor guide rollers corresponding to the conveyor rollers ,3, 4 and 5 have been arranged outside the machine, thereby causing sealing difficulties. To overcome such difiiculties, the bearings of the displaceable conveyor rollers 4 arranged to adjust the tension of the conveyor belt 2 have been arranged in'the interior of the machine of the present invention. With such a design, the entire machine can be made air tight so that the proper pressures will build up auomatlcally in the various compartments. At the end of the suction tube 31 and the pressure duct 30 in the blasting medium tank 50, a hydrodynamically designed nozzle of known construction is advantageously provided.

The present invention is characterized by the simplicity of its design. No addti'onal mobile members subject to wear and tear need be provided for conveying the blasting medium. The machine is equipped with only a few bearings and lubricating points. The machine automatically adjusts to the proper operating pressure.

' What is claimed is:

l. A blasting machine for surface treatment of work pieces by blasting media, an upright housing provided in the upper region thereof with a chamber accommodating work pieces to be treated, the lower region of said housing providing a blasting medium tank, a suction duct having its lower extremity open and communicating with said blasting medium tank, a pressure return duct surrounding said suction duct and having its lower extremity opening intothe blasting medium tank, a combination impeller and fan carried by said machine above said work piece chamber, said impeller and fan being mounted for rotation about a substantially horizontal axis and said suction duct being connected to said combined impeller and .fan to discharge thereinto substantially axially thereof,

said fan being surrounded by a housing and said housing being directly connected to said pressure return duct, and

said impeller being located immediately adjacent said fan but downstream ofthe path of air movement within said suction duct and having a housing surrounding the same 4 provided with a discharge directed into said work piece chamber, whereby blasting media conveyed by the air stream moving in said suction duct is discharged into the region of said impeller whereas the entraining air is constrained to follow a path through said fan and its housing directly back to the pressure return duct and back into the blasting medium chamber.

2. A blasting machine for surface treatment of work pieces by blasting media, an upright housing provided in the upper region thereof with a chamber accommodating work pieces to be treated, the lower region of said housing providing a blasting medium tank, a suction duct having its lower extremity open and communicating with said blasting medium tank, a pressure return duct surrounding said suction duct and having its lower extremity opening into the blasting medium tank, a combination impeller and fan carried by said machine above said work piece chamber, said impeller and fan being mounted for rotation about a substantially horizontal axis and said suction duct being connected to said combined impeller and fan to discharge thereinto substantially axially thereof, said fan being surrounded by a housing and said housing being directly connected to said pressure return duct, and said impeller being located immediately adjacent said fan but downstream of the path of air movement within said suction duct and having a housing surrounding the same provided with a discharge directed into said work piece chamber, whereby blasting media conveyed by the air stream moving in said suction duct is discharged into the region of said impeller whereas the entraining air is constrained to follow a path through said fan and its housing directly back to the pressure return duct and back into the blasting medium chamber, said housing being provided with a sloping wall extending between opposite side walls there of below said work piece chamber and terminating at its lower extremity above said blasting medium chamber, a counterweighted flap mounted within said chamber and normally urged toward the lower edge of said sloping wall whereby spent blasting media accumulating in the nip formed between said sloping wall and said flap will force said flap away from the lower edge of said sloping wall to permit the spent blasting media to flow therethrough to return to said blasting medium chamber in a veil-like sheet, a second wall in said housing extending between opposite sides thereof and having an upper edge terminating in closely spaced adjacency to the lower extremity of the first mentioned sloping wall so as to provide therebetween a passageway immediately adjacent said veillike sheet of spent blasting media, secondary air means for circulating air through said machine including an outlet directly communicating with the region within said housing provided between said walls and on one side of said veil-like sheet of spent blasting media, said housing having external openings therein for admission of secondary air into said blasting medium chamber on the opposite side of said veil-like sheet of spent blasting media whereby the secondary air passes from the blasting medium chamber through said veil-like sheet of spent blasting media and through said passageway to the exhaust opening to entrain non-usable smaller particles contained in said veil-like sheet into the area of the housing between the stated two walls thereof.

3. A blasting machine for surface treatment of work pieces by blasting media, said machine comprising a housing, a chamber accommodating work pieces to be treated disposed within the upper region of said housing, means for conveying and impelling blasting media from the lower extremity of said housing downwardly through said work piece chamber to treat work pieces therein and to fall therefrom by gravity downwardly from the work piece chamber, said housing having a sloping wall extending between opposite side walls thereof beneath said work piece chamber and said wall terminating at its lower extremity in a horizontally extending free edge portion, a counter-weighted flap mounted within said housing and having its lower edge portion normally urged into engagement with said horizontal lower edge of said wall whereby the sloping wall and the flap form a hopperlike crotch therebetween to retain an accumulation of spent blasting media, the weight of accumulated spent blasting media being such as to force said counterweighted flap away from the lower edge of said sloping wall to permit the spent blasting media to pass therebetween and return to the lower region of the housing in a veil-like sheet, a second wall extending between opposite side walls of said housing and having a free edge portion disposed closely adjacent the lower free edge portion of the first mentioned wall to define therewith a passageway immediately adjacent said veil-like sheet of spent blasting media, and means for forcing air through said veillike sheet of spent blasting media from one side of the second wall to the other to entrain from such veil-like sheet smaller, non-usable particles.

4. A blasting machine for surface treatment of work pieces by blasting media, said machine comprising a housing, a chamber accommodating Work pieces to be treated disposed within the upper region of said housing, means for conveying and impelling blasting media from the lower extremity of said housing downwardly through said work piece chamber to treat work pieces therein and to fall therefrom by gravity downwardly from the work piece chamber, said housing having a sloping wall extend ing between opposite side walls thereof beneath said work piece chamber and said wall terminating at its lower extremity in a horizontally extending free edge portion, a counter-weighted flap mounted within said housing and having its lower edge portion normally urged into engagement with said horizontal lower edge of said wall whereby the sloping wall and the flap form a hopperlike crotch therebetween to retain an accumulation of spent blasting media, the weight of accumulated spent blasting media being such as to force said counterweighted flap away from the lower edge of said slop-ing.

wall to permit the spent blasting media to pass therebetween and return to the lower region of the housing in a veil-like sheet, a second wall extending between opposite side Walls of said housing and having a free edge portion disposed closely adjacent the lower free edge portion of the first mentioned wall to define therewith a passageway immediately adjacent said veil-like sheet of spent blasting media, and means for forcing air through said veil-like sheet of spent blasting media from one side of the second wall to the other to entrain from such veil-like sheet smaller, non-usable particles, said means for conveying blasting media to said chamber including a substantially vertical suction duct having an open lower extremity disposed within the lower region of said housing and a pressure return duct surrounding said suction duct and having a lower extremity discharging at substantially the same level as the lower extremity of said suction duct, a combined air fan and impeller mounted above said chamber and said suction duct including a portion discharging thereinto substantially axially thereof, the fan portion of said combined fan and impeller having a housing surrounding the same communicated directly with said pressure return duct whereby air flow effected by said combined fan and impeller is constrained to follow a path through said suction duct, through the fan and its cooperative housing directly back into the pressure return duct whereas blasting media carried by such air stream is carried into the impeller, the impeller being located downstream of the air fiow with respect to said fan but immediately adjacent thereto, said impeller having a housing surrounding the same discharging directly into said work piece chamber.

5. The assembly as defined in and by claim 4, wherein that portion of the suction duct immediately adjacent the combined fan and impeller is of 'arcuate configuration whereby blasting media entrained within the air strearn flowing therein will tend to collect at the side of said portion of greatest radius of curvature to localize the stream of blasting media thus being conveyed for discharging to said impeller in :localized fashion.

6. The assembly as defined in and by claim 5, wherein means is provided in said housing for collecting spent blasting media in a region Spaced vertically above the lower extremities of said pressure and suction ducts and for permitting such accumulated spent blasting media to fall by gravity back into the lower region of said housing in a 'veil-like sheet, and means for passing air through 8 7 said veil-like .sheet to entrain smaller, non-usable particles and carry them to a point isolated from such lower region of the housing. I I

References Cited in the file of this patent UNITED STATES PATENTS 2,286,754 Minich June 16, 1942 2,357,599 NIOtt Sept. 5, 1944 ,422,786 Keefer June 24, 1947 2,424,955 Potter July 29, 1947

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