US1955465A

US1955465A - Apparatus for propelling gas carrying abrasive suspended material

Info

Publication number: US1955465A
Application number: US536427A
Authority: US
Inventors: Marcel A Lissman
Original assignee: International Precipitation Co
Current assignee: International Precipitation Co
Priority date: 1931-05-11
Filing date: 1931-05-11
Publication date: 1934-04-17
Anticipated expiration: 1951-04-17

Description

p 31934 M. A. LISSMAN APPARATUS FOR PROPELLING GAS CARRYING ABRASIVE SUSPENDED MATERIAL 1951 5 Sheets-Sheet 1 Filed May 11 INVENTQR. j faficelAjzssma Aprifi R7, 1934. M. A, ussMAN APPARATUS FOR PROPELLING GAS CARRYING ABRASIVE SUSPENDED MATERIAL Filed May 11, 1931 5 Sheets-Sheet 2 Aprili 17, 3934., A, LISSMAN Filed May 11, 1931 5 SheetsSheet 3 INVENTOR.

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M. LISSMAN 1,955,465 APPARATUS FOR PROPELLING GAS CARRYING ABRASIVE SUSPENDED MATERIAL Filed May 11, 1951 5 Sheets-Sheet 5 INVENTOR. m g

Patented! Apr. I17, W34

r ea res APPARATUS FOR IPRGPELUING GAS CARRY- ENG ABRASIVE SUSPENDED IM'IPIERIIAL Marcel A. lLissman, Aihambra, @alif., assignor to International lrecipitation {Jem ma Les Angelles, Calif a corporation at California Application May ill, 1931, Serial No. 536,42?!

12 Claims.

This invention relates to apparatus for blowing or propelling air or other gas carrying abrasive suspended material, such as cinders, sand or other angular particles of hard material. The apparatus is adapted, for example, for propelling combustion gases from a furnace or other combustion apparatus to a stack for the purpose of creating induced draft, such combustion gases ordinarily carrying cinders which tend to abrade or cut the blades of ordinary fans when used for this purpose. This abrasive or cutting action is particularly severe when the fan is required to create a large difference in pressure, necessitating high speed of the fan rotor.

The principal object of this invention is to prevent cutting or abrasion of the fan blades by abrasive materials carried in suspension in the gas. More specifically, it is an object of this invention to provide an apparatus in which suspended material, and particularly suspended material of suflicient size and weight to exert serious abrasive action, is separated from the incoming gas stream before the gas reaches the fan blades and is prevented from coming in contact with the fan blades.

A further object of the invention in its pre-- ferred embodiment is to provide for separation and collection of suspended material carried by the gas so that the apparatus is enabled to perform the function of adust collecter as well as a fan.

In the apparatus of this invention, the gas drawn inwardly from the inlet means toward the central portion 'of the fan is caused to pass with a whirling motion through a fan chamber which is disposed concentrically about the axis of rotation of the fan, and said chamber is axially extended at the inlet side of the fan and is of sufficient diameter to permit suspended material to be thrown by centrifugal force out of the whirling stream of infiowing gas before such gas reaches the fan blades. into the central portion of the fan chamber at a position axially removed from the fan, and at 5' least a portion of said chamber between said inlet means and said fan is of larger diameter than said inlet means, so as to permit this outward movement of suspended material to take place. A suitable gas outlet means is connected to the fan chamber at a position further removed from the axis of the fan than the position of communication of the inlet means, so that the gas forced outwardly by the fan blades is caused to pass with increased whirling velocity toward said outlet means and be discharged therethrough. Ac-

The inlet means opens cording to the preferred embodiment of this invention, the outlet means communicates with the fan chamber at the same side of the fan as the inlet means, and is, furthermore, preferably axially spaced from the fan, said position of communication of the outlet means being, for example, adjacent the same end as said inlet means and around said inlet means, or being axially between the inlet means and the fan but radially outside the prolongation of the inlet opening. Said gas inlet means is preferably provided with means for imparting to the gas entering therethrough a whirling motion about the axis of the fan chamber. However, satisfactory operation for certain purposes may be obtained without such whirling motion imparting means in the inlet means, due to the fact that the gas delivered into said chamber and passing toward the central portion of the fan is subjected to frictional action by the surrounding whirling stream of gas passing from the outer portion of the fan back to the outlet means, and the incoming gas is thus also set in whirling motion before it reaches the fan. In the latter case the outlet means preferably communicates with the fan chamber at the same end as the inlet means, and said fan chamber is made relatively long, so as to provide .5

a considerable length of concentric travel of the incoming gas stream and the outgoing gas stream and thus enable the desired whirling velocity to be imparted to this incoming stream by the frictional action of the outgoing whirling stream.

It is also preferable to provide the gas outlet means with means for substantially tangential discharge of gas therefrom so as to conserve the energy imparted to the gas and reduce the draft consumption in the apparatus itself.

When the apparatus is to function also as a dust collector, asin the preferred embodiment thereof, such apparatus is also provided with a circular deflector surrounding the opening from the fan chamber to the gas'outlet means, while the casing is so formed as to define an annular space surrounding said deflector to receive suspended material thrown outwardly by centrifugal force beyond the position of said deflector, and means are also provided for collecting material entering said receiving space.

The accompanying drawings illustrate embodiments of my invention and referring thereto Fig. 1 is a vertical section of a preferred form of apparatus embodying my invention and pro-- vided with means for separating and collecting suspended material removed from the gas stream by centrifugal action.

Figs. 2, 3 and 4 are transverse sections on line 2-2, 33 and 4-4 respectively, in Fig. 1.

Fig. 5 is a vertical section of another modified form of apparatus.

Fig. 6 is a section on line 6-6 in Fig. 5.

Fig. 7 is a vertical section of another modification of the invention.

Fig. 8 is a vertical section of another form of apparatus.

Figs. 9, 10 and 11 are horizontal sections on lines 99, 1010 and 11-l1 in Fig. 8.

Fig. 12 is a vertical section of the lower portion of another form of apparatus, the upper portion of which may be the same as shown in Fig. 8.

Figs. 13 and 14 are horizontal sections on lines 13-l3 and 1414 in Fig. 12.

Fig. 15 is a vertical section of another form of the invention, in which no means are provided for separately collecting the suspended material contained in the gas.

Figs. 16 and 17 are transverse sections on lines 16l6 and 17-17 respectively, in Fig. 15.

In the form of the invention shown in Figs. 1 to 4 inclusive, the axis of the apparatus is horizontal. Such apparatus comprises casing means defining a fan chamber 1 of circular cross-section having a horizontal axis indicated at HI-I, a centrifugal fan 2 mounted for rotation about said axis within and adjacent one end of said chamber, a circular gas inlet pipe 3 whose axis coincides with the axis H-H, opening into the central portion of chamber 1 at the end opposite said fan and at a position axially spaced therefrom, and gas outlet means 4 communicating with said chamber, at the same end as said inlet pipe, through a circular gas outlet opening 19 of somewhat greater diameter than the inlet pipe 3 and concentric therewith.

The apparatus is also shown as provided with means for imparting a whirling motion to the gas admitted through inlet pipe 3, such means being shown as comprising an entrance chamber 6 of involute cross-section as shown in Fig. 2 communicating with the inlet pipe 3 at one side as shown at 7 and connected so as to receive gas supplied through pipe 8 which opens substantially tangentially into the outer end of said in volute shaped entrance chamber. The inner end portion 3' of the inlet pipe 3 is preferably flared outwardly somewhat as shown in Fig. 1.

The fan 2 is shown as comprising a plurality of equally spaced radial blades 9 secured to arms 11 on a hub 12 secured to shaft 13. Said shaft extends out through the end wall 14 of chamber 1 and is provided with means for driving the same at suitable speed, such as electric motor 15. The blades 9 are preferably disposed in planes extending radially with respect to the axis HH so as to impart only centrifugal motion to the gas between said blades. The space between the fan blades at both the central and outer portions thereof is in free and unobstructed communication with the interior of chamber 1 at the left side of the fan.

The outlet means 4 preferably comprises an involute shaped casing providing a similarly shaped discharge chamber 18, communicating at one side through opening 19 aforesaid with the chamber 1 and communicating at the outer end of the involute shaped entrance chamber with a discharge pipe 21 for conducting gas away from the apparatus.

The chamber 1 is preferably of frusto-conical shape, the fan 2 being disposed adjacent the smaller end thereof and the inlet and outlet means opening into the larger end thereof. Said larger end of the chamber is shown as somewhat greater in diameter than the outlet opening 19, and a deflector plate 17 extends inwardly somewhat from said opening, so as to provide an annular space 23 surrounding said deflector plate for receiving material thrown by centrifugal force out of the main gas stream and beyond the inner end of said deflector plate, and an annular passage 1'7, between said deflector plate and inlet pipe 3, through which the gas passes to outlet opening 19. A material receptacle 25 is provided below and separated from the discharge chamber 18 and also extending beneath the lower portion of the annular space 23 and communicating therewith through an opening 26 in the bottom wall of chamber 1. Said receptacle is provided with a hopper-shaped bottom portion 2'7 and discharge spout 28 having a suitable discharge valve 29.

In the operation of this form of the invention the fan 2 is set in rapid rotation and the blades 9 impart a rotary and centrifugal motion to the gas therebetween, thus causing a relatively reduced pressure along the axis HH and a relatively increased pressure at the outer portion of chamber 1. Gas is thus drawn in through the involute shaped entrance chamber 6 which imparts a whirling motion to such gas. This whirling motion continues as the gas passes through inlet pipe 3 and through the central portion of chamber 1 to the fan, causing suspended material contained in such gas to be thrown outwardly by centrifugal force. During the passage of this incoming whirling gas from the inner end of inlet pipe 3 to the fan, suspended material contained therein is thrown out of this incoming gas, the proportion of suspended material thus separated from the gas before it reaches the fan depending upon the size and density of the suspended particles, but including in any event the major portion of the relatively coarse particles, such as cinders, coarse sand and the like, which would tend to seriously abrade the fan blades, so that when the gas enters the fan and is exposed to contact with such blades it is substantially free of suspended particles of a seriously abrasive character. The gas receives additional rotational energy from the blades 9 and passes from the outer portions of the fan blades back along the chamber 1 and around the incoming whirling gas, while still whirling in the same direction, and is discharged through the annular outlet passage 1'7 and discharge chamber 18 to pipe 21.

It will be understood that the fan is rotated in the same direction as the whirling motion imparted to the incoming gas by its tangential introduction into entrance chamber 6. Furthermore, the apparatus is preferably so designed that the rotary component of velocity of the incoming gas, when it reaches fan blades, is approximately equal to the rotary velocity of the fan blades, so as to permit the blades to engage the gas stream without shock.

The suspended material thrown out of the inner whirling stream of incoming gas is picked up by the outer whirling stream of outgoing gas which exerts further centrifugal force thereon, causing all or part of such material to be thrown outwardly beyond the position of the circular deflector plate 17 and enter the space 23. The whirling movement of the outgoing gas also imparts sufficient whirling movement to the gas in the annular space 23 to cause all suspended material entering such space to be carried around until it reaches the opening 26 at the lower portion thereof and such material then passes through such opening into receptacle 25, whence it may be removed either continually or from time to time through the discharge means 28.

It will be understood that the pressure in the ouer whirling gas stream moving from the fan toward the outlet passage 17 is somewhat greater than the pressure in the inner whirling stream of incoming gas, and there may, in general, be a slight recirculation of gas in the fan chamber due to a resulting inward movement of a small portion of the gas from the outer stream to the inner stream, but the centrifugal force on the gas in the outer stream, due to its high rotating velocity, is sulficient to prevent this recirculation from becoming so great as to seriously reduce the efilciency of the fan, and the velocity of any such inward movement as may occur is insufficient to prevent the desired outward movement of the heavier, more abrasive suspended particles.

The apparatus shown in Figs. and 6 is similar to that above described with the exception that the means for causing whirling motion of the gas entering the inlet passage 3a is shown as comprising a plurality of relatively fixed radially disposed helically shaped or inclined vanes 32 mounted in the entrance portion 3a of said inlet passage, a conical deflector 33 being preferably provided inside said vanes so as to spread the gas stream toward the outer walls of the inlet pipe and increase the whirling velocity of the gases. The other parts of the apparatus are substantially the same as above described and are similarly numbered and it will be understood that the operation is also substantially the same, the vanes 32 serving as before to impart whirling motion to the incoming gas so that the suspended material contained therein, or at least the coarser portion of such suspended material is thrown out of the. incoming whirling gas stream before it reaches the fan blades, and the fan being rotated, as before, in the same direction as the whirling motion imparted to the gas by the vanes 32.

In Fig. 7 I have shown a form of the invention in which the inlet pipe 3b is not provided with any means for imparting whirling motion to the incoming gas. The fan chamber 12) is in this case preferably of somewhat greater length than in the forms of the invention above described, for the purpose of causing the incoming gas to pass a greater distance axially of said chamber from the inlet pipe before reaching the fan 2b. In traveling this distance along the axis of the champer, the incoming gas stream is subject to frictional action of the surrounding stream of whirling gas passing from the fan to the outlet means, which causes the incoming gas to be also set in whirling motion, and the length of the chamber is in this case sufficient to provide the necessary angular acceleration of the incoming gas by the above described action and to also provide for throwing out of suspended particles from the incoming gas by centrifugal force after it has thus been caused to whirl. In this form of the invention the gas outlet means and the means for collection of separated suspended material are substantially the same as in the form of the invention shown in Figs. 1 to 4, and are similarly numbered.

The operation of this form of the invention is substantially the same as above described with the exception of the difierent manner in which the incoming gas is caused to whirl, as pointed out above.

The apparatus may also be mounted with the axis thereof extending in other directions than horizontal. For example, in Figs. 8 to 11 inclusive, there is shown a form of apparatus having a vertical axis. The chamber is, as before, of circular cross-section, having a vertical axis VV, and is preferably of frusto-conical shape. The fan is disposed within the smaller end of said chamber and is mounted for rotation-about the axis VV by suitable driving means, such as electric motor 160. The circular gas inlet pipe communicates with the central portion of chamber 10 adjacent the end opposite the fan, that is, adjacent the larger end of said chamber. As shown in the drawings, the chamber 10 is disposed with the larger end downwardly, and with the fan located at the upper portion and the inlet pipe communicating with the lower portion thereof, but it will be understood that this relationship may be reversed if desired. An involute shape entrance chamber 60 communicates with the outer end of inlet pipe 3c,and gas supply pipe 80 opens tangentially into the outer end of said entrance chamber. A conical collecting chamber may, if desired, be provided below entrance chamber 60, for collection of relatively coarse or heavy particles settling by gravity from the gas passing through said entrance chamber and said collecting chamber may be provided at its lower end with suitable means 36 for removal of such col- 'lected material therefrom.

The apparatus also comprises a circular deflector plate 170 disposed concentrically about the inlet pipe 30 and of somewhat greater diameter, defining an annular passage 170 between said deflector plate and inlet pipe. The gas outlet means 40 is shown as being of involute shape closed at its lower side by means of wall 36 and opening at its upper side into the passage 17c and communicating therethrough with the interior of chamber 10 adjacent the larger end thereof. Gas outlet pipe 210 leads substantially tangentially from the outer end of the outlet chamber.

The upper edge of deflector plate 170 is somewhat smaller than the larger end of chamber 10, so as to provide an annular opening therebetween, and an involute shaped wall 38 extends around and spaced outwardly somewhat from said deflector plate so as to provide a space 230 for receiving suspended material thrown outwardly by centrifugal force beyond said deflector plate.

The means for collecting such material are shown,

in this case as comprising a pipe 41 leading substantially tangentially from the outer end of the involute shaped space 23c to a mechanical dust collector such as a cyclone collector 42 whose gas outlet is connected by pipe 43 with the gas supply pipe 80 aforesaid. The dust collector 42 may be provided with suitable means 44 for discharge of collected material therefrom. A damper 45 may, if desired, be provided in the gas circulating system comprising pipes 41 and 43, for example in the pipe 43 as shown, so as to provide for regulation of the amount of gas recirculated.

In the operation of this form of the invention, the rotation of fan 20 causes the gas carrying suspended material to be drawn in tangentially into the entrance chamber which imparts a whirling motion thereto, which whirling motion continues as the gas is drawn upwardly through the inlet pipe 30 and through the central portion of chamber 1c to the fan. Suspended particles exceeding a certain size or weight, such that the action of gravity thereon overcomes the lifting action of the upwardly moving gas, settle into the conical collecting chamber 35 and are thus removed from the gas stream. As in the forms of the invention above described, the suspended particles carried upwardly by the gas are caused to whirl therewith and are largely thrown by centrifugal force beyond the outer boundary of the upwardly moving gas stream before reaching the fan blades. The gas entering entering fan 2c receives additional rotative impetus andpasses downwardly, while still whirling in the same direction through the outer portion of chamber 10, the major portion thereof being discharged through the annular passage 17c, gas outlet means 40 and outlet pipe 210.

The suspended material, however, is largely thrown outwardly by centrifugal force beyond the position of the upper edge of deflector plate 170 and is concentrated in a relatively small proportion of the gas adjacent the outer wall of chamber 10, and this portion of the gas carrying such suspended material also passes with a whirling motion outside the deflector 17c and into the involute shaped space 230. Said gas passes thence through pipe 41 to the cyclone or other mechanical dust collector 42, in which the major portion of the suspended material is cooled, and the gas freed from such suspended material passes from the outlet 'of said dust collector through pipe 43 to the inlet pipe 80. By adjustment of damper 45 the proportional amount of gas thus recirculated may be regulated so as to provide the necessary gas velocity for carrying all the suspended material from the chamber 230 into the collecting apparatus 42.

Another form of apparatus having a vertical axis is shown in Figs. 12 to 14 inclusive. Ihis apparatus is shown as provided with an involute entrance chamber 6d into which leads the inlet pipe 8d, a frusto-conical fan chamber 101, and a circular inlet pipe 3d leading upwardly from the central portion of said entrance chamber to the lower portion of said fan chamber. It will be understood that a fan is mounted within the upper portion of chamber 1d, for rotation about the vertical axis VV, for example as shown in Fig. 8, the lower portion only of said fan being indicated at 2d. A circular deflector plate 17d is disposed concentrically about the inlet pipe 3d, the upper edge of said deflector plate being preferably somewhat below the upper end of said inlet pipe and being of somewhat greater diameter than said pipe so as to provide an annular outlet passage 17d, which communicates as before with the central portion of an involute shaped discharge chamber 18d inclosed in the involute shaped discharge casing 4d. Gas discharge pipe 21d leads substantially tangentially from the outer end of said discharge chamber. As shown, the chamber 18d and discharge pipe 21d are preferably of relatively great height and small width, so that the outer end of the involute lies wholly within the diameter of the lower end of chamber 1d. A frusto-conical plate 51 extends downwardly and outwardly from the upper edge of deflector plate 17d to the top wall 52 of the discharge casing 4d, and the radius of the lower edge of said plate 51 is preferably substantially equal to theradius of the outer end of said casing, so that the lower edge of said plate 51 meets the outer wall of said casing at 53 and an annular opening 54 is provided between the bottom of plate 51 and the wall of chamber 1d, thus causing all material entering the material receiving space 23d between plate 51 and the wall of chamber 1d to be directed outwardly beyond the wall of easing 4d at its largest point and to fall clear of said casing.

A material receptacle 2511 is provided below the lower edge of the chamber 1b, in position to receive material falling through the annular opening 54. Said receptacle is preferably provided with an inclined bottom wall 55 extending downwardly from one side of the receptacle to the other so as to direct all the material entering said receptacle to one side of the apparatus, where a discharge spout 2811 having a gate or valve 29d is provided.

The operation of this form of the invention is substantially the same as that shown in Figs. 1 to 4 inclusive, with the exceptions that the whirling movement of the gas takes place about the vertical axis VV instead of a horizontal axis, and the solid material thrown out of the incoming and outgoing whirling gas stream in the fan chamber falls through the space 2311, through opening 54 and into the receptacle 25d.

In Figs. 15, 16 and 17 is shown a form of abrasion-proof fan according to this invention in which no means are provided for permanent separtion and collection of suspended material carried by the gas, but which is nevertheless so constructed as to prevent or minimize abrasion of the fan blades by particles of abrasive materials carried by the gas. This form of apparatus comprises an involute shaped entrance chamber 6e having gas supply pipe 86 opening tangentially into the outer end thereof, a fan chamber consisting of two inverted frusto-conical portions 1e and 16 having their larger ends toward one another, inlet opening 3e leading from the central portion of said entrance chamber to the central portion of the fan chamber at the smaller end of the portion 16, centrifugal fan 26 mounted for rotation about the axis of said fan chamber adjacent the end of said chamber opposite said inlet opening, namely, within the frustoconical portion 10, and outlet means 4e communicating with the fan chamber at a position axially between the inlet opening and the fan but radially outside the prolongation of the inlet opening toward the fan. Said outlet means is shown as comprising an involute shaped casing disposed between the two frusto-conical casing portions 1e and 1e and providing a similarly shaped discharge chamber l8e which communicates interiorly with theperiphery of thefan chamber at the largest diameter thereof, and whose outer end is connected to tangential gas discharge pipe 216.

In this form of apparatus the suspended material is, as before, largely or wholly thrown by centrifugal force out of the incoming whirling gas stream before said gas stream reaches the fan blades and is again picked up by the outgoing whirling gas stream and carried along therewith and discharged from the apparatus along with the gas, through discharge chamber 18c and gas discharge pipe 21c.

I claim: I

1. An apparatus for propelling gas carrying abrasive suspended material comprising casing means defining an axially extended chamber of substantially circular cross-section, a centrifugal fan mounted for rotation about the axis of said chamber and within and adjacent one end thereracemes oi, gas inlet means communicating with the central portion of said chamber at a position axially removed from said fan, at least a portion of said chamber between said inlet means and said fan being of greater diameter than said inlet means, and gas outlet means communicating directly with said chamber at a position further removed from said axis than the position of communication of said inlet means and at the same side of said fan as said inlet means.

2. An apparatus for propelling gas carrying abrasive suspended material comprising casing means defining an axially extended frusto-conical chamber, a centrifugal fan mounted for rotation about the axis of said chamber and within and adjacent the smaller end thereof, gas inlet means of smaller diameter than the larger end of said chamber communicating with the central portion of said chamber adjacent the larger end thereof and at a position axially removed from said fan, and gas outlet means communicating with said chamber adjacent said larger end thereof and around said'inlet means.

3. An apparatus for propelling gas carrying abrasive suspended material comprising casing means defining an axially extended chamber of substantially circular cross-section, a centrifugal fan mounted for rotation about the axis of said chamber and Within and adjacent one end thereof, gas inlet means communicating with the central portion of said chamber adjacent the end opposite said fan and at a position axially removed from the fan, said chamber being of greater diameter than said inlet means at said lastnamed end, and gas outlet means communicating directly with said chamber adjacent the same end as said inlet means and around said inlet means.-

4. An apparatus for propelling gas carrying abrasive suspended material comprising casing means defining an axially extended chamber of substantially circular cross-section, a centrifugal fan mounted for rotation about the axis of said chamber and within and adjacent one end thereof, gas inlet means communicating with the central portion of said chamber adjacent the end opposite said fan and at a position axially removed irom the fan, said chamber having a portion between said inlet means and said fan of larger diameter than said inlet means, and gas outlet means communicating directly with said larger diameter portion of said chamber at a position further removed from the axis of the chamber than the periphery of said inlet means.

5. An apparatus for propelling gas carrying abrasive suspended material comprising casing means defining an axially extended chamber comprising two frusto-conical portions having their larger ends disposed toward one another, a centrifugal fan mounted for rotation about the axis of said chamber and within and adjacent the smaller end of one of said frusto-conical portions, gas inlet means communicating with the central portion of said chamber adjacent the smaller end of the other of said frusto-conical portions, and gas outlet means communicating with the peripheral portion oi said chamber adjacent the juncture of said two frusto-conical portions.

6. An apparatus for propelling gas carrying abrasive material comprising casing means defining an axially extended chamber of substantially circular cross-section, a centrifugal fan mounted for rotation about the axis of said chamber and within and adjacent one end thereof, gas

inlet means communicating with the central portion or said chamber at a position axially removed from said fan and provided with means for imparting whirling motion about the axis of said. chamber to gas drawn inwardly therethrough by said fan, at least a portion of said chamber between said inlet means and said fan being of greater diameter than said inlet means, and gas outlet means communicating directly with said chamber at a position further removed from said axis than the position of communication of said inlet means.

7. An apparatus as set forth in claim 6, in which said whirling motion imparting means comprises an entrance chamber whose central portion opens at one side into said first-named chamber and means for delivering gas substantially tangentially into said entrance chamber.

8. An apparatus as set forth in claim 6, in which said whirling motion imparting means comprises a plurality of radially disposed inclined vanes in said inlet means.

9. An apparatus for propelling gas carrying abrasive suspended material comprising casing means defining an axially extended chamber of substantially circular cross-section, a centrifugal fan mounted for rotation about the axis of said chamber and within and adjacent one end thereof, gas inlet means communicating with the central portion of said chamber adjacent the end opposite said fan and provided with means for imparting to gas drawn in therethrough by said fan a whirling motion about said axis, said chamber being of greater diameter than said inlet means at the end adjacent said inlet means, and gas outlet means communicating directly with said chamber adjacent the same end as said inlet means and around said inlet means.

10. An apparatus for propelling gas carrying abrasive suspended material comprising casing means defining an axially extended chamber of substantially circular cross-section, a centrifugal fan mounted for rotation about the axis of said chamber and within and adjacent one end thereof, gas mlet means communicating with the central portion of said chamber at a position axially removed from said fan, at least a portion of said chamber between said inlet means and said fan being of greater diameter than said inlet means, gas outlet means communicating directly with said chamber at a position further removed from said axis than the position of communication of said inlet means and at the same side of said fan as said inlet means, a circular deflector disposed inwardly of the side wall of said chamber and around the position of communication of said outlet means with said chamber and defining with said side wall an annular space adapted to receive suspended material thrown outwardly beyond said defiector,- and a material receptacle positioned to receive and collect material entering said space. I

11. An apparatus for propelling gas carrying abrasive suspended material and collecting such suspended material comprising casing means defining an axially extended chamber of substantially circular cross-section, a centrifugal fan mounted for rotation about the axis of said chamwith said chamber at the same end as said inlet means and around said inlet means, a circular deflector surrounding the opening from said chamber into said gas outlet means and spaced inwardly from the side wall of said chamber, and means for collecting material thrown outwardly into the space between said deflector and said side wall.

12. An apparatus for propelling gas carrying abrasive suspended material comprising casing means defining an axially extended chamber of substantially circular cross-section, a centrifugal fan mounted for rotation about the axis of said chamber and within and adjacent one end thereof, gas inlet means communicating with the central portion of said chamber at a position axially removed from said fan and provided with means for imparting whirling motion about the axis of said chamber to gas drawn inwardly there through by said fan, at least a portion of said chamber between said inlet means and said fan being of greater diameter than said inlet means, gas outlet means communicating directly with said chamber at a position further removed from said axis than the position of communication of said inlet means and at the same side of said fan as said inlet means, deflector means adjacent said gas outlet means and so positioned as to separate from the outgoing gas suspended material thrown outwardly from said gas by centrifugal force, and means for collecting material separated by said deflector means.

MARCEL A. LISSMAN.