US1843460A

US1843460A - Hopper feed

Info

Publication number: US1843460A
Application number: US468244A
Authority: US
Inventors: William A Rosenberger
Original assignee: Pangborn Corp
Current assignee: Pangborn Corp
Priority date: 1930-07-16
Filing date: 1930-07-16
Publication date: 1932-02-02
Anticipated expiration: 1949-02-02

Description

Feb. 2, 1932.

w. A. ROSENBERGER 1,843,460

. HOPPER FEED Filed July 16, 1930 4 Sheets-Sheet gwue ntoz duo: um I Feb. 2, 1932.

- HOPPER FEED 4 Shets-Sheet 2 Filed July 16 1930 Feb. 2, 1932.

W. A. ROSENBERGER HOPPER FEED Filed July '16, 1950 4 Sheets-Sheet 3 UEIEHjUUEI w 5 J w attozvmq Feb. 2, 1932. w RQSENBERGER 1343, 160

HOPPER FEED Filed July 16, 1950 4 Sheets-Sheet 4 Patented Feb. 2, 1932 is "rare Price WILLIAM A. nosnunnnenn, 0F rmennsrown, M RYL N assrenon To rnnenonn oonronarrou, or nn'snnsrown, MARYLAND, n COBPOBATIQN or AnYn nn 'norrnn' FEED,

Application filed July 16,

The invention relates to a hopper feed for the pneumatic handling of sand blast abrasive, dust and other waste materials which are mixed therewith after the sand blasting operation. This type of hopper feed is particularly adapted. for use beneath the floor of a sand blast room in collecting the used abrasive and delivering it to ,a pneumatic liit whereby it is returned to the pressure tank, being ordinarily passed first through an abrasive reclaiming apparatus. While it has been developed in this'connection, the device of the invention is capable of more general application.

T15 In accordance with the present practice in handling used abrasive from the sand blasting operation, such hoppers are formed with a single discharge opening at the bottom arranged transversely to the conveyor to pipe and the sides of the hopper are arranged at an angle slightly exceeding the angular flow of the material, which is about forty.- five degrees. With such a hopper it is necessary that the sides converge downwardly at this angle from an area at the top corresponding to the area of the sand blast room to an area at the bottom substantially equal to the discharge opening. As the hopper is ordinarily placed underground, this arrangement involves the necessity for a corresponding depth of excavation which, under ordinary circumstances, is considerably more than half the greatest horizontal dimension of the room. In some instances two or morehoppers are placed side by side or end to end correspondingly reducing the area of each hopper at the top and the depth of the excavation, but this is undesirable as two such hoppers require practically twice as much air as the single hopper and this arrangement is therefore not economical or efficient from the standpoint ofthe power consumed.

Sand blast rooms are not ordinarily square but elongated in one direction to :ac'commodate work of a given length or to provide for twoor more workment and for other reasons. The depth of the excavation corresponding under the present practice .to the greatest horizontal dimension, of the room is correspondingly great and correspondingly 0b- 1930; Serial No. 468,244.

jectionable. The apparatus of the invention,

While it may be applied with advantage to the hopper used in connection with any sand blast room, is of particularly great advantage in connection with the rooms of the elongated shapes,as the depth of the hopper corresponds not to the length of the room butzto its shorter horizontal dimension. i. e., the width.

The improved type of pneumatic hopper, particularly-adapted for use in handling sand blast abrasive, although it is capable of other application, preferably discharges the material into a tapered pipe, the larger area ofthe pipe being downstream, i. e., in the direction of flow. This pipe extends the entire length ofthe hopper which preferably corresponds in shape and area to'the floor of the room, and has a correspondingly elongated narrow bottom portion which is a:

slotted or otherwise apertured to form afeed opening or openings from the hopper into the pipe, the lateral dimension, hence the area of the feed opening for each correspondingunit of length decreasing from What may be termed the upstream end of the pipe or the corresponding end of the bottom of the hopper to the opposite .or downstream end of the bottom of the hopper, it being understood that the hopper tapers from the .top which is ordinarily the fioor grating of the sand blast room, toward the discharge out'letpreferably on all sides at an angle slightly exceeding the angle of flow of the material. V V

The larger end of the pipe is connected to an exhaust system creating a sufficient vacuum in the pipeto cause a flow of air from the hopper through the discharge opening into the pipe, the-abrasive and other material which drops into the hopper and is line enough to pass through the fced-openingor' slot being carried by the air current for deposit at any desired point,-the used abrasive being ordinarily in the operation of sand last apparatus delivered to the reclaiming apparatus before being returned to the pressure tank and to the nozzle.

{This arrangementof the feed openingand feed ,pipe .causes an equal amount of air (to enter the slot at all points of its length and maintains a uniform air velocity at all points inside the pipe. In this way a uniform speed of the abrasive being maintained, clogging of the passage is avoided and the necessity for baffles beneath the feed opening in accordance with the usual practice is avoided. But more important than this, the depth of the excavation providing for the hopper beneath the floor particularly in connection with sand blast rooms, is greatly reduced, the excavation necessary for such a hopper being little more than half the width of the room.

Nhile in the preferred form the opening from the bottom of the hopper into the pipe is in the form of a single slot, a number of openings of varying width or varying area decreasing in size or width from the up stream to the downstream end of the hopper may be substituted. Such an arrangement is of particular advantage in connection with long sand blast rooms where a con tinuous slot would have to be made very narrow at the downstream end which would prevent coarse particles from entering the pipe and would involve considerable difficulty by closing this portion of the slot.

The construction of the tapered slot arrangement of a multiplicity of graduated orifices may be accomplished in many different ways of which a few preferred designs are illustrated.

In the case of large sand blast rooms two or more hoppers with a corresponding number of feed or discharge pipes may be used. In an installation of this kind, the total amount of air handled through all of the discharge or elevating pipes is apt to be less than the number of hoppers times the quantity of air required for a single operator, onehopper installation. Therefore if more than one operator is to work in a single room, there would be a possibility of a discharge of abrasive into one hopper greater than the corresponding feed pipe could remove. This might result in flooding the particular pipe with abrasive which would in turn stop the air flow through the pipe and cause the gradual filling up of the hopper and consequently a reduction in the room ventilation, it being understood that the air which propels the abrasive, also serves either wholly or in part to ventilate the room above the hoppers.

To overcome this difiiculty, an adjustable air feed duct has been arranged in the hopper leading downwardly from a point near the top of the hopper above the'accumulated material to a level just above the feed opening, the lower edges of the air duct being spaced from the bottom of the hopper which may be termed the orifice plate. This air duct passes air through the accumulated abrasive in the hopper to the slot and is adjusted toward and from the orifice plate to govern the amount of abrasive flowing from the hopper. With this duct, all the abrasive which enters the hopper can be taken care of, as it accumulates without interfering with the air supply.

In the accompanying drawings I have illustrated pneumatic hoppers embodying the principles of the invention in the preferred form and in various modified forms in which theinvention may be applied.

In the drawings:

Figure 1 is a top plan view of the hopper in preferred form.

Figure 2 is a central longitudinal vertical section through the same and the vacuum or conveyor pipe on the

line

2, 2, Figure 1.

Figure 3 is a transverse section on the

line

3, 3 of Figure 2.

Figure 4: is a fragmentary top plan view of a modified form of hopper.

Figure 5 is a side elevation of the same.

Figure 6 is a transverse section on the

line

6, 6 of Figure 5.

Figure 7 is a fragmentary top plan of a sand blast hopper in modified form having a series of graduated rectangular openings instead of a single tapered slot.

Figure 8 is a similar view of another modified form showing a series of graduated openings of different shape to produce the same result.

Figure 9 is a similar view of a hopper having an adjustable slot.

Figure 10 is a transverse section on an enlarged scale on the line 1010 in Figure 9.

Figure 11 is a vertical longitudinal section through a hopper having an adjustable air feed duct.

Figure 12 is a transverse section on the

line

12, 12 of Figure 11.

Figure 13 is a diagrammatic view on a reduced scale showing a sand blast room provided with a hopper in accordance with the invention and showing in connection therewith an abrasive reclaiming apparatus and pressure tank.

Figure 1 1 is a vertical central longitudinal section on a reduced scale showing diagranr matically a series of three hoppers arranged end to end for use in an elongated sand blast room accommodating several workers, the slots in the bottom of the respective hoppers being separately controlled to close and open them as the number of workers is varied.

Figure 15 is a top plan view of the same on an enlarged scale with the gratings remmred.

Figure 16 is a fragmentary vertical section on

line

16, 16, Figure 7. Figure 1'? is a similar view of another form.

Referring to the drawings by numerals. each of which is used to indicate the same or similar parts in the difierent figures, the construction shown in Figure 1 comprises an elongated hopper 1, which is preferably of sheet steel. The sides 2 and the ends 3 of this hopper are inclined downwardly toward the bottom 4 which is narrow and shorter than the overall length of the hopper to provide a suitable inclination to the ends '3, which are shown as somewhat steeper than the sides,

which latter are inclined at'an angle slightly steeper than the minimum angle of flow of the material, which is about 45 degrees.

Beneath the bottom of the hopper and connected to the ventilating system or otherwise arranged to maintain a suitable vacuum is the sand and air pipe or conveyor duct otherwise referred to herein as the vacuum pipe. This pipe, which is preferably of square cross section, comprises a portion indicated by reference character 5 beneath the hopper, which is of a reducing taper toward the closed end at 6, being otherwise described as of increasing taper in the direction of flow, i. e., toward the left in Figures 1 and 2.

The bottom 4 of the hopper which forms the top wall of the tapered portion 5 of .the conveyor duct or vacuum pipe 5 beneath the hopper is slotted at 7 preferably for the entire length of the bottom of the hopper, the width of the slot being reduced in the direc tion of flow, .so that it is tapered oppositely to the taper of the tapered portion 5 of the conveyor duct 5.

The vacuum referred toas maintained within the pipe '5 maintains :a flow of air from the hopper "through the tapered .slot 7 and into the conveyor duct or vacuum pip-e 5. The abrasive and waste materials dropped into the hopper :in the sand blasting operation which are fine enough to pass through the slot 5?, willbe thus carriedby .the air current into and along the vacuum pipe for depositat any desired point, the important function resulting from the pipe of increasing taper in the direction of flow into which pipe the abrasive enters by wayof the elongated slot leading from the bottom of the hopper into the pipe and tapered oppositely :to the cross section of the pipe, is that an equal amount of air enters the tapered portion 5 of the pipe 5 by 'way'of the slot 7 atany and all points of its length and a uniformnir velocity :is maintained at all points in the length of the tapered slotted portion 5 of the :pipe 5 beneath the-hopper. 7

At present, as already pointed out, pneumatic abrasive lift systems, to which the present apparatus is particularly to be applied, :al-though'it is :capableof other application, :are equipped with the hopper which terminates at the bottom in acomparatively narrow slot which runs transversely to the pipe and .is therefore relatively short. Un-

50 derneath the slot is a system :of baffles for the purpose of preventing clogging of the jipe in case more abrasive enters the slot than canberemovedby:the air current. In order to maintain the downward flow of the abrasive in the hopper, the walls of the hopper must be inclined from'the top downwardly to said short narrow slot at an angle e22. ceeding the angle of flow of the abrasive already described, which makes the depth of the hopper necessarily more than half of the greatest dimension of the sand blast chamher, it being understood that sand blast hoppers of the type described ordinarily underlie the entire area of a sand blast chamber, as illustrated in Figure 13, the floor of the chamber indicated by reference character 10 being in the form of a grating which serves as the top of the hopper.

This chamber 11 is equipped with any suitable number of sand blast nozzles, a single sand blast nozzle 12 being shown connected by a hose 14 to a sand blast pressure tank 15. The illustration also includes a'sand blast abrasivereclaiming apparatus 16 to which the abrasive mixed with dust and dirt from the blasting operation is carried by a pneumatic lift or elevator 17, which is connected to the hopper 2 by means of the vacuum pipe or conveyor duct- 5, terminating beneath the hopper in the tapered portion 5. already described.

In this connection, it'will be understood that by means of the arrangement described, whereby the hopper is formedwith an elongated bottom portion l, beneath which is the tapered portion 5 of the vacuum pipe 5, the latter being connected to the bottom of the hopper by elongated slot the pipe being preferably of increasing taper in the direction of flow, and the slot of opposite taper, the necessity for tapering the hopper downwardly to a central point at an angle exceeding the angle of flow of the abrasive so that the depth of the hopper must exceed half its greatest dimension is dispensed with. I

In the improved form of the invention the depth of the hopper is reduced so that instead of being a little more than half of the greatest dimension of the floor of the sand blast chamber, it is a little more than half of the least dimension, i. e., the width of the sand blast chamber and as these chambers are ordinarily of elongated shape, the advantage of the apparatus, Figures 1, 2 and 3, it will be noted that the plates forming the sides 2 of'the hopperare flanged at their lower edges at 22, and the plate forming the bottom 4 of the hopper is secured to said flanges. The

side walls 24 of the tapered portion 5 of the duct are formed of plates flanged at the top and bottom at 25, 26, respectively, and the bottom plate forming the bottom of the duct indicated by reference character 27 is secured to these bottom flanges. The shape of the cross section of themain portion of the vacuum pipe or duct 5 is immaterial, although it may conveniently be formed as illustrated in Figure 3. The small end of the tapered i .portion 5 of the pipe 5 is shown as closed by a flat plate 28 connected to the side walls of the tapered duct 5 by angle irons 29 although. these exact details of construction are, of

a course, immaterial.

Figures l, 5 and 6 illustrate a slightly modified form of the apparatus in which the bottom of the hopper 20 is intersected by a tapered duct 21 whose vertical sides 23 diverge toward the closed end of the tapered portion 5 of the pipe. The side walls 23 of this duct and the walls of the hopper on each side are shown as formed of integral sheet metal 32, the bottom edges of which are turned out to form flanges as which are secured to corresponding flanges forming the top edges oi the sides 36 of the tapered portion 5 of the vacuum pipe 5. These side plates 36 are also flanged at their lower edges at 37, the bottom plate or bottom of the duct being a single flat plate 38 secured to these bottom flanges 37. The intersection of the inclined walls of the hopper 20 with the duct 21, the width of which in a horizontal direction increases oppositely to the direction of flow, which is most clearly shown in Figure 6, gives a tapered slot or passage 19, the width increasing oppositely to the direction of flow as shown best in plan in Figure l and in section in Figure This duct 21 is in turn connected throughout its length at the bottom to the top of the tapering portion 5 of the vacuum pipe 5, which vacuum pipe 5 as shown is of. a vertical dimension, which increases in the direction of flow, i. e., oppositely to the increase of the horizontal width of the slot 1.9 and of the duct 21.

Another form of construction which may be substituted for those previously described, is illustrated in fragmentary plan in Figures 7 and 8.

In Figure 7 the bottom wall or floor 40 of the hopper 1 is formed with a series of reetangular holes 41 in place of the slot 7, holes shown being elongated transversely to the length of the hopper, the holes in d series being of increasing length opposi. y to the direction of tow d opposite y to the increasing taper of the cross section of the tapering portion 5 of the exhaust pipe 5 fully illustrated in connection with. the constructi ons previously discussed. The arrangement of openings ll of reducing dimension in the direction of flow gives a result which is similar but not exactly the same that of the slot 7, as described in connection with Figures l, 2 and 3, the aperture 41 being better adapted to the longer hopper.

Figure 8 shows the hopper 1 having the bottom or floor portion 4% "formed with a series of round holes :5 instead of the rectangular openings 41, the same arranged in a series extended in the direction of the length or the hopper and the diameter of the holes in the series being reduced in the direction of flow so as to give the efiect of a slot which tapers oppositely to the taper of the tapered portion 5 of the exhaust pipe 5.

Figures 9 and 10 illustrate still another form of the invention in which the tapered slot leading through the bottom of the hopper into the tapered portion 5 of the exhaust pipe 5 is adjustable. To this end a slightly different arrangement of the hopper is provided; this hopper member has inclined walls indicated by reference character 4.6, with bottom flanges l? spaced upwardly from the top flanges 48 of the side walls 49 of the tapered portion 5 of the duct 5, both the flanges 47 and i8 being wider than in the previous structures. These flanges are connected by bolts or rivets 50, which pass through spacing blocks or strips 51 inserted between the flanges 47, 48 at the outer edge. The spacing of the flanges as aforesaid provides horizontal ways 52 in ,which are mounted the bottom plates 53 shown as pivoted at one end of the hopper on vertically extending pivot pins 54:, 55, which may be seated in the flanges 47, 48 above and below the plates 53 through which the pivot pins 54, 55 extend permitting these plates 53 to swing horizontally toward and from each other and about said pivot pins 54, 55.

The normal positions of the plates 53 as shown in Figure 9, provide a tapering slot through the bottom wall or floor 56 of the hopper composed of said plates, said slot connecting the hopper to the tapering portion 5 of the vacuum pipe, the taper of the slot being such that its width increases oppositely to the direction of flow and oppositely to the increasing taper of the portion 5 of the vacuum pipe. The position of these plates may be controlled in any suitable manner as by means of a link motion 57 Figure 9, consisting of links 58 connected together by pin 59 at their adjacent ends. At their opposite ends, said links are pivotally connected at 60 and 61 to the ends or" the respective plates 53 opposite to the pivot pins 54:, 55. The pin 58 which connects these links at their outer ends is, in turn, mounted in a slot 63, in a radial arm 64 mounted on a control shaft or rod 65, the slot 63 being parallel to the length of the arm 64, which extends in a radial direction regarding the shaft 65. This shaft may be provided with manually engageable means by which it is turned to a slight degree at the will or" the operator to adjust the position of the plates 53, and hence the width of the tapered slot 66. lVhenever it is found that due to changed conditions or otherwise, the relation of the taper of the slot in the bottom of the hopper to the other elements as the taper of portion 5 of the vacuum pipe, or the strength of the air current, is not satisfactory, the width of this tapering slot 66 and its taper, may be varied at the will of the operator or the plates 53 may be maintained in a single position without variation of adjustment at the will of the operator.

Figure 17 shows a hopper 1 provided with a series of discharge apertures 90 arranged in the direction of the length of the hopper, the size of which apertures is reduced in the direction of flow in pipe 5"a s in Figures7, 8 and 16. in this construction, however, applicant has. placed. triangular or inclined members 91. between the apertures toprevent lodging of the abrasive in the bottomof the hopper.

To prevent material too'large for free passage through slot 7 from reaching this slot and obstructing its area, a suitable screen 84 may be provided near the bottom of hopper 3with a clean-out door 85 in the sidewall of the hopper. See Figures 1, 2 and 3.

Two or more hoppers may be used in asingle room in case of a room of considerable length, see Figures 14, 15, the hoppers 70, 71, 72 like those in Figures 8 and 9, being arranged end to end with a single elongated tapering section 5 of the vacuum pipe 5. In this construction the use of the adjustable plates 53 is illustrated, the plates being controlled and operated by means of the shaft 65 and having a handle or crank or other operating means 74 at its upper end.

In the construction of Figure 14 the grids 10 forming the top of the hoppers and the floor of the sand blast room are shown. This construction is intended. to be used inconnection with an elongated sand blast chamber in which there are several workmen placed along the length of the room, ordinarily one over each hopper.

When the shape and area of the sand blast room seem to require it, the hoppers of the invention may be otherwise arranged as by grouping any desired number in any way with the necessary number of conveyor pipes, but the use of more than one slot tends to sac rifice power economy. 7

If in the operation of an installation of the multiple type as shown in Figures 14 and 15, the total amount of air handled through all of the lift pipes 17, see Figure 13, is less than the number of hoppers times the quantity of air required for a single operator, or if more than one operator is to work in a room, there is a possibility that more abrasive maybe discharged into one hopper than the corresponding vacuum pipe can remove, this would result in a clogging or choking of that particular feed pipe which would in turn stop the air flow through this pipe. As

the vacuum system emploved in this connection is also used to ventilate partially or wholly the blast room above the hoppers, this would cause gradual filling up of the hopper and a corresponding reduction in the amount of air withdrawn from the sand blast room, hence in a reduction of the ventilation of the room or sand blast chamber.

To overcome this difiiculty, an adjustable air feed duct 75, see Figures 11 and 12, is provided. This may be placedinside the hopper 1, of construction similar to that of Figure 1, the lower edges 76 of the duct being spaced above and inclined downwardly toward the bottom wall of'the floor 4 of the hopper 0ppositely to the direction of flow in pipe 5. The duct 75 is adjustable toward and from said bottom wall or plate't to vary the spacing of this bottom edge 76 fromthe plate or floor t and from the edges of the slot 7. The adjustment of this space governs the amount of abrasive flowing through slot 7 into the vacuum pipe. If more abrasive enters the hopper 2 than can flow through the slot 7, it accumulates in the hopper as shown at 77 in Figure 12, but under the circumstances it does not prevent the entrance of a suflicient and predetermined amount of air, as the air can at all times pass downwardly through the duct 75 into thetapered section 5 of the vacuum pipe 5, together with the abrasive.

The adjustment shown consists of lugs 78 projecting from the ends of the duct 75 and provided with threaded holes 79 extending in a verticaldirection and engaged by screws 80 having a suitable thumb wheel or other means of engagement 81 at the top and having a swivel connection at their lower ends at 82, with brackets or lugs 83 projecting inwardly from the wall of the hopper 2, or otherwise supported on the frame of the machine. I

In the operation of the machine, as pointed out in the preamble, the'pneumatic conveyor or vacuum pipe 5 is connected to the ventilat ing or exhaust system, causinga flow of air from the hopper through the tapered slot 7 into the vacuum pipe. The sand blast being in operation in the chamber, as illustrated in Figure 13, the mixed abrasive and dust and dirt-from the castings passes through the grating 10 and drops into the hopper 2, and

all of the material which is fine enough to passthrough the slot 7 is carried by the air current into. the vacuum pipe, and thence to the pneumatic lift 17 by which it is deposited at any desired point.

In the embodiment of the invention shown it is carried by the pneumatic lift 17 to the reclaiming apparatus 16 by which it is returned to the pressure tank 15, from which it is fed to the nozzle by way of the hose 14.

An important advantage of the invention is the provision of the elongated slot 7 preferably running almost the entire. length of the bottom of the hopper whereby it is made possible to greatly reduce the height or depth of the hopper and correspondingly reduce the depth of the excavation. In this connection it should be understood that the depth of the hopper in thisinstance, provided but a single hopper is used, is dependent not upon the greatest dimension of the chamber,

but on the shortest dimension, i. e., the width of the chamber, as distinguished from the length, the slot extending in the direction of the greatest dimension or length of the charm her, the sides of the hopper being arranged at an angle slightly steeper than the minimum angle of flow of the material which is about l5 degrees; the necessary depth of the excavation, i. e., the depth of the hopper, is about half the width of the chamber. The importance of this feature whereby the depth of the hopper is reduced, is particularly dependent on the fact that by increasing the number of hoppers, the consumption of power is correspondingly and proportionately increased and with a deep excavation ground water is apt to be encountered.

In accordance with the previously existing practice whereby the abrasive was discharged from the bottom of the hopper by way of a short slot or opening corresponding to the with of the vacuum pipe or duct, the depth of the hopper necessarily corresponded closely to the greatest dimension, being substantially in accordance with the principal above recited about half of the greatest dimension instead of in accordance with the present invention about half the least dimension or" the sand blast room.

In the operation of the device of the invention, as already pointed out, the provision of an elongated tapered slot in the bottom of the hopper extending almost the entire length of the hopper, in combination with the eX- haust pipe section 5, which is oppositely tapered, the slot being of a reducing taper in the direction of flow and the pipe being of an increasing taper in the direction of flow, gives the important result that an equal amount of air enters the slot at any and all points in its length, maintaining a uniform air velocity at all points in the

vacuum pipe

5, 5. This eliminates any tendency to accumulate abrasive at any point in the slot or the pipe beneath the slot, giving an equal tendency to remove the abrasive from the I hopper at all points in the length of the slot,

and the uniform flow further prevents obstruction of the pneumatic conveyor or vacuum pipe by giving a uniform tendency at all points in the pipe to move the abrasive in the direction of flow.

Another important advantage of this invention is the fact that the abrasive enters the suction or conveying pipe 5 in a Widely scattered state, i. e. distributed over a considerable length so that the conveying air, at any one point has to carry but a very small amount of solid material, whereas in the known types of pneumatic abrasive conveying systems, the abrasive enters the conveying air in a concentrated stream, practically at one point, which renders such installations subject to clogging much more ified forms of the invention in order that the manner of constructing, applying and using the apparatus of the invention may be clearly understood, however, the specific terms herein are used descriptively rather than in a limiting sense, the scope of the invention being defined in the claims.

hat I claim as new and desire to secure by Letters Patent is:

1. The combination with a sand blast chamber and a pneumatic air and sand pipe for removing the used abrasive, of a hopper beneath the chamber to receive the used abrasive, and a portion of said pipe of increasing taper in the direction of flow beneath said hopper, the hopper having a discharge slot or". a length corresponding to the length of the hopper connecting the tapered pipe to the hopper, the discharge slot being tapered oppositely to the taper of the pipe.

2. The combination with a sand blast chamber and a pneumatic air and sand pipe for removing the used abrasive, of a hopper beneath the chamber to receive the used abrasive, and a portion of said pipe of increasing taper in the direction of flow beneath said hopper, the hopper having a discharge slot of a length corresponding to the length of the hopper connecting the tapered pipe to the hopper, the discharge slot being tapered oppositely to the taper of the pipe, and means for adjusting the width of said slot.

3. The combination with a sand blast chamber and a pneumatic air and sand pipe for removing the used abrasive, of a hopper beneath the chamber to receive the used abrasive, and a portion of said pipe of increasing taper in the direction of flow beneath said hopper, the hopper having a discharge slot of a length corresponding to the length of the hopper connecting the tapered pipe to the hopper, the discharge slot being tapered oppositely to the taper of the pipe, apd means for adjusting the taper of said s 0t.

1. The combination with a sand blast chamber and a pneumatic air and abrasive pipe for removing the used abrasive, of a hopper beneath the chamber to receive the used abrasive, and a portion of said pipe of increasing taper in the direction of flow beneath said hopper, the hopper having an open portion at the bottom whereby the hopper is caused to discharge into said pipe for substantially the entire length of the hopper, the lateral dimension of said open portion being varied and reduced in a direction opposite to the direction of the taper of the pipe.

5. The combination with a sand blast hopper of a pneumatic pipe for removing abrasive from the hopper, said pipe having a tapered portion beneath the hopper, and a slot tapered in the direction opposite to the taper of the pipe connecting the hopper to the pipe, the length of the slot closely approaching and corresponding to the length of the hopper.

6. The combination with a penumatic pipe for transporting abrasive, of a hopper connected to said pipe, the pipe having a portion tapered oppositely to the direction of flow beneath said hopper, the bottom of the hopper being narrow, elongated in the direction of the length of the pipe and being open into said pipe, the open portion being varied in lateral dimension substantially throughout its length and reduced in the direction of flow, the long sides of the hopper being inclined outwardly and upwardly from said bottom.

7. The combination with a sand blast hopper of pneumatic means including a pipe for transporting abrasive from the hopper, a portion of said pipe being beneath the hopper, the bottom of the hopper being of a length closely approaching the entire length of the hopper and being open into the pipe throughout substantially its entire length, the sides of the hopper being sloped downward toward said bottom and said hopper having an upright air feed duct arranged inside the hopper elongated in the direction of the length of the hopper and having its bottom end adjacent said bottom opening of the hopper and spaced upwardly therefrom to a slight degree to permit the abrasive to pass at the sides of the duct from the hopper into the pipe, air being fed through said duct to said pipe.

8. The combination with a sand blast hopper of pneumatic means, including a pipe for transporting abrasive from the hopper, a portion of said pipe being beneath the hopper, the bottom of the hopper being of a length closely approaching the entire length of the hopper and being open into the pipe throughout substantially its entire length, said hopper having an upright air feed duct arranged inside the hopper and having its bottom end adjacent said bottom opening of the hopper and spaced upwardly therefrom to a slight degree to permit the abrasive to pass at the sides of the duct from the hopper into the pipe, air being fed through said duct to said pipe, and means for adjusting said duct in a vertical direction relatively to said hopper to vary the proportions of air and abrasive flowing to the pipe.

9. The combination with a sand blast hopper of pneumatic means for transporting abrasive, said means including a pipe beneath the hopper tapered oppositely to the direction of flow, said hopper having a narrow elongated bottom which is open throughout the length of the hopper into said tapered 1 e. I p l O. The combination with a sand blast hopper of pneumatic means for transporting abrasive, said means includinga pipe to meet the hopper, tapered oppositely to the direction of flow, said hopper having a narrow elongated bottom, the sides of this hopper being sloped toward said bottom, which is open throughout the length of the hopper into said'tapered pipe and an air duct in the hopper having an elongated opening corresponding to the open portion of the bottom of the hopper, the air duct being spaced upwardly from the bottom of the hopper to permit the abrasive to pass downwardly along the sides and bottom ofthe air duct into said plpe.

11; The ,combination with a hopper of pneumatic means for transporting abrasive, including a pipe beneath the hopper having a reducing taper opposite to the direction of How, the hopper having a bottom portion of a length corresponding to the length of the hopper and aligned with said pipe, the bottom of the hopper comprising two laterally movable plates providing an adjustable opening between said plates connecting the hopper to the pipe substantially throughout the entire length of the hopper.

12. The combination with a hopper of pneumatic means for-transporting abrasive, including a pipe beneath the hopper, the hopper having a bottom portion of a length corresponding to the length of the hopper and aligned with said pipe, the bottom of the hopper comprising two plates pivoted at their ends to swing laterally, providing an adjustable opening between said plates connecting the hopper to the pipe substantially throughout the entire length of the hopper and means for moving said plates to adjust the width of the opening.

13. The combination with a hopper of pneumatic means for transporting abrasive, including a pipe beneath the hopper, the hopper having a bottom portion of a length corresponding to the length of the hopper and aligned with said pipe, the bottom of the hopper comprising two plates pivoted at their ends to swing laterally, providing an adjustable opening between said plates connecting the hopper to the pipe substantially throughout the entire length of the hopper and means for moving said plates to adjust the width of the opening, giving it a variation of taper.

14. The combination with a hopper for comminuted materials or abrasive of a pneumatic pipe for removing abrasive from the hopper, said pipe having a portion beneath the hopper and a slot elongated in the direction of the length of the pipe connecting the 15. The combination with a hopper for connninnted materials or abrasive of a pneumatic pipe for removing abrasive from the hopper, said pipe having a portion beneath the hopper, openings extending from the hoper into the pipe, said openings being arranged in the direction of flow, the successive openings being of decreasing area in the direction of flow.

16. E'he combination with a hopper for connninnted materials or abrasive of a pneumatic pipe for removing abrasive from the hopper, said pipe having a portion beneath the hopper, said portion being tapered, the transverse area of the pipe increasing in the direction of flow and an open portion elongated in the direction of How connecting the hopper to the pipe.

17. The combination with a hopper for comminuted materials or abrasive of a pneumatic pipe for removing abrasive from the hopper, said pipe having a portion beneath the hopper, said portion being tapered, the transverse area of the pipe increasing in the direction of flow and a series of openings arranged in the direction of flow connecting the hopper to the pipe, said openings being of successive Width decreasing in the direction of flow.

Signed by me at Hagerstown, Maryland, this 1st day of July, 1980.

WILLIAM A. ROSENBERGER.