US1941572A - Conveying apparatus - Google Patents

Description

Jan. 2, 1934. J. H. MoRRow CONVEYING APPARATUS Filed May 20, 1952 i wm um.

ATTORNEY Patented Jan. `2, 1934 UNITED STATES PATENT OFFICE CONVEYING APPARATUS Joseph H. Morrow, Hokendauqua, Pa., assignor to Fuller Company,

ware

a corporation of Dela- Application May 20, 1932. Serial No. 612,616

Claims.

as by gravity from storage bins, conveyors, railroad cars and pulverizing mills. The invention is particularly directed to certain improvements or modifications of the apparatus shown and described in Kinyon Patent 1,553,539, and also to modifications of the mechanism shown in detail in Fig. 4 of my Patent No. 1,804,565.

The method of operation and the principles of conveying involved are fully described in the patents referred to above. Briey stated, the method involves the propelling of material delivered to the pump hopper through the barrel by means of a rapidly rotating impeller screw, compacting the material to form a seal, and injecting compressed air or other gas into the barrel beyond the terminal flight of the impeller screw to uidize and thus increase the mobility of the material, whereby the latter is forced through the conveyor conduit by the impulse of the screw in displacing material into the conduit, and the normal expansion of the aerating medium. The purpose of forming a seal of compacted material is to prevent the compressed air admitted beyond the seal from escaping backwardly and aerating the material being advanced by the screw flights. Should material become aerated in the pump barrel, the screw would tend to slip and the eniciency of the pump would be seriously decreased and in many cases a dust nuisance would be created.

In the Kinyon patent, three arrangements for forming the seal are disclosed. These include the use in a pump of, rst, a conically shaped barrel and a screw having flights of progressively decreasing diameter for the discharge or terminal flight in the barrel section; second, a cylindrical barrel and screw of uniform flight diameter, but of progressively decreasing pitch toward the point of air admission; and, third, a cylindrical barrel provided with a screw having ights of uniform pitch and diameter, with the air admitting device spaced a distance beyond the terminal flight, whereby the resistance compacts the material and forms a seal by the natural friction of the mass and to some extent by the back pressure which reacts against it. Ordinarily, for simplicity in manufacturing, so that similar pumps may be adapted to the operating conditions which normally may be anticipated, it

is customary to combine the two latter arrangements. Thus, the usual pumps are provided with a screw of differential pitch and a dead space or seal between the terminal flight and the point of air admission. This seal can accordingly'be shorter than that illustrated in Fig. 6 of the rst Kinyon patent. It will be understood that the density of the seal required is Variable, depending upon the relative capacity of the pumpand the actual quantity of material delivered to it; the density of material being handled; the static resistance of the piping system, its bends and valves; and of combinations of these. It will also be evident that more favorable power conditions result from maintaining the seal density at the lowest possible working minimum, in order to avoid excessive friction; and that for commercial purposes it is difficult to reach this ideal condition, as the length of the pump barrel, the screw and associated parts would have to be specifically designed for each condition. This, of course, would be impractical, as in normal service the quantities of materials in ordinary manufacturing processes differ from time to time in many systems.

Although the apparatus of the Kinyon patent referred to is satisfactory for all ordinary purposes, it is subject to improvement, as referred to in Kinyon Patent No. 1,677 ,119, particularly in connection with the conveying of heavy and abrasive materials such as Portland cement. For the conveying of Portland cement, it has been found necessary, in order to provide a seal satisfactory under all conditions of operation, to provide a barrel and screw of considerable length, so that the resistance of the compacted material will always be greater than the back pressure of the transport line or system. The relatively high speed of the impeller screw necessary to advance material at the necessary capacities, and to create suicient centrifugal force to assist in forming the seal make complete filling of the screw diicult, because of the tendency of all pulverized materials, and particularly cement, to flow unevenly into the screw and to form rat holes or pipes" in the hopper, by the natural lling of the conveyor screw at the rearmost ight, which sometimes causes arches to form over the remainder of the hopper, and ultimately to delay filling of the flights. To anticipate these conditions, pump screws have been made of excessive length and driven at high speeds in proportion to capacity, as the volumetric eiciency of pumps with such screws is relatively low. Frequently it has been the practice to deliberately raise the operating pressures of the system so that the reaction will assist in compacting the material, and this obviously is wasteful both of motor power and compressed air.

Among the purposes of the present invention are to provide a pump requiring a minimum of both air and screw motor power, to simplify the flights where'the total distance of conveying will not require a seal density beyond that which can be created in a relatively short dead space between th'e terminal flight and the point of vair admission.

'In general, the new apparatus comprises a pump having a hopper provided with a short barrel section, which is provided with a longituv dinally movable liner bushing, which forms the actual working part of the barrel. This liner extends into the hopper and beyond the barrel vinto the' barrel section, where it is arranged concentrically with respect to the latter. TheA distance between the terminal flight of the screw and the vertical centerline of the .air' admitting device is changeable by advancing the liner bushing or moving it toward the hopper. The seal space can thus bel adjusted exactly to su it the actual operating condition, and theI power lost in friction considerablyI reduced.

The volumetric eiciency of the screw is increased by causing it to lill uniformly throughout the flight section within the hopper by providing flights of progressively increasing diameter from the rear toward or to the barrel section, beyond which their ldiameter is vprogressively uniform. x

By giving the screw this progressively increased volumetric capacity materials to be conveyed descend uniformly and arching and diminished flow are reduced or avoided. It will be apparent that by causing the filling of the screw to approach the actual volumetric capacity, the proper density necessary to form a seal can be created in a short barrel section, as compared for example to that illustrated in Kinyon Patent 1,677,119. It will further be\ apparent that the power required to rotate the screw will be considerably decreased.

The screw shaft passes through the rear wall ofthe hopper and is preferably surrounded by a bushing or quill carried in spaced bearings, 'arranged in a unitary bearingsupport. The bearing support is aligned with the hopper, and both are secured to a common base. By this arrangement, alignment is preserved even after screw replacements have been'made and the maximum desired clearance of 312 between-the periphery of the flights and the inner wall of the barrel lining bushing need not be exceeded.

The unitary bearing support, together with the lemployment of a short screw, which latter is pref- An impeller screw passes The resistance the discharge elbow and the by the shaft further decreases power consumption and diiculties due to wear.

A further advantage of the construction described is that the present bearing support permits the screw shaft to operate in compression without vdanger of contact with the barrel lining, in contrast to the arrangement employed in the last named Kinyon patent, and my patent above mentioned, wherein the shaft was maintained in tension by the reaction of the material.

The arrangements above described, which per-` ymit a fulll and uninterrupted advancing of the material, make it possible to form a seal without resorting to the expedient of increasing the operating pressure of thev system, in order that the reaction will assist in compacting the mass.` the new pump' operates satisfactorily with a minimum pressure and volume of compressed air, thereby effecting a considerable power saving.

The new apparatus thus includes novel features in the improved form of conveyor screw and its unitary bearing support and arrangement for alignment, the improved and adjustable sealing arrangement, and various other details now to be described.

For a better understanding of the invention, reference is made to the accompanying drawing, in which:

Fig. 1 is a side elevation, partly in section,

Fig. 2 is a detail of the barrel and air ring assembly, showing the maximum sealing position of the pump as contrasted from the minimum illustrated in Fig. 1, and

Fig. 3 is a fragmentary detail of a thrust bearing and dust seal assembly, with relation to the rear wall of the pump hopper.

Referring now to the drawing, and particularly to Fig. 1, the pump is seen to consist generally of a hopper section 1, a screw .shaft 2, and a unitary bearingsupport 3 forI the latter, the hopper and bearing support being secured to a common base 4. .A short' barrel 5 is preferably formed as an integral part of the hopper casting, and opens into the front wall of the hopper, and is arranged concentrically with respect to the screw shaft 2.

For reasons that will be explained later, the working portions of the screw shaft are overhung, the shaft being supported and aligned solely by the arrangement now to be described. The/bearing support 3 may be conveniently of cylindrical form, and is cast as a unit so that screw alignment is assured and maintained by machining from one center. The support is provided with integrally cast pedestal flanges or feet 6 and '7, which may be bolted as at 8 to the base 4. The end of the shaft 2-extends through the head 9, which closes the end of the bearing support and is provided with a keyway 10 so -that the shaft may be coupledgto any suitable prime constriction in the dischargeelement presented mover, such as an electric motor or gasoline engine. A slinger seal 11 is secured to the shaft by a set screw 12 and precludes the entrance of dust inti the support. Within the bearing support 3 is a bushing 13. which surrounds the shaft and extends from the slinger seal, as at 14, forwardly beyond the support to the shoulder 15 of A the shaft 2. As the thrust of the screw is rearward, no securing device other than the shoulder 15 is necessary, and this arrangement makes it possible to withdraw the shaft from the bushing and the bearing assemblies by loosening the set screw 12 of the seal 11, and by displacing certain of the parts at the forward end of the pump.

in the recess in the pump hopper.

racebeing retainedinarecess19intl1ebearing` support.

'I'he forward or thrust bearing 20 is preferably -of the double ball type, and is similarly secured in a recess`21 in the support 3. The entire assembly is closed and the outer race secured by the` bearing cover 22. The rear wall 23 of the hopper is provided with a hollow cylindrical recess24, to receive the dust sealing device, which comprises a spring-actuated double seal ring 25, shown in detail in Fig. 3, and generally similar to that disclosed in Fig. 4 of my patent, above referred to. The purpose of the seal 25 is to assist in preventing abrasive dusts. such as cement, from entering the bearing assembly. Lubricating oil may be admitted from any suitable reservoir (not shown) through the piping connection 26.

Between the sealing device 25 and the pump hopper 1 is a gland inthe form of a sleeve 27, which extends a considerable distance into the hopper and surrounds the shaft 2. The gland is provided with a nange 28 whereby it is centered A slight clearance is provided between the sleeve 27 and the shaft, in order that a small quantity of compressed air admitted at the rear of the nange 28 will escape into the hopper around the shaft and form a eounterfcurrent to resist the entrance of dust. 'I'he total quantity of air required at this point should be the minimum sufficient t perform this function, and this is controlled by the back-pressures involved in the physical nature of the material. An excess of air should not be used, as it would tend to aerate the material in the hopper and cause slippage of the screw. When the material pressures are relatively low or the material handled not especially abrasive, this air may be reduced to a minimum or omitted altogether by increasing the clearance of the container of the seal ring 25 to permit lubricating oil to work forwardly along the shaft and through the gland 27.

The first or rear night 30 of the impeller screw is secured to the shaft slightly beyond the gland 27 and is of relatively narrow diameter, the remaining night diameters increasing progressively to a maximum at or near the liner bushing 31 of the barrel 5. By the use of diameters thus progressively increasing, material will be withdrawn from the hopper throughout the length of these nights, rather than by the nrst night 30. l

The remaining nights are of uniform diameter and the pitch decreases, usually from the opening into the barrel liner 31 toward the terminal night 32. It should be remembered that in accordance with common practice, the peripheries of the terminal night 32 and one or more of the additional discharge end nights may be protected by a thin surface of Stellite or other wear-resisting alloy. In order to balance a screw of the type shown, to avoid a tendency to whip, and thereby frictionally engage the inner wall of the bushing 31, metal may be added to or removed from the rear surface of the night 32. If the now of material to the pump is to be uniform, the pitch of the nights within the bushing 31 may be uniform or be decreased very slightly, as the seal space will be suflicient to prevent the rearward escape of air. The walls of the hopper 1 are spaced a substantial distance from the screw to cause the material to assume natural angles of now to facilitate feed and reduce friction. This arrangement also allows grinding mill media and other tramp materials to become lodged in the hopper and decreases the danger of screw night breakage.

The barrel 5 terminates in a nange 33, which is secured to a similar nange 34 of the liner-.bushing 31, by means of through bolts 35, the-position of the liner being regulated by manipulating the lock nuts 36 on the through bolts 35. 'I'he liner bushing is preferably made of or protected by wear-resisting material and it will be evident that it may be quickly replaced. The face of the nange 34 is carefully machined to receive the face of the air ring 37, and leakage of compressed air is avoided by the usual gasket or other simple expedient.

The air ring 37 comprises the usual circular casting provided with a cored air channel 39, the latter being connected through suitable piping connections (not shown) to a source of compressed air. The pressure of the entering air or ring pressure is indicated by the gauge 40. The channel 39 communicates with the interior of the pump through the usual multiplicity of small orifices 4l, the latter being protected by the usual layer 42.of wear-resisting alloy, such as Stellite.

The through bolts 35 extend through the air ring and likewise support and engage the blowout valve assembly 38, which comprises a chamber 43, having an opening concentric with and ofthe same diameter as the barrel liner bushing 31. The inner wall of the blowout valve is sloped and is provided with a hardened and renewable seat 46 for the check or non-return valve 47. The valve disc is an oval, and its inner surface is protected by a layer of wear-resisting material 48, which may be rubber, if cold materials are to be handled, or a hard metallic alloy if hot, freshly ground cement, nue dust or the like are to be conveyed.

The valve disc 47 is connected through an arm 49 to the shaft 50, which is free to turn in the walls of the chamber 43, in order that materials advanced by the screw will raise the disc adjacent to the cover 5l of the chamber 43.

The check valve normally rests on the upper surface of the stream of material. When the pump is stopped, it falls to its seat by gravity. If the system is to remain idle for a sunicient time for the material to lose its fluidity by the seepage of air from it, and to avoid overloading the driving motor when the system is again started, it is customary to cut oi the air supply from the air ring 37 and to admit air at the receiver pressure and in large volumes through the jet and pipingindicated generally at 52 in the lower portion of the chamber 43 for a sunicient time to cause the pressure to free or clear the line. During this time the back pressure tends to hold the valve disc 47 on its seat. The chamber 43 is provided with a nanged outlet 53, which is connected to the usual piping system (not shown). The diameter of the outlet normally does not exceed that of the liner bushing 31 and is usually somewhat smaller to maintain the proper velocity in conveying.

Near the outlet 53, a connection 54 is made to a pressure gauge 55, the purpose of the latter being to indicate the back pressure of the system and to determine, by reference to the gauge 40, the proper relative operating pressure of the pump. It further serves to indicate when the line has been freed of material, after the pumpo is stopped and the line blown out by showing` a minimum or zero line pressure.

' By reference to Fig. l, it will be noted that the liner 31 occupies an innermost position, limited by the actual contact of the interior lock nuts 36. At this point, the distance between the vertical centerline of the air orifices 41 and the terminal night 32 provides a minimum seal space. It ia obvious that the shorter the seal. the less power will be required to force material through it against the static head or back pressure of the system. The seal, however, may be increased to the maximum position as indicated in Fig. 3 by advancing the position of the liner by bmking away the lock nuts on opposite sides of the flange 33, which causes the liner 31 to advance. It will be understood that for proper operation, the liner and air ring should only be advanced to the minimum working position necessary to provide the seal.

Ordinarily no provision need be made in the piping system to absorb movement of these parts, as an adjacent pipe bend can be suiliciently detlected. but where long horizontal runs of piping are involved, any simple expedient such as spacing gaskets, flexible hose, couplings or expansion joints may be used.

The conveyor screw may be withdrawn and a new one substituted simply by unbolting the blowout valve assembly 43 and displacing it together with the pipe line, removing the slinger seal ll and forcing the screw shaft forwardly through the bushing 13.

The operation of the apparatus will be apparent from the foregoing description, taken in connection with the patents above mentioned, and it will be understood that the device may be employed for generally the same purposes.

I claim:

l. Apparatus for conveying pulverulent material through a conduit comprising the combination oi' a receiving hopper, a cylindrical barrel forming a portion of the conduit and opening into a wall of the hopper, a conveyor screw' extending through the hopper and into the barrel, a movable bushing for the barrel, means for 'admitting compressed air to the barrel secured to the bushing and means for changing the position of the bushing to vary the distance between the air admitting means and .the end of the conveyor screw.

2. Apparatus for conveying pulverulent material through a conduit comprising the combination of a receiving hopper, a cylindrical barrel forming a portion of the conduit and opening into awallofthe barreLamovablebushingliningmeimi-rel,mmmrorelnmnngtnelongitudi-V nalposition ofthebushing,meansforadmitting compressed air to the conduit beyondthe terminalnightof the screw.saidmeansbeingsecured tothe bushing andmovable withittovarythe sealspace betweensaidightandtheairadmi ting means.

3. Apparatus for conveying pulverulentmaterial through a conduit which comprises the comrial, comprising the-combination of a'receiviug hopper, a hollow cylindrical barrel opening into a wall of the hopper, a screw shaft extending through the hopper and into the barrel in concentric relation therewith, the shaft being subject to compression loading, the shaft extending through the opposite wall of the hopper, a bushing surrounding the shaft beyond the wall, a

shoulder on the shaft abutting the bushing, due to thrust, the bushing being supported in spaced bearings, the forward bearing being a thrust bearing to receive the compression load at an intermediate point on the shaft to maintain it in concentric alignment with the barrel and the rear bearing being a radial bearing.

f 5. Apparatus for conveying pulverulent material, comprising the combination of a receiving hopper, a hollow cylindrical barrel opening into a wall of the hopper, a screw shaft through the hopper and into the barrel in concentric relation therewith, the shaft being subject to compression loading, the shaft extending through the opposite wall of the hopper, a bushing surrounding the shaft beyond the wall, a shoulder on the shaft abutting the bushing, due to thrust, the bushing being supported in bearings, aligned and arranged at opposite ends of a unitary support secured to the wall of the hopper and aligned with the latter on a common base, the forward bearing being a thrust bearing to receive the compression load at an intermediate point on the shaft to maintain it in con# centric alignment with the barrel and the rear bearing being a radial bearing.

JOSEPH H. MORROW.

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