US3637115A

US3637115A - Apparatus utilizing sonic vibrations to facilitate the movement of particulate material along a sloping surface

Info

Publication number: US3637115A
Application number: US7623A
Authority: US
Inventors: Bengt L Holm
Original assignee: Kockums Mekaniska Verkstads AB
Current assignee: Kockums Mekaniska Verkstads AB
Priority date: 1969-02-03
Filing date: 1970-02-02
Publication date: 1972-01-25
Anticipated expiration: 1989-01-25
Also published as: GB1288862A; AT305894B; ES376131A1; DK126925B; FR2037060A1; SE321894B; BE745392A; YU216169A; YU32245B; FR2037060B1; CA922283A; DE2004144A1

Abstract

An apparatus for initiating and facilitating sliding of material along a sloping bottom comprises upper and lower members secured on opposite sides of the bottom and covering an opening provided therein, the upper member being a gas-permeable member. A sound transmitter carried by the lower member opens into a chamber formed by the two members and is directed towards the gaspermeable upper member. The bottom provides together with the elements thus supported thereby a vibrationable unit and forms a fixedly mounted diaphragm thereof in order to vibrate when material supported by the bottom is activated by sound oscillations produced by the sound transmitter.

Description

d States Patent l l olm Jan. 25, 1972 [72] Inventor: Bengt L. Holm, Malmo, Sweden [73] Assignee: Kockums Melcaniska Verkstads Aktiebolag, Malmo, Sweden [22] Filed: Feb. 2, 1970 [21] Appl. No.: 7,623

[30] Foreign Application Priority Data Feb 3, 1969 Sweden ..1383/69 [56] References Cited UNITED STATES PATENTS 2/1967 Caldwell ..222ll95 1/1966 Bodine ..259/DIG.43

FOREIGN PATENTS OR APPLICATIONS 214,889 8/1967 Sweden ..222/196 OTHER PUBLICATIONS E. B. Steinberg, Ultrasonics in Industry lO/65/All Primary Examiner-Samuel F. Coleman Assistant ExaminerNorman L. Stack, Jr. An0rneyEugene E. Geoffrey, Jr.

[57] ABS'IIRACT An apparatus for initiating and facilitating sliding of material along a sloping bottom comprises upper and lower members secured on opposite sides of the bottom and covering an opening provided therein, the upper member being a gas-permeable member. A sound transmitter carried by the lower member opens into a chamber formed by the two members and is directed towards the gas-permeable upper member. The bottom provides together with the elements thus supported thereby a vibrationable unit and forms a fixedly mounted diaphragm thereof in order to vibrate when material supported by the bottom is activated. by sound oscillations produced by the sound transmitter.

7 Claims, 2 Drawing Figures APPARATUS UTILIZING SONIC VIBRATIONS T lFACllLlTATE TlhlE MOVEMENT 0E" PARTTCULATE MATERIAL ALONG A SLOPING SURFACE This invention relates to an apparatus for initiating and facilitating sliding of material along an essentially plane sloping surface.

in containers intended for storage of pulverulent, granular or viscous material it is as a rule advisable to empty the materials by letting them slide downwards along a sloping bottom or bottom portion (sloping conveying plate) under the action of gravity only. The same method is applied in principle in many cases for conveying materials from a container down into a well or chute or an opening of a relatively small cross-sectional area.

For economical reasons it is intended not to give the sloping bottom, or the sloping bottom portions greater inclination than necessary, since the space beneath the bottom or the bottom portions may very seldom be used for useful purposes. It is, however, necessary to pay due attention to the fact that the slope must be sufficient in order that the materials may not get stuck on account of their adhesion to the bottom portions or for other reasons.

A known method of preventing such difficulties is to impart vibrations to the bottom or to a part thereof. For that purpose it is possible to provide sufficient amplitudes for instance by striking the bottom with a hammer or by using continuously operating mechanical vibrators. Another method is to blow air or another gas into the materials, generally from beneath, so that they are loosened and consequently more easily movable (fluidized). The latter method is efficient in particular when it is important to keep the materials easily movable within relatively limited zones, for instance around the outlet opening in transport containers. For bigger containers of the silo type there would be required considerable quantities of air or other gases in order to provide sufiicient mobility along the large surfaces of which the sloping bottom portions consist. Furthermore, it would entail considerable difficulties and costs to make these surfaces or the greater part thereof permeable in the required manner, i.e., with very closely spaced openings, for instance by means of porous bottom plates, cloth or the like, since the weight of the quantity of materials stored in the container places great demands on the strength of the bottom.

The present invention relates to an apparatus for initiating and facilitating the sliding of materials along an essentially plane sloping bottom or one or more essentially plane portions of a bottom, said apparatus combining a relatively simple construction and the property of bringing about an efficient loosening or fluidizing effect on the material carried by the bottom, over a large surface without considerable consumption of air. For this purpose, there is provided an apparatus utilizing on one hand the loosening or fluidizing efiect of a gas pressed into the materials, preferably air, which is vibrated at sound frequency by means of a sound transmitter, and on the other hand the reaction of the pressure variations generated thereby when the gas flow thus vibrating is pressed into the materials through the gas permeable bottom portion, which must of course be so strong and of such a construction that it will withstand the high-static pressure generated by the materials located on top of the bottom. The vibrations, which appear as pressure variations, are attenuated during the flowing of the gas through the material and are transformed into kinetic energy in the various material particles, which are thus more easily separated from each other as well as from the surrounding walls.

According to the invention there is provided an apparatus for initiating and facilitating the sliding of materials along an essentially plane sloping bottom, wherein there is a cap rigidly fixed to the underside of the bottom and carried thereby, said cap being disposed over an opening provided in the bottom spaced from the defining margins thereof, said opening being covered on the top of the bottom by a gas permeable bottom member which together with the cap defines a chamber into which there opens a sound transmitter carried by the cap and directed towards the gas permeable bottom member, said transmitter being intended to activate the materials on the bottom by loosening them and activating said materials by means of sound oscillations from the sound transmitter, and wherein said cap provides together with the bottom a vibrationable unit, said bottom forming a fixedly mounted diaphragm.

Further objects and advantages of the invention will be described in greater detail in the following with reference to the accompanying drawings, in which FIG. 1 is a vertical sectional viewof a container of materials having a sloping bottom and embodying the apparatus according to the invention, the members covering the opening in the bottom, the permeable bottom portion, and the cap with the sound transmitter being shown in side view; and

FIG. 2 is a fragmentary plan view of the bottom portion of the container.

The container shown in the drawings comprises sidewalls l0 and an essentially plane sloping bottom (or bottom portion) 11 as well as a discharge opening -12 located below and is presupposed to be filled with a pulverulent, granular or viscous material which is indicated at 13. In the bottom (the sloping conveying plate) 111 which slopes towards the discharge opening 12 there is provided a circular opening which is covered on the underside of the bottom with a frustoconical outer cap 14 disposed as an outer lid or cover over the opening, and on the top of the bottom with a bottom member made as a gas-permeable frustoconical inner cap 15, said caps defining a space between them and being fixed to the bottom by means of

clamping rings

16 and 17 having the same diameter and being clamped opposite each other at opposite sides of the bottom lll concentrically with the opening by means of a screw and bolt connection 18, so that the caps together with the bottom form a mechanically stable homogeneous construction. On the outer cap 14 a pipe stub 19 is fixed with one of its ends, and the interior of said pipe stub is in communication with the space defined by the

caps

14 and 15 through the end of the pipe stub connected with the outer cap, while the other end of the pipe stub is closed by means of an end plate 20 carrying a sound transmitter of the pneumatic siren type having a diaphragm valve housing 21 located on the outside of the end plate 20 and a resonator horn 22 located inside the pipe stub l9, said horn having its opening directed towards the end of the pipe stub 19 which is connected with the outer cap 17. To the diaphragm valve housing 21 there is connected a line 23 for supplying gas under pressure (generally compressed air) which is used for operating the sound transmitter. This. gas is supplied to the space defined by the outer cap 14, the inner cap 15, the pipe stub 19 and the end plate 20 and having a vide discharge surface formed by the mantle surface of the frustoconical inner cap 15. For that purpose the inner cap consists of a number of bars (not shown) which are fixed to the clamping ring T7 and a ring 24 concentrical therewith and being of minor diameter and extending along the generatrix between these two rings, and a gas-permeable cloth 25, for instance or Perlon, covering and resting on the bars. The bars are preferably sewn into the cloth. The ring 24 is covered by a tightly sealing lid 26 which is fixed by means of screw and bolt connections 27. The structure of the gas permeable inner cap 15 is of such a kind and of such dimensions that neither the cloth nor the bars are subjected to greater stresses than can be received and carried by these elements. This is made possible by relatively weak dimensions, largely thanks to the conical shape of the inner cap. Of course, the inner cap may have another shape, e.g., spherical, but in that case the manufacture thereof will become more complicated.

The space defined by the caps 14 and TS forms an expansion volume for the vibrating gas flow which is discharged by the

sound transmitter

21, 22 through the resonator born 22 when compressed air is supplied through the line 23. By means of the vibrating gas flow passing through the gas-permeable wall of the inner cap 15 formed by the cloth 25 and the supporting bars, and penetrating into the material 13 which is set in motion, as described above, within an area adjacent the inner cap. In addition, however, the unit formed by the bottom and the sound activating device rigidly secured thereto will vibrate in time with the sound oscillations as a result of the momentaneously alternating resistance at the penetration of the gas into the boundary layer between the cloth 25 and the material 13. These vibrations are transmitted on account of the rigid connection between the sound activation device and the bottom directly to the latter, which forms a fixedly mounted diaphragm.

In order to increase the reaction power from the pressure variations it is important that the sound wave, which propagates essentially spherically from a point immediately inside the opening of the resonator horn 22, as shown in dot and dash lines 28 in FIG. 1, meets the reflecting material along a boundary surface whose shape coincides with the wave front. At a certain point of time the whole surface is then hit by a pressure wave of the same phase. The inner cap 15, which determines the shape of the boundary layer by means of its gas permeable cloth 25, is frustoconical in the embodiment described here, which provides for a relatively good coincidence with the shape of the wave front in combination with a very good strength against the pressure forces acting from the interior of the container towards the inside cap. A spherical cap may be used, as mentioned above, and is slightly more ideal in view of a reflection effect of almost correct phase. It is, however, considerably more complicated to manufacture. It should be mentioned in this connection that a reflection of almost correct phase is particularly important in the cases where materials in the container have become densely packed in the area adjacent the inner cap. The percussion effect arising against the material during such reflection may form cracks, which may spread also in relatively hard layers and may consequently create the sliding effect aimed at.

In order to increase the loosening and fluidizing effect exerted on the material 13 in the container it may be advisable to provide a line 29 to the space defined by the outer cap 14 and the inner cap 15 in order to supply extra pressure gas (usually compressed air) to the said space. This added gas will then be discharged through the cloth 25 together with the gas vibrating at sound frequency from the

sound transmitter

21, 22 and pressure oscillations will be imparted thereto by the sound waves propagating from the opening of the resonator horn 22. In the line 29 there may be provided a valve making it possible either to supply additional gas in the manner just described, or to connect the space defined by the outer cap and the inner cap, with the surrounding atmosphere. In the latter case the material 13 in the container will be affected by the percussion effect provided by the sound oscillations and the consequent vibration of the bottom 11 but gas will not be pressed into the materials, which it may be desirable to avoid in order that the materials may not create a great deal of dust.

The apparatus proposed according to the invention for initiating and facilitating the sliding of materials along a sloping bottom has three functions, the internal relation of which is dependent upon the constructional embodiment of the apparatus:

l. Loosening the material in the container by pressing gas under pressure into it.

2. Percussion effect against the material in the container in its boundary surface against the inner cap by reflection of essentially correct phase.

3. Vibrations generated by the reaction from the percussion effect in the unit formed by the bottom and the sound activating means rigidly fixed thereto.

When a line 29 is arranged and provided with a valve of the kind described above the effect indicated under item I may be left out but in that case vibrations which are sufficiently efficient for many types of materials may be obtained through the effect according to items 2 and 3.

In order to avoid that the gas introduced into the materials may have to pass upwards through the whole quantity of material in the container, air outlets may be provided in the walls of the container at suitable distances above the activation means.

As mentioned above, the embodiment shown may be modified, and additional modifications may be made within the scope of the appended claims.

I claim:

1. Apparatus for initiating and facilitating the sliding of particulate material along an essentially plane sloping surface, comprising a container having a bottom outlet and a resilient sloping member adjoining said'outlet and forming said surface, said member having an opening spaced from the defining margins thereof, a lower cap rigidly fixed to the lower side of said member and carried thereby, said lower cap underlying and closing said opening, a gas-permeable member covering said opening on the upper side of said sloping member, said gas-permeable member and said lower cap defining a chamber, and a sound transmitter carried by said lower cap, said sound transmitter opening into said chamber and being directed toward said gas-permeable member to activate said material by loosening and activating the material by means of sound oscillations produced by said sound transmitter, said lower cap and said gas permeable member imparting sonic vibrations to said resilient sloping member which thereby forms a diaphragm further aiding in the movement of said particulate material.

2. Apparatus as claimed in claim 1, wherein said gas-permeable member forms a supporting surface for the material on the upper side thereof, the shape of said gas-permeable member essentially coinciding with the wave front produced by said sound transmitter.

3. Apparatus as claimed in claim 2, wherein said gas-permeable member consists of a frustoconical upper cap projecting from the upper side of the sloping member.

4. Apparatus as claimed in claim 1, wherein said lower cap provided on the lower side of the sloping member consists of a frustoconical cap projecting from the lower side of the last said member.

5. Apparatus as claimed in claim 4, wherein said upper and lower caps are rigidly fixed to said sloping member concentrically with said opening.

6. Apparatus as claimed in claim 1, further comprising a pipe stub extending from said lower cap and said sound transmitter and resonator horn being disposed inside said pipe stub and directed toward the chamber formed by said lower cap and said gas-permeable member.

7. Apparatus as claimed in claim I, further comprising a gas line connected to said chamber formed by said lower cap and said gas-permeable member for supplying gas to the chamber for discharge through said gas-permeable member.

Claims

1. Apparatus for initiating and facilitating the sliding of particulate material along an essentially plane sloping surface, comprising a container having a bottom outlet and a resilient sloping member adjoining said outlet and forming said surface, said member having an opening spaced from the defining margins thereof, a lower cap rigidly fixed to the lower side of said member and carried thereby, said lower cap underlying and closing said opening, a gas-permeable member covering said opening on the upper side of said sloping member, said gas-permeable member and said lower cap defining a chamber, and a sound transmitter carried by said lower cap, said sound transmitter opening into said chamber and being directed toward said gas-permeable member to activate said material by loosening and activating the material by means of sound oscillations produced by said sound transmitter, said lower cap and said gas permeable member imparting sonic vibrations to said resilient sloping member which thereby forms a diaphragm further aiding in the movement of said particulate material.

7. Apparatus as claimed in claim 1, further comprising a gas line connected to said chamber formed by said lower cap and said gas permeable member for supplying gas to the chamber for discharge through said gas-permeable member.