TECHNICAL FIELD

The present invention relates to an apparatus for the discharge and dosing of a paste-like or vault-forming material, and includes a container for the material, a discharge screw disposed in associ- ation with an opening in the container, and an agitation or vault demolition device disposed in the container. BACKGROUND ART

This Art abounds in a multiplicity of different apparatuses for the discharge and dosing of intractible materials. In this context, the term intractible materials in this context is taken to mean, on the one hand, paste-like materials which readily adhere to container walls, conduits and the like, and, on the other hand, such pulveru¬ lent and other materials as possess a manifest tendency to form arches or vaults if they are removed from beneath in a container. Materials which may be considered as extremely intractible in this context are such materials as, in addition to the above-outlined properties, also include sensitive parts or particles which under no circumstances are to be damaged, crushed or comminuted to smaller fragments during the handling of the material proper. DE 21 65 230 discloses an apparatus of the type mentioned by way of introduction. This apparatus includes a container in which there is disposed an agitator which is formed as a rotary bar from which project, in approximately radial directions, a number of agi¬ tator fingers. Beneath the agitator, there are then disposed two discharge screws, in which the one screw is of greater diameter and

larger pitch than the other. The concept according to this prior publication is that the agitator ensure a reliable supply of mate¬ rial to both of the discharge screws, in which the larger screw dis¬ charges the major fraction of the material, whereat the smaller sc- rew takes over and effects a carefully and accurately dosed final discharge.

The apparatus according to this patent specification is a good exponent of a technique which has proved not to function in prac¬ tice. Thus, if this apparatus were used in, for example, the dis- charge of such a viscid material as shrimp cheese paste, there, would rapidly be formed in the agitator a solid body of rotating cheese mass. In the same way, both of the discharge screws would probably also be choked, such that they formed approximately cylindrical, solid rotating bodies. It would hardly be possible to realise any advancement of a material of a paste-like, and viscid and adhesive consistency using an apparatus according to this prior art pub¬ lication. PROBLEM STRUCTURE

The object -of the present invention is to realise an apparatus of the type disclosed by way of introduction, the apparatus being designed in such a manner that it may, in a controlled and operatio¬ nally reliable manner, discharge and dosage dispsense even extremely intractible materials, for example such materials as include, in a viscid and paste-like basic mass, sensitive particles, small pieces or larger aggregates. The invention further has for its object to realise an apparatus of the type disclosed by way of introduction which is designed in such a manner as to permit complete emptying of the container even if the container is filled with an extremely in¬ tractible material. The invention has still further for its object to realise an apparatus of the type disclosed by way of introduction which may, in a strikingly efficient manner, even handle such pul¬ verulent and other materials as show a manifest tendency to form arches or vaults on discharge. In addition, the present invention has for its object to realise such an apparatus as permits good cleaning or stripping of the discharge screw employed while in oper¬ ation, and moreover to realise an arch or vault demolition or agi¬ tation device which permits free movements in the material and which

runs no risk of becoming choked or forming a solid rotating body of the material. Finally, the present invention further has for its ob¬ ject to realise an apparatus which permits simple washing, in that parts employed within the container may easily be removed after op- eration. SOLUTION

The objects forming the basis of the present invention are at _¬ tained if the apparatus intimated by way of introduction is charac¬ terised in that the agitation or vault demolition device includes a rotary wheel whose plane of rotation is approximately parallel to the centre of axis of the discharge screw; and that the wheel has a peripheral contour with recesses which are of a circumdistribution which is intended to accommodate at least parts of the thread crests of the screw. According to the present invention, the apparatus is further suitably characterised in that the agitation or demolition device includes sweeper dogs projecting laterally from the wheel, these be¬ ing placed and aligned in order, at least in the unloaded state on rotation of the wheel, to describe approximately cylindrical paths of movement about the axis of rotation of the wheel; and that the bottom of the container is of a form which geometrically follows these paths of movement.

As a result of this design of the vault-demolition or agitation device, there will be ensured, on the one hand, a vault demolition effect in a large volume of the material accommodated in the con¬ tainer, and, on the other hand, it will be ensured that the con¬ tainer, and even its lowermost region, may be substantially com¬ pletely emptied, since the dogs sweep along, and thereby clean, the bottom surface of the container. Further advantages will be attained according to the present invention if the apparatus is also characterised in that the reces¬ ses of the wheel are of a form which is approximately complementary to the thread profile of the screw; and that the wheel is provided, between two mutually subsequent recesses, with intermediate portions which are substantially complementary to portions of the circum¬ ferential surface of the screw disposed between the threads.

Because the wheel extends in this way down into the thread pro¬ file of the screw and engages therewith, it will be ensured, on the one hand, that no lumps of material rotating together with the screw will adhere to the screw as a solid body, and, on the other hand, that the corresponding phenomenon does not occur as regards the wheel and its sweeper dogs. The screw and the wheel will, hence mut _¬ ually scrape each other clean, so that adequate engagement with the material will be achieved. Thus, during, operation, the wheel will, in a highly advantageous manner, keep the discharge screw clean, such that its function can always be guaranteed.

Further advantages will be attained according to the present invention, if the invention is also given one or more of the charac¬ terising features as set forth in appended Claims 4 to 6. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS . The nature of the present invention and its aspects will be more readily understood from the following brief description of the accompanying Drawings, and discussion relating thereto» In the accompanying Drawings: Fig. 1 is a vertical section through the subject matter of the present invention, the section including the centre axis of the screwj

Fig. 2 is a vertical elevation, partly in cross-section, of the subject matter of the present invention, seen approximately at right angles to the longitudinal axis of the screw; and Fig. 3 is a top plan view of the subject matter of the present invention. DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the Drawings, it will be apparent from Fig. 1 that the apparatus according to the invention comprises a container 1, which has an upper portion 2 which, in horizontal section, has a quadratic or rectangular cross-sectional configuration. Round, oval or other cross-sectional configurations may also be employed, even though certain practical limitations are placed, in such alterna¬ tives, on the design of the bottom of the container. The upper por- tion 2 may, in principle, be of any optional height and its horiz¬ ontal cross-section m be constant or possibly diminishing in an upward direction. The container is further provided, in its wall,

with an insulation 3 such that the material which is accommodated in the container may be kept at an intended temperature which differs from the ambient temperature. Thus, there may be provided, in the container, both heating means and cooling means. In such cases when the temperature of the material accommodated in the container is of no critical importance, the insulation 3 may, of course, be dis¬ pensed with and the container wall may consist of a single layer of sheet metal, plastic or the like.

The container is further provided with a bottom or lower por- tion 4 which is approximately of the form of a hemicylinder, in which the axis of the cylinder lies at right angles to the plane of the Drawing in Fig. 1.

Beneath the container 1, or in the lower region thereof, there is disposed a discharge channel 5 which is in communication with the lower portion 4 of the container by the intermediary of an opening in the lower, hemicylindrical wall of the container.

The discharge channel 5 accommodates a discharge screw 7 which is provided with a longitudinal bore for accommodating a rod 8 which is shiftable in its longitudinal direction for opening a closure lid 9 provided for closing the discharge channel 5. The lid 9 may, suitably but not necessarily, be stiffly spring-biased in a di¬ rection towards its closed position as shown in Fig. 1. As was men¬ tioned above, the rod 8 extends/ through the screw 7, through a jour- nalling member for driving the screw, and out towards the rear face of the subject matter of the present invention where it is inter¬ connected with an operating arm 10 which is movable under the action of an operating rod 11 on an operating device 12. It will further be apparent from the Drawing that the discharge channel 5 inclines up¬ wardly in the discharge direction, whereby the risk of spillage at the end of a discharge cycle is reduced. However, in certain cases, both horizontal and downwardly inclined channels 5 may be employed.

The screw 7 is connected, by the intermediary of a claw clutch (not shown), to its drive and journalling unit 13 which, in its turn, is connected to a drive motor 15 by the intermediary of a cogged belt transmission or some other suitable form of trans¬ mission. '

Since the screw 7 will be urged in a direction to the left in Fig. 1 when it operates for discharging materials from the container 1, the screw need not be fixed in any way in the discharge channel 5 other than by being guided on the rod 8 or being positively guided by the inside face of the channel 5. As a result, the screw 7 may readily be dismounted when the hatch or lid 9 is opened, such that the screw may thereby easily be cleaned.

In the lower portion 4 of the container 1, there is provided an agitation or vault-demolition device which comprises a wheel 16 and sweep dogs 17 projecting laterally therefrom. The wheel is further provided with a shaft 18 which is parallel with or coincides with the centre axis of the lower, approximately hemicylindrical portion 4 of the container. The shaft 18 may be secured in opposing side walls of the container, for example in that it is provided with a spring-loaded telescopic section such that its effective length may be reduced, whereby the opposing end portions of the shaft may be inserted into journal sleeves 19, 20 recessed into the container wall. As a result of this construction, the entire agitation or vault demolition device may readily be lifted out as a unit from the container 1 and be remounted in place. Thus, no opening in the inner wall of the container or through-passage through the insulation 3 and the outer wall need be provided, whereby washing of the con¬ tainer is facilitated. However, in certain cases it is conceivable that the shaft 18 be passed through the container wall and possibly be connected to drive means disposed outside the container.

The wheel 16 is of open construction, which permits passage of the material through the wheel, from one side to the other, in di¬ rections approximately parallel to the longitudinal direction of the shaft 18, the wheel being composed of a peripheral annulus of heavy- -duty wire material, the annulus being connected by the intermediary of spokes 21 to the shaft 18. The peripheral annulus may be con¬ sidered as planar, as is apparent from both Fig. 2 and Fig. 3 and has, viewed from the side (according to Fig. 1) a number of recesses or depressions 22 whose circumdistribution corresponds to the pitch of the screw 7. Suitably, these recesses 22 are designed in such a manner that they are complementary, with slight play, to the profile

of the screw thread. The recesses 22 are interconnected to each other by the peripheral annulus via intermediate portions 23 which may be designed to coincide with the peripheral circle of the wheel, but which may also be substantially straight so that, thereby, the wheel more closely approximates the configuration of a regular poly _¬ gon. The intermediate portions 23 are formed in such a manner as to mate with the circumferential surface of the screw 7 in the valley between two adjacent threads on the screw. The size of the play be¬ tween the contour of the screw and the peripheral annulus of the wheel 16 may vary from case to case, often depending upon the type of discharged material, and may be of the order of magnitude of from a few fractions of a millimetre to several millimetres and, in cer¬ tain cases, centimetres. Naturally, considerably larger dimensions may also be selected if the apparatus is built on a correspondingly larger scale, for example in giant silos or the like. It may gen¬ erally be said of the wheel that it has a peripheral configuration for such cooperation ^" with the screw 7 that it may function as a doc¬ tor blade or stripper device for the screw and possibly be driven by the screw itself, or conversely, transmit driving forces to the screw.

As an alternative to the wheel 16 composed of heavy-gauge wire material, a plate-formed wheel of disk material, for example sheet metal, is conceivable. Naturally, the design of the periphery of the wheel with the recesses 22 and the intermediate portions 23 will be retained as that described above. The sweeper dog and its anchorage ^' device (which will be described in greater detail below) are dis¬ posed, in this embodiment, in apertures in the wheel proximal to its periphery.

In the alternative using a wheel of sheet metal or disk mat- erial, the wheel may, naturally, be solid as was intimated above in certain embodiments, but as a rule it is to be preferred that even such a wheel be provided with one or more apertures disposed in the wheel plate so as to permit material in the container 1 to pass through the wheel.

Irrespective of the rest of the design of the wheel 16, it is possible to provide the periphery of the wheel with a scraper or doctor blade element of deformable or resiliently yieldable material which cooperates with the screw 7 for cleaning the screw. On rotation of the screw 7, this will engage with the wheel 16 approximately as a worm gear, so that thereby the wheel 16 will also be set in rotation. Because of the close contact, or at least the proximity, between the circumferential surface of the screw and the peripheral annulus of the wheel, the occurrence of a solid body .of material adhering to the screw and rotating therewith will be pre¬ vented, since such a body will, as has been intimated above, enter into engagement with the peripheral annulus of the wheel 16. Some¬ what simplified, the peripheral annulus of the wheel acts as a scraper which keeps the surface of the screw 7 clean of adhering material. Conversely, it could also be said that the screw 7 func¬ tions as a cleaning device which prevents the wheel 16 from building up a solid rotating body of material about its periphery.

As was intimated above, the wheel is provided with a number - suitably two or more - of laterally projecting dogs 17 which may be formed as projecting resilient wires or flagella, planar scraper blades or the like. The dogs 17 are yieldably anchored in the wheel in that they are provided with helicoid spring mounts which accommo¬ date pins 24 which are secured interiorly on the peripheral annulus of the wheel. The pins 24 may be considered as pivotal axes about which the dogs 17 may be pivoted in the event of extreme loading. In the normal position, as will be apparent from Fig. 3, the dogs are slightly advanced in the direction of movement, such that their outer, free ends lead in the direction of movement, while their in¬ ner ends anchored in the wheel trail behind. The consequence of this will be that, when the container 1 begins to empty, the dogs will move the material inwardly towards the wheel as they sweep closely along the bottom surface of the container.

No matter whether the bottom of the container 1 is hemi- cylindrical or is of any other configuration to be disclosed in greater detail below, the dogs 17 are designed to follow, as closely as possible, the profile of the bottom, at least in the region be¬ neath the shaft 18 of the wheel 16, if the bottom is not rotationally symmetrical about the shaft.

The pins 24 are directed inwardly towards the centre of the wheel and lie in the plane of the peripheral annulus or the wheel 16. On the other hand, the pins are not radially directed, but are directed obliquely forwardly in the direction of movement, such that they make an acute angle with a radius through their anchorage in the peripheral direction. As a result, the advantage will be af _¬ forded that when the dogs are reflexed rearwardly in relation to the direction of movement on extreme loading, these will be deflected away from the cylindrical surface in the bottom portion 4 of the container 1, in other words the outer, free ends of the dogs 17 will describe a circular path of lesser diameter than would be the case when they move in the unloaded or non-reflexed state. Naturally, the pins 24 may also be approximately radial or refused in the rearward direction. The discharge channel 5, which accommodates the screw 7, may suitably be provided with an approximately hemicylindrical lower wall portion 25 and approximately parallel, vertical upper wall por¬ tions 26, so that it essentially corresponds to the periphery of the screw along at least a portion of the extent thereof. Furthermore, the discharge channel 5 is provided with a rear wall 27 which, on the one hand, is at right angles to the longitudinal axis of the screw 7 and, on the other hand, is directed so as to constitute a tangent to the lower hemicylindrical portion 4 of the container 1. That aperture which places the interior of the container 1 in com- munication with the discharge channel 5 proper will, thus, at the inner end thereof, discharge at an elevated level, an insignificant distance below the level of the shaft 18. Since the discharge chan¬ nel 5 inclines slightly upwardly and, at its outer end, mates with the periphery of the screw 7, the discharge channel will disect the substantially hemicylindrical lower portion 4 of the container at a low level which is approximately at a height which but insigni¬ ficantly exceeds the height of the thread profile above the lower¬ most point of the container. As a result, the thread profile of the screw 7 will lie substantially freely exposed interiorly within the lower, hemicylindrical portion 4 of the container in the central re¬ gion thereof, while being freely accessible from above via the inner portion of the discharge channel 5 proximal the rear wall 27.

DESCRIPTION OF ALTERNATIVE EMBODIMENTS

According to the present invention, it is not necessary for the dogs to be provided, at their inner ends, with the above-discussed helicoidal springs. Instead, the dogs may be provided with a sleeve for accommodating the pin 24. However, this embodiment also includes the provision of a spring which pre-tensions the dogs forwardly in the direction of movement. Possibly, an abutment may be provided so that the dogs are prevented from being pivoted excessively in the forward direction, and so that they may also possess a certain in- herent pre-tensioning even in their most advanced positions.

According to the present invention, it is also possible that the lower portion 4 of the container 1, described in the foregoing as being of hemicylindrical form, may be of another design such that it could instead be composed of two frusto-conical surfaces whose major diameter approximately coincides in both size and disposition with the wheel 16. In, this case, the dogs 17 are also, naturally, designed in a corresponding manner, such that they sweep across these conical surfaces. In this embodiment, the bottom of the con¬ tainer, viewed according to Fig. 2, will be V-shaped with the nadir point at the screw 7» The nadir line in a V-shaped bottom may, nat¬ urally, also be approximately parallel to the shaft 18.

Further embodiments which are conceivable for the bottom 4 of the container are a) a V-shaped, or b) a hemispherical or cupolate design. In the alternative of the V-shaped bottom, the valley of the V will lie with its longitudinal direction coinciding with the longi¬ tudinal direction of the screw 7. In such instance, the screw may lie completely free above the nadir valley of the V or be lowered intoan upwardly open channel of U-shaped or hemicylindrical cross- section. Also in this embodiment, the wheel 16 and the screw 7 en¬ gage with one another in the above-described manner.

No rotational symmetry about the shaft 18 of the wheel 16 will be attained in the V-shaped valley. Instead, the dogs 17 will ap¬ proach the valley and possibly tangentially sweep the valley along a corridor straight beneath the shaft 18 of the wheel.

In the alternative with the hemispherical bottom, full rota¬ tional symmetry about the shaft 18 will be achieved. On the other hand, the situation regarding the agitators or dogs 17 will be as disclosed above for the V-shaped valley, if the bottom is cupolated and shallower than the hemisphere. If, on the other hand, the bottom is deeper than the hemisphere, the dogs or agitators will lie most proximal the bottom in two elongate corridors parallel to the shaft 18 and either side thereof, in other words at the beginning and end of the screw and at right angles to its longitudinal direction. In particular in the embodiments with the V-shaped, hemi¬ spherical or cupolated bottom - but also in the hemicylindrical em¬ bodiment, the container may be round in cross-section.

Irrespective of the design of the bottom, for best discharge feeding capacity of the screw 7, the screw should be provided with more or less closely disposed surfaces, such as the discharge chan- nel 5 which partly encloses the screw. In such cases where the dis¬ charge capacity of the screw is not of a critical nature and it may, possibly, be desirable to provide the screw with an agitative fun¬ ction, the screw may be wholly or partly exposed interiorly in the container and thus be as good as devoid of closely adjacent channel surfaces.

The present invention should not be considered as restricted to that described above and shown on the Drawings, many modifications being conceivable without departing from the spirit and scope of the appended Claims.