SURFACE COVERING, SELF-CLEANING FOR APPENDANT BULK MATERIALS

Abstract: Wall (3, 12) which is self-releasing relatively to adhesive bulk material (2, 10) clinging to it. The wall is made of flexible, resilient material such that its specific area is increased as it is pressed into contact with the adhesive bulk material and is reduced when the pressure is released. The wall is composite and comprises a single circumferential contact wall (3, 12) to be contacted with said adhesive bulk material and made of a flexible, resilient material, and a circumferential wall (6, 9) spaced from the contact wall and shielded from direct contact with the adhesive bulk material by the contact wall. When the member is inoperative, the contact wall is connected free from tensile stress, at an interspace from the wall of the member shielded from contact with the adhesive bulk material and, in operation, said contact wall is deformable into surface-to-surface contact with at least a portion of the shielded wall.

Description: Surface covering, self - cleaning for appendant bulk materials. The present invention relates to a method of manufacturing a wall which is self-releasing relatively to adhesive bulk material appendant to the wall through contact therewith. A member having such a wall is known from US-A-2 687 682 (W.P. Oehlet et al) in which it serves as a pressure wheel forming part of a planting device. Said pressure wheel is arranged behind a member also forming part of the planting device for making furrows in the soil, serving the double purpose of controlling the planting depth of seeds in the furrows and compacting the earth surrounding the planted seeds. Said pressure wheel can be defined as a cylindrical wheel rim, with a troughed radial cross section of the rim body whose bottom faces the rim axis with a rubber cylindrical case having open ends being provided around the rim under axial tensile stress. The rubber case is only supported at the edge regions thereof by the wheel rim edges, the edge regions of the case being applied and clamped about the rim edges. Thus, that portion of the planting wheel forming the tread and contacting the earth is entirely formed from the flexible, resilient rubber case being under tensile stress. Between said tread and the inside of the troughed wheel rim, there is sufficient space in order that as the planting wheel travels over the earth ridge being formed in the planting region in the soil, the tread is resiliently depressed in the area of contact with the soil without touching the inside of the troughed wheel rim. Partly under the influence of the resilient tread being under tensile stress, the earth ridge is thereby compacted. During displacement of the contact region of the tread with the soil during travel, the tread automatically springs outwards again. This is claimed to shake off the soil, which only sticks to the rubber tire in the edge regions thereof, which are supported by the wheel rim edges. US-A-4 489 790 (L. Lattin) also discloses a planting wheel forming part of a planting device, and having a wall with self-releasing properties, constructed especially for use even under heavy working conditions, i.e. for tilling highly moist soils. The pressure wheel also comprises a cylindrical wheel rim having a troughed radial cross section whose bottom portion faces the rim axis. About the wheel rim there is applied a flexible, resilient hollow tire having a substantially flat radial cross section and being wider than the rim, so that it projects on either side beyond the rim edges. The tire is partly, e.g. for 75%, filled with a liquid, e.g. water. The rest of the tire volume is filled with a gas, e.g. air, the pressure of which may be slightly above atmospheric pressure, e.g. 0.2 ato (20.7 kPa) . The operation of the pressure wheel is such that when the wheel travels over the seed bed, the tire is flattened in the region of contact with the soil, with the insides against one another. The non-compressible • liquid is thus pressed upwards in the tire and the compress- ible gas is simultaneously compressed, whereby the outer half of the tire is stretched. In general, owing to the stretching of the portion of the tire containing the compressed gas volume, tensile forces will occur in the sticky soil layer which in the first place aggravates the adherence of the soil layer to the tire. If, in spite of this, the soil layer is shaken off, other forces will have to play a role, which finally produce this desired result. All in all, however, it must be concluded that the forces actually opposing the desired result and adverse¬ ly affect the process underlying the self-cleaning effect, which is a drawback. The special construction of the tire and the necessity to employ the liquid and gaseous adjuvants in specific quantitative ratios moreover renders the whole apparatus complicated. It is an object of the present invention to provide a method of the above described type which can be used with a few complicated steps also in those cases wherein the fouling with adhesive bulk material due to adherence or caking took place over substantially the entire, at least major portion of the wall area. Another object of the present invention is to provide a member having a wall that is self-releasing to adhesive bulk material appendant to said wall. The invention is characterized in that the wall is made of a flexible, resilient material whose specific area is increased during the contact with the adhesive bulk material and is reduced after the contact with the adhesive bulk material. The invention is based on the insight that on reduction of the specific area (area/weight unit) of a material, shearing forces will be produced in the contact regionbetween a surface of that material and bulk material, such as earth, sticking to said surface. Due to the occur¬ ring shearing forces, the points of adherence of the sticky soil to the surface are broken and simultaneously the cohesion between the soil particles is reinforced, so that it may be expected that the soil is lifted in relatively large, more or less cohesive lumps off the surface and discharged, and all this to an increasing extent according as the resulting reduction in -specific area is stronger. The invention also relates to a member having self-releasing properties for coaction with an adhesive bulk material to be contacted therewith, comprising a circumferential composite wall serving for the contact with the adhesive bulk material, said wall comprising a single circumferential contact wall to be contacted with such adhesive bulk material and made of a flexible resilient material and a circumferential wall spaced from said contact wall and shielded from direct contact with the adhesive bulk material by the contact wall, the distance between said contact wall and the shielded wall being sufficiently large when the member is inoperative in order that, in operation, upon contact with the adhesive bulk material, the flexible resilient contact wall is deformable with area enlargement, thereby producing tensile stress therein, and is characterized in that when the member is inoperative, the contact wall is connected, free from tensile stress, at an interspace from the wall of the member shielded from contact with the adhesive bulk material and that, in operation, the contact wall is deformable into surface-to-surface contact with at least a portion of the shielded wall. The adhesive bulk material includes particulate materials, e.g. pulverulent, granular, squamiform and the like materials having adhesive properties. Examples are earth, concrete mortar, powdered milk, snow, but also those materials having a cohesive but rupturable structure, such as a layer of ice. In selecting the elastic material to be used for the member according to the present invention, attention will naturally also be paid to the specific material properties, such as elasticity or flexibility, tearing strength and wear resistance and the hysteresis of the material, which, with a view to a proper reproducibility of the deformation of the member, should preferably be as low as possible. An elastic material to be suitably employed according to the present invention is rubber; the source for this rubber material may be natural rubber or a synthetic rubber material, preferably styrene-butadiene rubber (SBR) . A major application of the present invention concerns a so-called ridge roller as used in a potato harvester. Such a ridge roller, which is made of steel, is advanced by the machine during the harvesting over the potato beds or ridges, with said roller being coupled to the digging share of the potato harvester in such a manner that this is adjusted to, and maintained at, the proper digging depth. Mainly in the case of wet weather, this roller, however, becomes easily caked with soil, and will thus slip and/or be raised with the digging blade so that the latter is no longer adjusted to the correct digging depth, which results in damage to the potatoes. In accordance with the present invention, an hourglass-shaped member of the type usable as adjusting member for the digging blade in a potato harvester may be provided with a case of rubber material so as to form, coaxially with said hourglass-shaped member, a cylindrical envelope therefor. As such an hourglass-shaped member is rolling over a potato bed, as a part of a potato harvest- er, the elastic cylindrical envelope will be depressed substantially into contact with the sidewall of the roller at the area where the envelope contacts the potato bed, whereby its specific area is increased. As the roller rolls on, the depressed portion of the cylindrical envelope will spring back again, thereby pushing earth 'caked' at that location of the surface and discharging the same. In agriculture, the use of clod rollers is known, the side wall of which can be defined as being formed by a series of hourglass-shaped rollers interconnect- ed at their front faces. For the purpose of removing earth (in the form of clods or also as loose material) from a pile of harvested potatoes an assembly of two of such clod rollers is used, the rollers being rotatable in opposite directions, and the flanges of the hourglass profile of the side wall of one roller rotating in the recesses of the hourglass profile of the side wall of the other roller. Depending on the humidity of the soil to be removed from the pile of harvested potatoes, the clod rollers will be fouled more or less quickly by the clod rollers owing to 'caked' soil. When, according to the present invention, both rollers are enveloped by a rubber case, the rubber cases will be depressed in the region where the flanges of the hourglass profile of one clod roller turn into the recesses of the other profile, thereby enlarging the specific area and thus generated tensile stress. Upon further rotation of the clod rollers, the rubber cases beyond the depressed regions will again spring outwards and assume their original configuration, with simultaneous reduction of the specific area, thereby pushing appending soil off the case surface and discharging the same. The application of such clod roller systems can be found e.g. in harvesting devices, chutes and sorting machines. In the concrete industry, concrete mortor is mixed in a concrete mixer and mostly transported in a truck mixer. The container for the mortar in the mixer or truck mixer is a vessel having a substantially circular radial cross-section and being made of steel. On the inside, the wall of the vessel becomes increasingly encrust¬ ed with concrete. To remedy this effect, according to another embodiment of the present invention, the container is internally provided with a second flexible, resilient wall of one or more rubber sheets fitted in such a manner that, as viewed in a radial cross section of the concrete mortar container, they manifest themselves as four chords of a circle, preferably as four chords forming a closed quadrangle. Through the weight of the mortar in the contain¬ er, on rotation of the container, one or more of the wall portions corresponding with the chords of the flexible, resilient second wall or contact wall will alternately be bent towards the container wall and be pressed against said wall, so that the specific area of the contact wall is enlarged. Upon further rotation of the container, the weight of the mortar is displaced toward the adjoining portion of the flexible, resilient contact wall, so that the earlier depressed portion of the contact wall, under the influence of its resiliency, and with simultaneous reduction of its specific area, resumes its original unloaded position. Any 'caked' concrete mortar will then be pushed off said receding portion. As an additional advantage of this embodiment of the present invention can be mentioned a reduced noise load, improved corrosion resistance and wear resistance. Some embodiments of the member according to the present invention will now be described by way of example, with reference to the accompanying drawings, in which: Fig.l is a diagrammatic view of a potato harvest¬ er having a ridge roller: Fig.2 is a diagrammatic axial cross section of a ridge roller as a part of the potato harvester accord¬ ing to Fig.l on a potato bed or ridge, and having a case-like envelope of natural rubber; Fig.3 is a diagrammatic axial cross section of an assembly of two coacting clod rollers, each having a case-like envelope of natural rubber; and Fig.4 is a diagrammatic radial cross section of a steel mixing-vessel of a concrete mixer internally provided with two contact walls of natural rubber, substan¬ tially shielding the inside of the wall of the vessel from direct contact with the concrete mortar contained in the vessel. In the drawings, the same reference numerals relate to members having similar functions. The potato harvester shown on the drawings (Fig.l) is a so-called bulk hopper harvester comprising a ridge roller 100 connected to the digging share 101 for the purpose of digging depth adjustment. Arrow P indicates the direction of travel of the harvester during harvesting. The potatoes harvested by means of the share 101 arrive on the riddle chain 102 and are transported further upwards therewith. During this transport sticky dirt, such as earth, can be removed by beating against the elevator by means of beaters 103. From elevator 102, the potatoes arrive on the haulm divider 104, having springs 105 entraining the haulm, whereas the potatoes roll downwards into elevator drum 106. From the anti-clockwise circulated elevator drum, the potatoes fall onto a sorting belt 107 and via said belt into bulk hopper 109. Bulk hopper 109 at the head is adapted to tip mechanically or hydraulically so that the potatoes can be transferred onto a truck, not shown. The ridge roller 1 (Fig.2) is provided with a case-like envelope 3 made of natural rubber. Envelope 3 extends to beyond the flanges 4 of the ridge roller or is applied about flanges 4. The protecting rings 5 connected to said rollers at the location of flanges 4, clamp the rubber envelope thereon. In the region where said roller bears on the potato bed 2, the envelope 3 is depressed against the side wall 6 of the roller under the influence of the weight of said roller, whereby the envelope assumes more or less the shape of the profile of the side wall 6 of the roller. As the ridge roller rolls further over the potato bed 2, the rubber envelope, when losing contact with the bed, bends back outwardly while contracting, so that any earth sticking to it will be pushed off envelope 3. Fig.3, 7 and 8 depict a pair of coacting clod rollers, each enveloped by a case 3 of rubber. Each of the clod rollers 7,8, rotating in opposite direction, can be considered to be a series of longitudinally inter- connected rollers having the typical hourglass shape of a ridge roller. In the region of the nip of the clod rollers 7,8, the envelopes 3 are mutually depressed, so that these too, will again assume approximately the profile shape of the side wall in longitudinal direction of the clod rollers 7,8. On further rotation of rollers 7,8, the portions of envelopes 3, beyond the nip, will be contracted and be bent outwardly again. Any appendant earth will then be pushed off the surface of the envelope. Mixing vessel 9 of a concrete mixer not shown in detail in Fig.3, having a direction of rotation indicated by arrow P, is partly filled with concrete mortar 10. At 11, 12, 13 and 14 are indicated walls made of natural rubber. In the lower half of the mixing vessel shown in Fig.3, walls 13,14 of natural rubber are bent outwards under the influence of the weight of the mortar and pressed against the corresponding wall as a liner. On further rotation of the mixing vessel, the concrete mortar rolls onto the walls 11,12 which, in turn, are pressed against the wall of the mixing vessel. Walls 13,14 move away from the wall of the mixing vessel, while being contracted, and any appendant concrete mortar is pressed off the surface of the walls, so that said walls 13,14 will occupy the position of walls 11,12 as shown in Fig.3. Naturally, alterations are possible in the invention as described above and as shown in the drawings, without departing from the scope of the invention.

Claims: - . o - CLAIMS 1. A method of manufacturing a wall which is self-re¬ leasing relatively to adhesive bulk material appendant to the wall through contact therewith, characterized in that the wall is made of a flexible, resilient material whose specific area is increased during the contact with the adhesive bulk material and is reduced after the contact with the adhesive bulk material. 2. A member for coaction with an adhesive bulk material having self-releasing properties to be contacted therewith, comprising a composite circumferential wall serving for the contact with the adhesive bulk material, said wall comprising a single circumferential contact wall to be contacted with such adhesive bulk material and made of a flexible, resilient material, and a circumferent wall spaced from said contact wall and shielded from direct contact with the adhesive bulk material by the contact wall, the distance between said contact wall and the shielded wall being sufficiently large when the member is inoperative in order that, in operation, upon contact with the adhesive bulk material, the flexible, resilient contact wall is deformable, with concomitant area enlargement, producing tensile stress therein, characteri in that when the member is inoperative, the contact wall is connected, free from tensile stress, at an interspace from the wall of the member shielded from contact with the adhesive bulk material, and that, in operation, said contact wall is deformable so as to abut on the shielded wall. 3. A member according to claim 2, characterized in that the shielded wall is the side wall of a ridge roller. 4. A member according to claim 2, characterized in that the shielded wall is the internal wall of a mixing vessel of a concrete mixer or truck mixer, in which portions of the internal wall of the mixing vessel, in operation, are shielded from contact with concrete mortar by rubber walls connected to the inside of the wall, which walls, as viewed in a radial cross section of the mixing vessel, are recognizable as chords of the cross section of the wall of the mixing vessel.

Inventors: VAN VUREN MARIUS, VAN VUREN, MARIUS
Applicants: TRELLEBORG B V, TRELLEBORG B.V.
Application year: 1987
Main classification: A01B29
IPC codes: A01B29, A01D33, B01F15, B28C5