US2943599A - Apparatus for applying pulverulent substance to a base - Google Patents

Description

July 5, 196 F. HECK 2,943,599

APPARATUS FOR APPLYING PULVERULENT SUBSTANCE TO A BASE Filed Nov. 15, 1954 Un ed ta es at n APPARATUS FOR APPLYING SUBSTANCE TO A BASE Friedrich Heck, 16 Huttenstrasse, Hemer-Sundwig, Germany Filed Nov. 15, 1954, Ser. No. 468,961

Claims priority, application Germany Nov. 26, 1953 7 Claims. (Cl. 118--308) stationary applying device. Variations in the thickness of the application are brought about by a change in speed of the motion of the base or by a variable feed of the quantity of powder by varying the speed and the feed.

The known methods and devices have the disadvantage that the distribution of the powdery material to be sintered will not be perfectly uniform on the base. When producing plated surfaces on band-shaped bases, any uneven distribution has the eiiect, that, after rolling, surfaces of unequal thickness will result. Moreover, there will be differences in the thickness of the plated, bandshaped bodies, so that the desired tolerance is exceeded and the product has to be rejected.

Should the distribution of the powdery substances not be uniform, there will also be difficulties in the rolling process itself, which render the latter difiicult or make necessary several successive rolling operations whichv nevertheless will not sufiice completley to overcome the faults. If, for instance, the distribution of the powdery substance over the cross-sectional area of the plate (parallel to the roll gap) is not uniform, the product will during the rolling itself become curved, when viewed in the longitudinal direction. Should the lateral marginal parts of the plate receive more powdery substance than the centre strip, there will in the region of the marginal strips be a greater extension than in the central strip. A subsequent rectifying of the plate will no longer be able to correct the applied irregularities or at least not sufiiciently. Further rolling will also not help in removing the different thickness of substance which has been formed.

The described difficulties occur specially, when producing platings, in which the plating layer itself has a high lead content. In these cases it is therefore necessary to effect a particularly uniform distribution of the powdery substance on the base. Should this not be the case, the result will be, that during the separate sintering processes, which take place between the rolling operations, the lead which becomes fluid at 327 C. will creep into the'spaces of greater porosity and produce surface disintegration. Moreover, the lead will emerge at the already solidified surfaces during sintering at the surface of the plated layer and will solidify there as it cools.

Various devices are known, which however provide no certainty for a uniform distribution of the amount dusted on per unit of time. In so far as it is a question of using powdery mixtures of substances, the known de vices tend'to bring about a segregation of the mixtures.

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To this class belong moreparticularly the conveying 1 ing to the invention the applying device comprises afiexible and very thin conveying band which has a thickness of the order of magnitude of about 0.1 mm. and with which the powdery substances are deposited on the base. This conveying band may consist of a synthetic material of very high tensile strength or of a woven fabric of nylon or Perlon. A further feature of the invention consists in this, that the very thin conveying band is taken round a roller of very small diameter at the feeding place or round a slightly rounded edge in such a manner that the depositing of the conveyed material will not be substantially influenced by a curvature at the place of deflection.

According to the invention the feeding of the conveying band with powdery material takes place by way of a supply hopper which is provided above the conveying band with an adjustable gap for the passage of the powdery material. The gap can be adjusted for instance by the displacement of a hopper wall.

The supply of the powdertakes place inthe upper part.

of the hopper by way of a chute extending into the hopper, such that there will be a definite height of deposit, which determines the density of the powder above the gap. Under certain operative conditions the height of the deposit and the density are to remain constant, so that the supply of powder to the band will also remain constant. The means for supplying the powdery material to the hopper may be displaceable, such that the displaceability serves the purpose of adjusting the upper pass gap and the height of deposit of the material in the hopper itself. The lower limitation of the gap may be provided by a sill which projects slightly above the plane of the table and somewhat raises the band, so that the band will be caused positively to bear over its entire width against the sill. Between sill and table slots are provided which allow particles carried along between band and table to fall through. The sill itself may be made displaceable in height.

In the drawing a constructional example of the invention is illustrated.

Figure 1 shows diagrammatically the side elevation of the applying device according to the invention.

Figure 2 shows to a larger scale the form of the deflecting edge according to the invention.

Figure 3 is a detailed representation of the sill below the hopper and,

Figure 4 is a fragmental vertical sectional view showing the use of a roller at the delivery end of the conveyor.

The conveyance of the plate 10 is efiected in a known manner by a conveyor band or the like. Above the conveyor band 11 is the depositing device. Round a driving roller 1 with constant drive 2 there runs an endless, very thin conveyor band 8 consisting of flexible snythetic material of high tensile strength or of a nylon or Perlon fabric. This conveyor band travels at the delivery end round a rigid edge 6, the point of which is slightly rounded, as will be seen from the illustration in Figure 2. In place of this edge a thin roller 6a as illustrated in Figure 4 may also be used. The radius of the roller or of the rounded edge is in the order of magnitude of about 0.2 mm. In the upper region, that is where the conveyance takes place, the conveyor band 8 is supported by a table 3. Above the conveyor band 8 is a wall 12 which is adjustable in height and the lower edge of which forms a gap 4 with the conveyor band 8. The wall 12 at the Patented July 5,1960

same time forms part of'the hopper 5 which is closed by this wall in the conveyingdirection.

In order to insure the conveyor band 8 being constantly carried along on the driving roller 1, it is advisable to provide a separate pressure-exerting roller 7' which will run round without any separate drive. In order that the feed from the hopper 5 should take place uniformly,

the level of material in the hopper 5 must be kept con-- st'a'nt. For this purpose a supply chute or supply" surface 13 is provided, which extends to a certain length into" the hopper 5. The result of this arrangement is, that below the supply chute 13 anempty space 14 is formed in the hopper; from the" length of the supply chute 13 extending into the hopper 5 and the angle of slope which forms from the endof the supplychute 13% to the wall of the hopper. For enabling a line adjustment to be made, the supply chute may be made displaceable in its longitudinal direction. The bottom limit of the gap 4 may be formed by a sill 9 which extends above the surface of the table 3" and provides that the band 8 will bear securely on the sill 9 (see Figure 3). Between the sill 9 and the table 3 passage slots may be provided. The width of the gap 4 may be varied by raising or lowering the sill 9 by means of a rack 16 secured thereto and a rotatable toothed pinion 17 meshing therewith.

The device illustrated is used in thefollowing manner:

While the conveyor band 8 moves steadily but in a regulable manner in the direction indicated by arrows, the powdery material is deposited on the band in dependence on the adjusted gap 4 and the height of deposit and is' conveyed by means of the band 8 uniformly to the place of delivery, where is the edge 6 or roller 6a. At this place the scattering on to the base travelling through at a definite speed below the supply device takes place. In this connection the advantage of the smallness of the radius of the deflecting edge or roller in conjunction with the thinness of the conveyor band consists in this, that it produces a very small deflecting radius of the conveyor band 8. Hence, only those powder particles will fall down in constant succession, which just owing to the deflectiorr of the band 8 lose their support.

Should a greater radius of deflection be used, then the falling off of the powder particles would not take place evenly, for the reason that the individual powder particles would be conveyed under the influence of static friction to where the deflection commences. Such a static friction will however not occur in practice with a very small deflection radius. Hence, with a large deflection radius an extended transition from static friction through dynamic friction to falling freelywould take place, which would hinder a steady and uniform dropping off of the powder particles; for if large radii are used, as the conveyor band passes from the uppermost point of the roller 6a to a point on a level with its axis its inclination would progressively increase, and the heavier particles of a pulverulent mixture, or those with a lower coefficient of friction, would begin slipping sooner and would slide more quickly (as static friction gives way to dynamic friction) than the adjacent lighter or rougher particles, thus promoting segregation, so that the strewed surface on the base will have mottled appearance. Such a picture is always presented when the powder particles are not deposited uniformly. On the other hand when a small radius of curvature is used, a uniform distribution is always obtained, even if the amount is quantitatively regulated to only l-2 gr. per dm.- I

It is also of great importance for the table 3 to be given a slight downward slope in the direction of conveyance. Such an incline in combination with thin bands further helps a uniform forward feed. The carrying along of the powder in the gap is improved, because through the inclination the static friction on the band in opposition to the d rection of conveyance is increased. There is the The height of the material level is determined 4 possibility that moist powder may cause caking, when the device is set for very thin deposits. In such cases a simple or multiple sieve 15 arranged under the edge 6 or the roller 6a enables the lumps to be broken up, so that there will nevertheless be a good distribution.

I claim: i

1. Means for applying pulverulent substances. to metallic bases for the. purpose of plating, comprising: a driving roller, a very thin and flexible conveyor band having upper and lower nuns. passing about the driving roller, a deflecting element havinga' v'erw small radius of curvature about which. the conveyor band also passes, a rigid table supporting the upper run of the conveyor band, the said table and the said upper. run; having a. slight downward inclination in the direction of conveyance, and a hopper immediately above the upper run of the conveyor band, so located that the upper run of the conveyor band itself forms the bottom of the hopper, and a narrow gap being left between the upper run of the conveyor band and the front wall. of the hopper.

2. Means for applyingpulverulent substances to metallic bases as claimed in claim 1, in which the deflecting element is a rigid bar with a rounded edge.

3. Means for applying pulverulent substances to metallic bases as claimed in claim 1, in. which the radius. of curvature of the deflecting element is of the order of one-fifth of a millimeter.

4. Means for applyingpul'verulent substances to metallic bases as claimed in. claim 1,, further comprising a Inngitudinally adjustable feed chute extending into and so far across the interior'of the hopper. as to limit thestatic pressure of the contents of'the hopper upon the material passing through the gap, the said static pressure being adjustable by longitudinal adjustment of the chute.

5. Means for applying pulverulent substances to metallic bases as claimed in claim 1, further comprising a second conveyor band at a lower level than the first-mentioned conveyor band, and said second conveyor band being adapted to carry along the metallic base to be plated underneath the deflecting element.

6. Means for applying pulverulent substances to metallic bases as claimed in claim 1, in which the thickness of the conveyor band is about one-tenth of a millimeter.

7. Means for applying pulverulent substances to metallic bases for the purpose of plating, comprising: a driving roller, a very thin and flexible conveyor band having upper and lower runs passing. round the driving roller, a deflecting element of very small radius of curvature round which the conveyor band also passes, a rigid. table supporting the upper run of the conveyor band, the said table and the said upper run having a slight downward inclination in the direction of conveyance, a hopper im mediately above the conveyor band, so arranged that the conveyor band itself forms the bottom of the hopper, and a narrow gap is left between the conveyor band and the front wall of the hopper, the rigid table being formed with a slot facing the lower edge of the front wall of the hopper, and an adjustable sill adapted to extend upwards through the said slot and to raise the conveyor band slightly at that portion if required, so as to vary the width of the gap between the conveyor band and the front wall of the hopper.

References Cited in the file of this patent UNITED STATES PATENTS

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