Flake like metal chips, a method of and an apparatus for making the same

Produced flake like metal chip has a shape being convexed in one side and concaved in the other side in its cross section. These metal chips are produced by dipping spherical or cone shaped projections provided on an outer surface of a rotary drum into molten metal contained in a molten metal reservoir, the molten metal adheres to each projections being dipped then the adhered molten metal is stripped off of each projection after at least a part of the molten metal has solidified. The apparatus for working the above-mentioned method includes, a molten metal reservoir, a rotary drum carrying on its outer surface a number of aforesaid projections, to the tip end of which the molten metal is adhered, and a means for stripping off the adhered molten metal after at least a part of the adhered molten metal has solidified.

BACKGROUND OF THE INVENTION 
1. Field of the Invention: 
This invention relates to flake like metal chips or particles for use in 
strengthening the surface zone of a laid concrete floor by embedding such 
chips and to a method of and an apparatus for producing the same. More 
particularly, this invention relates to a method of making such chips of 
comparatively small size (for instance, 3.0 mm or less) by a simplified 
manner and by using an apparatus of simplified construction also in mass 
production. 
2. Prior Art: 
Since a laid concrete floor itself is generally soft and low in hardness, 
it is liable to be worn due to abrasion not only by articles of high 
hardness but also by such soft articles as those made of wood. 
By taking these situations into consideration, the laying of concrete in 
modern construction adopts a way of improving wear resistant property and 
of preventing cracks from occurring on the surface of the concrete by 
embedding or scattering metal particles in the surface layer of the 
concrete floor. 
Such metal particles as have heretofore been used for reinforcing concrete 
floors were supplied in the form of finely crushed machine tools chips or 
as cut chips obtained in making nails. Due to these facts, there have been 
many problems of not only a poor production efficiency but also poor 
uniformity in size and shape, thereby rendered uniform embedding of these 
particles in concrete floor very difficult. 
As a prior art that the inventor of this invention recognises, there are 
such a method of and an apparatus for forming flake particles as disclosed 
by Japanese Laid-Open Patent Publication Sho-54(1979)-40262. The method of 
forming the flake particles comprises the steps of: 
(a) rotating a heat-extracting drum which is provided around its peripheral 
rim with a plurality of tapered serrations; 
(b) advancing the serrations formed on the drum onto the surface of molten 
material to form a number of independent flake particles, then letting 
said particles partially solidify on said serrations by extracting heat 
from said serrations; 
(c) releasing the particles from the serrations; and 
(d) cooling the thus released particles in a surrounding air. 
However, the particles obtained by the above method are formed as mere flat 
flakes, so they are not relevant to the main object of the present 
invention. 
THE OBJECT OF THE INVENTION 
The present invention aims to solve the problems as mentioned above, for 
this purpose, it aims to provide flake-like metal chips each having a 
convex front face and a concave rear face in its cross section, and also 
to obtain such metal chips having uniformity both in their shape and size 
in mass production. 
SUMMARY OF THE INVENTION 
The present invention relates to flake-like metal chips themselves each 
having a convex face at one side and a concave face at its the other side. 
The present invention also provides a method of producing flake-like metal 
chips comprising the steps of: (a) advancing and dipping inverted 
cup-shaped projections provided on the outer periphery of a rotary drum 
into the molten metal contained in a molten metal reservoir so that a part 
of the molten metal can adhere to the tip end of the projection; and (b) 
releasing the thus adhered molten metal from the projection after the 
adhered molten metal has partially solidified. For carrying out the method 
as mentioned, the present invention further provides an apparatus for 
producing flake-like metal chips which comprises, a molten metal reservoir 
for receiving molten metal therein, rotary drum having a plurality of 
projections of inverted cup-like configuration around its outer periphery 
to the surface of which the molten metal is adhered, and a means for 
stripping the thus adhered molten metal from the projections after the 
adhered molten metal has partially solidified.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Example 1 
FIGS. 1-6 are drawings showing an example of the present invention. 
Explanation will now be made, at first, on the construction. 
In FIG. 1, numeral 1 is a rotary drum of circular shape, the radially outer 
surface of which is provided with a large number of projections 10, as 
shown being enlarged in FIGS. 2-5, which project radially outwardly from 
the outer peripheral surface. 
These projections 10 are arranged as a set consisting of two rows 
constituting two rings. Each of the projections 10 is crowned with a tip 
end portion 10a of an inverted cup-like configuration onto which suitable 
amount of molten metal 2 adheres. 
Such a rotary drum 1 can be made of suitable material having high thermal 
conductivity such as pure copper, copper alloys (for example 0.2% Zr-Cu, 
9% Cr-Cu and so on), thereby promoting solidification of the molten metal 
adhered to the tip end portion 10a by fast heat extraction. 
Numeral 3 in FIG. 1 is a driving means for rotating aforesaid rotary drum 1 
composed, for example, of an electric motor, transmission means and so 
forth and is coupled to the rotary shaft of the rotary drum 1. This 
driving means 3 is a substantial example of a stripping means for 
stripping the adhered molten metal off from the projection 10 by imparting 
centrifugal force. To this end, rotating speed of the rotary drum 1 is set 
at such a rate that the molten metal 2 adhered to the projections 10 
provided on the outer surface can be stripped off from the tip end portion 
10a to form discrete chips by a centrifugal force imparted through the 
rotary drum 1, after at least a part of the adhered molten metal has 
solidified. 
Moreover, the rotary drum 1 is constructed so as to be raised or lowered in 
vertical direction by any suitable lifting means (not shown) and is 
positioned above the level of the molten metal when it is not used, while 
it is lowered in operation such that the tip end 10a of the lowermost 
projections 10 can be dipped into the molten metal 2. The molten metal 10 
is received in a molten metal reservoir 6 of a melting means 5. As metal 
particles to be used, various materials such as cast steel, plain carbon 
steel, stainless steel, aluminum alloys, lead and so on can be used as 
suitable starting material. 
The melting means 5 is composed of a molten metal reservoir 6 made of 
refractory material such as graphite, alumina or the like and a heating 
element 7 wound around the reservoir 6. The heating element 7 heats the 
reservoir 6 to maintain the molten metal 2 received therein normally at a 
pre-determined temperature. 
In FIG. 1, there is a wiper 4 being used as another example of the 
stripping means, which is disposed to wipe off any metal chip still 
remaining being adhered to the tip end 10a without having been stripped 
off even by the centrifugal force explained above. Moreover, a level block 
8 can also be provided for adjusting the level of the molten metal 2. The 
level block 8 is made of a refractory material such as bricks and can be 
moved up and down depend upon the yield rate of the metal chips 20 so that 
the level can be maintained at a desired height. Numeral 9 in the drawing 
is a heating means for heating both the lower side of the rotary drum 1 
and the portion of the molten metal 2 into which the lower side of the 
rotary drum is dipped, thereby prevents undesired cooling of the molten 
metal from occurring due to the surrounding atmosphere. 
Next, explanation will be made on the operation of the invention. 
At first, a suitable amount of molten metal 2 is stored in the molten metal 
reservoir 6 of the melting means 5. For example, molten metal such as 
stainless steel melted in a melting furnace (not shown) is poured into a 
molten metal reservoir 6 being heated by the heating element 7, thereby 
keeping the molten metal 2 at a desired temperature. At the same time, in 
order to prevent the air sucked by the rotary drum 1 and blown to the 
surface of the molten metal 2 from causing temperature drop of the molten 
metal 2, surface of the molten metal 2 is kept at sufficiently high 
temperature by the heating means 9. Temperature control of the molten 
metal 2 is automatically performed by using a suitable temperature control 
means (not shown). 
From this condition, the driving means 3 is started to rotate the driving 
means 1 at high speed. The rotary drum 1 is lowered by operating the 
lifting means for dipping the tip end 10a of the projection 10, coming at 
the lower side of the rotary drum 1, into the molten metal 2. Then the 
molten metal 2 will adhere as shown in FIG. 5 to the tip end 10a of the 
projections 10, as the result, a pre-determined amount of molten metal 2 
depending upon the extent of dipping is taken up and rotated together with 
each projection 10. 
Then, each of the droplets 2a adhered to the tip end 10a will begin to 
solidify with its heat being extracted either by the rotary drum 1 alone 
having high thermal conductivity or, in addition, by the surrounding 
atmosphere. The moment a part of the molten droplet starts to solidify, 
each droplet is stripped and made to fly off from the tip end 10a and then 
scattered into the atmosphere. 
Since the droplet 2a has at least partially solidified at the time when it 
is stripped off, it can be allowed to solidify without being substantially 
deformed during its flight under sufficient cooling effected by the 
surrounding atmosphere. Accordingly, flake-like metal chips 20 of almost 
hemispherical shape having its one side convex, while the other side 
concave in their cross section, as shown in FIGS. 5 and 6, can be obtained 
by the present invention. 
Some metal chips 20 which have not been stripped off from the tip end 10a 
even by the imparted centrifugal force, can be wiped off from the tip end 
portion 10a by means of the wiper 4. Accordingly, by using centrifugal 
force imparted by the driving means 3 combined with the wiper means 4, all 
the formed metal chips 20 can be exactly stripped off from the rotary drum 
1. 
Here, explanation will be made on the working examples carried out 
according to the present invention. 
Table 1 shows the kind of material and the dimension of the rotary drum 1. 
The Table 2 shows the results of the operation. 
TABLE 1 
______________________________________ 
Material Pure Copper Pure copper 
______________________________________ 
Drum Diameter (D) 
310 mm 200 mm 
Number of Rings 
2 5 
of Projection 
Width of the Base of 
4.0 mm 4.0 mm 
the Projection 10 (M) 
Height of the 2.5 mm 2.5 mm 
Projection 10 (H) 
Pitch of the 4.0 mm 4.0 mm 
Projection 10 (P) 
Number of Projection 
243/ring 157/ring 
10 
______________________________________ 
TABLE 2 
______________________________________ 
Stainless Steel 
AISI 430 Cast Iron 
Molten Metal (18Cr--Fe) 3C--4Si--Fe 
______________________________________ 
Atmosphere Air Air 
Heating Temperature 
1540-1580.degree. C. 
1350-1380.degree. C. 
Number of Rotation 
250 rpm 360 rpm 
of the Rotary Drum 
Peripheral Speed of 
4.1 m/sec 3.8 m/sec 
the Rotary Drum 
Heating Means Propane Flame 
Propane Flame 
Material of Wiper 
Stainless Steel 
Stainless Steel 
Wire Wire 
Peripheral Speed of 
2.1 m/sec 2.4 m/sec 
Wiper 
______________________________________ 
Through this working example, obtained metal chips included both 
hemispherical metal chips 20 as shown in FIGS. 5 and 6 having a diameter 
of 1.0-2.0 mm and somewhat deformed oval or similar shape ones within 
permissible range. Among the obtained metal chips, the portion of the 
largest wall thickness of each chip varied 0.19-0.27 mm, while their 
weight per each piece was 1.0-1.5 mg and the yield rate per one hour was 
proved to be 8 Kg. 
As can be seen from the aforesaid working examples, large number of 
flake-like metal chips 20 of cup-like or similar shape were produced in 
continuous manner directly from molten metal 2 by using an apparatus of 
very simple construction. 
The flake-like metal chips 20 thus produced can be used, for example, as 
reinforcing material for building floors either by embedding in the 
surface layer of the concrete floors or by scattering therein. This 
improves wear resistance and increases the strength of the floor itself 
and prevents cracks from occurring. The metal chips 20 obtained by the 
present invention are almost circular in their flat position and have no 
pointed sharp edges, so there is no fear that any sharp edge or point 
projects above the laid floor surface, so they can be used for making 
concrete building of high safety. Especially, by making the metal chips 20 
by using stainless steel, formation of any rust on the metal chips can be 
entirely prevented. Consequently, remarkable advantage can be expected for 
the floors or the passages of the buildings such as refrigerated 
warehouses or perishable foods warehouses where good appearance is 
required and yet normally being highly damped. 
In this example, droplets 2a of the molten metal 2 were allowed to fly in 
the air so as to be cooled thereby, however, the apparatus can be 
constructed in such a different way, that the droplets are made to fly in 
an inert gas such as argon gas, wherein the droplet is cooled by the inert 
gas atmosphere. 
It goes without saying that the number of rows, namely, the number of rings 
and the number of projections per each ring shall not be limited to that 
shown in those examples, but they can be suitably selected when occasion 
demands. Alternately, a large number of hemispheres can be formed to 
constitute protrusions for forming metal chips. 
FIGS. 7-11 show other working examples for forming metal chips of pyramidal 
or cone shaped ones. Each projection 10 is formed as a cone-shaped unit, 
to the tip end of which a desired amount of molten metal 2 is adhered. A 
rotary drum 1 having such projections is made of a material having 
comparatively high thermal conductivity such as pure copper, copper alloys 
(e.g. 0.2% Zr-99.8% Cu, 0.9% Cr-99.1% Cu or the like), thereby extract 
heat in the molten metal 2 adhered to the tip end 10a of the projections 
10 so as to promote faster solidification of the adhered metal. 
The metal chips obtained by the method of this example take a configuration 
having a convex conical front portion and a convex conical rear portion. 
For this purpose the projections 10 differ from those of the previous 
example in that they are formed as cone-shaped units. The remaining 
portion of the drum is the same as that of the previous working example. 
The driving means 3 is rotated for rotating the rotary drum 1 at high 
speed. The rotary drum 1 is, then, lowered by operating the lifting means. 
Thus, the tip end 10a of the projection 10 coming at the lower end of the 
rotary drum 1 is dipped into the molten metal 2. Molten metal 2 will 
adhere to the tip end 10a of cone shaped projection 10 as shown in FIG. 
10, as the result, a certain amount of molten metal determined by the 
extent of dipping is taken up by each projection and is rotated together 
with the projection 10. 
The heat of droplet 2a of the molten metal 2 which has adhered to any of 
the tip end 10a is extracted by the drum 1 of high thermal conductivity, 
or additionally by the surrounding atmosphere and begins to solidify. 
Upon starting of such partial solidification of the droplets 2a, the 
droplets will be swung away from the tip end 10a by centrifugal force 
imparted by the rotary drum 1 and scattered into the atmosphere. 
The droplets 2a, which are at least partly solidified when they left the 
tip end 10a, are fully cooled by the atmosphere during their flight to 
solidify without being materially deformed in their shape. By virtue of 
these conditions, metal chips 20 having convex front faces and concave 
rear faces in cross section as shown in FIGS. 11(a)-(c) can be obtained. 
Some of the metal chips 20 which remained on the tip end 10a without being 
stripped off by the centrifugal force are wiped away by the wiper 4. 
Accordingly, by the combined use of the wiper 4 in addition to the 
centrifugal force imparted by the driving means 3, all the adhered metal 
chips 20 can be completely stripped off from the rotary drum 1 entirely in 
the same manner as mentioned in the previous example. 
The material selected and the dimension of the shaped drum 1 used for this 
example are shown in Table 3, while Table 4 shows the result of the test. 
Through these working tests, cone shaped metal chips 20 as shown in FIGS. 
11(a)-(c) having diagonal length W ranging 1.0-5.0 mm and other similar 
cones were obtained. The size of the obtained metal chips at the largest 
wall thickness portion were 0.10-0.40 mm and the weight per each chip 
varied in a range of 1.0-10.0 mg. Yield rate per hour per each ring of 
projections was 5 kg-20 kg. 
As can be apparent from these examples, cone shaped metal chips 20 were 
continuously produced in large amounts directly from molten metal 2 by 
using an apparatus of very simple construction. 
TABLE 3 
______________________________________ 
Chromium 
Material Pure Copper Copper 
______________________________________ 
Drum Diameter (D) 
310 mm 250 mm 
Number of Rings 
2 40 
of Projection 
Width of the Base of 
4.0 mm 5.0 mm 
the Projection 10 (M) 
Height of the 2.5 mm 6.0 mm 
Projection 10 (H) 
Pitch of the 4.0 mm 10.0 mm 
Projection 10 (P) 
Number of Projection 
243/ring 78/ring 
10 
______________________________________ 
TABLE 4 
______________________________________ 
Stainless Steel 
AISI 430 Cast Iron 
Molten Metal (18Cr--Fe) 3C--4Si--Fe 
______________________________________ 
Atmosphere Air Air 
Heating Temperature 
1540-1580.degree. C. 
1340-1370.degree. C. 
Number of Rotation 
250 rpm 360 rpm 
of the Rotary Drum 
Peripheral Speed of 
4.1 m/sec 2.6 m/sec 
the Rotary Drum 
Heating Means Propane Flame 
Propane Flame 
Material of Wiper 
Stainless Steel 
Stainless Steel 
Wire Wire 
Peripheral Speed of 
2.1 m/sec 2.4 m/sec 
Wiper 
______________________________________