Knurling tool

A composite assembly knurling tool for forming uniformly-spaced horizontal serrations continuous across the surface of a metal flake producing drum is disclosed. The knurling tool comprises an alternating array of spacer and forming discs substantially conforming to the contour of the metal flake producing drum.

BACKGROUND OF THE INVENTION 
This invention relates to metal flake production technology, more 
particularly, this invention relates to a knurling tool useful for forming 
multiple uniform serrated edges on a heat extracting drum such that the 
drum would have uniform discrete serrations transversely along the 
peripheral surface, or in other words, parallel to the axis of rotation. 
In producing metal flake, the leading surfaces of the serrations contact 
molten material and have formed thereon flake particles. 
As used herein the terms flake particles, flakes and flake refer to 
particles of relatively small size, in the hundreths of an inch range, and 
the terms include particles frequently referred to as powders because of 
their relatively small size. 
U.S. Pat. No. 4,154,284, commonly assigned, disclosed a method for 
producing metal flake of small length-to-width ratio directly from a pool 
of molten metal. Said method involved use of a generally circular 
serrated-edge, heat-extracting disk-like member touching the surface of a 
molten pool. 
U.S. Pat. No. 4,215,084 disclosed an advancement in the art consisting of a 
drum-like heat extracting member consisting of a serrated copper-sleeved, 
water-jacketed drum. Said application disclosed that the flake production 
rate can be increased by the use of multiple molten streams projected upon 
a serrated drum-like member. A substantially rectangular flake product is 
produced. For certain application such as roofing, a flake product with 
length and width being substantially equal is preferred. The length, 
width, and thickness of the flake product are influenced and controlled by 
factors such as the width or diameter and flow rate of the molten metal 
stream, the viscosity of the molten metal, the speed of rotation of the 
serrated drum, and the configuration of the serrated drum and serrations, 
including the length of the angular surfaces and the height of the radial 
surfaces. 
While a serrated drum-like member can markedly increase flake production, 
manufacture of acceptable serrated drums required painstaking precision to 
achieve acceptable and reproducible results. Copper drum surfaces are 
difficult to uniformly serrate while maintaining precise tolerances. On a 
22" diameter drum, and a serration of 0.06 inches in width (0.0025" depth) 
about 1152 uniform transverse serrations are required 
(22.multidot..pi.+0.06=1152). In addition the angular surface of the 
serrated drum wears with time and usage thus requires periodic 
reconditioning. Each serration consists of a radial surface and an angular 
surface inclined at an angle .theta. to the tangent of curvature of the 
drum. For optimum flake product dimensions and product uniformity it is 
necessary that each of the multiple radial and angular surfaces comprising 
the drum surface be formed substantially uniform in size and orientation, 
and continuous across the surface of the drum. 
It had been the practice to form the serrations in the drum surface by 
means of repetitive dropping of a weighted (170-190 lbs./force) precisely 
shaped chisel following incremental movements of the drum. When a full 
turn of the drum was made and a serrations impacted to the surface, the 
chisel was incrementally moved sideways and the process repeated. This 
would continue until the full width of the drum was serrated. Besides 
being time consuming since thousands of uniform serrations were necessary, 
the final drum had rows of serrations which were not always in perfect 
registry with each other. These imperfections would give rise to a 
coproduced stringly scrap product when flake was being produced. 
Later processes used a paddle wheel shaped tool to impress multiple rows of 
serrations into the drum surface by turning both wheels while in pressed 
contact. This method also yielded nonuniform serrations often not in 
registry transversely across the surface of the drum. 
The above factors made the metal flake production process expensive in 
terms of tooling and machining costs. Commercial acceptance of metal flake 
production using serrated drum technology could be enhanced if efficient 
precision serrating of the drum surface would be feasible. The present 
invention provides a knurling tool for forming multiple uniform serrations 
precise in size and orientation and in registry transversely across the 
surface of a metal flake forming drum. 
SUMMARY OF THE INVENTION 
The invention as herein disclosed is a composite assembly knurling tool for 
forming uniformly-spaced horizontal serrations in the surface of a drum. 
The serrations are formed horizontal, in other words, parallel to the axis 
of rotation of the drum. The drum has radial symmetry about this axis. 
The knurling tool of the present invention is comprised of alternating 
spacer and cutting discs. The alternating spacer and cutting discs are 
sized to substantially conform to the curvature of the drum surface. Thus, 
for example, if the center cutting disc is lined up to serrate in line 
with the axis of the drum, the discs placed on either side of the center 
cutting disc will each be incrementally of larger diameter to compenstate 
for the curvature of the drum surface. Additionally the angular surface of 
each cutting disc is incrementally adjusted to maintain a constant angle 
.theta. relative to the tangential surface of the drum. 
The knurling tool is held by a rigid housing means preferably having 
adjustable pressure controls. The housing means guides and presses the 
knurling tool across the surface of the drum. The knurling tool serrates 
the drum surface by means of impression when the knurling tool is moved 
and rolled longitudinally across the surface of the drum.

DETAILED DESCRIPTION OF THE INVENTION 
The knurling tool of the present invention is comprised of multiple cutting 
discs, substantially conforming to the curvature of the drum, held in a 
composite assembly and designed to transversely serrate the surface of a 
metal flake producing drum. The knurling tool is designed to be guided by 
a rigid housing and while pressed against the surface of the drum, rolled 
transversely across the drum surface to impress a precisely spaced and 
formed series of serrations continuous across the surface of the drum. The 
serrations have an angular surface and a radial surface. The knurling tool 
of the present invention is designed to substantially conform and mesh 
with the general surface contour of the finished serrated drum. 
The knurling tool of the present invention is illustrated in FIG. 3. The 
knurling tool consists of a composite assembly of multiple stacked 
knurling or forming discs or plates having a peripheral edge of precise 
geometry. Each forming disc has a protruding radial surface and has an 
angular surface around its perimeter forming an acute angle with one 
surface of the disc. Between each knurling or forming disc, an optional 
but preferred spacer disc or plate can be sandwiched. The forming disc is 
designed to form the angular surface in the drum serrations by application 
of pressure while the knurling tool is moved transversely across the face 
of the drum. When the optional spacer discs are included, a tangential 
surface is also formed on the surface of the drum between the angular 
surface and the radial surface. The forming disc also forms the radial 
surface of the serrations on the drum. 
Bolt 24 holds the stack of forming discs 16, 18, 20, and 22 and spacer 
discs 15, 17, 19, 21 and 23 in position. 
The knurling tool is rotated about axial member 1 by being designed to be 
journaled or inserted in a chuck or bearing housing and rotated. A free 
rolling bearing housing is preferred such that the knurling tool serrates 
the drum surface by means of impression when rolled across the surface of 
the drum. 
Since the forming discs and spacer discs are removable, the tool can be 
readily customized to drums of different diameters. 
The edges of the forming discs and spacer discs of the knurling tool are 
matched to correspond with and mesh with an arc of a circle as defined by 
the tips of the drum serrations when the drum is viewed sideways from 
either end and the knurling tool is positioned to be rolled longitudinally 
across the surface of the drum. In other words, forming discs set on 
either side of the forming disc knurling at top dead center are 
progressively larger in diameter to correspond to the curvature of the 
drum. 
Looking at FIG. 4 the knurling tool knurling edge is comprised of spacer 
discs 15, 17, 19, 21 and 23. Between the spacer discs, forming discs 16, 
18, 20 and 22 are set. Spacer discs 15, 17, 19, 21 and 23 have tangential 
surfaces 6, 7, 8, 9, and 10 respectively. Forming discs 16, 18, 20 and 22 
have angular surfaces 2, 3, 4 and 5 respectively and also protruding 
radial surfaces 11, 12, 13 and 14 respectively. Axial member 1 accepts and 
retains the forming discs and spacer discs. In FIG. 4 the spacer discs 
shown on the ends form part of the axial member and thus also function in 
disc retainment. 
In the preferred embodiment to knurl a 22" diameter drum angular surface 2 
is inclined relative to horizontal at 8.degree. 45'. Angular surface 3 is 
inclined at 7.degree. 18'. Angular surface 4 is inclined at 5.degree. 51'. 
Angular surface 5 is inclined at 7.degree. 18'. 
In the preferred embodiment, the diameter of forming disc 16 was made 
0.001" greater than the diameter of forming disc 18 and 20. A basic 
diameter of 2.000" was used. The diameter of forming disc 22 was made 
0.001" greater than the diameter of spacer discs 17 and 19. Radial 
surfaces 11, 12, 13 and 14 each measured 0.0025" in height. Spacer discs 
17, 19, and 21 generally measured 0.0375" in thickness. Each forming disc 
measured 0.0225" in thickness. 
It is possible to make each of the angular surfaces of identical 
inclination. In one embodiment one forming disc sandwiched between two 
spacer discs was employed, however, multiple n forming discs are 
preferred. In the preferred embodiment 4 forming discs were employed with 
3 spacer discs set alternately between the 4 forming discs. Spacer discs 
were also set on both ends and are part of the array of forming discs and 
spacer discs. Thus, n+1 spacer discs are preferred. 
The spacer discs have a circumferential periphery generally parallel to the 
axis of rotation of the disc. In the preferred embodiment the periphery of 
each spacer disc would be made tangential to the metal flake forming drum. 
With multiple spacer discs, each spacer disc is made tangential to the 
drum, and thus would substantially conform to the curvature of the metal 
flake forming drum. 
The knurling tool of the present invention consists of multiple stacked 
plates or discs corresponding to an arc of the circle defined by the base 
of the drum at the edge formed by the base and peripheral surface of the 
drum. The stacked discs consist of forming discs having an angular 
surface, and spacer discs. Each forming disc has an angular surface as a 
circumferential periphery designed to coincide with the angular surface 
.theta. desired in the drum surface serration. To maintain a constant 
angular surface on the drum at angle .theta., each successive forming disc 
set on either side of the disc in radial alignment with the axis of the 
drum must have its angular surface slightly or incrementally adjusted. 
Spacer discs are set on opposite sides of the forming discs and between 
succesive forming discs. Each forming disc has one edge defining a circle 
of diameter similar to the diameter of one abutting spacer disc and one 
edge, being the edge formed by the protruding radial surface and angular 
surface, defining a circle of diameter larger than the diameter of the 
abutting spacer disc on the other side. The larger diameter edges of 
successive forming discs should be on the same side. 
A housing or framing means such as a pivot frame can serve as a means for 
guiding the knurling tool transverely across the peripheral surface of the 
drum while pressing the knurling tool against the surface of the drum to 
form an impression. Force was exerted by a cylinder behind the knurling 
tool. 800 to 1500 lbs/sq.in. pressure have been used. Approximately 1200 
lbs/sq.in. has been found optimum when the forming disc is composed of 
high speed tool steel and the drum is copper. Different pressures may be 
required depending upon the particular copper surface and its metallic 
state, whether annealed or work hardened. 
A worm gear or notching system or pin and pin retractor with spaced holes 
types of systems, well known to those skilled in the art, can be used to 
incrementally turn the drum or knurling tool such that a new sectional 
surface of the drum is exposed after each transverse serration is formed. 
It is herein understoood that although the present invention has been 
specifically disclosed with the preferred embodiments, modifications and 
variations of these concepts herein disclosed, such as for example making 
the forming discs and spacer discs an integral one piece unit or assembly, 
may be resorted to by those skilled in the art all without departing from 
the spirit and scope of the appended claims. Such modifications and 
variations are considered to be within the scope of the invention and the 
appended claims.