Note: Descriptions are shown in the official language in which they were submitted.
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DUAL AI~B0~ SCI~AP CIIOPP~n
Back~round o~ the Invention
Technical Field:
. This invention rela-tes to high speed choppers that are
used in scrap edge trimming ol ila-t sheet metal or other
scrap strip producti.on processes that require effective
collection and removal of large quantities of scrap strip
material.
Description o~ Prior Art:
Prior Art devices of this type have relied on a variety
of different configurations all aimed at the same end
result o~ high speed incremental choppi.ng of strip scrap,
see for e~ample U.S. Patents 2,125,939, U.S. Pa-tent 3,084,582
and U.S. Paten-t 3,799,020.
In U.S. Patent 2,125,939, a ro-tary shear kniie is
disclosed tllat uses raked cutting edges on cutting knives
positioned on drums so that they register as opposing
knives are brought together to shear the material. Each
of the knives cutting edges are of an involuted curved
20 con~iguratlon so that the cut will be square in relation to
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the strip being cut.
Patent 3,084,582 discloses a ro-tatable shearing
blade device Ior progressive transverse CUttillg using a
pair o~ blades each mounted on a separate splndle with a
gear teeth mecilanislll inner-connec-ting them. ~ach blade is
held by bolts and springs for relative adjustmellt. ~ach
blade has only vne cutting edge Ior engagement against the
material tv be cut.
In U.S. Patent 3,799,020 a scrap chopper is shown
having a fixed sta~ion lsniIe and a multiple bladed rotary
arbor aligned Ior cut-ting registra-tion therewith.
Summarv_o~ the Inven-tion
A dual arbor scrap c.hopper ~or use with high speed
flat sheet trimming processes that uses multiple edge
cutting blades on dual arbors Ior progressive registration
CUttillg using .curved cutting edges conIiguratioll Ior
reduced blade wear and decrease noise which is desireable
in manuIac-turing environnients.
Description o~ the Drawin~s
Figure 1 is a perspective view of the dual arbor scrap
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chopper with associated drive unit;
Figure 2 is a transverse end section of the dual
arbor scrap choppered arbors with blade portions and
material feeding guide;
Figure 3 is an end view on lines 3-3 o~ Figure 2;
Figure 4 is a top plan view of relative blade position
on the arbor.
Figure 5 is graphic illustrat:ion of blade curve determina-tion; and
Figure 6 is a perspective view of a single blade and its
associated cutting edges.
Descrip-tion of the Preferred Embodiment
A dua]. arbor scrap chopper can be seen in Figure 1 of
the drawings comprising a mounting enclosure 10 securing
to a base 11 by a plurality of fasteners 1~. The mounting
enclosure 10 has an opening at 13 in which is posi-tioned a
pair of rotating arbors 14 and 15 with associated support
bearings and inner-connected speed regulator gearing reduction
mechanism connected to a motor 16 as will be well understood
and known in the art.
Referring now to Figures 2,3, and 4 of the drawings, each of
the arbors 14 and 15 has an unique contour outer surface
configuration defined by a pair o~ oppositely disposed
angularly aligned transverse recesses 17 and 1~. A flattened
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surface area 19 extends from each transverse recess and provides
material c].earance as will be explained in greater detail
later.
Each of the transverse recesses 17 and 18 ex-tend from the
flattened sur~ace area 19 to an angular upstanding edge mount
20 which is apertured at 21 for a blade fastener bolt 22.
The surface o~ the transverse recess 17 and 18 are concave
transversely parallel with the upstanding edge mount 20 de~ining
a blade seat 23. A pair of identical blades 24 are positioned
on each drum, one in each blade seat 23. Each of the blades 2~
is made from a bar blank of a known length, height and thickness
having spaced parallel side surfaces 24A and B~ which is then
machined to form longitudinally curved transversely flat upper and
lower surfaces 25 and 26 at right angles to said side suriaces
24A and B. Each curved surface having t~o matching oppositely
disposed cutting edges 27 and 28. The curved upper and lower
surfaces 25 and 26 are defined by true radius not requiring any
extensive or difficult compound curved or helical blade formation.
The blade seat 23 conforms to the blade surfaces 25 and 26
so that the blades 24 when mounted thereon by the blade fastener bolt
22 are reversible both front to bac~ and top to bottom giving access
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to all :Eour cut-ting edges.
Due to the arbor con~igura-tion and blade configuration
a unique cu-tting ability is available upon matched counter
rotation of the arbors -to bring a pair oI oppositely disposed
blades and there associated cutting edges into progressive
shearing relationship required for cutting strip scrap
material at high speed.
To achieve such blade configuration and placement for
maximum progressive blade engagement it was necessary to
determine the correct blade radius to be formed
by use o~ a true ellipse or the equivalent avoiding a helical
blade as here before used. To determine such a radius it
is necessary to view the nature of the cutting required on
a cylindrical surface and con~ert same to a radius that would
perform as a helical blade without the time and expense
of helical blade nlanufac-ture.
Referring now to figure 5 of -the drawings, a
graphic of the comparison between a true elliptical line E and
a true radius R on the blade 24 is shown.
A portion of an ellipse is represented on the line E.
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The representative blade area i.e. the portion o~ the line E
over which ideally the cutting edge of the blade would fall
is de~ined by the letters BA, since in reality only a small
portion o the true ellipse can be used in a dual arbor con-
figuration. The relative line position shown in Figure 5 and6 is exaggerated ~or illustration purposes.
One of the cutting edges 27, 28 on the blade 24 is shown
in broken lines superimposed over the elliptical line E. To
determine a exceptable simple radius R for the curved sur~aces 25
and 26, a crossover point CP is calcula-ted as the dis-tance
from the center o~ the blade where the line E is intersected
by the proposed radius of the curved surface of the blade. An
example o~ the same is illustrated in Figure 5 as having a
cross over point o~ 1.75 inches ~roM center wi-th a calculated
radius of 19.~845 having a O deviation from the true elliptical
line E at A, which is the center o~ the blade, and at the cross
over point o~ 1.75 inches indicated by CP. ~he deviation of the
selected radius (19.8~5) R is under the elliptical line E and is
indicated graphically as~a shaded area indica-ted by the letter U.
Conversely pass the cross over point CP at 1.75 ~rom the cen-ter
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of the blade the deviation of the selected radius is over or
above the elliptical line E as indicated by the letter 0.
The amount of deviation of the selected radius from the elliptical
line E that is acceptable is in direct relation to the thickness
of the material to be cut. The greater the material thickness,
the greater the amount of deviation can be tolerated while the
thinner material must have lsss deviation.
Referring to Figure 2 of the drawings, a resilient sound
pad 29 is shown fastened to the arbors 14 and 15 between their
respective angularly upstanding edge mounts 20 to the angularly
aligned transverse recesses 17 and 18 forming in opposition a
quiet resilient path for the material being cut to follow
between the arbors prior to cutting. The resilien-t sound pad
29 is contoured to compensate for arbor shape varia-tion and is
accordingly of varying thickness.
It wlll thus be seen that a new and novel dual arbor chopper
has been illustrated and described and that a method for blade
configuration has been illustrated whlch effectively determines
the simple radius on a curved blade which is within the realm
of a true three dimensional elliptical surface shear configuration
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required ~or increased e~iciency and low sound emissions.
There~ore, having thus described my invention I claim:
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