Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to apparatus for chopping scrap
sheet metal strips. In particular, it relates to the chopping
of sheet metal strips of narrow gauge which are easily bent or
crumpled, and are difficult to feed to the chopper,although the
invention is not exclusively restricted to such narrow gauge ~trips.
BACKGROUND OF THE INVENTION ~-
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In the preparation of strip sheet metal for subsequent
use, the edges of the rolled sheet metal strips are often dis-
carded as scrap. For example, when thin sheet metal is being '~
slit into separate strips for use in making for example beveragecans or the like, the edges of the strip will often be wrinkled
and jagged and will be unsuitable for prcduction. Accordingly,
as they leave the slitter or trimmer, the two edge strips are
passed through rotary choppers whîch simply chop the strips up
into short lengths of typically six to twelve inches which are
then collected in a waste receptacle and returned to the mill
a~ scrap.
In the past, such rotary choppers have consisted of a
drum member provided, typically with two or three radially extend-
ing blade3. Two such drums one above and one beneath the stripwere provided, and the blades on the two drums were arranged to
overlap so as to provide a shearing action on the strips. Such
prior art choppers have been,generally speaking,adequate for use
with the thicker gauges of strip sheet metal. However, they are
found to be unsuitable for various reasons, for use with thinner
gauges of sheet metal such as are now coming into wider usage for
example in the manufacture of beverage cans. One of the problems
of such prior art rotary choppers is the fact that no satisfactory
method had been developed for continuously feeding the scrap edge
~trip to the chopper blades. Thu~ when u~ng a thinner more flex-
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ible strip, it was possible for the scrap edge portion to become
deflected so that it did not in fact reach the chopper blades,
but became bent and crumpled up. This would then require shutting
down the line while the crumpled portion was removed, and then re-
starting it again.
In addition,as the speed of the entire line was increased,
the rotation of the upper and lower drums, with their blades ex-
tending outwardly from the drum surface, acted somewhat like a fan
and created air currents which tended to deflect the scrap edge
portions of the strip causing them to flutter or shake, so that Y
they frequently became deflected from between the upper and lower
drums, again causing a misfeed and involving shutting down the line b
while the crumpled or deflected scrap edge portion was cleared up.
BRIEF SUMMARY OF THE INVENTION
The invention therefore seeks to overcome the foregoing
disadvantages by the provision of a rotary chopper having upper
and lower chopper rolls,in which the rolls run in contact with one
another, with the chop~er blades being formed flush with the surface
of the rolls, the surface of the rolls between the chopper blades
being formed of a relatively hard stiff resilient material, of such
a nature, that at least adjacent to the location of the chopper
blades themselves, it may be deflected inwardly to accomodate the
overlap of the chopper blades, and then will spring outwardly again
so as to constitute the smooth cylindrical surface of the roll. In
this way, the scrap edge portion of the strip is permanently gripped
between the nip of the rolls at all time, and at the same time
the fan-like action of the blades is eliminated, since they are
flush with the surface of the rolls.
More particularly, it is an objective of the invention
to provide a scrap chopper having the foregoing advantage~ in which
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segments of the rolls may be removed so as to adjust and position f
the blades.
More particularly, it is an objective of the invention
to provide a scrap chopper having the foregoing advantages in which
the cutting blades are formed of steel bars having an essentially
rectangular cross section,and including releasable attachment means
for attaching and adjusting them in the rolls in at least two and
preferably four different positions so as to make use of at least
two and preferably four edges of the bar one after the other.
It is a further and related objec~ive of the invention
to provide a scrap chopper having the foregoing advantages which
is additionally provided with anti-backlash gearing, including ~-
adjustment means for taking up any backlash in the gearing system,
so as to enable precise adjustment of the meshing of the cutting
blades to be achieved.
The various features of novelty which characterize the
invention are pointed out with particularity in the claims annexed
to and forming a part of this disclosure. For a better understand-
ing of the invention, its operating advantages and specific objects
attained by its use, reference should be had to the accompanying
drawings and descriptive matter in which there are illustrated and
described preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective illustration showing a scrap [
chopper according to the invention; ~
` Figure 2 is an exploded perspective illustration showing ~;
the construction of one of the rolls of the scrap chopper of
Figure 1:
Figure 3 is a greatly enlarged end elevation of the scrap
chopper rolls par~ially cut away;
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Figure 4 is an enlarged sectional side elevation along
the line 4-4 of Figure 1, and,
Figure 5 is a cut away perspective illustration of a
portion of the anti-backlash gearing system.
DESCRIPTION OF A SPECIFIC EMBODIMENT
Referring now to Figure 1, it will be seen that the
scrap chopper according to the invention is shown generally as 10 t
consisting of a housing 12, and upper and lower chopper rolls 14
and 16 driven through a single drive shaft 18 extending out of the
rear of housing 12. The scrap edge portion of the steel strip is
shown as S, passing between the upper and lower rolls 14 and 16.
It will of course be appreciated that the remaining portion of
the strip metal is not shown, for the sake of simplicity. m e
strip S as shown is merely the scrap edge portion as trimmed off
at a cutter or slitter, forming part of the complete sheet metal
working line (not shown).
It will of course be appreciated that the scrap edge
portion S is moving in the direction of the arrow A at a contin-
uous adjustable steady speed, which may typically be up to six
thousand feet per minute. As will be seen from Figure 1, the strip
S is unsupported and once it is chopped up by the chopper 10, it
~;~ is then n~ longer subject to any continuous traction pulling it
through the sheet metal working line.
According to the present invention, the problem of con-
trolling the strip S may be overcome by the use of chopper rolls
14 and 16 in which the blades are located more or less flush with
the cylindrical frictional surface of the roll and the other in-
ventive features as claimed herein. This type of construction is
shown in Figures 2 and 3. According to thi~ particular example of
the invention, a chopper roll 14 or 16 may be made up with a cyl-
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indrical surface in the following manner. A central solid core 20
is formed of steel, having an essentially generally triangular
shape in cross section and a central bore 22. At each corner of
the triangular shape of the core 20, a blade receiving groove 24
is formed, preferably having one side 26 lower than the other side
28. The surface of the core adjacent the high side 28 of the f
groove 24 is formed into an arc having a predetermined radius con-
centric with the center of the bore 22.
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The core 20 defines three flat generally rectangular
lD shaped surfaces 32, preferably provided with registering means such
as dowel pins 34 or any other suitable means. In order to form a
completely cylindrical roll surface, three arcuate segments 36 of
any suitable material are provided, having bores therein for re-
ceiving the dowel pins 34, and having further bores 3~ for receiving
attachment bolts 38. ~olts 38 fit within the threaded recesses 40
- in the core 20. Around the exterior of the arcuate segments 36
- there is provided a hard resilient tread portion 42 adhesively
bonded to the arcuate surface of the segments 36, and having holes
44 extending therethrough in registration with the bores 37. Pre-
ferably,the tread portions 42 are made of hard resilient frictional
material such as polyurethane plastic material or the like such that
it will make a good frictional grip with the strip metal S, and at
the same time be sufficiently resilient to be deformed under pressure.
A tread strip 46 of similar material is also adhesively
bonded to the arcuate surface 30 so as to give the entire roll a
smooth regular cylindrical surface of the same material.
~; In order to shear the strip S, three blades 48 are pro-
vided located in the grooves 24 as shown. The blades 48 are rec-
tangular ~teel bars having four corners or edges 50, and provided
with bores 52 extending therethrough which are preferably counter-
sunk from both sides 80 that fastening screws 54 may be pa~od
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through the bores 52 in either direction, ~o that the blades 48
may be used either way round. The screws 54 pass through bore
52 ana through the longer siae wall 26 of the groove 24. The
side walls 26 may be provided with threaded recesses for reception
of the bolts 54, or alternatively, a portion of the core may be
cut away to provide a recess as at 56 to permit the use of a thread- ~
ed nut 58. In order to locate the blades 48 in the correct position ~'
and to support it during use, shims 60 may be provided both between
the blade and the high side 28 of the groove 24, and also between
the blade and the bottom of the groove 24 as shown. The blades
will be so adjusted that the outer corner~ or edges can be located
relative to the cylindrical surface of the tread 46.
Referring now to Figures 4 and 5, it will be seen that
the lower roll 16 is mounted on the drive shaft 18, and the upper
roll 14 is mounted on a driven shaft 62. The drive shaft 18 is
seen to extend completely through the housing 12 from one end to
the other, and the driven shaft 62 is located within the housing
and exten~s beyond the housing only to the left hand side thereof
60 that it may carry the other roll 14.
Both drive shaft 18 and driven shaft 62 are carried in
suitable roller bearings 64, or any other suitable bearing means
which are adequate for the purpose.
Mounted on drive shaft 18 is a helical drive gear 66
and mounted on driven shaft 62 is an anti-backlash gear indicated
generally as 68, which is shown in more detail in Figure 5. The
anti-backlash gear 68 will be seen to comprise a fixed gear portion ~,
70 having a sleeve 72 extending therefrom, and keyed to the shaft
62 by means for example a key 74. The fixed gear 70 will be seen
to be formed with helical teeth, and is somewhat less than half the
width of the gear 66. It is however of the same diameter and will
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have the same number of teeth so that both shafts 18 and 62
rotate in the same speeds in opposite directions.
A movable gear portion 76 is slidably located on the
sleeve 7~, and is adjustably fastened to the fixed gear 70 by means
of the bolts 78 extending through the gear 70 and fastening in suit- !
able threaded recesses in the gear 76.
The gear 76 is formed with an annular recess 80, and a
spring 82 is located within the annular recess 80, and extends be- ¦
tween the gear 76 and the gear 70, normally urging them apart from
one another. The gear 76 is also formed with helical teeth and is
of the same diameter and has the same number of teeth as the gear
70. The gear 76 is of slightly less than one half the width of
the gear 66. In this way, when the chopper 10 is being installed,
any backlash in the gears may be taken up by simply tightening up
the bolts 78 thereby drawing the gear 76 towards the gear 70 and
closing up the gap.
Once the backlash in the gear system is eliminated, then
the positions of the blades 48 may be adjusted on the upper and
lower rolls 14 so that they make a shear like engagement as
20 shown in Figure 3. Preferably, there will be substantially no
clearance between the adjacent corners 50 of the blades 48 on the
upper and lower rolls 14 and 16, and the adjacent corners 50 will
in fact overlap one another so that there is a shearing action ap- ¦
plied to the strip S as it passes between them.
The portions of the tread 46 adjacent to the blades 48
will be c~mpressed by such overlapping engagement of the blades 48,
and will then spring back again as the upper and lower rolls 14 and
16 continue to rotate. It will be notcd however that while such
compression is taking place, the continuous portion of the strip S
ie. that portion which has not yet passed between the upper and
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lower rolls 14 is still subject to the gripping action of the por-
tions of the tread 46 which are in contact therewith on both sides
thereof, and are subject to the frictional action of the portions
of the tread 46 which apply continuous traction to the portion of
the strip S and thereby prevent it from becoming deflected away
from the nip of the upper and lower rolls 14. f
At the same time, since the adjacent corners S0 of the
blades 48 are more or less flush with or very close to the surface
of the tread 46, there is virtually no fan-like effect created by
10the blades 48 and therefore the tendency for the blades and rolls
to set up disturbing air currents is greatly reduced.
In this way, the chopper rolls can be operated at greatly
increased rotational speed, and can accomodate thinner sheet metal
strips with a far greater degree of reliability than in the past.
When the corners 50 of the blades 48 become dull, all
that is required is for the segments 36 to be removed, and the
bolts 54 of the blades 48 are removed and the blades 48 are simply r
rotated around to locate another corner S0 in the operative posi- t
tion. '~
Any tendency for clearance to develop between the upper
and lower blades 48 can be eliminated by inserting or removing
shims between the blades 48 and the back wall 28, and by adjusting
the anti-backlash gearin~ unit.
It will of course be appreciated that various changes
- can be made without departing from the scope of the invention.
For example, the invention has been described specifically in
relation to the use of three blades 48, this being a convenient
number to arrange around a cylindrical rotor as shown, for the
particular type of operation. ~owever, it would of course be
equally possible ~o provide merely a single blade or two blades
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or four blades, depending upon the size of the rotors, the
speed of operation, and the nature of the material to be chopped
up. Furthermore the invention has been described specifically
in relation to the chopping of thin strip sheet metal. It will
however be equally applicablë to the chopping of other strip
materials for example paper, sheet plastic and the like.
Having described what is believed to be the best mode
by which the invention may be performed, it will be seen that
the inven~ion may be paricularly defined as follows:
A rotary chopper for strip sheet material, for chopping
a strip thereof into shorter lengths, said chopper comprising,
-~ upper and lower roll members of generally cylindrical shape,
b~, ~ mounting means for supporting said upper and lower rolls in
contact with one~another, and drive means for driving the same
in unison, in opposite directions, at least one pair of upper
and lower chopper blade means mounted in said upper and lower
rolls respectively, and having cutting edges located in the
periphery of said rolls whereby said cutting edges overlap
one another on each complete revolution of said rolls
and provide a shearing action, and, resilient tread means
arranged around the remainder of each said roll, said tread
means on one said roll being adapted to be deflected by pressure
of said blade means of the other said roll during rotation to
permit said overlapping shearing action of said blade means,
and said tread means being mutually deflected by one another
during the remainder of said rotation to provide a gripping action
; on a strip passing therebetween.
The foregoing is a description of a preferred embodiment
of the invention which is given here by way of example only. The
invention is not to be taken as limited to any of the specific
features as described but comprehends all such ~ariations thereof
as come within the scope of the appended claims.
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