Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
" ~ 3 ~7324
CORE PLUG
Background of Invention
The present invention relates generally to an
improved core plug for protec-ting the ends oE hollow paper
cores on which paper, plastic, fabric and other materials
are wound for storage, shipment and use. More
particularly, the present invention relates to a core plug
formed from wood, plastic, or a composite woody material,
that has increased strength over existing core plugs as a
result of the development of a novel means for removing
the core plugs frorn cores after use.
In paper mllls, textile mills and the like, rolls
of paper and/or ~abric are generally wound on tubular
cores which are usually made of a paper material such as
cardboard or paperboard~ These cores are relatively
strong except tha-t they are vulnerable at their ends where
they can be easily damaged. During shipment and handling,
the rolls of paper and other materials are repeatedly
picked up and moved, and if the core ends become de-formed
in any way, the entire roll of paper or other material
becomes unusable because it cannot be properly chucked.
Thus in order to protect such cores, core plugs are
commonly inserted into the ends o-f the core.
Core plugs are presently available in a number of
sizes to accommodate different sized cores. Such core
plugs are formed from a variety of different types of
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materials, and lnclude various dis-tinctive features to
increase their streng-th and utility. However, in general,
the majority of such core plugs are formed froin wood or
molded wood material. Molded wood core plugs are
available from Moldwood Corporation, Drawer 430, York,
Alabama 36925. Core plugs supplied by Moldwood
Corporation and as described in their sales literature are
conventional in design with a centrally located hole for
removing the core plugs from cores. Most core plugs must
be removed be-fore the rolls of paper, fabric or the like
can be used. The core plugs may be removed by inserting
a metal bar or rod into the hole provided in the plug
where the plugs are wedged or pulled out. However, in
general the metal bar or rod is inser-ted in the hole in
one core plug and butted against the inside of the
opposite core plug so that it can be driven out~ Since
core plugs may differ in size, the holes provided therein
may also be o~` different size. Generally the bars or rods
that are used to remove the core plugs are metal stock of
from abou-t l/2 to 3/4 inch in diameter. Thus the holes in
the core plugs must be at least as large as the bars or
rods used to remove them.
Other core plug designs are disclosed in U.S.
Patent No. 4,015,711; U.S. Patent No. 3,627,220; U.S.
Patent No. 3,547,367; U.S. Patent No. 2,196,378; and U.S.
Patent No. 1,919,769. The core plugs described in the
aforementioned patents are in the form of shells made from
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plastic materials or metal, and with the excep-tion of -the
core plug disclosed in U.S. Elatent No. 2,196,378, all in-
clude a centrally located hole for removing the core plugs
from a core. In U.S. Patent No. 2,196,37~, the core plug
includes a pair of intersecti.ng ribs which divide the face
of the core plug into four q~ladrants. Thus, in order not
to inhibit the increased strength provided by the inter-
secting ribs, the hole for removing the core plug is located
off center in one of the quadrants.
Notwithstanding the features and advantages descri
bed for the core plugs presently in use, the core plug of
the present invention offers increased strength and durabil-
ity over existing core plugs.
The present inventi.on provides a core plug for
reinforcing an end of a tubu].ar core for paper or the like,
the core plug comprising a solid, elongate cylindrical
body having a core plug removal opening spaced from the
center thereof and extending for the full length of the
cylindrical body.
Preferably, the plug is made from wood, plastic,
or a composite woody materia].. In a preferred embodiment
of the invention, the core plug comprises a solid body
portion with an integral tapered forward portion of substan-
tially cylindrical shape. The outer face of the body por-
tion has a diameter that is substantially equal to the
inside diameter of the core for which the core plug is
intended. Meanwhile, the inner face of the forward portion
of the core plug is of slight:ly less diameter than the
outer face to facilitate entry of the core plug into the
I 1~'7~32'1
end of a core. In this form, the core plug has eonsiderable
strength since it does not contain the usual center hole
which is used to remove a conventional core plug from a core
when it is desired to ehuek the core for mounting on an un-
winder, rewinder or the like.
Thus, in contrast to the prior art, the core plug
disclosed herein is provided with an opening or groove spaced
from the eenter of the plug and at or near its remote outer
surface which extends the full length thereof. This arrange-
ment permits the core plugs of the present invention to be
readily and easily removed from cores in the normal fashion
using a standard core plug remover as described hereinbefore.
However, beeause the core plugs of the present inventicm do
not contain the usual center hole, they are much stronger than
eonventional prior art core plugs made from the same material.
Accordingly, it is an object of the present inven-
tion to provide an improved core plug for protecting the ends
of hollow paperboard cores, with plain or reinforced ends,
on which paper, plastic, abric and other materials are wound
for storage, shipment and use.
Another object of t:he present invention is to pro-
vide a core plug of increased strength that is a result of
the omission of the usual center hole required for removing
the core plug from a core.
As indicated above, the core plug is pre-
ferably made of wood, plastic or a composite woody
material in a mold, or machined from stock where desired.
An example of a composite woc,dy material is molded wood
which may be defined as a composition of wood shavings,
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chips or sawdust, resins and/or glue which is mixed
together and heated under pressure in a mold to produce
the desired shape. The significant point is that the core
plugs of the present invention are substantially solid
bodies which include the core plug removing opening or
groove spaced ~`rom the center.
Other and further objects of the invention will
become more apparent from a consideration of the following
detailed description taken with the accompanying drawing.
Description of DraWinK
FIGURE 1 is a perspective view of a typical core
having conventional prior art core plugs located in each
end;
FIGURE ~ is a perspective view with one end in
section showing a tubular paper core with both ends
reinforced with core plugs made according to an embodiment
of the present invention;
FIGURE 3 is an enlarged perspective view of a core
plug embodying the present invention;
FIGURE 4 is an end ~riew of a core plug embodying
the present invention showing a typical shape for the
core plug opening or groove; and,
FIG[lRE 5 is a view similar to Figure 4 showing a
modified shape for the opening or groove.
Detailed Description
As shown in Figure 1, an elong~ted paper core 10
is illustrated with a pair of conventional end core plugs
11, 12 inser-ted in each end. The conventional core plugs
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1 3 ~ 7 ~3 2 ~1
eACh include centrally located holes 13,14 through which a
core plug removing bar can be inserted ~or removing the
core plugs. These core plugs 11, 12 serve to pro-tect the
ends of the core 10 dllring storage and shipment by
absorbing impact shocks during handling and crushing loads
durlng shipment. Meanwhlle, Figure 2 illustrates a
novel core plug design embodying the present invention.
In Figure 2, a typical paperboard core 15 is
illustrated with core plugs 16,17 inserted in each end.
These core plugs 16,17 are preferably made from wood or a
molded woody material but may be fabricated from other
materials such as plastic where cost is no ob~ect. Each
core plug 16,17 is provided with a core plug removlng
opening or groove 18,19 located at the outer surface
thereo~ which gives the core plugs 16,17 greater crush
strength than the conventional core plugs 11,12 shown in
Figure l. The increased strength has been demonstrated by
the results of crush tests conducted on sample core plugs.
A series of core crushing e~periments were
conducted on wooden pine core plugs and molded wood core
plugs to measure their resistance to crushing. The tests
were conducted according to standard testing procedures
established by the Composite Can and Tube Institute
(CCTI). Each of the core plugs had a nominal outside
diameter of about three inches.
In each case a core containing a core plug is
placed in a compression testing machine having upper and
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lower platens which are held rlgidly parallel during
testin~ permitting movement in a vertical direction only.
The speed O:e the moving platen is set at 1/2 inch per
minute. The core containing core plug is placed at the
center between the two platens, and a crushing load is
applied until the load becomes constant, or drops,
indicating core plug failure, or the equipment reaches i-ts
load limit. The data is recorded on a strip chart and the
applied load readings are taken -from the curve on 0.1 inch
increments.
Example I
In this example a serLes of core crushing tests
were conducted wit~l wooden pine core plugs. The results
obtained Erom four separate -tests using conventinal core
plugs and core plugs made according to the presen-t inven-
tion were averaged to produce the data shown in Table I.
The da-ta shows tha-t for wooden pine plugs, grain direction
plays a major role in overall crush resistance. In the
tests where -the grain direction is aligned with the
direction of applied force, crush strengths are generally
higher than those obtained with -the grain direction
oriented perpendicular to the applied force. Where the
grain direction is perpendicular to the direction of
applied force, crush strength is influenced primarily by
compression of the wood grain.
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Table I
&rain Direction Parallel to Force Applied
Load Applied
IncrementsCenter HoleSide Opening Top Opening
(inches)(lbs.) (lbs.)~
.1 880 870 890
.2 1270 1~70 1100
.3 1770 1800 1370
.5 3200 3740 2530
Failed @ 0.51
(3540)
.7 8310 ~960
Failed ~ 0.80
(6620)
9 10000~
*:Load I.iml-t oi' Compression Testing Machine
Grain Direction Perpendicular_to Force Applied
__
Load Applied
Increments Center Hole Side Opening Top Opening
(inches)(lbs.) (lbs.) (lbs.)
.1 810 910 800
~2 1110 1180 970
.3 1500 1530 1120
.5 24~0 2390 1820
.7 3230 3050 2770
Failed @ 0.84
(3610)
.9 3830
Failed ~ 1.02
(3830)
1 3 67~2~
In the data shown in Table I, the re-ference
"center hole" is to a conventional wooden pine plug with a
core plug removing hole in the center. The references
"side openlne" and "top opening" are to core plugs made
according to the present invention with the core plug
turned so that the removal opening is loca-ted either at
the side or top of the core plug. The data shows that the
conventional core plug failed in each case bei'ore reaching
the 0.9 inch increment of compression and a load of about
3600 pounds. With the grain aligned with the applied
force, the center hole core plug failed at 3610 pounds
compression. Meanwhile, the core plugs embodying the
presen~ invention resisted failure until at least a
greater force was applied. With the grain parallel to the
applied force, and the core plug turned so the opening was
on one side, there was no fallure with the maximum of
10,000 pounds o~ load applied. With the same grain
direction and the opening at; the top (or bottom) the core
plug ~ailed at 6620 pounds. With the grain perpendicular
to the applied force, and the opening at one side, the
core plug failed at 3830 pounds. Meanwhile, with the
opening at the top (or bottom~, the core plu~ withstood
the same load without failure.
Example II
In this example a series of core crushing tests
were conducted with molded wood plugs. The results ob-
tained from several separate tests using both styles of
core plugs were averaged to produce the data shown in
Ll
~able II. Only orl~ se-t o~ data points were gathered since
molded core plugs do not have the same grain effects
encountered with solid wooden plugs.
Table Il
Load Ap~lied
Increments Center Hole Side Opening Top Opening
(inches) _ (lbs.~ _~lbs.) _ (lbs.)
.1 9~0 l160 1030
.2 1700 1700 1370
.3 24~0 2430 1780
.5 4910 5230 3380
Failed ~ 0.50
(4980)
.7 1000~* 6160
~ 10000*
~Load Limit of Compression Testing Machine
In the data shown in Table II, the references to
"center hole", I'side opening" and "top opening" are the
same as described for Example I. In this test with molded
plugs, the conventional center hole core plug failed at an
average load of 49~0 pounds. With the core plug
embodying t~e present invent:ion, and the
opening located at one side, there was no failure at
10,000 pounds and a deflection of 0.70 inch. When the
core plug was turned to orient the opening at the top (or
bottom), there was no failure at 10,000 pounds with a
deflection of 0.89 inch. Accordingly, it may be seen that
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both solid wooden core plugs and molded core plugs made
according -to the present invention are stronger in crush
strength -than conventional center hole core plugs made
from the same materials.
An example of -the core plug of the present
inven-tion is shown enlarged in Figure 3. The core plug 20
has a solid cylindrical body portion 21 that fits tightly
into the end of a core and an integral tapered -forward
portion 22 for facilitating entry oE the core plug into
the core~ The outer face 23 of the core plug and the
cylindrical body portion 21 are formed with a diameter
that is substantially equal to the inside diame-ter of the
core for which the core plug is intended. The inner ~ace
24 of the core plug and the tapered forward portion 22 is
of slightly less diameter than the outer face 23. The
core plug 20 includes a core plug removal opening or
groove 25 spaced from the center thereof at the outer
peripheral surface which extends the full length of the
core plug. In the case of solid wooden core plugs, the
opening or groove may he applied to the core plug by
milling, routing or drillng. Where the core plugs are
molded, the opening or groove may be molded in place~
As shown in FIGURES 4 and 5, the shape of the
opening or groove 25 is not particularly significant.
However, in order to accommodate a core plug removing rod
or bar, the geometry of the opening or groove mus-t meet
certain minimum dimensions. For instance, the opening
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should have a minimum area of about 0.2 square inch, and
a maximum area no greater than about 20% of the total area
of the outer face of the core plug. Other exemplary di-
mensions for the opening 25 in a core plug of nominally
three inches diameter are a depth "a" as measured from
an edge of the core plug equal to or less than about one
inch; a width "b" as measured along the outer edge of the
core plug equal to or less than aboutone inch; or a dis-
tance "c" from the center line of the outer end 23 of the
core plug to the bottom of opening 25 less than about one-
third the diamet.er of the outer end 23. It should be under-
stood in this regard that or the paper industry, core
plugs are used which vary in. size from about two inches
up to fourteen inches in diameter. For core plugs having
an outer face diameter of three i.nches or greater~ the
edge of the opening closest to the center of the core plug
should be spaced from the nearest edge of the core plug
by a distance equal to or less than about one-third the
diameter of the outer face of the core plug. Conventional
center holes in these plugs vary in si~e from about one
inch up to four inches in diameter. However, in order
to increase the strength of a core plug the opening in
the core plug to facilitate its removal should be as small
as possible. In such a case, the opening should be at
least large enough to accom~odate the rod or bar normally
used to remove core plugs from cores.
It will thus be seen that the core plug of the
present invention is distinct from prior art core plugs
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and because of this distinct:iveness achieves a strength
greater than conventional core plugs. Accordingly, while
the detailed disclosure set forth above fully describes
the new core plug in at leask one embodiment, it is ob-
vious that modifications and variations may be made to
the core plug by those skilled in the art within -the limi-
tations of the claims appended hereto.
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