Note: Descriptions are shown in the official language in which they were submitted.
~LZ~91~
This invention relates to a lock-up mechanism for
mounting a printing blanket onto a surface of a printing cylin-
der of rotary type printing presses.
BACKGROUND OF THE INVENTION
.
Various means have been used by the printing industry
to secure printing blankets to the outer surfaces of printing
cylinders. A typical means is that in which the cylinder has a
gap formed in its outer surface which extends inwardly to form
a pocket or recess in which one or more reel rods are rotatably
mounted. These reel rods generally have an axial groove in
their surfaces for receiving the ends of the printing blanket.
The blanket ends are reinforced with a strip of metal known as
blanket bars, which ~tiffen the blanket end, making it easier
to insert into the reel rod grooves. After insertion of the
ends into the grooves of the reel rods, the reel rods are rota-
ted in a direction away from the gap so as to pull the blanket
into the pocket and tighten it over the surface of the printing
cylinder. See for example, U.S. 4,~26,931 showing a dual reel
rod system and U.S. 4,510,868 showing a single reel rod system.
These lock-up means work adequately, however, they do
suffer several drawbacks, one of which is termed "blanket pull-
out". Blanket pullout refers to the tendency of the blanket
ends to pull out of the groove of the reel rods, causing the
blanket to separate from the printing cylinder. The result of
blanket pullout is a damaged blanket which often must be
replaced; substantial down time of the press while the blanket
is inspected and reattached or replaced; and the loss of the
printed material affected by the loose blanket.
This phenomenon has become even more problematical in
the "narrow gap" technology which is now being developed.
Narrow gap refers to the concept of reducing the size of the
gap in the cylinder. Narrow gap cylinders generally have a gap
-- 1 --
~2898~5
width of less than .210 inches and ideally, a width of approxi-
mately .180 inches. Gap width on a conventional cylinder is
generally about .250 inches. Narrowing the gap reduces the
incidence of "bounce" during printing. Bounce is a vibration
caused by the impact of the edges of the gap against the ad-
joining printing roll. Bounce affects printing quality, caus-
ing streaks and runs, and machine life, causing an increase in
the rate of wear on the blankets and cylinders. Using a narrow
gap also increases the number of available print lines for a
given cylinder size. Because of these benefits, narrow gap
technology has become increasingly more popular~
As the gaps have narrowed, the thickness of the
printing bars have correspondingly decreased. These thinner
bars are more difficult to hold in the reel rods and exhibit a
significantly greater occurance of blanket pullout than blan-
kets with conventional bars. Various devices have been design- -
ed or suggested to cure the problem of blanket pullout in
narrow gap cylinders.
One such suggestion has been to reduce the width of
the groove in the reel rod to Eorm a tighter hold on the blan-
ket end. This suggestion has not yet been proven or accepted
in practice and would require replacement of the entire reel
rod and would make insertion of the blanket end into groove
more difficult.
Another attempt is that shown in U.S. 4,261,262 where
one or more support rods are placed between the two reel rods
to lock the blanket ends in the grooves of the reel rods and
. , .
` prevent their pulling out. This requires a redesigning or new
; purchase of the press cylinder to accommodate the additional
support rods. Further, the support rods interfere with the
easy insertion and removal of the blankets from the reel rods.
-- 2
-: . .: - - . . :
.
~289~
The presen~ inven~ion overcomes these difficultiés
and provides an easyr effective and inexpensive means for
preventing blanket pullout, especially in narrow gap cylinders.
OB~ECT~ T~E INVENTION
The invention provides a process for securing a
blanket to a blanket cylinder on a rotary printing device
comprising the steps of wrapping the blanket around an exterior
cylindrical surface of the blanket cylinder, placing respective
ends of the blanket in a gap formed in the outer surface of the
cylinder and into an axial groove in one or more reel rods
located in the gap, the axial groove having an inner edge and
an outer ed~e, the inne~ and outer edges extend parallel to
each other and to a same diameter o~ the reel rods, the inner
edge being located closer to the diameter than the outer edge,
the outer edge being located closer to the center of the
cylinder, the reel rods having a substantially planar surface
from the inner edge of the ax.tal groove to a further edge of
the reel rod beyond the diameter and closest to the yap,
. rotating the one or more reel rods so as to draw the respective
ends of the blanket further into the gap and to tighten the
blanket to the cylinder, causing the blanket to conform to the
. substantially planar surface which forms an angle with the
inner edge of the groove and holds the respective blanket ends
. in the groove to prevent their release.
The invention also provides an arrangement for
clamping a blanket on a blanket cylinder o~ a rotary printing
machlne comprising a printing cylinder having an outer
cylindri~al surface formed with a gap extending parallel to an
axis of the cylinder, the gap having a radially inward area,
one or more reel rods being rotatably mounted within the
radially inward area, an axial groove in the one or more reel
B
39~
rods, the groove being located o~ center of ~ diameter of one
or more reel rods, a substantially planar surface on the one or
more reel rods from an inner edge of the axial groove closest
to the diameter of the one or more reel rods to an edge of the
one or more reel rods beyond the diameter of the one or more
reel rods.
The invention further provides a printing cylinder
having an improved lock-up mechanism comprising a narrow gap in
a surface of the printing cylinder, the gap extending inwardly
of the cylinder surface to form a recess, one or more reel rods
rotatably mounted in the recess, the one or more reel rods
having an axial groove in a surface of the reel rod, the groove
being offset and parallel to a diameter of the reel rod, the
groove having an inner edge and an outer edge, the inner edge
being located closer to the diameter of the reel rod than the
outer edge and the outer edge being located closer to the
center of the cylinder then the inner edge, the one or more
, reel rods being located in the recess so that the groove when
rotated toward the gap is in alignment with the gap to receive
a printing blanket end, the surface of the reel rod contalning
the groove being substantially flattened from the inner edge to
a surface beyond the diameter of the reel rod so as to form a
planar surface between the groove and the gap over which the
blanket extends when the reel rod is adjusted to its locking
position.
The disclosed device for securing a blanket to a
printing cylinder of a rotary printing machine is easy and
inexpensive to manufacture and use and affords uniform or even
and reliable securing of the blanket to the cylinder and which
prevents blanket pullout. It is easily interchanged with
preexisting reel rods and provides easy and reliable securing
B
:. ~
.
1~89~5
of a blanket while preventing blanket pullout.
The substantially planar surface on the reel rod
adjacent the axial groove preferably forms an angle from about
85 to about 97 with ~he edge of the groove.
The printing cylinder lock-up mechanism ensures the
blanket will not pullout by eliminating all components of
blanket force which tend to pull the blanket out.
4a
B
: . ..
-
~Z~39~
A further object is to provide a simple means by
which existing reel rods may be modified to prevent blanket
pullout.
Another object is to provide a substantially planar
surface on a reel rod adjacent its axial groove so that when
the reel rod containing a blanket end is in its locked posi-
tion, the blanket portion adjacent the substantially planar
surface has intimate contact with and conforms to that
surface.
A further object of the present invention is to pro-
vide a lock-up means which prevents blanket pullout and allows
the use of thin, flexible blanket bars instead of thick and
rigid bars.
An object of the present invention is to provide a
lock-up means for securely fastening sheet materials having a
rotating spindle means with an axial groove for holding the
ends of the sheet and a substantially planar means forming an
angle with the axial groove so as to hold the sheet in place.
IN THE DRAWINGS
Figure 1 shows a cross-sectional view of a printing
cylinder lock-up mechanism used in the printing industry
today.
Figure 2 shows cross-sectional view of a preferred
embodiment of the present invention.
Figure 3 shows a cross-section of a conventional reel
rod in the lock-up position with the various forces acting upon
it and the blanket.
Figure 4 shows a cross-section of a preferred embodi-
ment of the present invention in the lock-up position with the
various forces acting upon it and the blanket.
Figure 5 shows another preferred embodiment of the
present invention in cross-section.
-- 5
12898~L5
DETAILED DESCRIPTION AND PREFERRED EM~ODI~ENTS
Figure 1 shows a conventional printing cylinder 1
having a printing blanket 2 extending around its outer cylin-
drical surface. The gap 3 which may be either of a convention-
al or narrow type extends radially inward from the surface of
the cylinder to form a recess 4. In the recess are two reel
rods 5a, 5b. The reel rods are rotakably mounted in the recess
4 in a manner well known in the art and not shown, as not being
a necessary part of the present invention.
Each reel rod, 5a and b, has an axial groove 7 which
is spaced off center of the reel rod, but in alignment with the
gap 3. The groove 7 extends along the entire length of the
reel rod and therefore across the width of the cylinderO
In Figure 1, an end 6 of the printing blanket is
shown as it is being inserted through the gap into the longitu-
- dinal groove 7 of the reel rod 5a. The blanket bar is a rein-
forcement used to stiffen the blanket end. The bar makes the
insertion of the blanket end into the reel rod groove easier
and it also tends t:o help keep the end in the groove.
Reel rod 5b of Figure 1 is shown in the locked or
engaged position. The reel rod is shown as having been rotated
in a counter-clockwise direction so that the blanket 2 has been
tightened to the cylinder 1. The blanket end 6 with its bar 8
is shown as being braced against the side of the axial groove
of the reel rod. The blanket also is shown as extending out of
the groove and across the circumferential surface 9 of the reel
rod. The blanket portion in the area of the curved surface 9
forms an obtuse angle with the inner edge of the groove 10.
The angle can vary depending upon the location of the groove to
the center line of the reel rod. As the groove is located
:~289~3~ S
further away from the cen-ter of the reel rod, the angle becomes
greater. Generally, the grooves of the reel rods are located
as far away from the center of the reel rod as practicable to
maximize its alignment with the cylinder gap. In the prior art
presses discussed herein, the angle is generally greater than
112.
In practice, the blanke-t ends are inserted into the
reel rods which are then rotated to a position similar to that
shown by reel rod 5b. This draws the blanket 2 tight against
the cylinder 1 which is now ready for use.
A preferred embodiment of the present invention is
shown in Figure 2.
The printing cylinder 11, blanket 12, cylinder gap 13
and recess 14 are all similar to that described in Figure 1.
The surface 19 of the reel rods 15a, 15b, nearest the
inner edge of the axial groove 17 is substantially flattened
when compared to the edge 9 of Figure 1.
This substantially planar surface 19 insures that the
blanket end 16 with its bar 18 i5 kept in the axial groove when
the reel rod is rotated to its l.ocked or engaged position, as
shown by reel rod 15b.
The operation of the present invention is similar to
that described for the conventional system of Figure 1. The
reel rods 15a and b are turned to align their longitudinal
grooves 17 with gap 13, the blanket ends 16, each having a
blanket bar 18, are inserted through the gap 13 and into the
reel rod grooves 17. The reel rods are then rotated in a
direction which draws the blanket 12 into the cylinder recess
14 and tightens the blanket to the outer surface of the cylin-
der 11. As the reel rods 15a and b are rotated, the blanket
' ~
P~ 8~L5
meets and conforms to the substantialLy planar surface 19,which directs the forces perpendicular to the groove edge 20 to
prevent the blanket bar from pulling out when in the engaged
position.
The angle between the substantially planar surface 19
and the inner edge 20 of the reel rod groove 17 can be from
about 85 to about 97, while the preferred angle is about 90.
An angle greater than about 97 suffers from blanket pullout as
frequently as a conventional reel rod with an angle of at least
112. An acute angle of less than about 85 is not desirable,
as it introduces an added stress concentration factor in the
blanket which decreases the breaking strength of the blanket to
an extent where the blanket breaks upon locking.
An angle of 90 is therefore preferred as it optimi-
zes the prevention of blanket pullout while minimizing the
reduction in blanket strength.
It is believed that blanket pullout is caused by the
larger angle (greater than 112) imposed upon the blanket end
by the curvature of the ree] rod surface adjacent the inner
edge of the axial groove as shown in a conventional printing
cylinder of Figure 1. Applicant believes that the use of a
substantially planar surface (19) adjacent to the inner edge
(20) of the groove (17) eliminates blanket pullout by redirect-
ing the forces in the blanket end in a direction which inhibits
pullout. Figures 3 and 4 and the following discussion on those
; Figures are submitted as a non-binding illustration of the
cause of blanket pullout and Applicant's cure for that problem.
Figure 3 shows a conventional reel rod of Figure 1
with the various forces and variables acting upon it and the
blanket during lock~up. It can be seen that the blanket force
-- 8 --
~2898~S
F is tangent to the circumference of the reel rod and perpendi-
cular to the radius, R. Since the inner edge 10 of the groove
is not along the radius but is offset by a distance, ~, the
blanket force F departs the surface 10 at an angle, O, which is
at least 112. This force F acts upon the blanket end in
groove 7 and during normal printing operations tends to pull
the blanket end out of the groove. It can also be clearly seen
that the further the reel rod is rotated away from the gap, the
greater the blanket force beco~es, and the greater the tendency
for blanket pullout becomes.
In Figure 4 is an isolated reel rod, a preferred
embodiment of the present invention having the same parameters
as in Figure 3. The preferred embodiment of Figure 4 shows the
angle of 90 between the substantially planar surface 19 and
the inner edge 20 of the groove. It can be seen that the blan-
ket force F' is parallel to the substantially planar surface 19
of the reel rod, and perpendicular to the inner edge of the
groove 20. The blanket force F', being perpendicular, does not
tend to pull the blanket end out of the groove.
When the angle is less than about 97 the blanket
force F' will not pull the blanket end out of the groove.
Further, when the angle is less than 90, the blanket force F'
actually forces the blanket end into the groove rather than
just maintaining the blanket end in place as occurs from 90 to
about 97.
While Applicant believes the above explanation fully
~- discloses the cause of and cure for blanket pullout, Applicant
does not intend to be bound by the illustration presented
above. It is possible that other explanations could be found
to show why blanket pullout occurs and why Applicant's inven-
tion eliminates the problem.
12~
Another embodiment of the present invention is shown
in Figure 5, in which a single reel rod lock-up mechanism is
used.
The cylinder 21 has a blanket 22 extending through
the cylinder gap 23 and into the recess 24 where a single reel
rod 25 is rotatably mounted offcenter of the gap so that its
longitudinal groove 27 is aligned with the gap in its non-
engaged or unlocked position. The single reel rod lock-up
mechanism operates in the same way and achieves the same result
as the two reel rod system of Figure 2 discussed previously.
The single reel rod system may be as shown or set up in mirror
image on the other side of the gap or in any manner convention-
al in the printing art so long as the substantially planar
surface 29 forms an angle from about 85 to about 97 with the
inner edge of the groove 30.
The present invention may be formed by milling or
otherwise forming a substantially planar surface on each reel
rod from the inner edge of the groove across to the outer cir-
cumferential surface of the reel rod. The amount taken off of
the reel rod should be sufficient to form a substantially
planar surface over which the blanket may extend, while at the
same time, it should not be so deep or extensive as to hinder
retention or insertion of the blanket end in the groove. Pre-
` ferably, the substantially planar surface should extend from
the inner edge of the groove which is on the circumference of
the reel rod to a point on the circumference on the other side
of the center line of the reel rod that is parallel to the
inner edge of the groove. An important factor in determining
the location of the substantially planar surface is that the
blanket should never be forced in a direction where the blanket
-- 10 --
~8~38~5
force F or F' can cause blanket pullout. The actualconfiguration depends upon the angle chosen and the location
and width of the groove desired in each application. The
length of the substantially planar surface should be
sufficiently long as to ensure that the proper angle between
the inner groove and the surface is achieved and to allow the
blanket which conforms to that surface to achieve a similar
angle as it exits the reel rod groove. A non-limiting example
consists of a reel rod having a diameter of 1.5 inches, and a
substantially planar surface of approximately .6 inches in
length. Existing reel rods may be modified to incorporate this
invention or new reel rods having the substantially planar
surface may be used.
Another advantage of the present invention is its
ability to use thinner and more flexible blanket bars than the
reel rods now in operation, especially in -the narrow gap
technology.
In conventional printing blankets, the bars are
typically quite tlick, rigid and strong. The bars serve two
~0 purposes; they allow for easy insertion into the lock-up
mechanism by providing a straight, solid edge to be pushed down
into the reel rod groove and they help, to some extent, in
countering the blanket force, F, described in Figure 3. The
bars by their rigidity and strength butt up against the outer
edge of the reel rod grGOVe to counter blanket pullout, but
they do not insure against blanket pullout completely.
With the advent of narrow cylinder gap technology,
blanket bars have been made out of increasingly thinner
materials so as to fit easily into the narrower cylinder gaps.
This has rendered the bars more susceptible to bending or
kinking, making insertion and removal more difficult and
reducing the bar's ability to counter the blanket force
- 1 1 -
12898~
which causes blanket pullout. Higher strength alloys and exo-
tic materials have been used to remedy the problem. However,
these materials are difficult to use, are very expensive and do
not prevent blanket pullout, thereby limiting their use.
In the present invention, as the blanket force is
substantially perpendicular the inner edge of the groove, there
is essentially no tendency for the blanket to be pulled out the
groove by the force. Therefore, conventional metals, such as
steel or aluminum, may be used in thinner pieces and still
achieve the desired effect. In addition, it has been found
that in the present invention, the need for a bar that rein-
forces the blanket end is almost eliminated. Strips of plas-
tic, or thermoset or rigid thermoplastic adhesives built up on
one or both sides of the blanket provide all of the necessary
reinforcement needed for the blanket in the present invention.
This advantage eliminates the need for high strength, expensive
alternatives and allows one to use any material of sufficient
stiffness which is capable of being permanently attached to the
blanket and is compatible with the blanket.
Table 1 shows the results of tests on reel rods hav-
ing various angles between the inner edge of the groove and the
adjacent surface o~ the reel rod and the effect upon blanket
pullout.
The angles tested are from 112.6, that of a conven-
tional reel rod, to 85.6, at succeeding increments of 2.3.
The width of the longitudinal groove is varied, using
three widths .225, .175 and .125 to show the effect on blanket
pullout.
- - 12 -
12898~ 5
Likewise, the width of the blanket bar, (i.e. how far
it extends up the blanket) is in two widths of .475 and .750
inches. The blanket bar is a 4 ply flexible graphite composite
manufactured by A & M Engineering Composites Corp. of Marlboro,
Massachusetts, having a thickness of .022 inches, which is
~ glued to one side of the blanket sample.
POLYWEB printing blankets, manufactured by W. R.
Grace & Co~, are used as the blanket samples in the tests.
The force, reflected in pounds, represents the amount
of force required for a failure to occur. All samples are
tested until such a failure happens. The failures are either
caused by blanket pullout (represented by P in Table 1) or by
blanket breakage, (represented by B in Table 1) wherein the
blanket tensile strength is exceeded and the blanket rips
rather than being pulled out of the axial groove.
- 13 -
12B~8i~5
TABLE 1
Groove Bar
Width WidthForce Failure
( B=Blanket B reakage )
(degrees)(inches) (inches) (pounds) (P=Pullout)
0.225 0.875 78 P
0.225 0.750 L10 P
112.6 0.175 0.875 75 P
0.175 0.750 70 P
0.125 0.875 125 P
0.125 0.750 115 P
0.225 0.875 120 P
0.225 0.750 60 P
110.3 0.175 0.875 120 P
0.175 0.750 175 P
0.125 0.875 135 P
0.125 0.750 140 P
0.225 0.875 155 P
0.225 0.750 75 P
107,9 0.175 0.875 255 B
0.175 0.750 117 p
0.125 0.875 222 P
0.125 0.750 140 p
14
~as~s
TABLE 1 (Continued)
Groove Bar
Width Width Force Failure
( B=Blanket Breakage)
(degrees) (inches) linches) (pounds) (P=Pullout)
0.225 0.875 307 p
0.225 0.750 183 P
105. ~ 0.175 0.875 200 P
0.175 0.750 155 P
0.125 0.875 250 P
0.125 0.750 205 B
0.225 0.875 280 P
0.225 0.750 235 P
103.3 0.175 0.875 140 P
0.175 0.750 270 B
0.125 0.875 205 P
0.125 0.750 220 P
0.225 0.875 265 B
0.225 0.750 175 P
101.1 0.175 0.875 135 P
0.175 0.750 185 p
0.125 0.875 245 B
0.125 0.750 250 B
~LZ8~8~
TABLE 1 (Continued)
Groove Bar
e Width Width Force Failure
( B=Blanket Breakage )
(degrees) (inches~ ~inches) (pounds) (P=Pullout)
0.225 0.875 270 P
0.225 0.750 170 P
98.8 0.175 0.875 247 P
0.175 0.750 157 P
0.125 0.875 250 B
0.125 0.750 245 P
0.225 0.875 265 B
0.225 0.750 250 B
96.6 0.175 0.875 230 B
0.175 0.750 240 B
0.125 0.875 260 B
0.125 0.750 255 B
''
0.225 0.875 260 B
0.225 0.750 238 B
94.4 0.175 0.875 273 B
0.175 0.750 255 B
0.125 0.875 250 B
0.125 0. i50 260 B
:'
16
.
~:89~S
TABLE l (Continued)
Groove Bar
e Width Width Force Failure
(B=Blanket Breakage)
(degrees) (inches) (inches) (pounds) (P=Pullout)
0.225 0.875 233 B
0.225 0.750 247 B
92.2 0.175 0.875 253 B
0.175 0.750 255 B
0.125 0.875 245 B
0.125 0.750 255 B
0.225 0.875 255 B
0.225 0.750 268
90.0 0.175 0.875 247 B
0.175 0.750 257 B
0.125 0.875 248 B
0.125 0.750 252 B
0.225 0.875 270 B
0.225 0.750 249 B
87.8 0.175 0.875 258 B
0.175 0.750 274 B
0.125 0~ 875 250 B
0.125 0.750 269 B
1289815
TAB LE 1 ( Continued )
Groove Bar
e Width Width Force Failure
( B=B lan ket B rea kage )
(degrees) (inches) (inches) (pounds) (P=Puilout)
0.225 0.875 290 B
0.225 0.750 260 B
85.6 0.175 0.875 271 B
0.175 n . 750 257 8
0.175 0.875 300 B
0,125 0.750 284 B
18
~ ~l39815
It is clear from Table 1 that variations in groove
width and bar length have little or no effect upon blanket
pullout. The results clearly demonstrate that the angle at
which the blanket exits the groove of the reel rod and meets
the adjacent surface, controls whether blanket pullout will
occur. This is dramatically shown in that at all angles below
about g7, the failures are all caused by blanket failure, not
pullout.
Even more dramatic is the comparison between the
conventional reel rod having an angle of greater than 112 and
a preferred embodiment of the present invention having the
angle at 90. In the conventional reel rod, all samples fail
from blanket pull at very low applications of force, while in
the preferred embodiment of 90, all of the samples fail from
blanket breakage at levels of force three to six times greater
than those imposed on the corresponding conventional reel rod.
The present invention represents a significant
improvement in the printing industry, eliminating one of the
problems which has prevented the large scale development and
use of narrow gap type cylinders and bars.
Most of the discussion of the present invention has
been directed to its use in the narrow gap printing area.
However, it is not the intention of the applicant to so limit
its use. The present invention is useful on conventiGnal
printing cylinders as well as narrow gap cylinders.
While this invention has been described with refer-
ence to its preferred embodiment in the printing industry,
other embodiments of the present invention can be used in other
industries where the need for fast and secure retention of
sheet material is desired. In particular, the present
- 19 -
~8g8~
invention is useful in any application which requires or
desires the secure attachment of sheet materials to a
cylinder.
While this invention has been described with refer-
ence to its preferred embodiments, other embodiments can
achieve the same result. Variations and modifications of the
present invention will be obvious to those skilled in the art
and it is intended to cover in the appended claims all such
modifications and equivalents as fall within the true spirit
and scope of this invention.
- 20 -
.. -~ . . . .
' :
