Background of the Invention
Technical Field
[0001] The present invention relates to controlling fluid flow at a flow control location,
and is particularly directed to an apparatus for preventing undesired fluid flow past
a flow control location defined by a nip formed by a pair of rollers. The apparatus
of the present invention is especially applicable to a dampening system of a printing
press.
Background Art
[0002] A dampening system for a printing press typically includes a plurality of rollers
for transferring dampening fluid to a printing plate during operation of the printing
press. The printing plate is secured to a plate cylinder of the printing press. One
of the plurality of rollers is a pan roller rotatable about its longitudinal central
axis. Another one of the plurality of rollers is a slip roller rotatable about its
longitudinal central axis and located adjacent to the pan roller. A nip is formed
between the two rollers along the axial extent of the two rollers. The nip has a fluid
entrance side at which fluid enters the nip and a fluid exit side from which fluid
flows from the nip.
[0003] During operation of the printing press, the pan roller rotates about its longitudinal
central axis in one direction while the slip roller rotates about its longitudinal
central axis in the opposite direction. Thus, at the nip between the two rollers,
the pan and slip rollers rotate in the same direction. The pan roller is partially
immersed in a supply of dampening fluid, and the dampening fluid adheres to the outer
surface of the pan roller as the pan roller rotates. The fluid is carried on the outer
surface of the pan roller to the entrance side of the nip. Thus, the fluid enters
the nip between the two rollers.
[0004] When the dampening fluid carried on the outer surface of the pan roller enters the
nip between the two rollers, some of the fluid is transferred onto the outer surface
of the slip roller. The fluid not transferred onto the outer surface of the slip roller
remains adhered to the outer surface of the pan roller. The fluid adhering to the
outer surface of the slip roller is subsequently transferred by other rollers onto
the outer surface of the printing plate. The fluid which remains adhered to the outer
surface of the pan roller is carried back to the supply of dampening fluid.
[0005] As known in the art, it is desirable to control the amount of fluid transferred to
the outer surface of the printing plate. One way to control the amount of fluid transferred
to the printing plate is to control the rotational speed of the pan roller and the
rotational speed of the slip roller. An increase in the speed of each of the rollers
increases the amount of fluid transferred to the printing plate. Likewise, a decrease
in speed of each of the rollers decreases the amount of fluid transferred to the printing
plate. Another way to control the amount of fluid transferred to the printing plate
is to skew one of the two rollers along the axial extent of the two rollers. Still
another way is to increase or decrease the pressure between the two rollers at the
nip. Thus, the nip is a flow control location in the dampening system.
[0006] If the amount of fluid carried on the outer surface of the pan roller to the entrance
side of the nip exceeds the amount of fluid flowing out of the nip at the exit side
of the nip, a buildup of excess fluid at the entrance side of the nip occurs. The
excess fluid at the entrance side of the nip tends to flow to the opposite axial ends
of the nip. Although some of the excess fluid drips from the opposite axial ends of
the pan roller back into the fluid pan due to gravity, some of the excess fluid may
flow around the opposite axial ends of the nip (the flow control location) and onto
the slip roller. Some of the fluid transferred onto the slip roller in this manner
is subsequently transferred to the printing plate. This fluid flow around the opposite
axial ends of the nip onto the slip roller is undesirable because such flow is uncontrolled
and unintended.
Summary of the Invention
[0007] The present invention provides an apparatus for controlling fluid flow at a flow
control location between two rollers. The apparatus includes means connected at the
opposite axial ends of one of the rollers for preventing undesired fluid flow past
the flow control location. The apparatus of the present invention is particularly
suitable for use in a dampening system of a printing press.
[0008] In a preferred embodiment of the present invention, the apparatus includes a pan
roller having a collar fixedly connected at each of the opposite axial ends of the
pan roller. The pan roller is partially immersed in a fluid pan filled with dampening
fluid. The pan roller is disposed adjacent to a slip roller to form a nip between
the pan roller and the slip roller. The nip has an entrance side and an exit side
and extends along the axial direction of the pan and slip rollers. The slip roller
is disposed adjacent to a vibrator roller which, in turn, is disposed adjacent to
a form roller. The form roller is disposed adjacent to a printing plate secured to
a plate cylinder of a printing press. The rollers are rotatable about their longitudinal
central axes.
[0009] The pan roller is rotated about its longitudinal central axis to carry fluid on its
outer surface from the fluid pan to the entrance side of the nip. The fluid at the
nip is either transferred onto the outer surface of the slip roller or remains adhered
to the outer surface of the pan roller. The fluid on the outer surface of the pan
roller is carried back into the fluid pan. The fluid transferred onto the outer surface
of the slip roller is subsequently transferred to the printing plate.
[0010] In the event of an excess fluid condition at the entrance side of the nip, the excess
fluid tends to flow to the opposite axial ends of the nip. When the excess fluid reaches
the ends of the nip, some of this fluid drips back into the fluid pan due to gravity.
In accordance with the present invention, some of the excess fluid is prevented from
flowing around the opposite axial ends of the nip onto the slip roller by the collars
at the opposite axial ends of the pan roller. The two collars rotate with the pan
roller about the longitudinal central axis of the pan roller. Thus, the two collars
pick up excess fluid at the opposite axial ends of the nip and move the excess fluid
away from the slip roller. This fluid is transferred back into the fluid pan by rotation
of the collars with the pan roller. By preventing the excess fluid at the entrance
of the nip from flowing around the opposite axial ends of the nip onto the slip roller,
accurate control of the amount of fluid transferred to the printing plate is maintained.
Brief Description of the Drawings
[0011] Further features of the present invention will become apparent to those skilled in
the art to which the present invention relates from reading the following specification
with reference to the accompanying drawings, in which:
Fig. 1 is a schematic illustration of a dampening system for a printing press and
constructed in accordance with the present invention;
Fig. 2 is a schematic perspective view of a portion of the dampening system shown
in Fig. 1 illustrating the relationship between two rollers and a flow control location
between the two rollers;
Fig. 3 is an enlarged, partial schematic illustration of Fig. 2 taken approximately
along line 3-3 of Fig. 2 illustrating the manner in which dampening fluid is transferred
from one roller to the other roller; and
Fig. 4 is an enlarged, side view of Fig. 2 taken approximately along line 4-4 of Fig.
2 further illustrating the relationship between the two rollers and the flow control
location between the two rollers.
Description of a Preferred Embodiment
[0012] The present invention relates to a fluid flow control apparatus for preventing undesired
transfer of a fluid past a flow control location. The application and construction
of the apparatus of the present invention may vary. The apparatus of the present invention
is particularly suitable for use in a dampening system of a printing press and will
be described herein as applied thereto.
[0013] A dampening system for use in a printing press, constructed in accordance with the
present invention, is illustrated in Fig. 1. The dampening system 10 includes a pan
roller 12 partially immersed in a fluid pan 14 filled with a dampening solution. A
typical dampening solution includes water, alcohol, and gum arabic.
[0014] Referring to Figs. 1 through 4, the pan roller 12 is rotatable about its longitudinal
central axis 25 and has a cylindrical outer surface. The longitudinal central axis
25 of the pan roller 12 lies on a vertical line 19. The outer surface of the pan roller
12 as is conventional is made of a chrome material. The pan roller 12 is located adjacent
to a slip roller 16. The slip roller 16 is rotatable about its longitudinal central
axis 27 and has a cylindrical outer surface. A line 21 extends through the longitudinal
central axis 27 of the slip roller 16 and the longitudinal central axis 25 of the
pan roller 12. The position of the slip roller 16 relative to the position of the
pan roller 12 is such that the lines 19 and 21 intersect to form a predetermined angle
therebetween. The outer surface of the slip roller 16 as is conventional is made of
a rubber material.
[0015] A nip 18 is formed between the pan roller 12 and the slip roller 16 along the axial
extent of the two rollers 12, 16. The nip 18 has a fluid entrance side 11 and a fluid
exit side 13. The entrance side 11 of the nip 18 and the exit side 13 of the nip 18
are located on opposite sides of the line 21. One side of the line 21 is at a higher
elevation than the other side of the line 21. The entrance side 11 of the nip 18 is
on the side of the line 21 at the higher elevation. The exit side 13 of the nip is
on the side of the line 21 at the lower elevation.
[0016] The slip roller 16 is located adjacent to a vibrator roller 20. The vibrator roller
20, in turn, is located adjacent to a form roller 22. The vibrator roller 20 and the
form roller 22 have cylindrical outer surfaces and are rotatable about their respective
longitudinal central axes. The form roller 22 is disposed adjacent to a printing plate
23 secured to a printing plate cylinder 24 of the printing press.
[0017] During operation of the printing press, the pan roller 12 rotates about its longitudinal
central axis 25 in one direction, while the slip roller 16 rotates about its longitudinal
central axis 27 in the opposite direction. As shown in Figs. 1, 2 and 3, the pan roller
12 is rotating in the clockwise direction and the slip roller 16 is rotating in the
counterclockwise direction. Thus, the pan and slip rollers 12, 16 rotate in the same
direction at the nip 18 between the pan roller 12 and the slip roller 16. Since the
pan roller 12 is partially immersed in the fluid pan 14, the dampening fluid in the
fluid pan 14 adheres to the outer surface of the pan roller 12 as the pan roller 12
rotates about its longitudinal central axis 25. The fluid adheres to the outer surface
of the pan roller 12 because of the affinity between the fluid and the chrome outer
surface of the pan roller 12.
[0018] Referring to Figs. 3 and 4, the fluid is carried on the outer surface of the pan
roller 12 from the fluid pan 14 to the entrance side 11 of the nip 18 between the
pan roller 12 and the slip roller 16. The fluid at the entrance side 11 of the nip
18 moves through the nip 18 to the exit side 13 of the nip 18 as the two rollers 12,
16 continue to rotate about their longitudinal central axes 25, 27. Since the entrance
side 11 of the nip 18 is at a higher elevation than the exit side 13 of the nip 18,
gravity assists in the movement of the fluid through the nip 18.
[0019] As the fluid moves through the nip 18 to the exit side 13 of the nip 18, some of
the fluid is transferred from the outer surface of the pan roller 12 onto the outer
surface of the slip roller 16. This transfer occurs because the affinity between the
fluid and the rubber outer surface of the slip roller 16 is greater than the affinity
between the fluid and the chrome outer surface of the pan roller 12. The fluid not
transferred onto the outer surface of the slip roller 16 remains adhered to the outer
surface of the pan roller 12. The fluid which remains adhered to the outer surface
of the pan roller 12 is carried back to the fluid pan 14.
[0020] Referring to Figs. 1 and 4, as the slip roller 16 continues to rotate about its longitudinal
central axis 27, the fluid carried on the outer surface of the slip roller 16 is transferred
onto the outer surface of the vibrator roller 20. The vibrator roller 20, in turn,
transfers the fluid on its outer surface to the outer surface of the form roller 22.
In the same manner, the fluid carried on the outer surface of the form roller 22 is
transferred onto the outer surface of the printing plate 23. Thus, the pan roller
12, the slip roller 16, the vibrator roller 20, and the form roller 22 of the dampening
system 10 cooperate together to transfer fluid from the fluid pan 14 to the outer
surface of the printing plate 23 secured to the plate cylinder 24 of the printing
press.
[0021] The amount of fluid transferred from the fluid pan 14 to the printing plate 23 can
be varied. One way to vary the amount of fluid transferred from the fluid pan 14 to
the printing plate 23 is to change the rotational speed of either the pan roller 12
or the slip roller 16. A speed control mechanism 38, as known in the art, for varying
the rotational speed of either the pan roller 12 or the slip roller 16 is operatively
connected to the two rollers 12, 16 as schematically illustrated in Fig. 1. The speed
control mechanism 38 can be one of a multitude of conventional designs. Thus, details
of its construction will not be discussed. An increase in the speed of either of the
two rollers 12, 16 increases the amount of fluid transferred to the printing plate
23. A decrease in the speed of either of the two rollers 12, 16 decreases the amount
of fluid transferred to the printing plate 23.
[0022] Another way to control the amount of fluid transferred from the fluid pan 14 to the
printing plate 23 is to skew the pan roller 12 relative to the slip roller 16 along
the axial extent of the two rollers 12, 16. When the two rollers 12, 16 are skewed,
the contact pressure between the two rollers 12, 16 changes. An increase in the contact
pressure between the two rollers 12, 16 decreases the amount of fluid transferred
from the fluid pan 14 to the printing plate 23. A decrease in the contact pressure,
up to a certain point, increases the amount of fluid transferred from the fluid pan
14 to the printing plate 23.
[0023] The amount of fluid transferred from the fluid pan 14 to the printing plate 23 can
also be controlled by varying the size of the nip 18 between the pan roller 12 and
the slip roller 16. The contact pressure between the two rollers 12, 16 varies as
a function of the size of the nip 18 between the two rollers 12, 16. The amount of
fluid transferred from the pan roller 12 to the slip roller 16 varies as a function
of the contact pressure between the two rollers 12, 16 in the manner as described
hereinabove. An adjustment mechanism 40, as known in the art, for adjusting the size
of the contact area between the pan roller 12 and the slip roller 16 is operatively
connected to the two rollers 12, 16 as schematically illustrated in Fig. 1. The adjustment
mechanism 40 can be one of a multitude of conventional designs. Thus, details of its
construction will not be discussed.
[0024] The fluid in the nip 18 is either transferred onto the outer surface of the slip
roller 16 or remains adhered to the outer surface of the slip roller 16 as the two
rollers 12, 16 continue to rotate about their longitudinal central axes 25, 27. The
amount of fluid flowing out of the nip 18 at the exit side 13 of the nip 18 is the
sum of the amount of fluid on the outer surface of the pan roller 12 and the amount
of fluid on the outer surface of the slip roller 16. A buildup of excess fluid at
the entrance side 11 of the nip 18 occurs if the amount of fluid transferred from
the fluid pan 14 to the entrance side 11 of the nip 18 exceeds the amount of fluid
flowing out of the nip 18 at the exit side 13 of the nip 18.
[0025] If an excess fluid condition occurs, the excess fluid which builds up at the entrance
side 11 of the nip 18 tends to flow to the opposite axial ends of the nip 18. Most
of the excess fluid flowing to the opposite axial ends of the nip 18 eventually flows
off the opposite axial ends of the pan roller 12 back into the fluid pan 14. Some
of the excess fluid at the opposite axial ends of the nip 18 tends to flow around
the opposite axial ends of the nip 18 onto the slip roller 16. This tendency occurs
because of the greater affinity between the fluid and rubber outer surface of the
slip roller 16 relative to the affinity between the fluid and chrome outer surface
of the pan roller 12, and the flow characteristics of the dampening solution.
[0026] The flow of excess fluid at the entrance side 11 of the nip 18 around the opposite
axial ends of the nip 18 onto the slip roller 16 is undesirable. Such flow is undesirable
because of its uncontrolled nature and its adverse effect on the accurate control
of the amount of fluid transferred to the printing plate 23. One way to prevent this
undesirable flow is to pick up the excess fluid at the opposite axial ends of the
nip 18 and move the excess fluid away from the slip roller 16.
[0027] Referring to Figs. 2, 3 and 4, a collar 30 is secured to the pan roller 12 at one
end 15 of the pan roller 12. The collar 30 is made of a brass material. The brass
collar 30 has a shape like a ring with an outer diameter greater than the outer diameter
of the pan roller 12. The brass collar 30 is made of two separate pieces. Each piece
has a semi-circular shape and forms one-half of the brass collar 30. The two pieces
are held together by suitable fasteners. When the fasteners are tightened to hold
the two pieces together, the brass collar 30 is fixedly secured to the pan roller
12. As shown in Fig. 2, a brass collar 35 identical to the brass collar 30 is fixedly
secured to the pan roller 12 at the other end 17 of the pan roller 12.
[0028] The two brass collars 30, 35 located at the two opposite axial ends 15, 17, respectively,
of the pan roller 12 are used to pick up the excess fluid at the opposite axial ends
of the nip 18. Since the function of each of the brass collars 30, 35 is identical
to the other collar, only the brass collar 30 at the one end 15 of the pan roller
12 will be described in detail. The affinity between the fluid and the brass collar
30 located at the end 15 of the pan roller 12 is greater than the affinity between
the fluid and the rubber outer surface of the slip roller 16. This greater affinity
between the fluid and the brass collar 30 tends to pick up the excess fluid at the
end nip 18 as the brass collar 30 rotates with the pan roller 12. As the brass collar
30 continues to rotate with the pan roller 12, the fluid picked up by the brass collar
30 moves away from the slip roller 16 and back to the fluid pan 14. Thus, the excess
fluid at the end of the nip 18 is picked up and moved away from the slip roller 16.
By preventing the excess fluid at the end 15 of the nip 18 from flowing onto the slip
roller 16 in this manner, accurate control of the amount of fluid transferred to the
printing plate 23 is maintained.
[0029] The preferred embodiment described hereinbefore includes the pair of collars 30,
35 in which the collars are disposed at the opposite axial ends 15, 17 of the pan
roller 12. However, it is contemplated that the two collars 30, 35 could instead be
disposed at the opposite axial ends of the slip roller 16. Furthermore, it is conceivable
that only one collar be used instead of two collars. Thus, if one collar is used,
the collar would be disposed at one end of either the pan roller 12 or the slip roller
16.
[0030] This invention has been described above with reference to a preferred embodiment.
Modifications and alterations may become apparent to one skilled in the art upon reading
and understanding this specification. It is intended to include all such modifications
and alterations within the scope of the appended claims.
1. An apparatus comprising:
a fluid source;
a first roller rotatable about its longitudinal central axis and having an outer cylindrical
surface for receiving a fluid from said fluid source;
a second roller rotatable about its longitudinal central axis and having an outer
cylindrical surface, the outer surface of said second roller and the outer surface
of said first roller defining a nip between said first and second rollers, fluid being
transferrable at said nip from the outer surface of said first roller to the outer
surface of said second roller;
said nip having a fluid entrance side at which said first roller carries fluid to
said nip and a fluid exit side at which said first and second rollers carry fluid
away from said nip, an excess fluid condition being formed at the entrance side of
said nip if the amount of fluid said first roller carries to said nip exceeds the
amount of fluid said first and second rollers carry away from said nip; and characterized
by
means disposed at at least one end of said nip and on one of said first and second
rollers for preventing flow of the excess fluid at the entrance side of said nip around
the at least one end of said nip to the exit side of said nip, and for transferring
excess fluid from the entrance side of said nip back to said fluid source.
2. The apparatus of claim 1 further characterized by including means operatively connected
with said first and second rollers for controlling the rotational speed of said first
roller about its longitudinal central axis and the rotational speed of said second
roller about its longitudinal central axis.
3. The apparatus of claim 1 further characterized by including means operatively connected
with said first and second rollers for adjusting the contact pressure at the nip between
said first and second rollers.
4. The apparatus of claim 1 further characterized by a first axis extending vertically
and perpendicularly through the longitudinal central axis of said first roller and
a second axis extending perpendicularly through the longitudinal central axis of said
first roller and the longitudinal central axis of said second roller, the first and
second axes intersecting to form a predetermined angle therebetween, the entrance
and exit sides of said nip being disposed on opposite sides of the second axis, the
entrance side of said nip being at a higher elevation than the exit side of said nip.
5. The apparatus of claim 1 further characterized by said first and second rollers
being operatively coupled with each other to form a part of a dampening system of
a printing press, said first and second rollers cooperating with each other and with
other rollers to transfer fluid from said fluid source to a printing plate of the
printing press.
6. The apparatus of claim 1 further characterized by said means disposed at at least
one end of said nip and on one of said first and second rollers including a collar
connected to one end of said one roller, said collar having a cylindrical ring shape,
the outer diameter of said collar being greater than the outer diameter of said one
roller on which said collar is disposed.
7. The apparatus of claim 1 further characterized by said means disposed at at least
one end of said nip and on one of said first and second rollers including a first
collar connected at one end of said first roller and a second collar connected at
the other end of said first roller, each of said first and second collars having a
cylindrical ring shape, the outer diameter of each of said first and second collars
being greater than the outer diameter of said first roller.
8. The apparatus of claim 7 further characterized by each of said first and second
collars being made of a brass material.
9. An apparatus for transferring excess fluid away from a longitudinally extending
nip formed between a first roller rotatable about its longitudinal central axis and
a second roller rotatable about its longitudinal central axis to a fluid source, said
apparatus being characterized by:
a collar disposed at one end of one of said first and second rollers for receiving
excess fluid from the nip and for transferring the excess fluid to the fluid source,
said collar operating to prevent excess fluid in the nip from flowing around the one
end of said one roller as the first and second rollers rotate about their longitudinal
central axes.
10. The apparatus of claim 9 further characterized by said collar having a cylindrical
ring shape, the outer diameter of said collar being greater than the outer diameter
of said one roller on which said collar is disposed, and said collar being made of
brass material.