Note: Descriptions are shown in the official language in which they were submitted.
CA 02259768 1999-O1-20
SHOE PRESS
Field of the Invention
The present invention relates to shoe presses for
applying pressure to a running web of paper, paperboard,
or the like. More particularly, the present invention
relates to a shoe press of the type having a support
which supports a press shoe adjacent to a counter roll or
other backing member such that the press shoe and backing
member form an extended nip therebetween, and having a
hydraulic device for urging the press shoe toward the
backing member to apply pressure to the web running
through the nip.
Background of the Invention
In a papermaking machine, a wet web of paper or the
like from the forming section of the machine is typically
carried through the nip of a~shoe press of the above-
described type, where the web is pressed between two
layers of absorbent felt or the like for wicking moisture
from the web. Such shoe presses can also be used for
calendering the web downstream of the forming section.
Various shoe presses of the above-described type
have been proposed. For example, U.S. Patent No.
4,917,768, which is commonly owned with the present
application, discloses a shoe press in which the press
shoe is carried on the support by tubular sleeves rigidly
affixed to and spaced apart on the support along the
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cross-machine direction, the sleeves being slidably
received within cylindrical recesses in the press shoe to
permit the press shoe to be moved toward and away from a
counter roll for varying the nip pressure. The shoe
press includes hydraulic jacks upstream and downstream of
the sleeves for urging the press shoe toward the counter
roll and for pivoting the shoe about a cross-machine axis
so as to vary the nip pressure in the machine direction.
The sleeves fit somewhat loosely in the recesses in the
';. 10 shoe and a resilient seal encircles each sleeve for
sealing the interface between the sleeve and recess.
Accordingly, the press shoe is capable of pivoting
relative to the support for varying the nip pressure in
the machine direction.
One of the difficulties encountered in shoe presses
is thermal expansion of the shoe from frictional heating
of the shoe by the belt that carries the paper web
through the press, as well as from hot hydraulic fluid
which is circulated through the shoe for various
purposes. Thermal expansion of the shoe causes
elongation in the cross-machine direction. In the shoe
press disclosed in the '768 patent, such thermal
expansion of the shoe causes the sleeves to be placed
under bending stresses, which is undesirable. Moreover,
although the shoe in the '768 patent is slidable on the
pistons of the hydraulic jacks, the large normal forces
exerted on the shoe by the pistons during operation of
the shoe press result in substantial frictional forces on
the pistons when the shoe expands through thermal action.
Consequently, the pistons are placed in bending within
the cylinders of the hydraulic jacks, and such bending
can lead to malfunction of the jacks, particularly for
the cylinders toward the outer ends of the shoe farthest
from the centerline where thermal expansion results in
relatively greater translation of the shoe relative to
the support and pistons. Bending of the pistons is
undesirable from the standpoint of wear on the pistons,
~ , CA 02259768 1999-O1-20
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cylinders, and seals, and can also interfere with proper
functioning of the press. Additionally, thermal
expansion of the shoe can cause leakage of hydraulic
fluid when the seals are excessively deformed.
In part because of the problems noted above with
respect to the bending of the sleeves, the assignee of
the present application developed an alternative shoe
press similar to that disclosed in the '768 patent but
eliminating the sleeves. However, this shoe press still
suffered from the problems of bending of the pistons of
the hydraulic jacks as noted above. Additionally,
because the shoe was freely supported on the pistons of
the hydraulic jacks, the shoe was free to take a variety
of positions relative to the support beam and counter
roll. More particularly, the shoe could become slanted,
wherein one end of the shoe was displaced towards the
downstream end of the machine and the opposite end was
displaced toward the upstream end of the machine.
Because of frictional forces between the shoe and the
pistons, once the shoe became slanted it was .difficult
for the shoe to readjust into a correct position.
Summary of the Invention
The present invention provides a shoe press capable
of tolerating relatively large cross-machine elongations
and other deformations of the press shoe without the
problems associated with some prior shoe presses noted
above. In one embodiment of the invention, the shoe
press includes a press shoe that extends in a cross-
machine direction along the full width of a web being
carried through the press, and a plurality of articulated
hydraulic loading cylinders spaced apart along the shoe
in the cross-machine direction and supported by a
support. The loading cylinders define working chambers
that are pressurizable by hydraulic fluid so as to cause
the loading cylinders to urge the press shoe away from
the support and toward a counter roll or other backing
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member for applying pressure to the web being carried
through the nip defined between the shoe and the backing
member. Each loading cylinder comprises a piston member
disposed within a cylinder member. One of the piston and
cylinder members comprises a two-piece member having a
first member fixed relative to the press shoe and a
second member fixed relative to the support, while the
other of the piston and cylinder members comprises a
coupler. For example, in one preferred embodiment, the
two-piece member comprises first and second cylinders and
the coupler comprises a piston which is slidably received
within both of the cylinders. In an alternative
preferred embodiment, the two-piece member comprises
first and second pistons and.the coupler comprises a
cylinder which surrounds both of the pistons.
The coupler sealingly engages both the first and
second members such that the first member is urged away
from the second member in a loading direction by
pressurization of the working chamber to cause the press
shoe to be urged toward the backing member. In order to
enable the loading cylinders to accommodate cross-machine
elongation of the press shoe, each coupler engages the
respective first and second members at seals which enable
the coupler to pivot relative to the first and second
members about axes parallel to the machine direction.
Thus, the press shoe is free to thermally expand in the
cross-machine direction without causing bending of any
piston and/or cylinder members of the loading cylinders.
In accordance with a preferred embodiment of the
invention, each loading cylinder includes first and
second cylinders and a single piston. A first working
chamber is defined by the first cylinder and a first end
of the piston which is slidably received therein, and a
second working chamber is defined by the second cylinder
and a second end of the piston which is slidably received
therein. Each working chamber is pressurizable with
hydraulic fluid for urging the press shoe in the loading
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direction away from the support and toward the backing
member. Preferably, the piston includes a passage
connecting the two working chambers to enable fluid
communication therebetween. One of the press shoe and
the support includes a supply passage for supplying
pressurized hydraulic fluid into one of the first and
second working chambers. Advantageously, the supply
passage is in the support for supplying fluid to the
second working chamber.
Various configurations of cylinders and pistons are
possible within the scope of the invention. In
accordance with one preferred embodiment, the piston
comprises a tubular member having generally cylindrical
inner and outer surfaces. Each of the first and second
ends of the piston has an annular flange which projects
radially outward beyond the cylindrical outer surface of
the piston, and each flange supports a resilient
compressible seal. The radial dimensions of the flanges
are sufficiently large in relation to their axial extent
and to the axial lengths of the portions of the piston
residing within the cylinders, that a substantial degree
of pivotal movement of the piston is enabled relative to
the cylinders about axes parallel to the machine
direction. Preferably, the second cylinder includes a
stop member which extends radially inward to a diameter
smaller than the flange on the second end of the piston
so as to limit movement of the piston in the loading
direction away from the support.
In accordance with yet another preferred embodiment
of the invention, a hydraulically operated shoe-
retracting actuator is disposed within the interior of
the piston of at least one of the loading cylinders.
Either the support or the shoe includes a passage adapted
to supply hydraulic fluid to~the shoe-retracting
actuator, the actuator being operable by hydraulic
pressure to retract the shoe away from the counter roll
and toward the support. The shoe-retracting actuator
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preferably comprises an actuator piston attached to the
support and extending into the interior of the piston of
the loading cylinder, and an actuator cylinder sealingly
surrounding the actuator piston so as to define a chamber
pressurizable by hydraulic fluid to urge the actuator
cylinder toward the support. The actuator cylinder
engages a projection affixed to the press shoe such that
actuation of the shoe-retracting actuator causes the
press shoe to be urged toward the support.
It will thus be appreciated that the invention
provides a shoe press in which the press shoe is
supported so as to be freely movable in the cross-machine
direction without wear, bending, or other undesirable
consequences to the loading cylinders. The loading
cylinders also can accommodate deformations or
translations of the press shoe in the machine direction,
as well as pivoting of the press shoe about an axis
parallel to the cross-machine direction. Additionally,
the articulated loading cylinders prevent the press shoe
from assuming a slanted position.
Brief Description of the Drawings
The above and other objects, features, and
advantages of the invention will become more apparent
from the following description of certain preferred
embodiments thereof, when taken in conjunction with the
accompanying drawings in which:
FIG. 1 is a cross-sectional view of a shoe press in
accordance with a first preferred embodiment of the
invention, taken on a plane parallel to the machine
direction through an axis of one of the loading
cylinders;
FIG. 2 is a view similar to FIG. 1, showing the
press shoe pivoted relative to the support about an axis
parallel to the cross-machine direction;
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FIG. 3 is a cross-sectional view of the press shoe
of FIG. 1 taken on a plane parallel to the cross-machine
direction through the axes of the loading cylinders;
FIG. 4 is a cross-sectional view similar to FIG. l,
showing a second preferred embodiment of the invention
having two rows of loading cylinders spaced apart in the
machine direction for imparting pivotal motion to the
press shoe to vary the nip pressure in the machine
direction;
FIG. 5 is a view similar to FIG. 3, showing a third
preferred embodiment of the invention;
FIG. 6 is a view similar to FIG. l, showing a fourth
preferred embodiment of the invention having two pistons
and a common cylinder;
FIG. 7 is a view similar to FIG. 1, showing one of
the loading cylinders of a fifth preferred embodiment of
the invention;
FIG. 7A is a top elevation of the shoe of the shoe
press of FIG. 7, showing pins and stops along the side
and downstream edges of the shoe for restraining motion
of the shoe;
FIG. 8 is a view similar to FIG. 7, showing another
of the loading cylinders which includes an internal shoe-
retracting actuator within the piston of the loading
cylinder; and
FIG. 9 is a view similar to FIG. 8, showing a
loading cylinder in accordance with a sixth preferred
embodiment of the invention.
Detailed Description of the Drawings
The invention is now explained by reference to
certain preferred embodiments thereof as shown in the
drawings. It will be understood, however, that the
invention is not limited to the embodiments shown and
described herein.
With reference to FIGS. 1-3, a shoe press 10 in
accordance with a first preferred embodiment of the
CA 02259768 1999-O1-20
_g_
invention is illustrated. The shoe press 10 includes a
press shoe 12 which is configured on one surface 14
thereof so as to be generally complementary in contour to
a backing member such as the.counter roll 16 depicted in
the drawings. The shoe 12 and counter roll 16 define a
nip N through which a moving web W of paper, paperboard,
or the like is carried. The web W typically is carried
by an endless belt B and is in contact with one or more
press felts F or other absorbent material. The shoe
press 10 can be used in the press section and/or calender
of a papermaking machine, and can also be used as a pre-
press in a forming section of a papermaking machine. It
will be recognized that when used in a calender or
forming section of a machine, the web W would be passed
through the device 10 without any absorbent felt.
The shoe press 10 further includes a support 18.
The shoe 12 and the support 18 extend lengthwise in the
cross-machine direction (as best seen in FIG. 3) along at
least the full width of the web W, and preferably the
shoe 12 is slightly wider than the web W. The shoe 12 is
supported by the support 18 and is urged toward the
backing member 16 for applying pressure to the web W by a
plurality of articulated hydraulic loading cylinders 20
arranged between the support 18 and the shoe 12 and
spaced apart in the cross-machine direction.
Each loading cylinder 20 comprises a piston member
and a cylinder member, one of the members being formed in
two parts and the other member forming a coupler between
the two parts. More particularly, the two-piece member
of the loading cylinder 20 includes a first cylinder 22
that is fixed relative to the shoe 12, a second cylinder
24 that is fixed relative to the support 18, and a piston
26 slidably received with each of the cylinders. In the
embodiment depicted in FIGS..1-3, the first cylinder 22
comprises a recess formed in the shoe 12. The second
cylinder 24 is a member formed separately from the
support 18 and affixed thereto.
CA 02259768 1999-O1-20
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A first end 28 of the piston 26 is slidably received
within the first cylinder 22 and a second end 30 of the
piston is slidably received within the second cylinder
24. A resilient compressible seal 32 surrounds each end
of the piston 26 for sealing against the inner surfaces
of the cylinders. A first working chamber 34 is thus
defined between the first end 28 of the piston 26 and the
side and end walls of the first cylinder 22, and a second
working chamber 36 is defined between the second end 30
of the piston and the side and end walls of the second
cylinder 24. The piston 26 includes a passage 38
connecting the first and second working chambers so that
there is fluid communication between them. The support
18 includes a supply passage 40 for supplying pressurized
hydraulic fluid into the second working chamber 36. The
supply passage 40 connects with a bore 42 in a fastener
44 which is used for securing the second cylinder 24 to
the support 18. Thus, pressurized fluid supplied through
the passage 40 into the second working chamber 36 causes
the first and second cylinders 22 and 24 to be urged away
from each other. The shoe 12 is thus urged toward the
backing member 16. The first working chamber 34 is also
pressurized substantially equal to the second chamber by
virtue of the passage 38 in the piston 26. Where the
first and second ends 28 and~30 of the piston are
essentially equal as shown in FIGS. 1-3, the net axial
force on the piston 26 is thus nearly zero.
The piston 26 preferably includes spherical surfaces
46 which confront the inner surfaces of the cylinders 22
and 24. The resilient compressible seals 32 extend
radially outward of the spherical surfaces 46 into
contact with the inner surfaces of the cylinders.
Accordingly, the piston 26 is able to pivot about axes
parallel to the machine and cross-machine directions
relative to both of the cylinders while maintaining
proper sealing of the working chambers. FIG. 2 depicts
the shoe 12 and first cylinder 22 pivoted relative to the
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0-
piston 26 about an axis parallel to the cross-machine
direction. Although only one of the loading cylinders 20
is depicted in FIG. 2, it will be understood that the
pistons of all of the cylinders 20 along the cross-
machine direction can pivot relative to the shoe 12 so
that the shoe can pivot as a unit relative to the support
18. FIG. 3 depicts a pair of the loading cylinders 20 in
which the pistons 26 have been pivoted relative to both
cylinders 22 and 24 about axes parallel to the machine
direction as a result of the shoe 12 being translated in
the cross-machine direction (to the left in FIG. 3).
Thus, the loading cylinders 20 allow substantial freedom
of movement of the shoe 12 in terms of both pivotal and
translational movements.
Because the shoe 12 is capable of translating in the
machine direction relative to the support 18, the shoe
press includes a guide rail or stop 48 for limiting the
extent to which the shoe can move. The loading cylinders
also include stop rings 50 for limiting the movement
20 of the pistons 26 in the loading direction away from the
support 18. The stop rings 50 are affixed to the
outermost ends of the second cylinders 24 and extend
radially inward to a diameter smaller than that of the
spherical surfaces 46 on the second ends of the pistons
26. Each piston 26 has an axially extending portion 52
of reduced diameter located about midway along the axial
length of the piston between the spherical surfaces 46 at
each end. The reduced diameter portion 52 is smaller in
diameter than the inner surface of the stop ring 50 over
a sufficient axial length of'the piston 26 so that the
piston is capable of some range of axial movement within
the second cylinder 24.
The shoe press 10 also includes hydrostatic
compartments 54 in the surface 14 facing the counter roll
16 for lubrication purposes, as well known in the art.
The compartments 54 are supplied with hydraulic fluid by
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a pipe 56 attached to the shoe 12 and communicating with
the compartments via passages 58 in the shoe.
FIG. 4 depicts a second preferred embodiment of the
invention in the form of a shoe press 10' having two rows
of loading cylinders 20' generally as described above
(the primary differences being the smaller diameters of
the loading cylinders 20'), the two rows being spaced
apart in the machine direction for varying the nip
pressure in the machine direction.
FIG. 5 illustrates a third preferred embodiment of
the invention. The shoe press 110 of FIG. 5 includes
loading cylinders 120 in which the first cylinders 122
are formed not as recesses in the shoe 112 but rather as
separate members, similar to the second cylinders 124.
Hydraulic fluid is supplied to the loading cylinders 120
through passages 140 in the shoe 112 and through openings
142 in the first cylinders 122. The passages 140 may be
supplied with fluid via a pipe (not shown) attached to
the shoe 112 in a manner similar to that depicted in
FIGS. 1-2. It will also be noted that FIG. 5 illustrates
the type of deformation of the shoe 112 caused by thermal
expansion, whereby the two loading cylinders 120 on the
left-hand side which are located on one side of the
machine axial centerline have their pistons 126 pivoted
in one direction about axes parallel to the machine
direction, and the two loading cylinders 120 on the
right-hand side of the centerline have their pistons 126
pivoted in the opposite direction about axes parallel to
the machine direction. It will also be noted that the
pistons 126 are hollow tubular members, as opposed to the
generally solid pistons 26 and 26' of the presses shown
in FIGS. 1-4. This construction of the pistons 126
results in savings in material relative to the solid-type
pistons.
FIG. 6 depicts a fourth.preferred embodiment of the
invention. The shoe press 110' of FIG. 6 employs loading
cylinders 120' in which the two-piece member is the
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piston and the coupler is the cylinder. Thus, the
loading cylinder 120' comprises a first piston 126a
affixed to the shoe 112', and second piston 126b affixed
to the support 118', and a cylinder 122' within which
both pistons are slidably received. A common working
chamber 134' is defined between the pistons 126a and
126b. Pressurized fluid is supplied to the working
chamber 134' by a passage 140' in the support 118' which
connects with a passage 142' that extends through a
fastener 144' which secures the second piston 126b to the
support 118'. A ring 50', similar in function to the
ring 50 of FIG. 1, is affixed to the end of the cylinder
122' adjacent the shoe 112' for preventing the first
piston 126a from being withdrawn from the cylinder 122'.
FIG. 7 depicts a fifth preferred embodiment of the
invention. The shoe press 210 of FIG. 7 includes
hydraulic loading cylinders 220 in which the pistons 226
are formed as hollow tubular members, and the first
cylinder 222 and second cylinder 224 are separate members
affixed to the press shoe 212 and the support 218,
respectively. The first cylinder 222 has an end wall 223
which abuts the shoe 212 and a hollow tubular portion 225
projecting normally from the end wall 223 toward the
second cylinder 224. Similarly, the second cylinder 224
has an end wall 227 which abuts the support 218 and a
hollow tubular portion 229 projecting normally from the
end wall 227 toward the first cylinder 222. Each of the
tubular portions 225 and 229 has a cylindrical inner
surface .
The piston 226 includes flanges 231 adjacent each
end of the piston. The flanges 231 are generally annular
and project radially outward beyond the cylindrical outer
surface of the piston. The radially outermost surfaces
233 of the flanges 231 are preferably but not necessarily
spherical. Each flange 231 includes a groove 235
continuously encircling the piston and housing a pair of
resilient compressible seal rings 237a and 237b. The
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inner seal rings 237a are preferably rubber or a material
having compressibility and resilience properties similar
to rubber. The outer seal rings 237b which make contact
with the inner surfaces of the cylinders are preferably
made of a material somewhat stiffer than that of the
inner seal rings. A suitable material is, for example, a
polymer having bronze additives, although other materials
may alternatively be used. The outer seal rings 237b
project radially outward of the spherical surfaces 233 of
the flanges and are larger in diameter than the inner
surfaces of the cylinders 222, 224 in their undeformed
conditions, such that there is an interference fit of the
seal rings in the cylinders. The seal rings 237a and
237b therefore are compressed, and their resilience keeps
them in sealing contact with the cylinders throughout the
range of pivotal movement of the piston 226.
Additionally, the lengths of the flanges 231 in the
radially outward direction are sufficiently large in
relation to the axial lengths of the flanges and the
axial length between the two flanges so that the piston
226 is capable of pivoting over a relatively large
angular range while maintain proper sealing contact of
the seal rings 237b with the cylinders.
To aid in assembling and disassembling the shoe
press, the first cylinders 222 are affixed to the shoe
212 by a pair of clamps 239 and 241 adjacent the upstream
and downstream sides, respectively, of the shoe. The
clamps include ledges 243 which clamp an annular flange
245 of the first cylinder 222 between the shoe 212 and
the ledges 243. It will be noted that the holes 247 in
the clamps 239 and 241 through which fasteners are passed
for securing the clamps to the shoe are not identically
located relative to the ledges 243. This enables the
clamps 239 and 241 to be interchanged so as to alter the
location of the first cylinder 222 relative to the shoe
212 in the machine direction. Although not shown, the
support 218 also includes an adjustment mechanism for
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moving the support and the second cylinder 224 in the
machine direction. This adjustment mechanism may be, for
example, a pair of clamps (not shown) similar to the
clamps 239 and 241 for securing the support 218 to a
frame structure, or alternatively, a pair of such clamps
for securing the second cylinder 224 to the support 218.
Accordingly, the entire loading cylinder 220 can be
shifted in the machine direction relative to the shoe 212
for changing the center of load on the shoe.
With reference to FIGS. 7 and 7A, the shoe press 210
includes features for limiting motion of the shoe 212 in
the upstream, downstream, and cross-machine directions.
As previously noted in connection with FIGS. 1 and 2, a
stop 48 is positioned adjacent the downstream side of the
shoe 212 for limiting the extent of downstream motion of
the shoe 212. Additionally, a pin 49 is affixed to the
downstream side of the shoe 212 and projects outward
therefrom in the machine direction. The stop 48 includes
a slot 51 into which the pin 49 extends. The pin 49 is
located at a midpoint of the width of the shoe 212 in the
cross-machine direction, as shown in FIG. 7A. The slot
51 extends in the loading direction so that the shoe 212
is free to move toward and away from the counter roll.
However, the slot 51 is only slightly wider than the pin
49, and accordingly, the shoe 212 is restrained from
moving in the cross-machine direction. Furthermore, the
pin 49 engaged in the slot 51 ensures that thermal
expansion of the shoe 212 in the cross-machine direction
does not all occur in a single direction but rather
occurs in opposite directions on either side of the
longitudinal centerline of the shoe press 210.
The shoe press 210 also includes pins 249 affixed to
the opposite side edges of the shoe 212 and projecting
outward therefrom in the cross-machine direction. A pair
of stops 248 are positioned adjacent the opposite sides
of the shoe 212 so that they~can be abutted by the pins
249 when the shoe 212 moves in the upstream direction.
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Thus, the stops 248 and pins 249 limit the extent of shoe
movement in the upstream direction, and also help prevent
the shoe 212 from assuming a slanted position in which
one side is further upstream than the other side. It
will of course be appreciated that instead of the stops
248 and pins 249, a single elongate stop (not shown)
could be positioned adjacent the upstream edge of the
shoe 212 so as to serve the same purposes as the stops
248 and pins 249.
Preferably, at least one and more preferably several
of the loading cylinders of the shoe press 210 include
internal shoe-retracting actuators operable to retract
the shoe 212 away from the counter roll. FIG. 8 shows
one of the loading cylinders 220' having a shoe-
retracting actuator 260. The actuator 260 comprises an
actuator piston 262 having a stem 264 secured to the
support 218 and projecting normally therefrom toward the
shoe 212. An actuator cylinder 266 surrounds the
actuator piston so as to define a working chamber 268
pressurizable with hydraulic fluid to cause the actuator
cylinder 266 to be urged toward the support 218. The
stem 264 of the actuator piston includes a passage 270
for supplying fluid into the chamber 268, and the support
218 includes a fluid passage 272 which connects with the
passage 270 in the stem. The chamber 268 is constantly
pressurized during operation~of the shoe press so that
the pressure within the chamber 268 of the shoe-
retracting actuator is not substantially less than that
in the working chamber 234 of the loading cylinder 220'
in order to avoid damage to the actuator. When the press
shoe 212 is to be retracted away from the counter roll,
the pressure in the working chamber 234 is decreased
below that in the chamber 268.
The actuator cylinder 266 at the end adjacent the
shoe 212 includes an annular ring 274 which extends
radially inward from the cylinder side wall. A
projection 276 is affixed to the first cylinder 222' and
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extends through the central opening of the annular ring
274. The projection 276 includes a head 278 larger in
diameter than the inner diameter of the ring 274 for
engaging the annular ring 274 such that movement of the
actuator cylinder 266 toward the support 218 causes the
shoe 212 to be pulled toward the support. The annular
ring 274 includes holes 275 for equalizing the pressure
on both sides of the ring. To aid in disassembling the
press, the annular ring 274 is removably threaded into
the actuator cylinder 266. The projection 276 is also
removably threaded into the first cylinder 222'. The
first cylinder 222' includes a reinforced boss 280 into
which the projection 276 is threaded. The shoe 212
includes a recess 282 for accommodating the boss 280.
The recess 282 is larger in diameter than the boss 280 so
that the first cylinder 222'.can be shifted in the
machine direction by interchanging the clamps 239 and
241, as previously described.
The shoe-retracting actuator 260 also enables a
further advantage in addition to its function of
retracting the shoe 212. Specifically, if the hydraulic
pressure within the chamber 268 of the actuator 260 is
reduced below the pressure existing in the working
chamber 234, the net loading force exerted on the shoe
212 is increased above that exerted if the pressures are
equal in the chambers 234 and 268. Accordingly, the
actuator 260 can also be used to increase the loading
capacity of a loading cylinder without increasing the
size of the loading cylinder.
FIG. 9 shows a sixth preferred embodiment of a
loading cylinder 320 in accordance with the invention.
The loading cylinder 320 includes a first cylinder 322
which has a thickened end wall 323 which mounts the
projection 276 of the shoe-retracting actuator 260', and
accordingly the shoe 312 does not require a recess for
accommodating the projection 276. The first cylinder 322
can be shifted in the machine direction by interchanging
CA 02259768 1999-O1-20
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the clamps 239 and 241, as described above for the
loading cylinder 220'. In addition, the second cylinder
324 can be shifted in the machine direction in a similar
manner. To this end, the support 318 includes a recess
319 and the second cylinder 324 includes an end wall 325
upon which the stem 264' of the actuator piston 262' is
affixed. The stem 264' extends through a thickened
portion 326 of the cylinder end wall 325, and the
thickened portion 326 and a part of the stem 264' extend
into the recess 319 in the support 318. The recess 319
in the support 318 is wider in the machine direction than
the thickened portion 326 of the second cylinder 324 so
that the second cylinder 324 can be shifted in the
machine direction. The second cylinder 324 is secured on
the support 318 by a pair of asymmetric clamps 339 and
341 in similar manner to the attachment of the first
cylinder 322 to the shoe 312 by clamps 239 and 241.
Thus, the second cylinder 324 is shifted in the machine
direction by interchanging the clamps 339 and 341.
Pressurized hydraulic fluid is supplied to the shoe-
retracting actuator 260' by a flexible hose 342 which
connects to an end 328 of the stem 264' projecting from
the thickened portion 326 of the second cylinder end wall
325. This manner of making the fluid connection with the
actuator piston 262' facilitates shifting the second
cylinder 324 and the actuator 260' in the machine
direction.
From the foregoing description of certain preferred
embodiments of the invention, it will be appreciated that
the invention provides a unique shoe press having
significant advantages over prior presses, including the
ability to tolerate deformations such as thermal
expansion of the shoe without binding or malfunctioning
of the loading cylinders. The invention also provides a
simple mechanism for adjusting the center of load on the
shoe in the machine direction.
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Although the preferred embodiments of the invention
have been described in considerable detail, the invention
is not limited to these embodiments. Various
modifications and substitutions of equivalents will
readily be comprehended by persons of ordinary skill in
the art, and it is intended.that such modifications and
substitutions be encompassed within the scope of the
invention as set forth in the appended claims.
