Note: Descriptions are shown in the official language in which they were submitted.
2~38750
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Process and Apparatus Suitable for Effecting Steel Band
Guidance
The present invention relates to a process and to an
apparatus suitable for guiding the steel band of a
continuously-operating press along the longitudinal axis of
the press.
Continuously-operating presses normally comprise a press
bed and a press top which can be moved towards or away from
each other and define a press gap between them through which a
feedstock material is drawn and compressed by a pair of
endless flexible steel bands which recirculate about the press
bed and the press top. The steel bands normally pass over
drive drums and deflection drums at the inlet and outlet of
the press gap. Heater plates are generally provided on the
opposed faces of the press bed and the press top for the
purpose of heating the feedstock material as it is drawn
through the press gap and the steel bands roll on roller rods,
whose axes run transversely to the direction of movement of
the steel bands, provided between the steel bands and the
press top or the press bed.
Presses of this kind are used to form particle board,
fibre board, plywood sheets and compressed sheets of other
particulate feedstock material.
In such prior art heating plate presses, the press top
and the press bed usually comprise merely webbed plates and
cross ribs serving to connect the latter (e.g. as in DE-OS 31
49 243 and DE-OS 37 02 9g5). A number of such webbed plates,
which are further strengthened with cross ribbing are welded
together into single beams that are first grouped together and
then arranged in series. The attachment of heating plates to
the beam structure completes an assembly whose length
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corresponds effectively to that of press top and press bed and
thus also to the length of the heating plate press itself.
Attachments or protrusions that extend outwardly left and
right from the webbed plates provide contact surfaces for the
press columns, which form part of the frame, to raise and
lower the press top. In conventional systems, furthermore,
short-stroke pressing cylinder-and-piston assemblies are
arranged between the upper crossheads and the attachments to
the press top.
Practical use of continuously-operating presses employing
either hydrostatic or rolling support involving roller rods
has demonstrated that the all-important control of steel band
travel becomes problematic in longer presses that are employed
for the purpose of achieving higher product throughput.
Control of the steel band running path becomes difficult
in presses whose length exceeds 28 m. For example:
a) slight disruptions in the lubrication of the steel bands
or roller rods, or
b) uneven process material density distributions, may
negatively affect online control, rendering impossible the
return of the steel bands to their medial alignment by the
angular displacement of the axes of the drive and deflection
rollers.
The steel bands are, in the zone of the heating plate,
and especially in the first third of the high pressure zone in
the press gap, locked in position as in a vise. When the
roller axis is displaced through its displacement angle, the
steel band, not being locked in position in this region,
undergoes partially greater elongation than in its fixed
region. The same phenomenon occurs in the vicinity of the
exit-side roller. The relationship between the length of the
fixed section of the steel band in the high-pressure zone of
presses of greater length and the section of such band in
entry-side and exit side zones becomes increasingly
disadvantageous. In order, therefore, to avoid one-side
overstretching of the steel bands during adjustment of steel
band travel, the press must be shut down with obvious
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disadvantages.
An object of the present invention is, therefore, to
provide a process which enables, during operation, the steel
band to be adjusted relative to the longitudinal axis of the
press without becoming overstretched on one side.
Another object of the present invention is to provide an
apparatus whereby the above-mentioned process can be
implemented.
According to one aspect of the invention there is
provided a method of guiding first and second endless steel
bands about a longitudinal axis of a continuously-operating
press for the manufacture of pressed boards, the continuously-
operating press having short-stroke piston and cylinder
assemblies and multiple pressure regions of varying pressure
and said bands transmitting pressing pressure to the material
to be pressed and drawing said material through said press,
said method comprising the steps of (A) guiding said first and
second bands, via driving rollers and deflection rollers,
around a press top and a pressing bed, respectively; (B)
supporting said steel bands, with an adjustable press gap
formed therebetween, on a plurality of co-rotating steel rods
which are guided, with their axes of rotation extending
transversely to the direction of travel of said bands; (C)
altering a position of said press top so that a part of said
press top is inclined at an angle ~ relative to a horizontal
plane, said altering step comprising the steps of (i)
temporarily relieving pressing in said short-stroke piston and
cylinder assemblies which are located on one longitudinal side
of a high-pressure region of said press, and then (ii)
applying a pressure which opposes the pressure imposed by said
short-stroke piston and cylinder assemblies and which
overcomes the pressures imposed by those of said piston and
cylinder assemblies which are located on said one longitudinal
side, thereby adjusting the position of said one longitudinal
side so that said part of said press top is inclined at said
angle ~; and (D) altering an angle of at least one of said
rollers in a first direction through an angle ~.
7 ~ ~
: ~ 4
According to another aspect of the invention there is
provided a method of guiding first and second endless steel
bands about a longitudinal axis of a continuously-operating
press for the manufacture of pressed boards, the continuously-
operating press having short-stroke piston and cylinder
assemblies and having multiple pressure regions of varying
pressure, and said bands transmitting pressing pressure to the
material to be pressed and drawing said material through said
press, said method comprising the steps of (A) guiding said
first and second bands, via driving rollers and deflection
rollers, around a press top and a press bed, respectively; (B)
altering a position of said press top so that a part of said
press top is inclined at an angle ~ relative to a horizontal
plane, said altering step comprising the steps of (i)
temporarily relieving pressure in said short-stroke piston and
cylinder assemblies which are located on one longitudinal side
of a high-pressure region of said press, and then (ii)
applying a pressure which opposes the pressure imposed by said
short-stroke piston and cylinder assemblies and which
overcomes the pressures imposed by those of said piston and
cylinder assemblies which are located on said one longitudinal
side, thereby adjusting the height of said one longitudinal
side so that said part of said press top is inclined at said
angle ~; and C) altering an axis of at least one of said
rollers through an angle ~.
According to yet another aspect of the invention there is
provided a method of guiding first and second endless steel
bands about a longitudinal axis of a continuously-operating
press for the manufacture of pressed boards, the continuously-
operating press having short-stroke piston and cylinder
assemblies and multiple pressure regions of varying pressure
and said bands transmitting pressing pressure to the material
to be pressed and drawing said material through said press,
said method comprising the steps of (A) guiding said first and
second bands, via driving rollers and deflection rollers,
around a press top and a press bed, respectively; (B)
supporting said steel bands, with an adjustable press gap
B
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4a
formed therebetween, on a plurality of co-rotating steel rods
which are guided, with their axes of rotation extending
transversely to the direction of travel of said bands; and
(C) altering a position of said press top; and a part of said
press top is inclined at an angle ~ relative to a horizontal
plane; and (D) applying a varying pressure profile to the
material to be pressed via the inclined press top along a
direction transverse to the longitudinal axis; and (E)
altering an angle of at least one of said rollers through an
angle ~ at least at a beginning of step (C).
According to yet another aspect of the invention there is
provided a device for guiding first and second steel bands
about a longitudinal axis of a continuously-operating press
having a high-pressure region, said bands transmitting
pressing pressure to the material to be pressed and drawing
said material through said press, said device comprising: (A)
a press bed; (B) a press top composed of a plurality of beams,
at least two of which are located in said high-pressure
region;(C) connectors which connect the beams of said
high-pressure region while allowing said beams to flex with
respect to one another in the direction of a pressing plane of
said press; (D) driving rollers and deflection rollers which
guide said first and second bands around said press top and
said press bed, respectively, the axis of at least one of said
rollers being alterable through an angle ~; (E) a plurality of
co-rotating steel rods which are guided with their axes of
rotation extending transversely to the direction of travel of
said bands, said steel rods supporting said first and second
steel bands with an adjustable press gap formed therebetween;
(F) press pillars which support said press top, each of said
uprights comprising a plurality of removable drawbars and
parallel upper and lower crossheads which are connected to
eyes of said drawbars via one of pins and bolts; and (G)
short-stroke piston and cylinder assemblies which are located
on opposed longitudinal sides of said press and which apply
said pressing pressure to said steel bands, wherein the
pressure in at least one of said assemblies on one of said
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4b
longitudinal sides of said press is relieved when the axis of
said at least one roller is altered.
According to yet another aspect of the invention there is
provided a continuously-operating press having a high pressure
region, said press comprising (A) a press bed; (B) a press top
composed of a plurality of beams, at least two of which are
located in said high-pressure region; (C) connectors which
connect the beams of said high-pressure region while allowing
said beams to flex with respect to one another in the
direction of a pressing plane of said press; (D) first and
second steel bands which transmit pressure to a material to be
pressed and draw said material through said press, said bands
running around said press top and said press bed,
respectively; (E) press pillars which support said press top,
each of said pillars comprising a plurality of removable
drawbars and parallel upper and lower crossheads which are
connected to eyes of said drawbars via one of pins and bolts;
(F) means for raising a first longitudinal side of a portion
of said press ram which is located in said high-pressure
region with respect to a second longitudinal side so that said
first longitudinal side is inclined with respect to said
second longitudinal side by an angle ~; and (G) short-stroke
piston and cylinder assemblies which are located on said first
and second longitudinal sides of said press and which apply
said pressing force to said steel bands, the pressure in at
least one of said cylinders on said first longitudinal side of
said press being relieved when said one longitudinal side is
ralsed.
According to yet another aspect of the invention there is
provided a device for guiding first and second steel bands
about a longitudinal axis of a continuously-operating press
having a high-pressure region, said bands transmitting
pressing pressure to the material to be pressed and drawing
said material through said press, said device comprising: (A)
a press bed; (B) a press top composed of a plurality of beams,
at least two of which are located in said high-pressure
region; (C) connectors which connect the beams of said
4c
high-pressure region while allowing said beams to flex with
respect to one another in the direction of a pressing plane of
said press; (D) driving rollers and deflection rollers which
guide said first and second bands around said press top and
said press bed, respectively, the axis of at least one of said
rollers being alterable through an angle ~; (E) a plurality of
co-rotating steel rods which are guided with their axes of
rotation extending transversely to the direction of travel of
said bands, said steel rods supporting said first and second
steel bands with an adjustable press gap formed therebetween;
(F) press pillars which support said press top, each of said
pillars comprising a plurality of removable drawbars and
parallel upper and lower crossheads which are connected to
eyes of said drawbars via one of pins and bolts; and (G) first
short-stroke piston and cylinder assemblies which are located
on opposed longitudinal sides of said press top and which
apply pressure along a longitudinal direction of said press
top creating a first variable pressure profile in said
longitudinal direction.
The present invention enables the steel bands of both the
press top and/or the press bed to be adjusted during press
operation relative to the medial longitudinal axis of the
press with the aid of displacement cylinder-piston assemblies
that are located near the drive and/or deflection roller axes
without either damaging the steel bands or producing one-sided
elongation therein. A precondition to this arrangement is the
resilient design of the press top in the high pressure and if
need be, mid-pressure zone, of the roller gap, which enables
first a reduction in the pressure load on the short-stroke
pressure cylinders that are located on the longitudinal side
n questlon.
The above-mentioned process is effected by means of an
arrangement wherein the individual beams that are located in
the high-pressure zone and, if need be, in the mid-pressure
zone, move to a limited extent vertically relative to each
other under upward counter-pressure from the material to be
pressed during depressurization of the appropriate short-
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4d
stroke cylinders and wherein furthermore the press top in the
lower-pressure zone and, if need be along a section of the
mid-pressure zone, both remain in the horizontal attitude and
maintain effective pressing force.
The development of non-symmetrical pressure profile in
the press top together with the assumption of a slanted
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_ 5
orientation about an angle ~ is assisted by an arrangement in
which the suspension of the press top over the press bed via
the press columns is assisted by means of freely movable
drawbars.
A further advantage of the present invention is that, for
the purpose of per~orming maintenance tasks in the press, e.g.
in the region of one 4-5m long heating plate that is to be
replaced, the groups of drawbars located in this region can be
swung outwardly far enough so as to permit access to the area
of the press requiring maintenance.
The invention is described in more detail below with
reference to the accompanying drawings, in which:
Fig. 1 is a front view of a proposed press along a
section A-B, as shown in Fig. 3 minus steel bands, drive and
deflection drums;
Fig. 2 shows the press of Fig. 1, in schematic form, from
entry-side to middle;
Fig. 3 is a plan view of the press shown in Fig. 2;
Figs. 4, 5 and 6 show the elastic construction of the
individual beams relative to each other; and
Fig. 7 is a top schematic vièw of the proposed press.
Continuously-operating press 1 comprises, as Figs. 1 to 7
indicate, an immobile press bed 2, a movable press top 3 and
press frame pillars 36 that are disposed along both
longitudinal sides of press bed 2. Rigidly attached to the
press as extensions to the press are side plates 21 that serve
to anchor and bear the shafts of drive rollers 37, deflection
rollers 9 and 10 as well as to house adjustment cylinder-
piston assemblies 17, which are arranged along axes IV-IV and
V-V. Press top 3 and press bed 2 comprise only webbed plates
and cross ribbing serving to connect the latter. A plurality
of webbed plates are, together with the cross ribs, welded
together into single beams 8, which, when arranged in series
and fitted with heating plates 14, correspond to the length
"1" of press top 3 and press bed 2, and thus also to the
integral length of the heated plate press 1 itself.
The extensions of the webbed plates that project out to
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the left and right provide a bearing surface for the press
frame pillars 36 to raise and lower press top 3, whereby
short-stroke pressing cylinder-piston assemblies 15 and 16
are arranged between upper crossheads 23 and the extensions of
press top 3.
Each press frame pillar 36 comprises two drawbars 13,
upper crosshead 23 and lower cross head 22. Attached on both
left and right hand sides of upper and lower crossheads 23 and
22 are pins or bolts 26 that extend outwardly on each side.
Crossheads 22 and 23 are connected together by means of
drawbars 13 that are suspended from pins 26 or bolts 26 that
fit into eyes 27 of such drawbars.
Fitted to crosshead 22 or 23 are bolts 26 that can be
removed whenever required. The overall design of press 1
provides that a majority of drawbars 13 (see Fig. 3) may
remain standing vertically to the left and right of a group of
outwardly swung drawbars 13 and are thus able to freely
support press top 3 and so permit replacement of e.g. heating
plates 14 and maintenance or repair to other components in the
region of the outwardly swung group of drawbars.
Figs. l and 7 furthermore show the manner by which press
top 3 can be raised up on one side through angle ~ along one
longitudinal side I-I or II-II of press top 3 inside elastic
region "e", which encompasses preferably high pressure zone HD
and up to half of mid-pressure zone MD. The aim of this
procedure is to reduce the pressure bearing on steel bands 5
and 6 for instance during disturbances in press operation
which might necessitate the realignment in the vicinity of the
forward roller of the steel band with the medial longitudinal
axis III-III of press 1. The procedure of decreasing the load
on the short-stroke pressure cylinders 7 and 15 located inside
press frame pillar 36 can be so regulated, that short-stroke
pressure cylinders 7 and 15, which are disposed along each of
individual beams 8 across longitudinal axis III-III, are
loaded with steadily decreasing pressing force from opposing
longitudinal side I-I or II-II to the outer longitudinal side
II-II or I-I that is being adjusted.
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As shown in Fig. 2, the elastic region "e" of press top
3, in systems operating with very high pressing forces, can
encompass the entire mid-pressure zone MD.
The precondition for the elasticity of press top 3 is,
however, the resilient method by which the individual beams 8
are connected together, enabling the creation of an asymmetric
pressure profile in high pressure zone HD and, if required, in
mid-pressure zone MD. Figures 4,5 and 6 show three
alternative approaches to the elastic design of press top 3 in
the different regions. In Fig. 4, steel springs 28 are
provided between individual beams 8, which, under the
application of counter pressure from an element such as a leaf
spring, are caused to deform. The arrow and the broken lines
indicate in all three examples the vertical range of
adjustment possible amongst individual beams 8. Instead of
resilient steel members, the configuration shown in Fig.5
provides that elastic rubber blocks 33 be disposed between
spacing elements 39 and 40, the individual beams 8 being
connected together by means of bolts 29, which also deform
elastically during vertical motion. The individual beams 8
shown in Fig. 6 are also connected together by means of bolts
29 and interlock along slip faces 30. Spacing elements 31 and
32 that are installed so as to leave free spaces 34 and 35
provide for hydraulically actuated adjustment of the
individual bèams 8 relative to each other. Spacing element 31
interlocks with the left-hand individual beam 8, and spacing
element 32 interlocks with the right-hand individual beam.
Free spaces 34 and 35 comprise approx. O to 1,2 mm (to a
maximum of 2,4mm). The freedom of motion afforded by such
free spaces corresponds to the allowable elastic deformability
of bolts 29 within the admissible tension range and also
provides a means of relieving pressure in order to allow
repositioning of steel bands 5 and 6, without causing one-
sided over expansion of the steel band.
The proposed elastic design of one part of press top 3
permits the temporary development upon either the left or the
right side in the process direction of a pressure profile or
path of motion profile that effects overall adjustment needs.
In other words, press top 3 is shifted from its normally
horizontal attitude into a slanted attitude by means of short-
stroke pressure cylinders 15 that are installed on the outside
of the press. Press top 3 is, in the elastic region "e" of
high pressure zone HD and, if required, along up to half of
mid-pressure region MD, as viewed from the entry side looking
toward the exit of the press, moved temporarily through angle
~. Such upward tilting motion produces, on the left or right-
hand side, depending on whichever is selected, i.e. alonglongitudinal side I-I or II-II, a reduction in pressure, so
that steel bands 5 and/or 6 can be moved by means of
adjustment cylinders 17 through angle $ back into alignment
with longitudinal medial axis III-III. Both control
procedures must be coordinated in such a manner that the
displacement of the roller axes IV-IV and/or V-V begins only
after pressure relief on short-stroke pressure cylinders 7 and
15 has either been completed or at least begun. The process
by means of which the press top is moved into a slanted
attitude through the angle ~ with the aid of short-stroke
pressure cylinders 15 can be supported by the positioning to
the left or right of multipot cylinders 7, in each of which
the cylinder pressures can be individually adjusted. As soon
as the steel band has been realigned with the longitudinal
medial axis of the press, press top 3 is guided back into the
horizontal attitude, at which point angle ~ has a value of
zero. The above-described procedure permits the continuously-
operating press in the second half of the medium-pressure zone
MD and the low pressure zone ND to regain its horizontal
disposition and to allow such press to be employed in a
calibrating role.
Because the elastic press top can move through angle ~
across high pressure region HD, the particulate pressing mass,
can, after steel band adjustment, undergo the same degree of
continuous compression while traversing the region of the
entry-side angle as was the case prior to ad~ustment of the
steel band.
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Fig. 2 also indicates the manner in which deflection
rollers 9 and lO form entry gap 4 and in which roller rods 11,
which travel together with steel bands 5 and 6 about press bed
2 and press top 3, and being carried along by means of guide
chains 12, bear upon press bed 2 and press top 3. In other
words, circulating roller rods 11 are arranged between heating
plates 14 and steel bands 5 and 6 in such a way as to be able
to roll with the latter.
