Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2038751
Process and aPParatus suitable for effectina steel band
auidance.
The present invention relates to a process and to an
apparatus suitable for guiding a steel band along a
longitudinal axis of a continuously-operating 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 ,- es~ed by a pair of
lo 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 r011er 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 ~_ essed sheets of other
particulate feedstock material.
The rigid design of the press top and press bed in prior
art continuously-operating presses together with the static,
inflexible arrangement of the press bed and press top relative
to each other, make the precise alignment or adjustment of the
longitudinal axes of both the press top and press bed
difficult, if not impossible. This conventional arrangement
predisposes the longitudinal axes of the upper and lower steel
bands, which circulate about the press top and the press bed,
to become misaligned during the pressing operation, a
condition which necessitates remedial maintenance.
2038751
Experience of use of continuously-operating presses
employing either hydrostatic or rolling support by means of
roller rods for the rotating steel bands has demonstrated
that, in the case of larger presses that are employed to
achieve higher throughputs, the all-important control of steel
band travel becomes problematic.
The steel bands become difficult to control in presses
whose length exceeds 28 m. In longer conventional presses
approaching 40 m, upon (for example):
a) a slight disruption in the lubrication of the steel
bands or roller rods, or
b) uneven feedstock material thickness distribution,
negative effects on the online control may occur,
rendering impossible a return of the steel bands to their
medial alignment by angular displacement of the axes of the
drive and deflection drums.
The steel bands are, in the zone of the heating plates,
and especially in the first third of the high pressure zone,
locked in position as in a vise. When the drum axis is
displaced through its displacement path, the steel band, not
being locked in position in this region, undergoes partially
greater elongation than in its fixed region. The same
ph~nl -non occurs in the vicinity of the exit-side drum. 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 the entry-side and exit
side zones becomes increasingly disadvantageous. In order,
therefore, to avoid unilateral overstretching of the steel
bands during adjustment of steel band travel, the press must
be shut down; clearly, all of the disadvantages attending this
course of action are to be expected.
The present invention has, therefore, as its object the
provision of a process that will permit the longitudinal axis
of the press top to be adjusted to align with that of the
press bed, or, in other words, the precise superimposition of
the longitudinal axis of the press top over the longitudinal
axis of the press bed during the production runs, while not
3 203875 ~
occasioning unilateral stretching of the steel band.
Also provided is a device suitable for implementing the
above-described process.
According to one aspect of the invention there is
provided a method of guiding first and second steel bands
about a longitudinal axis of a continuously-operating press
having multiple pressure regions which are of different
pressure levels and short-stroke cylinder-and-piston
assemblies, said method comprising the steps of (A) guiding
said first and second bands around a press top and a press
bed, respectively; (B) realigning said first steel band with
respect to a longitudinal centre-line of said press and said
press bed, said realigning step comprising the steps of: (i)
relieving pressure in short-stroke cylinder-and-piston
assemblies located in a high-pressure region of said press,
and then (ii) horizontally rotating said press top through an
angle ~ about a vertical axis of rotation.
According to 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,
said press including a press top having a vertical axis and a
press bed, said bands transmitting pressing pressure to the
material to be pressed and drawing said material through said
press, said device comprising (A) devices which guide said
first and second bands around said press top and said press
bed, respectively; (B) a fixed frame; (C) stopping elements
which are connected to said frame and between which said press
top is rotatable about said vertical axis of said press top
through an angle ~; (D) press frame pillars which support said
press top, each of said pillars comprising a pair of parallel
support rods and parallel upper and lower crossheads
connecting said support rods to one another, said support rods
supporting said press top and being pivotable together as
opposite sides of parallelograms through an angle $; and (E)
means for driving said press top to rotate about said vertical
axis of said press bed.
4 203875 1
The invention is described in more detail in the
following with reference to the accompanying drawings, in
which:
Fig. 1 is a schematic top view of a press top comprising
drive and deflection drums;
Fig. 2 is a front view of the proposed press along
section A-B as shown in Fig. 4, with the steel bands being
omitted;
Fig. 3 is the press shown in Fig. 2 with the drawbars
swung out to the side; and
Fig. 4 is a partial top view of the press shown in
Fig 3
The present invention permits the entire press top to be
pivoted about its mid-point in the manner of a parallelogram
so as to cause precise orthogonal congruency of the
longitudinal axes of the press top and press bed during
operation, during which procedure the press top can be shifted
in the manner of a parallelogram by means of the freely-
moveable support rods approx. 1~ through angle ~1 in the
direction indicated by angle ~1 and through angle ~2 in the
direction indicated by angle ~2.
The press top can, in order to be able to accommodate
transverse forces in the upper and lower steel bands, and also
to be able to permit adjustment of the steel band running
path, be adjusted as a unit at all four of its corners about
the angle ~ relative to the press bed.
With respect to achieving effective control over the
running path of the steel band, this adjustment can be
accomplished either manually, or by means of hydraulic
adjusting members, assisted by motors. The use of this
process also obviates unilateral overstretching of the steel
band located on the press top.
A further advantage of the present invention is the
benefit to press maintenance, e.g. in a section of the press
comprising the length of one heating plate, wherein a section
4 to 5 m in length is to be replaced. This advantage can be
achieved by swinging a unit of support rods far enough to the
5 2038751
outside of the press so as to permit unimpeded access to the
section of the press requiring maintenance.
Referring in more detail to the illustrated embodiment,
continuously-operating press 1 comprises, as shown in Figs. 1
to 4, an immobile press bed 2 positioned in a fixed press
frame, a moveable press top 3 and press frame pillars 36
disposed along both longitudinal sides of press bed 2. Press
top 3 and press bed 2 comprise only webbed plates and
crossribs serving to strengthen such plates. A plurality of
webbed plates comprising crossribs are welded together to form
the individual beams 8, which, after being arranged in series,
are fitted with heating plates 14 running the length of press
top 3 and press bed 2, thus constituting the effective length
of the press. The extensions or protrusions extending left or
right outwardly from the webbed plates provide bearing
surfaces enabling press frame pillars 36 to raise and lower
press top 3. In the illustrated configuration, short-stroke
pressing cylinder-and-piston assemblies are disposed between
upper crossheads 23 and the extensions of press top 3.
One press frame pillar 36 comprises a pair of support
rods 13, upper crosshead 23 and lower crosshead 22. Fitted to
upper and lower crossheads 23 and 22 on both the left and the
right are protruding pins or removable bolts 26. Crossheads
22 and 23 are connected together by means of support rods 13
that are suspended on pins or bolts 26 that fit into eyes 27
in such support rods.
As Figs. 1 and 2 further illustrate, press top 3 is
designed to be able to be displaced or pivoted horizontally
about pivot axis 19 and longitudinal medial axis I-I in the
manner of a parallelogram with the aid of displacement
cylinders 18.
In the illustrated configuration, the pivoting motion of
press top 3 is limited by four stopping elements 38 that are
arranged about immobile press frame pillars 20. The adjusting
motion executed by longitudinal medial axis I-I of press top 3
about angle ~1 and ~2 relative to the longitudinal medial axis
of press bed 2 is mimicked through angles ~1 and ~2 by the
6 2038751
press frame pillars 36 due to the ability of support rods 13
to swing freely. The ability of press top 3 to be displaced
in a motion typical of a parallelogram permits the adjustment
of the travel of the press top steel band around drive and
deflection roller axes II-II and III-III, during which
procedure a temporary reduction in pressure in the high
pressure zone HD is effected by short stroke pressure
cylinders 7,15. When the press is operating at particularly
high pressure, the pressure may also be reduced in the medium
pressure zone MD. The pressure reduction alleviates lateral
forces on steel band 6 as the alignment adjustment is being
made. It is not necessary, at the pressures conventionally
employed, to reduce the pressure in the low pressure zone ND.
The three zones, HD, MD and ND are, in the present
configuration, each one-third the length of press 1.
Side plates 21 are rigidly attached to the press top and
serve as an anchor region and bearing site for drive rollers
37, deflection rollers 10 and for the displacement cylinders
18 which are arranged near axes II-II and III-III.
