Hatschek process for the production of fiber cement plates

Abstract

A Hatschek process for the production of profiled fiber cement plates is provided. The process comprises the steps of: (i) providing an endless fiber cement multilayered slab stacking at least one monolayer of a first type having a first width and at least one monolayer of a second type of monolayers having a second width, the at least one monolayer of a second type of monolayers extending in transverse direction beyond the at least one monolayer of a first type of monolayer: (ii) accumulating at least one layer of the endless fiber cement multilayered slab on a profiled accumulator roll having a recess along at least part of its circumference whereby the at least first monolayer is provided within the recess; (iii) removing the accumulated slab from the accumulator roll; and (iv) curing the uncured fiber cement plate.

Claims

1. A Hatschek process for the production of a profiled fiber cement plate, comprising the steps of: providing an endless fiber cement multilayered slab (101) in a production direction (103) by stacking a first monolayer (105) having a first width (W1) in a transverse direction (115) and a second monolayer (107) having a second width (W2) in said transverse direction (115), said first width (W1) being less than said second width (W2), and the second monolayer (107) extending in said transverse direction (115) beyond the first monolayer (105); accumulating at least one layer of said endless fiber cement multilayered slab on a profiled accumulator roll (117), said accumulator roll having a recess (125) in an axial direction (121) along at least part of a circumference (127) thereof, whereby the first monolayer (105) is situated within said recess (125), thereby providing an accumulated slab (133); removing said accumulated slab (133) from the accumulator roll (117), thereby providing an uncured, profiled fiber cement plate (130); and curing said uncured fiber cement plate (130) to provide said profiled fiber cement plate.

2. The Hatschek process according to claim 1, wherein the recess (125) has a depth of between 0.5 mm and 3 mm.

3. The Hatschek process according to claim 1, wherein the difference between said width (W1) of said first monolayer (105) in said transverse direction (115) and the width (W2) of said monolayer (107) is at least 40 mm.

4. The Hatschek process according to claim 1, wherein said multilayered slab further comprises n additional second monolayers, n being an integer of at least 1, said width of each of said n additional second monolayers in said transverse direction is more than the first width of said first monolayer (105), and each of said n additional second monolayers extends in said transverse direction beyond the first monolayer (105).

5. The Hatschek process according to claim 1, wherein said recess (125) has a trapezoid shape, the length of a radial projection of each of legs of said trapezoid shape on the axis of said accumulator roll (117) is in the range of 2 to 20 mm.

6. The Hatschek process according claim 1, wherein said multilayered slab further comprises m additional first monolayers, m being an integer of at least 1.

7. The Hatschek process according to claim 1, wherein said multilayered slab comprises a total of 2 to 8 monolayers of said first and second monolayers.

8. The Hatschek process according to claim 1, wherein the first monolayer has a thickness different from the thickness of the second monolayer.

9. The Hatschek process according to claim 1, wherein each of said first and second monolayers is formed by accumulating fiber cement slurry on a rotating sieve drum and removing said accumulated fiber cement slurry from said rotating sieve drum as a monolayer, the width of said first monolayer in said transverse direction being formed by obstructing at least part of the sieve at outer ends thereof in an axial direction of the rotating sieve drum.

10. The Hatschek process according to claim 1, wherein each of said first and second monolayers is formed by accumulating fiber cement slurry on a rotating sieve drum and removing said accumulated fiber cement slurry from said rotating sieve drum as a monolayer, the width of said first monolayer in said transverse direction being formed by removing part of the accumulated fiber cement slurry from the sieve extending beyond the width to be formed.

11. The Hatschek process according to claim 10, wherein the slurry is removed by spraying water onto the slurry to be removed.

12. The Hatschek process according to claim 1, wherein said accumulator roll has no recess (125) in the axial direction (121) along at least 40 mm of its circumference.

13. The Hatschek process according to claim 1, wherein said accumulator roll (11) has the recess (125) in the axial direction (121) along a complete circumference thereof, the process further comprising using means to contact the respective layer of said endless fiber cement multilayered slab in the recess at start of accumulation of the layer on the profiled accumulator roll.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematically view of a Hatschek process.

(2) FIG. 2 is schematically view of an accumulator roll used in a process according to the invention.

(3) FIG. 3 is schematically view of an endless fiber cement multilayered slab in a production direction according to the invention.

(4) FIG. 4 is schematically view of an accumulator roll on which multiple layers of endless fiber cement multilayered slab are accumulated, according to the invention.

(5) FIG. 5 is schematically view of an uncured, profiled fiber cement plate according to the invention.

(6) FIGS. 6 and 7 are schematically views of a series of rotating drum sieves as used in a process according to the present invention.

(7) FIG. 8 shows the density profile in transversal direction of an uncured, profiled fiber cement plate according to the invention.

(8) FIGS. 9a to 9j are schematically views of endless fiber cement multilayered slabs in a production direction according to the invention.

(9) The same reference signs refer to the same, similar or analogous elements in the different figures.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(10) The present invention will be described with respect to particular embodiments. It is to be noticed that the term comprising, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, steps or components as referred to, but does not preclude the presence or addition of one or more other features, steps or components, or groups thereof. Thus, the scope of the expression a device comprising means A and B should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

(11) Throughout this specification, reference to one embodiment or an embodiment are made. Such references indicate that a particular feature, described in relation to the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment, though they could.

(12) Furthermore, the particular features or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art.

(13) A typical Hatchek process is shown in FIG. 1. A number of monolayers, in the embodiment shown in FIG. 1, in total four, are created by four rotating sieve drums (145, 147, 149, 151). They are picked up and stacked on an endless transport belt 113, being a water permeable felt or fleece. This felt, after having passed the fourth rotating sieve drum 151, carries a fiber cement multilayered slab 101. As the system may continue to rotate, this is de facto an endless fiber cement multilayered slab. This slab 101, which is transported in production direction 103, is contacted by the rotating accumulator roll 117. On this accumulator roll 117, which according to the invention has a recess 125 in axial direction 121 along at least part of the circumference 127 as shown in FIG. 2, a plurality of fiber cement multilayered slab layers are accumulated by rotating the accumulator roll along its axis 119, until the predefined thickness is obtained. At that moment, the accumulated slab 133 is cut and taken from the roll 117, and laid down on a transport device 153. As such an uncured, profiled fiber cement plate 130 is provided. The uncured, profiled fiber cement plate 130 is further adjusted in dimension, and cured in an appropriate way, e.g. air cured or autoclave cured as the case may be.

(14) In a processes according to the invention, at least one of the sieves, e.g. the first sieve 145, provides a monolayer 105 which has a width W1 which is less than the width of the monolayers 107, 109 and 111, provided by the other sieves 147, 149 respectively 151. The sieves are aligned one to the other in such a way that on the endless belt 113, the monolayer 105 with the smallest width W1 is encompassed, or in this case covered, by the other monolayers, in this embodiment the other three monolayers 107, 109 and 111, which have all a substantially identical width W2.

(15) A cross section of the endless fiber cement multilayered slab 101, obtained on the transport device 113 is shown in FIG. 3. In transverse direction 115 to the production direction, one notices that the monolayer 105, laid down first on the transport device 113, is fully covered by the subsequent monolayers 107, 109 and 111.

(16) As shown in FIG. 4, several layers of this endless fiber cement multilayered slab (1001, 1002, 1003 and 1004) are accumulated on the accumulator roll 117. For each slab, the monolayer with reduced width (1011, 1012, 1013 and 1014) is provided within the recess 125, thereby providing an accumulated slab 133 Once the accumulated slab 133 has reached its desired thickness, the slab 133 is taken from the accumulator roll 117 and laid down on a transport device 153 as shown in FIG. 1, thereby providing an uncured, profiled fiber cement plate 130. The cross section of this uncured fiber cement plate 130, as shown in FIG. 5, has already a tapered of beveled edges 1301 and 1302 at both sides 1311 and 1312 in production direction 103.

(17) Curing the uncured fiber cement plate to provide a profiled fiber cement plate with tapered of beveled edges may be done by e.g. air curing or autoclaved curing. Optionally, at both sides 1311 and 1312, the plate can be cut to the required total width as is usually done in Hatschek production, before curing.

(18) As shown in FIG. 6a, a top view of a rotating sieve drum rotating in its slurry containing vat, i.e. sieves 145, 147, 149 or 151 is shown. Each rotating drum 2001 rotates around its axis 2003 in the vat 2005. Along a part of the surface of the rotating drum, the surface is provided with perforations, or is provided in a wire net material 2007, forming a sieve. The width of the sieve is the width W2 of the monolayer which will be formed on the sieve surface when the slurry is sucked from the outside of the sieve towards the inner side of the sieve. The cement, filler, fibers and other material will be retained on the sieve surface, forming the monolayer.

(19) For the first rotating drum sieve 145 in production direction 103, at both ends in axial direction, a zone 2009 and 2010 of the sieve is covered by a water impermeable coating, such as a paint. As such, the monolayer build on this sieve will not build along the covered zones 2009 and 2010, hence resulting in the fact that a monolayer with smaller width W1 will be formed.

(20) It is understood that also alternative sequences, with the sieve drum 145 positioned not in the first station but in one of the second, third or fourth position in the rotating drum sieve train can be used.

(21) As an example, four rotating drum sieves as shown in FIGS. 1 and 6 are used to form four monolayers. The first monolayer has a width W1 of 1100 mm, the three subsequent monolayers have a with W2 of 1400 mm. The density and composition of the slurry used to provide all four monolayers are identical. The composition of the slurry used is a typical fiber cement slurry comprising water, cement, cellulose fibers, sand and the typical additives. The thicknesses of the monolayers are identical and are 0.25 mm.

(22) As such a fiber cement multilayered slab 101, as shown in FIG. 3, is provided wherein the first monolayer is covered by the three other monolayers. The three other monolayers extend over the first monolayer over a width W3 being, in this sample 150 mm on both sides.

(23) This a fiber cement multilayered slab 101 is accumulated on an accumulation roll 117 with a maximum diameter Dmax of 875 mm, and having a trapezoid-like recess of depth R of 2 mm and a length L of the legs in axial direction of the drum 117 of 15 mm. The minimum diameter Dmin along the recess is 871 mm. So in a zone of length L, the diameter of the accumulator roll gradually changes from Dmin to Dmax.

(24) The accumulator roll, with an approximate circumference of 2750 mm is provided with this recess along 2600 mm, leaving a zone 128 of the circumference with length of 150 mm without recess.

(25) This absence ensured the fresh slab 101 to be picked up by the accumulator roll immediately after removal of the previous accumulated slab.

(26) In an alternative process, the accumulator roll has a recess along its complete circumference, while the installation comprises a means to contact the fresh slab to the accumulator roll immediately after removal of the previous accumulated slab. E.g air jets at the end of the transport belt 113, bowing the slab upwards to the accumulator roll, or vacuum sucking holes in the accumulator roll may lift the fresh slab towards the accumulator roll. A moveable roll fitting within the recess and contacting it with his circumferential surface can be used as well.

(27) 5 fiber cement products with tapered edges were made, with 5 different thicknesses (6.5 mm, 7 mm, 8 mm, 8.5 mm and 9.5 mm). 6, 7, 8, 9, respectively 10 layers of slab are accumulated on the accumulator roll to provide the accumulated slab. This accumulated slab is cut and laid down on the transport device. The uncured, profiled fiber cement plate obtained have a width 1400 mm, a maximum thickness of 6.5 mm, 7 mm, 8 mm, 8.5 mm and 9.5 mm and a minimum thickness at the thinner end of the beveled edge of 4.5 mm, 5 mm, 6 mm, 6.5 mm and 7.5 mm.

(28) The density profiles of the uncured, profiled fiber cement plate is shown in FIG. 8. On 5 positions, the density of the uncured, profiled fiber cement plate was measured. Position P3 is in the middle of the uncured, profiled fiber cement plate in transversal direction. P2 and P4 are at the of the width of the uncured, profiled fiber cement plate measured from the respective edges. P1 and P5 are at the tapered edges of the uncured, profiled fiber cement plate.

(29) The uncured, profiled fiber cement plate is reduced to the commercial width at both sides of the beveled edge profile, is air dried and hence a profiled fiber cement plate is provided.

(30) As an alternative set up shown in FIG. 7, for the first rotating drum sieve 145 in production direction 103, at both ends in axial direction, a zone 2009 and 2010 of the sieve sprayed by a water spraying device 2020, spraying water 2022 to the zones 2009 and 2010. The monolayer build in this zone is sprayed away from the sieve, forming a monolayer with smaller width W1. This has the advantage that the width of the monolayer can be varied in time, i.e. for providing the first layer of multilayered slab, the sprayers can be activated, hence a multilayered slab comprising a monolayer with reduced with can be provided and accumulated, while, for the all or some of the consecutive accumulated layers on the accumulator roll, the sprayers can be deactivated, providing multilayered slabs consisting of monolayers with all identical widths.

(31) It is understood that, in line with the invention, more or less than four, but at least 2 monolayers can be offered and accumulated on the accumulator roll. Also that the order of more wide and less wide monolayers may be varied. Also that that stacks of monolayers having mutually different widths may be used. Some alternative cross sections of the endless fiber cement multilayered slab are shown in FIGS. 9a to 9j, wherein 91, 92, 93, 94, 95 and 96 are monolayers stacked to provide an endless fiber cement multilayered slab 900 according to the present invention.

(32) It is to be understood that although preferred embodiments and/or materials have been discussed for providing embodiments according to the present invention, various modifications or changes may be made without departing from the scope and spirit of this invention.