Field of the invention

The present invention relates to a method and a plant for manufacturing gypsum plates, especially gypsum plates to be used as construction panels, which gypsum plates are manufactured in a production line, a web of gypsum slurry being introduced between covering layers of paper board and after hardening to a self-supporting plate string being subjected to cutting in suitable plate length and drying and curing.

The invention also relates to a plant for such manufac- turing of gypsum plates .

State of the Art

Previously known art has involved that gypsum plates are manufactured along a production line, wherein gypsum slurry is introduced between covering layers of paper board, this web being transported along a roller band including partly driven rollers and partly idle rollers. After the web has hardened to a self-supporting plate string, the string is cut into appropriate plate lengths, which are taken out from the production line, are stacked in suitable stacks and passed into a drier. Herein drying is performed for sequentially accompanied stacks of cut plates, the plates being subject to an appropriate heat influence, for example by means of hot air.

The cutting and stacking of the hardened, self-supporting plate string is a relatively complicated and space con¬ suming process, and the drying of the stacked plates can in certain cases entail an uneven drying because the circulation and distribution of the drying air around the plates will not be uniform for all plates in the stack.

From the article "GIPSOTEX MULTI/ELEMENT" and NO patent publication 134.359 (Walter Nilsen) there are know two endless gypsum plates, namely a lower web, as well as an upper web being turned 180°, and said two webs are guided parallelly above each other through a very long drying oven. At the outlet of the drying oven said two above each other parallelly arranged webs are supplied with elements which are placed between said webs, together with a blowing agent, whereafter the two continuous webs at the end of a calibration device are cut into suitably desired and completely optional lengths.

In contradiction to the plant associated with "Gipsotex Multi/Element" there is according to the present inven- tion suggested only one plate at one level in the dryer, whereas in the plant in connection with Multi/Element there are two levels. By having only one plate at one level there is secured a uniform plate quality. By having a plurality of plates above each other, there could easi- ly occur an uneven drying of the plates at the different levels.

Summary of the invention

The object of the present invention is to provide a novel method and a new plant for manufacturing gypsum plates, wherein it is possible to eliminate complicated apparatus which are necessary for cutting and stacking plates prior to the drying process, and otherwise suggest a production line which can be built in a more cost-saving manner, which is simpler in its construction and which can be controlled in a simpler manner involving less maintenance and fewer moving parts.

Another object according to the present invention is to suggest a method and a plant for manufacturing gypsum plates rendering a more uniform drying and thereby a more

homogeneous end product, the basic idea thereof being the application of only one plate at one level in the dryer, including one or more plates but then substantially at the same horizontal drying level.

A further object is to the fact of providing a method and a plant requiring a reduced length of the factory works, which entails cost-saving as regards building expenditure and utilization of heat resources.

According to the invention these objects are achieved in a method a stated in the preamble, which is characterized in that the more or less hardened self-supporting plate string is passed uninterruptedly in substantially one plane through a first dryer arranged on a first level for introductory plate string drying and curing, whereafter the plate string is passed along an approximately 180° arch having an appropriate radius, such that the plate string or the strings are turned prior to being passed into a second dryer arranged at a second level, and whereafter the dried and cured plate string is cut to appropriate lengths.

In other words it is suggested a production line which works with an unbroken plate string which is passed so to say directly into a first subsequent dryer for therein to be dried in one plane, which involves a more uniform drying and more easy regulation of the drying zones in the dryer, whereafter the plate string is turned 180° for drying in one plane in a second subjacent dryer.

Correspondingly, a plant for manufacturing gypsum plates according to the invention will be characterized in that the plant comprises means which bring a more or less hardened plate string unbroken in one plane through a dryer arranged at a first level for introductory plate string drying and curing, comprising turning means which

bend the more or less hardened plate string through an arch of approximately 180° having an appropriate radius, such that the plate string or the strings are turned prior to being introduced into a second dryer arranged .at a second level for subsequent curing and drying of the plate string, and comprising adapted cutting equipment at the outlet of the second dryer.

Further features and advantages of the present invention will appear from the following description and the enclosed patent claims .

Brief disclosure of the drawings

Fig. 1A is a top view, and Fig. IB is a side view on a larger scale of a part of a first plant for manufacturing gypsum plates, wherein the present invention is included.

Fig. 2 is a top view on a larger scale of the main parts illustrated in Fig. 1A and Fig. IB.

Figures 3A and 3B illustrate sections at different scales taken along the line A-A in Fig. 1A.

Fig. 4 illustrates on a _. larger scale a section taken along the line B-B in Fig. 1A, namely through two dryer sections of a plant wherein the present invention is applied.

Fig. 5A is a top view and Fig. 5B is a side view which schematically illustrates a part of a second plant for manufacturing gypsum plates, wherein the present inven¬ tion is included, comprising two parallel plate strings.

Fig. 5C illustrates on a larger scale a detail of an extruder or forming plate included in the plant illu¬ strated in Fig. 5B.

Figures 6A and 6B illustrate on a larger scale a top view and a side view, respectively, in the area of wreckage paths between extruder and the first dryer.

Fig. 7A is a schematical side view of a turning zone ac¬ cording to the invention.

Fig. 7B illustrates on a larger scale details of Fig. 7A related to the guiding of plate strings into the turning zone.

Figures 8A, 8B and 8C are side view, top view and front view, respectively, of the plant at the turning zone, whereas Fig. 8D illustrates on a larger scale details of Fig. 8A.

Fig. 9 illustrates schematically a specific arrangement of a group of transport rollers for transporting two sub¬ stantially parallel plate strings across a certain trans- portation length.

Fig. 10 illustrates schematically the same type of speci¬ fic arrangement as Fig. 9, but to a more pronounced degree.

Fig. 11 illustrates on a larger scale details of the transport rollers according to Figures 9 and 10.

Description of embodiments

As appearing from the enclosed drawings 1-4, which illus¬ trate a first embodiment of the method and plant accord¬ ing to the present invention, there is at a forming sta¬ tion 1 provided a gypsum slurry through a mixer 2, where- in are mixed gypsum and additives in an appropriate ratio. The gypsum slurry is guided between covering lay¬ ers of paper board which are passed by the forming sta-

tion 1 via paper board rollers 3, for thereby providing a gypsum plate string 4 which on both sides are covered by paper board and with folded-in paper board along the side edges thereof. This plate string 4 is transported away. from the forming station through appropriately driven and non-driven rollers, across such a long distance and dur¬ ing such a long time interval that the gypsum hardens for constituting a self-supporting plate string.

This more or less hardened self-supporting plate string 4 is passed, according to the invention, uninterruptedly to a first dryer 5A which can be divided into one or more drying zones, for the introductory plate string drying and curing, whereafter the plate string is passed along an approximately 180° arch 11 having an appropriate radius R, such that the plate string 4 or strings is or are turned prior to being passed into a second dryer 5B provided at a second level and comprising one or more drying zones, and whereafter the dried and cured plate string 4 is cut into appropriate lengths.

In the embodiment illustrated in the Figures, there can be used only one production line, but it is to be under¬ stood that according to the invention there can be used two or more substantially parallel plate strings, but then preferably with a smallest possible distance there¬ between, which will be further discussed in the follow¬ ing.

By using a plurality of plate strings there may appropri¬ ately be used a common mixer, or alternatively it can be used one mixer for each plate string.

In the embodiment illustrated in the enclosed Figures 1 - 5, only one forming station 1 is used, and one such form¬ ing station can be expanded also to be utilized for two parallel plate strings 4a and 4b, one being able at the

same time to choose whether forming rollers or extruding equipment should be used by the one or more chosen form¬ ing stations.

In the discussed embodiment the production line for the plate string 4 is suitably located at a first level which preferably is at the same level as the first dryer 5A, and after the plate string 4 emerges from said first dryer 5A the more or less hardened plate string 4 is passed through the approximately 180° arch 11 with a suitable radius R, such that the plate string 4, possibly the plate strings 4a and 4b, can be turned prior to being guided into a second dryer 5B.

It is appropriate that the first dryer 5A is at a first upper level, and that the second dryer 5B is at a second lower level, said first and second dryers being complete¬ ly or partly built together.

Further, it would be appropriate that the first dryer 5A has a longitudinal dimension corresponding approximately to one third of the overall drying length.

As especially appearing from Fig. 4, it could be approp- riate to use elongated dryers 5A and 5B which are divided into several zones, each zone being controlled as regards heat supply and ventilation. As the drying then takes place at one level, whether one uses one plate string or a plurality of plate strings, there is achieved a more uniform drying over the complete plate string, and there is avoided unevenly dried cut edges, as in previously know prior art. Further, the drying at one level will involve a simpler construction of the drying zones, which zones will be more easily regulated as regards air circu- lation and heat intensity.

At the outlet of the second dryer 5B there may appropri-

ately be provided suitable cutting equipment, for example an arrangement 6 including scissors, which appropriately may comprise so-called running scissors, which involves that cutting may take place synchronously with the out- feed of the finished dried and cured plate string.

As specifically appearing from figures 1A, 1B and 2, there may in the area of the wet end of the production line, i.e. in the area prior to the plate string 4 being introduced in the first dryer 5A, appropriately be arranged wreckage scissors 7, an acceleration path 8, a tilting path or a tilting lift 9, as well as a separate wreckage path 10, which elements will be operable if wreckage is to be cut off the wet end of the production string prior to this being passed on to the first dryer as an uninterrupted string.

In Figures 5A and 5B there is illustrated a top view and a side view, respectively, of a part of a plant of a second embodiment for manufacturing gypsum plates, there being here at a forming station 101 provided gypsum slurry via one or more mixers for the production of two substantially parallel gypsum plate strings 104a and 104b.

The gypsum slurry is passed through covering layers of paper board, there here being used four paper board webs, paper board webs 103a and 103b for the gypsum plate string 104a, and paper board webs 103c and 103d for gyp- sum plate string 104b, respectively, for thereby provid¬ ing said gypsum plate strings 104a and 104b with folded- in paper board along respective side edges. In Fig. 5C which illustrates a section of the forming station proper or the extruder for one of the gypsum strings, it is seen that the extruder 101 comprises an upper forming plate 112 and a lower forming plate 113 the gab therebetween, here designated 114, corresponding to a preselected con-

trollable thickness of the plate string in question. Upstream of the extruder there is adapted an upper lid 115 along which and via a pipe 116 one of the paper board webs 113b is passed, as well as a lower bent plate 117 along which the second paper board web 103a for the gyp¬ sum plate string in question is guided, and then carrying the previously applied gypsum slurry. At the outlet 118 of the extruder 101 there will thus be formed said plate strings 104a and 104b which are transported away from the forming station or the extruder 101 via a conveyor band

119 which via an end roller 120 is driven by appropriate¬ ly driven and idle rollers 121.

As previously mentioned each fresh plate string 104a, 104b is transported away from the forming station 101 so far and for such a time period that the gypsum hardens for constituting self-supporting plate strings. However, the plate strings 104a and 104b must pass a wreckage area, as this more specifically appears in Figures 6A and 6B, said Figures on a larger scale illustrating a top view and side view, respectively, of the area of the wreckage path provided between the extruder 101 and a first dryer 105A. The wreckage area comprises as in the previously discussed embodiment, wreckage scissors 107, an acceleration path 8, a tilting path or a tilting lift 9, as well as a wreckage path 110 which communicates with the tilting lift 9 and the acceleration path 8, in case there during the start-up or the production are observed gypsum strings which do not meet the requirements as regards quality, dimension and other parameters being of importance for the operation and the final results.

The wreckage path 110 can communicate with a grinder or chopper 122 as well as a waste funnel collecting the chopped and wrecked plates and communicating with a belt conveyor 124 for possible recirculation of wrecking goods. The acceleration path 108 has the function of

during a wrecking operation to accelerate the cut section out of the normal production line, such that the subse¬ quent production string can be passed on to the first dryer 105A as an uninterrupted string without the danger of colliding with the cut wreckage section.

Also in this embodiment the hardened self-supporting plate strings 104a, 104b are passed on uninterrupted to a first dryer 105A, which can be divided into one or more drying zones, for example three drying zones having an individual length of for example 50 , for the introduc¬ tory plate string drying and hardening, whereafter the plate strings 104a, 104b, as illustrated in Figures 7A and 7B, are passed into a turning zone, more specifically a 180° arch 111 having an appropriate radius, for example between three and five meters, such that the plate strings can still remain unbroken after the turning, whereafter said plates are guided into a second dryer 105B, as this also appears from Figures 8A-8C.

In Fig. 7A it is illustrated that one of the plate strings 104a enters the turning area or the arch 111 via two first guiding rollers 122a and 122b whereafter they pass a first set of rollers 123n which extend across app- roximately a quarter of a circle before the plate string 104a via a marker 124 is guided into a second set of rollers 124n giving the plate 104a abutting support against the opposite side for the remaining quarter of the circle in relation to the introductory quarter of the circle of the arch 111.

In Fig. 8A it appears that the first set of rollers 123n can be provided on a first set of supporting rails 125, whereas the lower second set of rollers 124n are carried by a second set of supporting rails 126. In Fig. 8A it also appears schematically a first separate driving means 127 for driving the upper drive rollers, comprising the

roller 122b as well as further drive rollers arranged upstream in relation to the turning zone 111, as well as a lower separate drive means 128 for operating lower drive rollers 124b, as well as further drive rollers arranged downstream in relation to the turning area 111. In the area of the marker 124 there may appropriately be provided a sensor 124x for sensing whether the gypsum string or strings 104a, 104b have an inlet angle, respec¬ tively a tensioning or slackening degree in the turning area, which should imply that the separate driving means 127 and 128 for the upper and lower rollers, respective¬ ly, should be regulated, see specifically Fig. 8D.

The turning area 111 may appropriately be built into an insulated housing 130 and may appropriately be provided without separate heating, but including suitable access and gangways 131n for simplified inspection and mainten¬ ance.

As especially appearing from Fig. 8A, compared with Fig. 6B, the production line for the plate strings 104a, 104b is located at a first level which preferably is on the same level as the first dryer 105A, and after the plate strings 104a, 104b, respectively, have emerged from the first dryer 105A, they will primarily be guided through the turning area 111 and then into the second dryer 105B which for example may comprise seven drying zones giving appropriate individual or co-operated drying prior to cutting and sorting at the outlet of the second dryer 105B.

In order to achieve a still more uniform drying when using one or more parallelly running gypsum plate strings, it is appropriate that the parallel plates, preferably in the area between the extruder 101 and the wreckage station 107-110, are guided towards each other for rendering as little difference therebetween as poss-

ible, a lesser gap between the plate strings resulting in a better drying of egdes facing each other, said edges then not to such a strong degree being subjected to de¬ hydration. This is somewhat dependent upon how the drying zones are constructed, but such a minimum or optimum gap width is of specific importance when the regulation of the drying air within the dryer can hardly be performed individually in said edge areas. The outer edges can, however, more easily be screened by means of cold air strata, for thereby also in these outer edge areas to achieve a homogeneous and optimum drying of edge zones.

Thus, in Figures 9-11 there is illustrated schematically a specific assembly of a group of transport rollers for driving various groups of transport rollers along a cer¬ tain transportation length, and for the purpose of bring¬ ing two current plate strings 104a and 104b closer to each other. Consequently, Fig. 9 illustrates the two plate strings 104a and 104b having a first mutual spacing 135A, for example 250 mm, but being transported on trans¬ port rollers 136n which are inclined in relation to each other under a certain angle αl , whereas Fig. 10 illu¬ strates corresponding rollers or cylinders 137 having a still larger angle α2 in relation to each other, which involves that the transported gypsum plate strings 104a and 104b have been influenced to let their enfacing edges define a very little mutual spacing 135B, or no spacing at all therebetween, prior to said plate strings 104a and 104b merging into another transportation length wherein the transport rollers have taken the original substanti¬ ally horizontal position in relation to each other.

In Fig. 11 there is illustrated a section through one of the gypsum plate strings 104a when said string is passed from a horizontal roller 136 onto an inclined roller 136n under the forming of the angle αl , which can represent an inclination per roller, for example of 1°, until the apex

of the inclined path and the angle α2 has been achieved, whereafter the path is flattened again and with the two parallel gypsum plate strings 104a and 104b having been brought together to a minimum mutual spacing or possibly abutting edges .

It is to be understood that such a converging of the initially mutually spaced and semi-manufactured gypsum plate strings can be effected downstream of the forming station also in other ways. For example, the rollers may be provided inclined in relation to each other in the horizontal plane, but in such a manner that two, possibly several plates, are subjected to being brought closer to each other prior to the arrival at the wreckage path and the first dryer.

Technical details:

The production line is arranged at the same level as a first longitudinal dryer, all of which is located above a second longitudinal dryer.

The production line consists of one, two, possibly a plurality of, parallel plate strings in the same plane but having a least possible spacing therebe¬ tween.

A common mixer, possibly two mixers.

- A common forming station, possibly two separate forming stations, comprising forming rollers or extruding system.

The wet end being equipped with wreckage scissors, acceleration path, tilting lift and wreckage path, in order to avoid passing wreckage from start-up through the first dryer.

After having removed wreckage from start-up, the plate strings are guided in continuous lengths into a first dryer, thereafter passed through an at least 180° arch having a selected necessary radius 4 . . This arch turns the plate string(s) before being passed into the second dryer.

The longest dryer is 350 long, and each of the dryers can be divided into a plurality of zones hav- ing an individual burner for each zone and ventila¬ tion from some of the zones . Height of each dryer 700 mm Width of each dryer 3000 mm

- The plates are cut at the dry end, possibly by runn¬ ing scissors.

Specific features according to the present invention can be summarized as follows:

Mixer, hardening path (forming band and rollers) as well as primary part of the dryer (approximately 1/3) are located at upper level.

- The continuous plate is turned 180° after the first part of the dryer and is guided into the second part of the dryer at lower level. In this manner there is achieved a fabric of shorter length than what is the case in previously known plants.

There will be only one plate at a single level in the dryer, whereas in plants related to Multi/Element there are two levels. By having only one plate level, there is secured a uniform plate quality. By having a plurality of plates at various height levels, one can easily achieve non-uniform drying of the plates at the various levels.

By providing such a long dryer having a plurality of burners, there might be achieved an optimum tempera¬ ture curve and shorter drying time than in a conven¬ tional plate dryer.