EP1062087B1 - Method and double strap press for continuously producing materials in the form of plates - Google Patents

Description

The invention relates to a method according to the Preamble of claim 1 and a double belt press the preambles of claims 4 and 8, respectively.

Such a method and such a double belt press are e.g. from DE 21 57 746 C3 or DE 39 04 982 C1 known. Support plates are provided in the press section, on which the forming belts run along roller chains are supported. The support plates are crossed by strong to the track above or below the respective support plate arranged supports supported outside the web width are pulled together by spindles.

There are holes in the support plates that run transversely to the path provided, the channels for passing a heat transfer medium, mostly a thermal oil. The canals too many follow each other in the direction of travel of the web. Successive channels are through on the edges of the U-shaped elbows attached to each other by support plates connected so that the heat transfer medium in a zigzag across runs to the web and in this way the uniformity heat transfer is improved. Several in the direction of travel form successive transverse bores on the path a group loaded with heat transfer medium.

In the manufacture of board materials, in particular Chipboard and similar materials must be in the first zone of the press section a significant amount of heat in the Material of the fill can be brought in to the curing reaction of the binder. The in the Bulk moisture is used for transport the heat in the fill and plasticizing the Bulk. In a rear, i.e. subsequent, against the end of the pressing section towards the must Heat supply is no longer as big, but it comes mainly on maintaining the distance of the Forming tapes perpendicular to the web for a certain time, in which the material hardens so that a calibrated Plate run out of the press section. By holding The thickness in the rear section will initiate bonds not due to premature within the plate material Relief torn open again before the complete hardening, what weaken the board material or even would destroy.

In the system known from DE 39 04 982 C1 Forming tapes, between which the plate material is formed is rolling over roller chains on the flat support surface supported by a support structure that is above the upper and below the lower forming belt in the pressing section are located. Even if the support structure in the rear Area of the press section no longer heated positively should be there by the leading form tapes with the roller chains and the path of the plate material transfer much heat to the rear section of the press section.

Much of that in the first zone of the press line. in the amount of heat brought in is therefore of the plate web, the forming tapes and in particular the Roller chains in the rear section of the press section transports and radiates unused into the environment from. For the panel track itself it is necessary in the rear Zone of the press section often no longer provides heat. in the On the contrary, it is sometimes even desirable to use the slab track to cool to a certain extent in the press.

To provide enough heat in the first zone of the press section To have available there must be an excess of heat be worked in the back of the Press line can no longer be used and energy costs elevated.

The invention has for its object the energy costs a system comprising the double belt press reduce.

This task is carried out in its procedural aspect solved the invention reproduced in claim 1.

Those from the front section through the forming Panel material, the two form belts and the chains in the heat transported through the rear section can Invention at least partially saved from getting lost be, so that the heat balance of the entire system improved. There is also an additional effect that the environmental compatibility of the operation of the double belt press improved: the removal of heat from the heat transfer medium the rear section is synonymous with cooling it. Thanks to the heat removal reduced temperature in the rear zone of the press section will be the evaporation of formaldehyde that comes from the Binder comes, and the leakage of other organic Vapors that can be flammable, e.g. out Grow, diminish.

On a larger or even any supply of heat can waived in the rear section in many cases because the tapes with their higher temperature continue to transport heat into the interior of the plate.

In the method according to claim 2 is in the rear Section of the press section extracted heat from another Place of the process for the production of the board materials used yourself, e.g. for preheating or drying the Particles from which the sheet material is formed or for heating water and / or thermal oil.

The use of those obtained in the rear area of the press section In another embodiment of the The method of claim 3 can e.g. for the purpose of heating the factory where the double belt press is located, or the associated offices, i.e. outside of Panel material manufacturing process.

The invention is embodied in its apparatus aspect in a system according to claim 4.

The "other aggregate" in which the heat gained can be used here, the already mentioned, the double belt press upstream unit for formation and pretreatment the bed or the heat exchanger for heating of water and / or thermal oil or a similar device his.

The rear section of the press section is used completely unheated heat transfer medium.

Claims 5 and 6 are on the possibilities of use the one obtained in the rear part of the press section Heat directed.

In another aspect of solving the task of lowering the energy cost is the transfer of heat in reduced the rear section of the press section by not for the entire press section and each forming belt a continuous roller chain or a group of side by side such roller chains are used but by at a suitable point on the press section made a chain separation according to claim 7 is, so that the first section of the press section has its own roller chains and the rear section of the Press section separate further roller chains. The of continuous roller chains otherwise in the rear section the portion of the heat transported remains thereby to a large extent in the first section of the Press section and does not go through the "downstream transport" lost. Simply by separating the roller chains can lower the temperature in the rear section of the press section of 20 ° C and more can be achieved. The front one Press section is here with a smaller Keep heat input at the required temperature.

The chain separation in double belt presses works on its own US-A-4,334,468, but is only mentioned here under the Aspect, successive sections in the direction of travel supply different amounts of heat to the press section or to be able to withdraw, but not under the aspect of Heat utilization.

In a double belt press of another type, which is for drying of fiber webs and which is known from WO 97/39187 one is heated with steam and the other with Water cooled. Between the fiber web and the cooled one Belt runs a felt web into which the cooled belt condensed water passes over. The heat from the cooling water is transferred to other water in a heat exchanger, which with its then increased temperature than Process water used in a paper or board machine can be.

The separation of the roller chain in a front section and at least one subsequent section also has one Meaning regardless of the question of other use obtained in the last section of the press section Warmth.

This is because partial evaporation can take place in this way gaseous components of the plate material before reaching the actual end of the press section. This affects not only water vapor, formaldehyde and the like, but also the flammable mentioned Vapors from waxes used in the plate material and the like, which, when total in large Only exit the quantity at the actual end of the press section can ignite there and cause fire accidents have led. Even the pure lowering of the vapor pressure the point of separation by partially blowing off to the side, what as a result of the brief "breathing" of the plate track the temporary cessation of support for the Form tapes at the separation points and the associated It is possible to reduce the flow resistance for the steam is of great practical importance as well the temperature reduction achieved in the last section of the press section.

According to the invention, however, are the separation points of the Roller chains not on at least one side of the web one at 90 ° to the running direction across the web straight lines (claim 8).

The separation points can at least according to claim 9 one side of the track lies on a straight line that however at an angle other than 90 ° to the Running direction runs, the angle according to claim 10 can also be different on the two sides.

The separation points, however, need according to the design not lying on a straight line according to claim 11, but can - seen in the running direction - in different positions, so that the Roller chain field at its lengthwise Boundaries are jagged or frayed to a certain extent. This will cause abrupt changes in pressure at one point - seen in the direction of travel - across the entire width of the web avoided at the same time.

This can be particularly true in the construction according to claim 12 can be realized in which the successive Roller chain fields, so to speak, in a zipper-like manner are interlocked.

The separation point at the last section of the press section can seen in the running direction for the respective upper forming tapes and on the same for the lower forming belts Place. Then the upper forming band bulges and the lower forming ribbon at the same time and insert it Temporary bilateral "sigh of relief" of what the Formation and maintenance of the resulting bonds is intolerable on the train.

An important embodiment of the invention with both even without heat recovery exists according to claim 13 in that the breaks in the roller chains on both Sides of the web against each other in the direction of travel of the web are offset.

In this way, the formation of bilateral inflation prevents the web between the forming belts and the partial blowing off of trapped gases, so to speak gradually upwards, the other time upwards below.

It does not matter whether the separation point for the roller chains of the upper forming belt in the running direction of the web or located in front of the separation point of the lower forming belt is.

The experiments have shown that manufactured according to the invention Chipboard significantly better technological values have chipboard produced by known methods.

Fig. 1 und 2 zeigen Längsschnitte durch erfindungsgemäße Doppelbandpressen;

Fig. 3 bis 6 zeigen schematisch Ansichten von oben verschiedener Konfigurationen von Trennstellen der Rollenketten;

Fig. 7 und 8 zeigen Schnitte nach den Linien VII-VII bzw. VIII-VIII in den Fig. 8 und 7 einer Trennstelle der Rollenketten in vergrößertem Maßstab;

Fig. 9 zeigt eine Ansicht einer einzelnen Rollenkette.

Exemplary embodiments of the invention are shown schematically in the drawing.

1 and 2 show longitudinal sections through double belt presses according to the invention;

3 to 6 schematically show top views of different configurations of separation points of the roller chains;

7 and 8 show sections along the lines VII-VII and VIII-VIII in FIGS. 8 and 7 of a separation point of the roller chains on an enlarged scale;

Figure 9 shows a view of a single roller chain.

The double belt press of 100 as a whole Fig. 1 is used for the production of chipboard, fiberboard and other plate-shaped materials that made from a binder that cures under pressure and heat bound particles exist. It includes one upper forming belt 1 made of smooth, closed steel sheet about 2 to 3 mm thick and a lower one Form tape 2. Between the form tapes 1, 2 is in a Pressing section 3, a web 4 is compressed from a bed 4 ', those from the particle material provided with the binder there is one of the aforementioned after pressing Materials results.

The upper forming belt 1 runs around arranged transversely to the web Rolls or drums 5.6 um and can pass between these drums 5.6 can be hydraulically tensioned. Runs accordingly the forming belt 2 via drums arranged transversely to the web 4 11, 12 um, which is also a hydraulic tension of the Achieve form tape 2. The form tapes 1, 2 are on the Drums powered.

The forming tapes 1, 2 run in the arrows 16 indicated meaning by the device. In the press line 3 move the lower run 1 'of the upper forming belt 1 and the upper run 2 'of the lower forming belt 2 in sync with one corresponding to the thickness of the web 4 Distance close to each other. The on the in the Drawing left on a conveyor belt, not shown applied bed 4 'is in the pressing section 3rd drawn in and between the runs 1 ', 2' of the forming tapes 1, 2 pressed together. The fill goes from the conveyor belt 4 'on a rolling tray 7, which the Filling onto the lower forming belt 2 just before the upper one Top of the drum 11 passes. The discontinued pressed and hardened sheet 4 of the plate material is on the right side according to the drawing by suitable Devices not shown divided and transported away.

In the press section 3 is in the inner region of the forming belt 1 above its lower run 1 'an upper support structure 17 provided with an inside of the lower forming belt 2 provided below their upper runs 2 ' lower support structure 18 cooperates. The Support structures 17, 18 support the web 4 facing Areas of the forming tapes 1, 2 against the web 4 and press them against each other with great force.

The support structures 17, 18 each consist of individual ones Carriers 19, 20, each lying in pairs one above the other above and below the forming tapes 1, 2 and Lane 4 are arranged. Each pair of carriers 19, 20 is through not shown laterally outside the press section 3 located strong spindles clamped together so that individual pressure elements that are self-contained are formed.

Are located between the carriers 19, 20 and the forming strips 1, 2 strong support plates 26, 27, which by the individual carriers 19, 20 applied force evenly the forming tapes 1, 2 and thus the web 4 transferred. The Support plates 26, 27 have transverse to the web 4 channels across the width through which a Heat transfer medium can be passed through. The channels follow in the running direction 16 close to each other and are at the ends connected by pipe elbows so that groups of channels meandering from a common heat transfer medium be flowed through.

Between the mutually facing sides of the support plates 26, 27 and the forming belts 1, 2 are roller chains 30 ', 30 " arranged on which the forming tapes 1, 2 on the support plates 26, 27 roll and the endless in a vertical Longitudinal plane around the support plates 26, 27 within the forming bands 1, 2 circulate. The rollers of the roller chains 30, '30 " transfer both the pressure and the heat of the support plates 26, 27 on the forming tapes 1, 2 and thus the forming web 4. The forming strips 1, 2 thus experience in the Press section 3 a purely rolling support.

The press section 3 is in two in the running direction 16 of the web 4 successive sections 3 'and 3 "divided that also have separate support plates 26 ', 27' and 26 ", 27". In the first section 3 'there is the Support plates 26 ', 27' by heating the heat transfer medium the heat supplied which causes vapor formation in the pressed together containing a certain amount of moisture Bulk 4 'causes. The steam is created first in the Close to the forming tapes 1, 2 because these are the highest temperature have and is distributed in the bed 4 ', whereby a rapid heating of the entire volume of the Filling 4 '(steam boost) and thus the curing of the binder contained therein can be effected. The heat transfer medium, e.g. a thermal oil, is in a heat exchanger 40 heated and circulated so that the just heated Heat transfer medium in the sense of arrow 41 am Beginning of the first section 3 'fed and in the sense arrow 42 at the end of the first section taken from the channels of the support plates 26 ', 27' and in a closed circuit in the heat exchanger 40 is returned. The heat exchanger can, as shown, in turn by using in a heating unit 43 Heating registers 44 heated further heat transfer medium be applied, or contain the heating itself.

In the rear, i.e. in the running direction 16 of the web 4 following Section 3 "of the press section 3 must be mechanical Pressure is maintained until the binder cured and the vapor pressure is sufficiently reduced, otherwise the bonds just formed in the binder tear open again. Through the support plates 26 ", 27" this section also becomes a heat transfer medium circulated so that it is at the beginning of section 3 "in Direction of arrow 51 fed and at the end of the section 3 "in the direction of arrow 52 is removed again.

Here, too, the heat transfer medium flows through a heat exchanger 50, in which no warmth was supplied to him, on the contrary, part of that in the first section 3 'supplied heat by the movement of the forming belts 1, 2 and the web 4 reaches the rear section 3 " is withdrawn again. The heat extracted relaxes the steam in the web 4 and thus reduces that in it prevailing vapor pressure.

The heat extracted in the heat exchanger 50 is in one in the drawing only symbolically indicated separate, not directly connected to the press section 3 standing unit 53 used, be it for heating purposes it around on an upstream on the left side of the drawing Place of the procedure for warming up the Particles, for drying the particles, for heating Water and / or preheating thermal oil or the like Purposes to be used. In this way the Improved heat balance of the overall system and also a contribution environmental protection, in so far as humiliation of temperature and vapor pressure in the end area of the Press section 3 the escape of substances such as formaldehyde and the like is reduced.

The trained across the web 4 in the support plates Channels can be different from 16 consecutive in the direction of rotation Be connected to groups. Accordingly is the fact that in section 3 "of the press plug 3rd only heat is removed, a feature of the embodiment; however, there are also mixed forms where at the beginning of Section 3 " added a certain amount of heat, and only completely in the end only cooled, d. H. Heat is removed.

The passage of another heat transfer medium, which is not heated by the second section 3 " can also take place when the support plates 26, 27 and the roller chains 30 over the entire length of the pressing section 3 are continuously formed.

In the illustrated embodiments of FIGS. 1 and 2, however, sections 3 ', 3 "are not only in terms of their loading with heat transfer medium, but also largely mechanically and thermally Cut. This is because in the first section 3 ' already mentioned own support plates 26 ', 27' each other Above and below the web 4 opposite that of the inlet up to separation points 28, 29 at the end of the first section 3 'range and from associated endless roller chains 30 ', which are still described with reference to FIG. 9 and of which across the width of the web 4 a number of z. B. forty immediately next to each other, however independently of each other in the sense of arrows 16 in the press section 3 and the one together in his Level in the running direction 16 shearable roller chain field form.

In Fig. 1 begin at the separation points 28, 29 from the Support plates 26 ', 27' separate support plates 26 ", 27", to the end of the press section 3 or the rear section 3 "same and own roller chains 30 "are circulated. The separating points 28, 29 at which the tapes 1, 2 from the first section 3 'in the rear section 3 "pass in the direction of rotation 16 made as short as it is constructively possible. Because of the required deflection of the roller chains 30 ', 30 " The support-free sections can have a radius at the separation points 28, 29 however not arbitrarily be made short and are about 150 mm what no role for the failure of the board material plays. At 28 is the separation point between the roller chains 30 ', 30 "above the web 4, i.e. for the forming belt 1 designated with 29 the separation point for the roller chains 30 ', 30 "below the web 4, i.e. for the forming belt 2. The separation points 28, 29 are located at transverse to the web 4 Straight lines, d. H. all roller chains 30 'and all roller chains 30 "in the area of the support plates 26 ', 27' or 26 ", 27" in the same places - in the running direction 16 seen - around the edges of the support plates 26 ', 27 'or 26 ", 27" deflected.

Due to the subdivision at the separation points 28, 29 remain the front roller chains 30 'in the very first section 3 'and can not heat in the rear section 3 "transmitted.

The heat generated by the forming strips 1, 2 and the web 4 stationary operation in the rear section arrives, which is partly in the heat exchanger 50 Support plates 26 ", 27" flowing through the heat transfer medium withdrawn and put to use.

In the embodiment 100 of FIG. 1, the Separation points 28, 29, seen in the running direction 16 of the web 4, on top of each other in the same place.

In the embodiment 200 of FIG. 2, however, lies the separation point 28 'for the roller chains 30', 30 "of the upper one Forming tape 1 in the direction of rotation 16 opposite the separation point 29 'of the lower forming belt 2 offset. 28 'and 29' do not lie on top of each other, but point in the direction of travel the web 4 a distance from each other, the is at least so large that between the separation points 28 ' and 29 'there remains a short distance 25 in which the web 4 as in the remaining press section 3 by means of both sides the roller chains 30 ', 30 "is supported. The direction the transfer plays a minor role. Important is just that the support free sections above and not in the same place below and that a Blow off dampers of all kinds from the plate material not in one go, but in two steps can.

Otherwise, the exemplary embodiments of FIGS. 1 and 2 except for the heat recovery still omitted in FIG. 2 match. This is to illustrate that chain separation have meaning even without heat recovery can.

3 to 6 are different configurations schematically in the area of the separation points 28, 28 ', 29, 29' shown. There are only ten next to each other Roller chains 30 ', 30 "indicated, although the number over the overall width of web 4 actually in general is much larger.

3 shows the standard case in which the separation point 28 along a path transverse to the web 4 extending straight line 31, i. H. perpendicular to the running direction 16 runs. Above and below the web 4 can the separation points 28, 29 lie one above the other, as is shown in 1 is shown, but they can also run in the direction be offset from one another, as in FIG. 3 at 29 ' is indicated and shown in Fig. 2.

4, the separation point 28 can also along a Just run 32, which with the direction 16 one of 90 ° takes different angles. Here too they can Separation points 28, 29 'above and below the web 4 either directly one above the other or different from each other Take the angle as shown in the drawing.

The configuration according to FIG. 5 differs from this 3 and 4 that each roller chain pair 30 ', 30 ", which lies on the same longitudinal line, has its own separation point, so to speak, and that the Separation points of adjacent roller chains in the running direction 16 are offset from each other. The separation points of the individual Roller chain pairs 30 ', 30 "thus grip like a zipper each other. This configuration can also be used as the dash-dotted line 33 'indicated above and a displacement in the longitudinal direction below the web 4 exhibit.

6, the configuration can also be zippered interlocking roller chain pairs 30 ', 30 "across the width of the web 4 along a separation zone one to the running direction 16 an angle different from 90 ° occupy line 34 form.

The embodiment of FIG. 5 is based on FIGS. 7 and 8 explained further. The each other in the direction of the 16th adjacent edges of the support plates 26 ', 26 "are rounded, so that the roller chains 30 'or 30 "over this Radius run around and up from the area of the facility be carried away on the forming belt 1, as in Fig. 8 can be seen.

The rounded, mutually facing edges of the support plate 26 ', 26 "do not lie on a common straight line, but it has every single roller chain 30 ', 30 " his own pair of rounded edge areas 35, 37 or 36, 38, which is only as wide as that Roller chain 30 'or 30 ". There is on the support plate 26' edge regions 35 projecting further in the running direction 16 and in between a recessed edge area 36. In the support plate 26 "is the projecting Edge region 35 of the support plate 26 'in the running direction edge region 37 located further forward, while the edge region 36 of the support plate 26 'is further back Edge area 38 of the support plate 26 "assigned is. The edge areas 38 engage between the adjacent edge areas 35, 35 so that the chain fields the support plates 26 ', 26 "into one another in a zipper-like manner are interlocked. The distance of the front edges of the Edge areas 35 and 36 - seen in the running direction 16 corresponds on the order of magnitude in the exemplary embodiment the width of a single roller chain 30 'or 30 ". Corresponding applies to the edge areas 37, 38 because of the Distance 39 between the opposing in the direction 16 Areas of the roller chains 30 'or 30 "at the adjacent roller chains 30 'or 30 "always is equal to.

The construction of a single roller chain 30 ', 30 "starts Fig. 9 shows. Each roller chain 30, 30 "comprises per chain pin 65 three adjacent rollers 68a, 68b and 68c, between which tab strands 61 and 62 with straight Tabs 61a, 61b, 61c and 61d run. These tabs are, however, not in a direction parallel to the running direction 16 aligned alley provided one behind the other but to several moved one after the other on the same side, after a certain number of tabs a reversal the direction of transfer. For example, that is Tab 61a offset relative to tab 61. The Tab 61b is again upward relative to tab 61a added. However, the tab 61c is opposite the tab 61b moved down again and four close other tabs, each set down, until Tab 61d, from the right again in the drawing there is an upward transfer. The one through the whole of the tabs 61a, 61b, 61c and 61d. strand 61 thus runs within the roller chain 30 ', 30 " in a zigzag, so that those left by some two rolls Bumps covered by any of the following roles become.

The link strand 61 is a correspondingly trained one Tab strand 62 assigned, the tabs to the longitudinal median plane the roller chain 30 ', 30 "opposite to Tab strand 61 are offset. Every link in the roller chain 30 ', 30 ", as already mentioned, consists of three roles 68a, 68b and 68c, which vary in width periodically change and overall to a single roller chain with parallel lateral boundary surfaces 63 and 64 add. The three rollers 68a, 68b and 68c of a chain link are held together by a roller pin 65, whose head 66 is housed in a recess 67 and not beyond the boundary surfaces 63 and 64 protrudes.

Adjacent roller chains 30 ', 30 "come along their end faces 63 and 64 each other, so that on these No significant distance remains and pressure and Temperature essentially over the entire chain surface are evenly transferred to the forming tapes 1, 2. The Joints between the individual rollers on a roller pin 65 are periodically followed by roles below Roll pin 65 rolls over so that there is essentially one even application of pressure transfer surface in the press section 3 results.

Claims (13)

1. A method of continuously producing wood chip boards and the like from materials in particle form held together by a binder which sets when compressed and heated, in a double strap press (100) in which the particles and binder are spread in a loose layer (4') on a horizontal run of a conveyor belt and are hardened, under pressure and with heating, in a pressing section (3) between the upper run (2') of an endlessly rotating metal lower moulding strap (2) and the bottom run (1') of an upper metal moulding strap (1) moving in synchronism in the forward direction (16) of the double strap press (100) and converted into a web (4) in the form of a board of material, wherein the working pressure and the heat for forming the material in the pressing section (3) is transferred from the support construction (26, 27) to the moulding straps (1, 2) and thence to the loose layer (4') and wherein heat is introduced into the supporting construction (26, 27) by a heat transfer medium conveyed through ducts therein,
   characterised in that
   the heat transfer medium for a rear portion (3") of the pressing section (3) is not heated and in this section (3") heat transmitted to the heat transfer medium in the front portion of the pressing section (3) is withdrawn from the heat transfer medium and used outside the pressing section (3).
2. A method according to claim 1, characterised in that heat withdrawn in the rear portion (3") of the pressing section (3) is used at another place in the process.
3. A method according to claim 1, characterised in that heat withdrawn in the rear portion (3") is used outside the process.
4. A double strap press for continuous production of wood chip boards and the like from material consisting of particles held together by a binder which sets when compressed and heated,
   comprising two metal moulding straps (1, 2) continuously rotating in a vertical plane, wherein the upper run (2') of the lower moulding strap (2) and the lower run (1') of the upper moulding strap (1) lie one above the other in a pressing section (3), abut a supporting construction (26, 27), and compress the loose material (4') in the pressing section under the action of pressure and heat, and comprising ducts formed in the supporting construction (26, 27) and through which the heat transfer medium can be conveyed,
   characterised in that
   the ducts in a rear portion (3") of the pressing section can be supplied with unheated heat transfer medium and are connected to a heat exchanger (50) wherein the heat withdrawn from the heat transfer medium in the rear portion (3'') is transferable to another unit (53) not belonging to the pressing section (3).
5. A double strap press according to claim 4,
   characterised in that the other unit (53) is disposed upstream of the double strap press (100).
6. A double strap press according to claim 4,
   characterised in that the other unit is separate from or independent of the process for continuous production of wood chip boards and the like from materials consisting of particles held together by a binder which sets when compressed and heated.
7. A double strap press according to any of claims 4 to 6, characterised in that co-rotating endless roller chains (30) are provided between the moulding straps (1, 2) and the support plates (26, 27) in the press section (3) and transfer pressure and heat from the support plates (26, 27) to the moulding straps (1, 2) and in that roller chains (30") for the rear portion (3") of the press section are separate from roller chains on the same line in the direction of advance for the front portion (3').
8. A double strap press for continuous production of wood chip boards and the like from material consisting of particles held together by a binder which sets when compressed and heated,
   comprising two metal moulding straps (1, 2) continuously rotating in a vertical plane, wherein the upper run (2') of the lower moulding strap (2) and the lower run (1') of the upper moulding strap (1) lie one above the other in a pressing section (3), abut a supporting construction (26, 27), and compress the loose material (4') in the pressing section under the action of pressure and heat, comprising ducts formed in the supporting construction (26, 27) and through which the heat transfer medium can be conveyed, and co-rotating endless roller chains between the moulding straps (1, 2) and the support plates (26, 27) in the pressing section and transferring pressure and heat from the support plates (26, 27) to the moulding straps (1, 2), the roller chains (30") for the rear portion (3") of the pressing section (3) being separate from the roller chains (30') in the front portion (3') situated on the same line in the direction of advance (16), characterised in that the parting places of the roller chains (30', 30") on at least one side of the web (4) are not on a line extending at 90° to the direction of advance (16).
9. A double strap press according to any of claims 4 to 8, characterised in that the parting places of the roller chains (30', 30") on at least one side of the web (4) are situated on a straight line (31) extending transversely to the web (4) at an angle different from 90° to the direction of advance.
10. A double strap press according to claim 9,
    characterised in that the angles are different on the two sides of the web.
11. A double strap press according to any of claims 4 to 8, characterised in that the parting places of neighbouring roller chains (30', 30") in the transverse direction of the web (4) on at least one side of the web (4) are not at the same height, considered in the direction of advance (16).
12. A double strap press according to claim 11,
    characterised in that the parting places of at least one roller chain (30', 30") are recessed, as considered in the direction of advance (16) relative to the neighbouring roller chain (30', 30") in the transverse direction, and the roller chain (30', 30") of the other portion on the same line in the direction of advance (16) extends into the gap.
13. A double strap press according to any of claims 4 to 12, characterised in that the parting places (28', 29') of the roller chains (30', 30") on both sides of the web (4) are offset relative to one another in the direction of advance (16) of the web.

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