US3685932A

US3685932A - Heating platen press

Info

Publication number: US3685932A
Application number: US67412A
Authority: US
Inventors: Heinrich Pfeiffer
Original assignee: Dieffenbacher GmbH Maschinen und Anlagenbau
Current assignee: Dieffenbacher GmbH Maschinen und Anlagenbau
Priority date: 1969-08-27
Filing date: 1970-08-27
Publication date: 1972-08-22
Anticipated expiration: 1989-08-22
Also published as: BE755021A; FI56138C; FI56138B; DE1943560B2; DE1943560A1; DE1943560C3; FR2059280A5

Abstract

Heatable single or multilevel platen press for the manufacture of wood composition panels or the like, includes a stationary base structure and a hydraulically displaceable structure, each of the structures being composed of a plurality of individual bridge members and rib members interconnecting the bridge members and forming conjointly therewith a grid extending over the entire width of the press; press platens loosely mounted on the grid at the workpiece-side thereof, the rib members having fluid circulation passages for equalizing longitudinal thermal tensions, and the bridge members having fluid circulation passages for equalizing transverse thermal tensions.

Description

United States Patent us; 3,685,932 Pfeiffer [451 Aug. 22, 1972 [54] HEATING PLATEN PRESS FOREIGN PATENTS OR APPLICATIONS Inventor: i i Pfeiffer, Eppingen, Baden, 714,544 9/1954 Great Britain ..18/17 F Germany 1,048,767 11/1966 Great Britain ..18/17 H 1,033,223 7/1958 Germany ..l8/17 H [73] Asslgneez J. Dieffenbacker GmbH Maschinenfabrik, Eppingen, Baden, Germany Filed: Aug. 27, 1970 Appl. No.: 67,412

Foreign Application Priority Data Aug. 27, 1969 Germany ..P 19 43 560.0

US. Cl. ..425/109, 425/339, 425/ 143, 144/281 Int. Cl ..B30b 7/02, B29j 5/00 Field ofSearch ..18/16 P, 17 P, 17H

References Cited UNITED STATES PATENTS l-luetter 18/17 H X Siempelkamp ..18/17 P Norton ..l8/l7 H X Hedin ..18/17HX Siempelkamp ..18/17 H X Van Elten ..18/16 P X Primary Examiner-J. Howard Flint, Jr. Attorney-Curt M. Avery, Arthur E. Wilfond, Herbert L. Lerner and Daniel J. Tick [57] ABSTRACT l-leatable single or multilevel platen press for the manufacture of wood composition panels or the like,

includes a stationary base structure and a hydraulically displaceable structure, each of the structures being composed of a plurality of individual bridge members and rib members interconnecting the bridge members and forming conjointly therewith a grid extending'over the entire width of the press; press platens loosely mounted on the grid at the workpieceside thereof, the rib members having fluid circulation passages for equalizing longitudinal thermal tensions, and the bridge members having fluid circulation passages for equalizing transverse thermal tensions.

15 Claims, 7 Drawing Figures PATENTEUA G I972 3.685.932

sum

2 or 7 PATENTEDAuc22 I972 SHEET R [If 7 PATENTED 1:22 1912 SHEET 6 0F 7 HEATING PLATEN PRESS The invention relates to a heating platen for the.

production of wood composition panels, such as chip or fiber boards and the like, and more particularly to a heating platen press constructed as a single or multilevel press, having a stationary table and a displaceable ram. Presses of this general type may be assembled of prefabricated parts formed of a plurality of individual crossbeams or struts, the individual crossbeams being subjected to the action of one or more circulatory loops.

The most pressing problem in heating platen presses employed for producing wood composition panels such as chip and fiber boards and the like is to maintain the press surfaces formed by the press platen in planar form as the pressure and heat are transferred to the material being compressed, so that the compressed panel or board can emerge from the press with the least possible deviation from the nominal or datum thickness thereof.

The more the thickness of the completely pressed chipboard, fiberboard or the like corresponds to the nominal or datum value over the entire surface area thereof, the more one can refer to the heating platen press as being able to effect a plane-parallel pressure transfer.

The heretofore known platen presses of this general type are unable to attain this goal completely. The reason therefor is that the large-area wood composition panels are deformed as to their relatively slight thickness, due to the effect of the relatively high compression and temperature, and lose the planar shape of the surface thereof which is imparted thereto during manufacture. This loss of planarity is sought to be compensated by the crossbeams which are located between the press-cylinder piston assemblies or the counter support, on the one hand, and the heating platen, on the other hand, which are also referred to as table and ram.

It has been found heretofore that, in order to attain plane-parallelism for the press surfaces when compressive force is being transmitted without heat transfer, it is sufficient to provide the crossbeam parts engaged in the transmission of the compressive force with adequately large dimensions. However, this constructive feature is inadequate if there is a transfer of heat up to 300 C together with transmission of the high compressive force even when the crossbeams are greatly overdimensioned.

In the known heating platen presses, the deformations in table and ram caused by thermal stresses are sought to be prevented by providing in compensation of the one-sided heat flow of the heatedpress plates on table and ram, a counter-heating on the opposite side thereof. This counter-heating system is connectible to the circulatory loop on the press platen or may constitute an individual circulatory loop. A detrimental effeet is produced by stresses that occur during the heating effected between the heated and the unheated portions of table and ram, and thereby, deformations which are produced have a negative effect also upon the planar faces of the press platens. Stresses deriving from both circulatory heating loops produce deformations in the length and in the width which cannot be entirely eliminated even through a controlled heat supply. Thus, the known heating platen presses do not offer a satisfactory solution despite their high costs of construction.

It is accordingly an object of my invention to provide heating platen press especially formed with crossbeams, which, in connection with a planned heating and cooling program, affords a trouble-free planeparallel pressure transmission to the material being compressed.

It is another object of my invention to provide heating platen press with crossbeams of considerably simplified construction and to reduce thereby the costs connected with the manufacture of the heating platen press.

In heating platen presses having several circulatory heating loops which are independent of each other, there is always a possibility that one of the heating loops will cease to function and that deformations caused by thermal stresses will occur in the table and ram, which can result in damage to individual components. It is therefore a further object of the invention to provide heating platen press with safety means for preventing such damage.

With the foregoing and other objects in view, I provide in accordance with my invention, heatable single or multilevel platen press for the manufacture of wood composition panels or the like, comprising a stationary base structure and a hydraulically displaceable structure, each of the structures being composed of a plurality of individual bridge members and rib members interconnecting the bridge members and forming conjointly therewith a grid extending over the entire width of the press; press platens loosely mounted on the grid at the workpiece-side thereof, the rib members having fluid circulation passages for equalizing longitudinal thermal tensions, and the bridge members having fluid circulation passages for equalizing transverse thermal tensions.

With a proper selection of heating and cooling temperatures, the structural features of the invention not only assure the balancing or compensation of heat stresses within the table and ram, but in addition provide a heat thrust in longitudinal direction of the heating platen press above the neutral axis, as a counterforceto the heat thrust emanating from the heated press platen which acts below the neutral axis and would otherwise cause deformation in longitudinal direction.

The heat thrust in longitudinal direction of the heating platen press may be intentionally controlled when the ribs are divided in two and are formed of counterheating ribs and operational heating ribs which can be supplied with heat separately and differentially. Heat stresses in the table and ram, which deform the planar surfaces of the press platen, can also result from the fact that during the compression process, heat energy will be removed too rapidly and in too large a quantity from the press platen. In order that enough heat energy will be available in the table and ram, in accordance with another feature of my invention, I provide the press platen, the bridge members and the rib members with a plurality of bores located in rows disposed one above the other in a plane.

To avoid damage to the press when a circulatory heating loop fails, I provide heating platen press, in accordance with a further feature of my invention, with a safety loop wherein the bores of the press platen, the bores of the bridge members adjacent the press platen below the neutral axis, and the bores of the counter- ,minimum deformation and consequent deformation in the width of the ram and table..Secondly, due to the small amount of the counter-heating with respect to the total heat volume, the temperature of thepress platen, the bridge members, as well as the rib members, will decrease uniformly if the operational heating fails, so that in this respect too, the necessary reliability is assured for the press.

In accordance with anadded feature of the invention, I provide heating platen press with a safety loop formed of a combination of the circulatory loops for the operational heating and the counter-heating into one loop, only the bores in the bridge members adjacent the press platen being provided with an individual heating and cooling circulatory loop with accurate control. In many publications dealing with the production of wood composition panels such as chip and fiber boards demand is made on the heating platen presses that the compression process should start with press platens bent convexly about the longitudinal center line, those press, platens first attaining their planar surfaces during the compression or pressing period. This is intendedprimarily so'that the steam cushion being formed can escape satisfactorily as it, too, may be responsible for a negative production tolerance when there is localizedinclusion. To meet this demand, in accordance with an additional feature of my invention, small heating plates mounted on the longitudinal center line of the press platen.

The bores of the small heating plates are connectible to the circulatory loop of the operational heating system or may have their owncirculatory loop. In both cases, the press platen'receives a greater supply of heat energy around the longitudinal center line, and a convex deformation of the press platenis a result thereof. This desired deformation of the press platen can be further facilitated if the bridge members also have higher temperatures in the center and are convexly deformed in direction towards the press platen.

I provide a further feature according to the invention toward this end, by disposing the bores of the bridge I that, accordingto the invention, the bridge members The realization of my'objective is aided by the fact are shaped in accordance with the courseor direction of the stress by, the bending moment. The inventive I structural feature for-realizing this solution provides for counter-heating system. This too can then help also to supply the press platen with more heat about the longitudinal centerline.

The advantages obtained by the invention are especially that through the novel construction of the individual crossbeams, there is provided an opportunity for a planned and sensitive, thermodynamic control which can result primarily in a trouble-free planar surface but which can also provide a convex bendingthrough of the press platen in due time.

Another great advantage deriving from my invention is that the press is constructed according to the static data or conditions by the maximal compressive force and that no overdimensioning of the components which transmit the compressive force is required since the thermalstress forces are-small, if they exist at all, and can be countered at the damaged locations quickly, for example, by distributing the heating or the cooling action over several controllable circulatory loops.

Otherfeatures which are considered as characteristic 1 Y for the invention are set forth in the appended claims.

member perpendicularly to the. press platen and providing less bores in direction from the center toward the edges, i.e. by disposing them farther apart. The bores of the rib members are also arrangedperpendicularly to the press platen.

, It has been found that plane-parallelism of the press surfaces is easier to obtain if the heat .or temperature bridge mernbers which are subjected to the counter heating. I

Although the invention is illustrated and described herein as embodied in heating platen press, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

FIG. 1 is a side-elevational view, partly in section, of the heating platen press according to the invention;

FIG. 2 is a front-elevational view of FIG. 1;

FIG. 3' is a view similar to that of FIG. 1 of another embodiment of the invention, wherein the heating platen press has trapezoidal bridge members;

FIGS. 4 and 5 are enlarged side-elevational and horizontal sectional views, respectively, of astructural the crossbeam is provided with two-part rib members and with small heating plates placed around the longitudinal center line'of the press platen.

Referring now to the drawing, and first particularly to FIGS. 1 to 3 thereof, there is shown a heating platen press constructed in accordance with the invention and having as its main parts a stationary table and a movable ram, with the stationary table being composed of a number of individual crossbeams 1, and the movable ram of a number of individual crossbeams 2. The movable ram is braced, with the aid of return stroke devices, against the press cylinder piston devices formed of the pressure pistons 26, the tension columns 27 and the press cylinders 25. The individual crossbeams 1 and 2 are erected as a relatively high structure having torsional stiffness and capable of coping with thermal expansion, the crossbeams being assembled so that their wide side e, i.e. the outer faces of their bridge members 4, define the length of the table and of the ram of the heating platen press. Rib members which-connect the bridge members 4 are of bipartite construction and, with respect to the heating effect, are referred to as operational heating ribs 19 and counter-heating ribs 20.

Ribs

22 and 23 are located along the longitudinal center line. In the effective compression surface region, the press platens 3 are loosely mounted at the table and 'ram. According to the invention, bores 9 are formed not only in the press platens 3, but bores 11 are also provided in the

rib members

20 and 23 and bores and 31 in the bridge members 4.

To equalize heat expansion during the heating and cooling of the press, and also to effect minimally stressed welding of the individual crossbeams l and 2,

heat expansion openings

7 and 8 are formed about the neutral axis A-B in the bridge members 4.

In the embodiment of the heating platen press according to FIG. 3, there are provided bridge members l6, shaped according to the invention in trapezoidal form corresponding to the curve 'of the bending moment. For the purpose of mounting the compression

cylinder piston assembly

25, 26 and 27, the bridge members 16 are again of planar form, extending from the longitudinal line 29 of the compressed material,

and in fact at the level i which corresponds to the bending moment at the longitudinal line of the compressed material. To provide a preferred means for supplying heat to the center of the bridge members 16, bores 28 are disposed therein at an inclination to the horizontal.

As shown in FIGS. 1 to 3, only the bores 11 of the

counter-heating ribs

20 and 23 interconnected by connecting lines 30, are included in a feasible heating and. cooling system for the table and ram.

Structural details of the individual crossbeams l for a table, are shown in FIGS.'4 to 7. The individual crossbeams according to FIGS. 4 to 5, are provided with

continuous rib members

5 and 6, while the rib members in FIGS. 6 and 7, are divided into

operatively heating ribs

19 and 22 and into

counter-heating ribs

20 and 23, so as to effect a separation of the heat flow above and below the neutral axis A-B. This affords an especially exact means for differentiatingly heating the operatively

heating rib members

19 and 22 and the

counter-heating rib members

20 and 23, of which the

middle ribs

22 and 23 are so heated relative to the

outer ribs

19 and 20, thereby to effect a thermodynamic influence upon a desired planar surface or upon a convexly bentthrough press platen. As an aid or reinforcement of this feature, the bridge members 4 are provided with bores 32, which run vertically in the direction of the press platen and, between bridge members 4, small heating plates 24 with bores 18 are situated upon the press platen 3.

The small heating plates 24 are so arranged on the longitudinal center line of the heating platen press that, although they have the best possible contact with the press platen 3, they have no contact with the bridge members 4. To prevent the occurrence of uncontrollable deformations during the heating or cooling of the table and ram, heat-

expansion openings

7, 8 and 15, are provided in the rib members and bridge members.

As shown in the drawing, the

bridge members

4 and 16 extend to the left and to the right hand sides across the effective compression surface region and form extensions 17. Spacers 12, through an interposition or pressure-distribution plates 14, are mounted on these extensions 17 in such a manner that, in cooperation with the extensions of the individual crossbeams 2, they define, with the aid of spacer plates 13, the desired press gap. The spacer plates 13 bear upon spacer supports 12 and are thus removed from the soiled region of the compressed material plane.

Iclaim:

'1. Heatable single or multilevel platen press for the manufacture of wood composition panels or the like, comprising a stationary base structure and a hydraulically displaceable structure, each of said structures being composed of a plurality of individual bridge members and rib members interconnecting said bridge members and forming conjointly therewith a grid-like crossbeam extending over the entire width of the press, said crossbearn having a relatively large moment of inertia and being of such dimensions as to transmit the entire compressive force of said structures; press platens loosely mounted on said grid at the workpieceside thereof, said rib members having fluid circulation passages for. equalizing longitudinal thermal tensions, and said bridge members having fluid circulation passages for equalizing transverse thermal tensions.

2. Heatable platen press according to claim 1, wherein said press platen, said bridge members and said n'b members are formed with a plurality of bores located in rows disposed one above the other in a plane.

3. Heatable platen press according to claim 2,

- wherein the bores formed in at least one of said platens,

said bridge members and said rib members extend perpendicularly to said press platens.

4. l-Ieatable platen press according to claim 2 having a neutral axis, and wherein small heating plates are mounted between said bridge members on said press platens, for controlling bending. of said press platens, said small heating plates being formed with bores. 5. Heatable platen press according to claim 4 wherein the bores of said small heating plates are comprised of an individual controllable circulatory loop.

6. Heatable platen press according to claim 1 having a neutral axis, and wherein said rib members are divided in two and are formed of counter-heating rib members and operatively heating rib members for separating the heat flow about the neutral axis.

7. l-leatable platen press according to claim 6 wherein the bores formed in said press platens, the bores formed in said bridge members below said platens, the bores formed in the remainder of said bridge members and the bores formed in said rib members form a safety circulatory loop for operative heat- Heatable platen press according to claim 6 wherein, respectively, the bores formed in said press platens, said bridge members and said rib members form an individual controllable circulatory loop.

10. l-leatable platen press, according to claim 1 wherein said bridge members, from the middle thereof to the marginal edges thereof are provided with a decreasing number of bores spaced increasingly farther apart from one another.

ll. Heatable platen press according to claim I having a neutral axis, including heat expansion openings formed in said bridge members and in said rib members and symmetrically disposed about the neutral axis.

12. Heatable platen press according to claim I having a neutral axis, and wherein said rib members are divided in two and are formed ,of counter-heating rib members and operatively heating rib members for separatingthe heat flow about the neutral axis, the bores formed in the bridge members adjacent said pressplatens being combined into a controllable circulatory loop, and the bores formed in said press platens, the bores formed in the remainder of said bridge members and .the bores forrned in said rib members fonning a safety circulatory loop for operative heating, said rib members having a temperature-several degrees centigrade higher, than the temperature of said bridge members which are subjected to the circulatory loop a for counter-heating.

l3. Heatable platen press according to claim 12 wherein said bridge members are shaped according to the course of the stress by the bending moment, and

have a trapezoidal section. a

. l4. Heatable platen press, according to claim 13 wherein said trapezoidal section of said bridge members are formed with bores extending-at an angle to the horizontal.

l5. Heatable platen press according to claim 14 wherein the bores formed in said trapezoidal sections are combined into an individual circulatoryloop.

Claims

1. Heatable single or multilevel platen press for the manufacture of wood composition panels or the like, comprising a stationary base structure and a hydraulically displaceable structure, each of said structures being composed of a plurality of individual bridge members and rib members interconnecting said bridge members and forming conjointly therewith a grid-like crossbeam extending over the entire width of the press, said crossbeam having a relatively large moment of inertia and being of such dimensions as to transmit the entire compressive force of said structuRes; press platens loosely mounted on said grid at the workpiece-side thereof, said rib members having fluid circulation passages for equalizing longitudinal thermal tensions, and said bridge members having fluid circulation passages for equalizing transverse thermal tensions.

2. Heatable platen press according to claim 1, wherein said press platen, said bridge members and said rib members are formed with a plurality of bores located in rows disposed one above the other in a plane.

3. Heatable platen press according to claim 2, wherein the bores formed in at least one of said platens, said bridge members and said rib members extend perpendicularly to said press platens.

4. Heatable platen press according to claim 2 having a neutral axis, and wherein small heating plates are mounted between said bridge members on said press platens, for controlling bending of said press platens, said small heating plates being formed with bores.

5. Heatable platen press according to claim 4 wherein the bores of said small heating plates are comprised of an individual controllable circulatory loop.

7. Heatable platen press according to claim 6 wherein the bores formed in said press platens, the bores formed in said bridge members below said neutral axis and the bores formed in said rib members are combined into a single safety circulatory loop for said operative heating while the bores located above said neutral axis form a circulatory loop for counter-heating.

8. Heatable platen press according to claim 6 wherein the bores formed in the bridge members adjacent said press platens are combined into a controllable circulatory loop, and the bores formed in said press platens, the bores formed in the remainder of said bridge members and the bores formed in said rib members form a safety circulatory loop for operative heating.

9. Heatable platen press according to claim 6 wherein, respectively, the bores formed in said press platens, said bridge members and said rib members form an individual controllable circulatory loop.

10. Heatable platen press, according to claim 1 wherein said bridge members, from the middle thereof to the marginal edges thereof are provided with a decreasing number of bores spaced increasingly farther apart from one another.

11. Heatable platen press according to claim 1 having a neutral axis, including heat expansion openings formed in said bridge members and in said rib members and symmetrically disposed about the neutral axis.

12. Heatable platen press according to claim 1 having a neutral axis, and wherein said rib members are divided in two and are formed of counter-heating rib members and operatively heating rib members for separating the heat flow about the neutral axis, the bores formed in the bridge members adjacent said press platens being combined into a controllable circulatory loop, and the bores formed in said press platens, the bores formed in the remainder of said bridge members and the bores formed in said rib members forming a safety circulatory loop for operative heating, said rib members having a temperature several degrees C higher than the temperature of said bridge members which are subjected to the circulatory loop for counter-heating.

13. Heatable platen press according to claim 12 wherein said bridge members are shaped according to the course of the stress by the bending moment, and have a trapezoidal section.

14. Heatable platen press according to claim 13 wherein said trapezoidal section of said bridge members are formed with bores extending at an angle to the horizontal.

15. Heatable platen press according to claim 14 wherein the bores formed in said trapezoidal sections are combined into an individual circulatory loop.