US2728939A

US2728939A - Apparatus for producing composite wooden boards and the like

Info

Publication number: US2728939A
Application number: US204209A
Authority: US
Inventors: Behr Erwin
Original assignee: Allwood Inc
Current assignee: Allwood Inc
Priority date: 1951-01-03
Filing date: 1951-01-03
Publication date: 1956-01-03
Anticipated expiration: 1973-01-03

Description

Jan. 3, 1956 E. BEHR APPARATUS FOR PRODUCING COMPOSITE WOODEN BOARDS AND THE LIKE Filed Jan. 3, 1951 INVENTOR.

Erwin Be h r ATTORNEY United States Patent M APPARATUS FOR PRODUCING COMPOSITE WOODEN BOARDS AND THE LIKE Erwin Behr, Wendiingen (Neckar), Wurttemberg, Germany, assignor to Allwood Incorporated, Glarus, Switzerland, a corporation of Switzerland My invention relates to apparatus for producing wood composition boards and the like products consisting essentially of wood chips or shavings.

Wood composition products have been made from short-fibered chips by agglomeration With a binder and compression. As a rule, chips resulting as waste from the planing or sawing of wood were used; and to obtain a comparatively uniform product, the larger chips were cut up into short-fibered particles. Obviously this treatment amounts to a destruction of the wood whereby the mechanical resistivity particular to wood fibers stressed in the longitudinal direction is lost. The destruction of this resistivity also requires considerable mechanical force.

For converting such a short-fibered material into boards, it is usually mixed with water which must subsequently be eliminated by drying. To secure a firm coherence of the short-fibered particles, high pressure is used. Hence, a considerable consumption of wood is needed to produce a comparatively thin sheet or board. Nevertheless, and despite the comparatively large amount of admixed binder, the strength of a wooden body produced in this manneris rather low and renders these products unsuitable for the production of furniture and g the like. i

It is an object of my invention to provide fabricating apparatus suitable for mass production of wood composition boards or the like products that combine low manufacturing cost with improved mechanical strength.

To this end, and in accordance with my invention, I provide a mixing and compressing extrusion apparatus for converting elongated and longitudinally fibered wood particles together with a binding agent into a precompressed sheet of material of substantially uniform thickness. The essential features of the apparatus described below will be better understood if first the particular character of the wood particle mass to be fabricated is taken into account.

The raw material to be used for the purpose of the invention consists of long fine chips or shavings which form narrow fiber bundles substantially spread straight in the longitudinal direction of the fibers and which measure in length at least about the twentyfold, and as a rule a much greater multiple, of their Width, while being very thin and measuring not more than about 1 mm. and preferably 0.3-0.5 mm. in thickness. These fiber bundles are obtained by cutting wood insucli a manner as to preserve as far as possible its natural longitudinal fiber structure. The long-fibered particles are so distributed in the product to be made that the fibers extend in every direction, longitudinally as well as laterally and through all three dimensions, thus imparting great strength and resistivity to the finished product.

Due to their very small width, amouning to only a few millimeters maximum, these fiber bundles undergo practically no swelling or shrinking so that the structural bodies such as sheets, plates or boards, are highly resistant to the action of moisture.

Patented Jan. 3, 1956 The long-fibered particles are mixed with a suitable binder, either by themselves or with the addition of shortfibered particles or smalllaminae, or together with uniformly subdivided chips which serve to fill any cavities. The mixture is then formed to the desired shape by pressure. It is neither necessary nor desirable that the Wood fibers be completely impregnated with the binder, but suffices if they are wetted on their surfaces with an agglutinant dissolved in water. Not more than about 20 percent of the solid agglutinant are then contained in'the mixture before it is compressed, while in the compressed product the solid binder is present in a proportion not exceeding 7.5 percent. A synthetic water-soluble glue is particularly suitable.

The particles thus prepared are mixed, in dry or moist condition, in such manner that fibers extend in practically all directions and are intimately felted with each other. The mass consisting of felted fibers and a binder is then shaped under pressure to form the desired product.

The apparatus according to the invention serves to perform and improve an essential portion of the abovedescribed fabricating process, namely to pre-compress and shape the wood particle mixture into flat sheets prior to subjecting them to the final pressing operation in conventional presses. The apparatus has a feed hopper for receiving the particle mixture mounted on top of a downwardly tapering housing which communicates at its bottom with an outlet conduit which is elongated in the feed direction and has along its length a fiat cross section. Forced feed means, particularly studded rollers, are provided to feed the particle material through the housing and extruding it through the flat conduit, whereby the material is precompressed as it passes through the tapering housing and is molded into a sheet of substantially uniform cross section as it is extruded from the conduit. The resulting coherent sheet is then ready for final pressing.

An embodiment of apparatus according to the invention is shown diagrammatically in Fig. 1 of the drawing in a vertical sectional view, and Fig. 2 shows another embodiment of said apparatus also in vertical section.

The apparatus shown in Fig. 1 has a housing 7 Whose cross section decreases gradually in the downward direction. A hopper 18 mounted on the top of the housing serves to provide a continuous supply of wood-particle material.

Several rollers

8, 9a, 9b, 9c are revolvable in the housing. When in operation, the top roller 8 revolves clockwise so that the portion of its periphery close to the housing wall moves in the feed direction of the descending particle material, while the other periphery portion moves in opposition to that direction. The

rollers

9a, 9b, 9c revolve counter-clockwise. All have studs or ribs 10 mounted on their circumferences.

The fiber bundles 1, which may be mixed with other matter, are introduced through hopper 18, and then gripped by the top roller 8. Some of the material is forced through the channel between the top roller and the housing wall. Thence the material comes into contact with the other rollers which mix it intimately and forces it gradually downward through the narrowing housing space thus compressing the particles until they enter into a flat horizontal conduit 11. The conduit is sufiiciently long in the feed direction to extrude the particle mass as a felted ribbon or sheet of sufiicient coherence to permit being withdrawn and introduced into the final shaping press.

In the apparatus of Fig. 2, two opposite walls of the housing are formed by

conveyor belts

12, 13 running at controlled speed. Their

top drums

14, 15 are spaced farther from each other than their

bottom drums

16, 17. The conveyor belts secure the downward flow of the fiber material. The fiber bundles 1 are fed through the hopper 18 along a studded roller 19 which vibrates in the axial direction and grips and mixes the bundles. The fiber material is gradually lowered, mixed and compressed until it enters a horizontal conduit 11 leading to the shaping press. Felting of the fibers can be improved by adjusting the relative position of the Walls of'the housing formed by the

conveyors

12, 13.

It willbe obvious to those skilled in the art upon a studyof this disclosure that my invention permits of various modifications and may be embodied in apparatus involving details other than those here specifically shown and described, without departing from the essential features of my invention and within the scope of the claims annexed hereto.

I claim:

'1. Apparatus for producing wood composition products from long-fibered wood particles, comprising a hopper for supplying a mass of particles, a housing disposed below said hopper and communicating therewith, said housing having a bottom opening and being gradually tapering from saidhopper to said Opening, an outlet conduit of horizontally fiat shape adjoining said bottom opening for extruding a tare-compressed she'et'of particles, and a number of studded revolvable rollers disposed within said housing above one another for's'equem tially forcing the particles from said hopper to said conduit, the uppermost one of said rollers having a direction of revolution opposite to that of the other rollers.

2. Apparatus for producing Wood composition products from long-fibered wood particles, comprising a hopper for supplying a mass of particles, a vertically elongated housing adjacent and below said hopper, said housing having a bottom opening and being gradually tapering from said hopper to said opening, a substantially horizontal outlet conduit of horizontally fiat shape adjoining said opening for extruding a pro-compressed sheet of particles, and a number of studded mixing rollers revolvably disposed in said housing above one another along side one of the vertical housing walls and having a downwardly decreasing spacing respectively from the opposite housing wall, a majority of said rollers having at the side of said opposite housing wall a downward 4 direction of revolution for feeding the particles through said housing and. conduit.

3. Apparatus for producing wood composition products from long-fibered wood particles, comprising a hopper for supplying a mass of particles, a vertically elongated housing disposed adjacent and below said hopper and having two substantially vertical side walls opposite each other, said housing having a bottom opening and being gradually tapering from said hopper to said opening, an outlet conduit of horizontally flat shape adjoining said opening for extruding a pre-compressed sheet of particles, and a number of studded rollers above one another along one of said vertical walls of said housing, an upper one of said rollers having on the side'of said other vertical wall an upward direction of revolution, and a majority of said rollers including the lowermost roller having on said other wall side a downward direction of revolution.

References Cited in the file of this patent UNITED STATES PATENTS 565,291 Meyers Aug. 4, 1896 618,916 Stewart Feb. 7, 1899 845,329 Bottomley Feb. 26, 1907 1,006,452 Anderson Oct. 24, 1911 1,321,576 Wakeman Nov. 11, 1919 1,560,313 Pittman Nov. 3, 1925 1,599,253 Skolnik Sept. 7, 1926 1,726,511 Henry et al Aug. 27, 1929 1,969,291 Antoni Aug. 7, 1934 1,977,515 Klippel Oct. 16, 1934 2,004,936 Dorn et al June 18, 1935 2,066,734 Loetscher Jan. 5, 1937 2,280,022 Banigan et a1 Apr. 14, 1942 2,446,304 Roman Aug. 3 1948 FOREIGN PATENTS 386,027 Great Britain Jan. 12, 1933 608,252 Great Britain Sept. 13, 1948 OTHER REFERENCES Wood Fibers From Veneer Waste, by A. Elmendorf, Paper Trade JournaL Feb. 9, 1950, pages 29-31.