RU2763098C1 - Method for producing flexible plywood "sveza flex" - Google Patents

Abstract

FIELD: woodworking industry.

SUBSTANCE: invention relates to the woodworking industry and relates to a method for manufacturing flexible plywood. The method includes sequential stages of forming veneer packs, cold pre-pressing the assembled packs before gluing, gluing the pre-pressed packs in a hot press, aligning the packs and cutting plywood sheets. When assembling the package, a scheme with non-alternating veneer layers with longitudinal and transverse directions of fibers is used. A set of a package is made of veneer with the same direction of fibers throughout the package, with the exception of one or two veneer layers, which are the guard for this package and have a grain direction perpendicular to the main direction of the fibers of the plywood sheet. All layers of the plywood package have the same thickness. Gluing of the pre-pressed package is carried out sheet by sheet and is performed in a hot press.

EFFECT: invention provides the possibility of using plywood as a formwork in the manufacture of curved, round and oval structures and round objects, due to the possibility of obtaining maximum twisting of plywood in a natural way without violating its integrity.

2 cl

Description

The invention relates to a method for manufacturing flexible plywood containing multiple layers of wood veneer for use as formwork in the manufacture of curved structures.

From the source RU 2654793 C1, B27D 1/04, 05/22/2018, a method for producing plywood is known, including sequential stages of assembling packages consisting of veneer layers, cold pressing of assembled packages before gluing, gluing the pressed packages in a hot press, standing, disassembling packs of finished sheets bakelized plywood, cutting and processing of bakelized plywood sheets.

The disadvantage of the known method of producing plywood is the lack of flexibility of plywood, which makes it impossible to use it as a formwork in the manufacture of curved structures, without deforming and breaking the integrity.

The technical result achieved by the claimed invention consists in obtaining plywood for use as formwork in the manufacture of curved, round and oval structures and round objects, due to the possibility of obtaining maximum twisting of plywood in a natural way without violating its integrity.

The specified technical result is achieved by means of a method for producing flexible plywood, which includes sequential stages of forming packages consisting of veneer with longitudinal and transverse directions of fibers, cold pressing of assembled packages before gluing, gluing the pressed packages in a hot press, aligning the packages and cutting plywood sheets, while when assembling a package, a scheme is used with non-alternating veneer layers with longitudinal and transverse directions of fibers, while the package is made from veneer layers with the same direction of fibers throughout the package, with the exception of one or two layers, the first of which is laid in the third layer from the outer one, which are the guard for this package and have the direction of the fibers perpendicular to the main direction of the fibers of the plywood sheet, all layers of the plywood package have the same thickness, while the glue is applied to the inner layers with the main direction of the fibers, made of lump veneer by sewing its or splicing end-to-end, and gluing of the pre-pressed package is carried out one sheet at a time and is carried out in a hot press according to modes that differ in the length of time the plywood is in the press, and increase depending on the thickness of the plywood.

The method of manufacturing flexible plywood is carried out as follows.

The veneer is installed on lifting tables located according to the technological layout. During assembly, debris should be removed from the surface of the veneer sheets with a brush on a long handle. Before assembling the packages, a special pallet with a thickness of at least 12 mm is placed on the roller conveyor.

The package is formed from veneer layers with longitudinal and transverse grain directions. For the production of plywood in the claimed method, birch veneer is used with tolerances for limiting wood defects and moisture content of no more than 6 ± 2% in accordance with GOST 99-96 "Peeled veneer", and for the face layers of plywood, birch veneer of BB (II) and CP ( III) according to STO 52654419-001-2018.

During the assembly of the package, a scheme with non-alternating veneer layers is used. A set of a package is made of veneer with the same direction of fibers throughout the package, with the exception of one or two veneer layers, depending on the required plywood thickness, which are the core for this package and have a grain direction perpendicular to the main direction of the plywood sheet. To give plywood the necessary flexibility, all layers of the plywood package have the same thickness, and the third veneer layer from the outer (including it) is laid perpendicular to the main direction of the plywood sheet fibers, is the top and has a fiber direction perpendicular to the main direction of the plywood sheet fibers. In this case, these top layers (one or two, depending on the required plywood thickness) can be located both in the center of the package and symmetrically relative to it.

The finished stack of veneer packs is transported on a driven roller table to a transport cart for onward transfer to the pre-pressing presses.

Before gluing, the assembled package of veneer layers is subjected to cold pressing, as a result of which the packages acquire the necessary rigidity and transportability.

For gluing veneer layers, phenol-formaldehyde resin of phenol-formaldehyde grade SFZh-301 is used, which is applied to the inner layers with the main direction of the fibers, made from lumpy veneer by sewing it together or splicing end to end.

Plywood is glued in a hot press at a temperature of 120-130 ° C under a pressure of 11-14 bar according to the modes set for each plywood thickness. The modes differ in the length of time the plywood is in the press and increase depending on the thickness of the plywood. To ensure the necessary strength of gluing of all packages in a hot press, the assembly time for stacked veneer packages should not exceed 30 minutes. Gluing is carried out sheet by sheet. In this case, gluing sheets of 2 in each press bay is not allowed.

The maximum output of full-size plywood from the glued base is ensured by aligning the edges of the sheets in a "hard corner".

Then the glued plywood sheets are sent for lining up. After that, the resulting flexible plywood is sent to the final cutting stage in the format, according to the requirements of the customer's documentation, followed by surface grinding.

If necessary, the plywood surface can be additionally covered with foil.

The use of this method for producing flexible plywood for use as a formwork in the manufacture of complex round and oval structures, object parts and formwork for round objects, allows you to obtain a flat concrete surface when stripping.

When making prototypes of flexible plywood according to this method, the following results were obtained.

The technology of manufacturing flexible plywood with an asymmetrical arrangement of layers was tested at thicknesses of 9, 12 and 15 mm.

In thicknesses of 6 and 9 mm, the number of layers with a perpendicular direction of fibers is 1, in thicknesses of 12 and 15 mm, the number of layers with a perpendicular direction of fibers is 2.

The deflection point of 12 mm plywood is 430 mm without breaking the film's integrity.

The deflection point of 9 mm plywood is 500 mm without breaking the film's integrity.

The deflection point of 15 mm plywood is 390 mm without breaking the film's integrity.

Thus, the deflection arrow on plywood with a thickness of 9 to 15 mm makes it possible to manufacture curved structures with a circle having a radius of 2 m.

The calculation of the minimum deflection boom for formwork with a circle radius of 2 m showed the following.

For construction work with curved formwork during the construction of tunnels with a radius of a circle of 2 m, the circle will be obtained from 5 sheets of plywood with a format of 2500 × 1250 mm. The circumference in this case is:

Lokr = 2 * π * R = 2 * 3.14 * 2 = 12.56 m.

Thus, this method of manufacturing flexible plywood with an asymmetric arrangement of layers makes it possible to use plywood as a formwork in the manufacture of curved, round and oval structures and round objects, due to the possibility of obtaining maximum twisting of plywood in a natural way without violating its integrity.

Claims (2)

1. A method for producing flexible plywood, including sequential stages of forming veneer packages, cold pre-pressing of assembled packages before gluing, gluing pre-pressed packages in a hot press, aligning packages and cutting plywood sheets, characterized in that when assembling the package, a scheme with non-alternating veneer layers is used. longitudinal and transverse directions of the fibers, while the set of the package is made of veneer layers with the same direction of fibers throughout the package, with the exception of one or two layers, the first of which is laid in the third layer from the outside, which are the guard for this package and have a fiber direction perpendicular the main direction of the fibers of the plywood sheet, all layers of the plywood package have the same thickness, while the glue is applied to the inner layers with the main direction of the fibers, made of lump veneer by sewing it together or splicing end to end, gluing the pre-pressed package is carried out one sheet at a time and yat in a hot press according to modes that differ in the length of time the plywood is in the press and increase depending on the thickness of the plywood. 2. The method according to claim 1, characterized in that the surface of the plywood is sheathed with a film.