RU2368495C1 - Method of wood particles orientation - Google Patents

Abstract

FIELD: wood working industry.

SUBSTANCE: according to the method of wood particles orientation rotation speed of even rolls is determined depending on rotation speed of uneven rolls, the distance between disks and their diametre due to that particles received rotational motion from the disks rotating with different speed go in a chip mattress with minimal orientation angle during fall.

EFFECT: quality increase of wood particles orientation and hardening of reconstituted particle board made of oriented particles.

2 dwg, 1 tbl

Description

The invention relates to the woodworking industry and can be used in the manufacture of chipboards.

A known method of orientation of wood particles, including the supply of chips to disks mounted on rotating rolls. Disks form intermediate overlappings, the distance between the disks is less than the length of the oriented particles, therefore, the particles turn around and pass between the disks, stacking on a forming conveyor (conveyor) in the direction of orientation [A. Leonovich Technology of wood slabs: advanced solutions: Textbook. allowance. - St. Petersburg: Khimizdat, 2005, - 208 p., Pp. 125-126].

A known method of mechanical orientation of wood particles, including the supply of chips on thin disks mounted on rolls in a checkerboard pattern with overlapping. Individual roll drive with stepless speed control. Wood particles fall between the disks and fit into the chip carpet, with 60% of the chips having an angle of deviation from the orientation direction ± 15 ° [Schwartzman G. M., Schedro D. A. Production of chipboards. 4th ed., Rev. and add. - M .: Forest. industry, 1987. - 320 p., pp. 213-214].

In the known methods, wood particles receive torque from the odd and even rolls disks rotating at different speeds and come off the disks at an initial angle α _beginning relative to the orientation direction. During the fall to the forming conveyor, the particles unfold at an angle α _p and fit into the chip carpet at an angle α (orientation angle), which is determined from the expression: α = | α _nach -α _p |. With decreasing angle α, the strength of the finished boards increases, approaching the strength of the original wood [Potashev O.E., Lapshin Yu.G. The mechanics of wood boards. - M .: Forest. industry, 1982. - 112 p., p. 52]. In the ideal case, the angle α is zero. In the known methods, as a result of arbitrary setting of the rotation speeds of the rolls, the condition | α _nach −α _p | = 0 is not fulfilled, that is, the orientation quality is reduced.

A known orientation method implemented in a device for orienting wood particles, comprising feeding chips on staggered disks overlapping even and odd rolls rotating at different speeds [Swedish patent No. 463627, M.cl ⁵ B29J 5/04. Spridarhuvudforsedd spridningsanordning för sprinding av en spänmaterialmatta. 1985].

The disadvantage of this method is that the rotational speeds of even and odd rolls are set arbitrarily, are not connected by a strictly defined ratio, therefore, the orientation angle of the wood particles α increases, which leads to a loss of strength of the manufactured plate.

The invention solves the problem of improving the quality of orientation of wood particles.

The technical result from the use of the invention is to improve the quality of orientation by minimizing the angle of orientation of wood particles, which increases the strength of the manufactured chipboards.

This is achieved by the fact that in the method of orientation of wood particles, including the supply of chips on disks mounted in a checkerboard pattern with overlapping even and odd rolls rotating at different speeds, according to the invention, the rotation speed of the even rolls ω _{2 is} determined by the formula:

where ω ₁ - the speed of rotation of the odd rolls, rad / s;

h is the distance between adjacent disks of odd and even rolls, m;

D is the diameter of the disks, m

The inventive method of orienting wood particles is characterized by setting the rotation speed of the even rolls depending on the speed of rotation of the odd rolls, the distance between the disks and their diameter, due to which the particles that have received rotation from the disks rotating at different speeds are stacked in the chip carpet with a minimum angle orientation.

The drawings show a fragment of a device that implements a method of orienting wood particles: in Fig.1 is a top view, in Fig.2 is a side view.

The formula for the speed of movement of the guiding organ at which the most complete orientation of the particles occurs is derived by the author for the first time.

The initial angle at which the particle comes off the disk depends on the length of the particle and the distance between adjacent disks of the odd and even rolls:

where h is the distance between adjacent disks of odd and even rolls (orientation step), m;

l is the length of the oriented particles, m

In modern orienting devices, the orientation step h is set in accordance with the length of the oriented particles l so that the optimal ratio h = l / 2 is fulfilled [see, for example, S. Plotnikov. Improving chip orientation system in the manufacture of wood-based panels. // Woodworking industry. - 2007. - No. 5. - C.4-6], in which the maximum amount of wood particles is oriented without clogging the device. Then α _nach has a value of 30 °. At the time of separation, the particle acquires a rotation speed:

where V ₁ , V ₂ - respectively, the linear speeds of the odd and even rolls when they come in contact with wood particles, m / s. Average particle fall time:

where g is the acceleration of gravity, m / s ² ;

D is the diameter of the disks, m;

d ₁ - the distance between the upper end of the disk and the average level of descent from the disks of wood particles, m;

d ₂ - the distance from the lower ends of the disks to the surface of the chip carpet, m

In modern forming machines, the distance d _{2 is} set to minimum, and the particles on average begin to fall not from the upper ends of the disks, but somewhat lower (from the level of descent), because disks are installed with overlap. The values of d ₁ and d _{2 are} equivalent and cancel each other, therefore, in further calculations they are neglected.

After a turn and passage between the disks during the fall time t, the particles turn around at an angle α _p :

Taking into account (2), (3) and d ₁ = d ₂ expression (4) has the form:

For the maximum particle orientation, at which the orientation angle α = 0, the condition must be satisfied: α _beg = α _p . Equating in expression (5) α _n = α _nach = 30 °, we obtain the linear speed of the odd disks relative to even (m / s), at which the particle orientation angle is minimal:

Assuming g = 9.81 m / s, we get:

получим угловую скорость вращения соответствующих валков (рад/с):Expressing the linear speed of odd and even discs

we obtain the angular velocity of rotation of the corresponding rolls (rad / s):

The coefficient 1.64 in equation (7) and 3.28 in equation (8) have a dimension of ^{-1 -1} m ^1/2 .

Formula (8), which relates the rotation speeds of even and odd rolls, the orientation step and the diameter of the disks, was first derived by the author.

Air resistance practically does not change the coefficient 3.28 in expression (8). Taking into account the air resistance, the oriented particle falls a little longer before laying in the carpet, i.e. should be rotated to a larger angle α. However, air resistance will also prevent the particle from turning. Thus, an increase in the angle α due to a longer fall is compensated by a decrease in this angle due to a smaller turn.

The method of orientation of wood particles is as follows.

The odd rolls (1, 3, ...) of the orienting device rotate with an angular speed ω ₁ (rad / s), the even rolls (2, 4, ...) with a speed ω ₂ determined by the formula (8). For example, with ω ₁ = 5 rad / s (47.75 rpm), h = 0.05 m and D = 0.16 m, we obtain ω ₂ = 7.56 rad / s (72.20 rpm) .

Wood particles are fed to discs. Due to the difference in the linear speeds of the odd and even disks, the particles acquire a torque, and as they move along the disks, their angle relative to the orientation direction is constantly reduced, the particles fall between the disks and turn around until they are placed in the chip carpet. When even disks rotate at the optimum speed determined from expression (8), the particles have a minimum orientation angle.

An example of the method

Wood chips from the feed conveyor are fed to disks, the ratio of the angular velocity of the rolls of which is determined by the formula (8). From the thus oriented chips on the forming conveyor, a single-layer chip carpet is obtained, which is divided into briquettes and pressed. Three batches of single-layer chipboards 10 mm thick were made from pine shavings having an average length of 100 mm (0.1 m). The height from the lower ends of the disks with a diameter of 0.15 m to the surface of the formed chip carpet was 0.02 m, the distance between adjacent disks (orientation step) was 0.05 m.

The optimal rotation speed of even rolls was calculated by the formula (8):

The rotation speed of even rolls with the help of individual electric drives was set to 5 rad / s, odd in various batches - 6 rad / s, 7.6 rad / s and 9 rad / s. The angles of particle deflection relative to the direction (axis) of orientation were measured for all completely visible particles on the upper and lower plate surfaces in arbitrary sections of plates with an area of 200 × 200 mm using a protractor. The measurement error was 1%.

The average results for 10 measurements are presented in table 1.

The weighted orientation angle α _{sr was} determined as the sum of the products of the average deflection angles α _i and the fraction of particles γ _i in the area:

For example, for ω ₂ = 6 m / s:

α _avg = 4.5 · 0.17 + 14.5 · 0.45 + 24.5 · 0.21 + 34.5 · 0.11 + 45 · 0.06 = 18.9 [deg].

Table 1 The limits of deviation of particles from the axis of orientation, deg. The average deviation angle α _i , deg. The proportion of particles in the plot γ _i ,% ω ₁ = 6 rad / s ω ₂ = 7.6 rad / s ω ₂ = 9 rad / s 0-9 4,5 17 61 12

10-19

14.5 45 21 42 20-29 24.5 21 12 23 30-39 34.5 eleven four fourteen 40-50 45 6 2 9 Weighted orientation angle α _avg , deg. 18.9 11.0 21.1

The experimental results show that the smallest average particle orientation angle has plates formed at an angular speed of even rolls close to that calculated by the formula proposed by the author.

The invention improves the orientation quality of wood particles and increase the strength of particle boards from oriented chips (OSB boards).

Claims (1)

The method of orientation of wood particles, including the supply of chips on disks mounted in a checkerboard pattern with overlapping even and odd rolls rotating at different speeds, characterized in that the rotation speed of the even rolls ω _{2 is} set by the formula:

where ω ₁ - the speed of rotation of the odd rolls, rad / s;
h is the distance between adjacent disks of odd and even rolls, m;
D is the diameter of the disks, m

Images