DEVICE FOR DISTRIBUTING PARTICLES

Abstract: This invention relates to a separation means (9) for distributing wood fibers on a running web (10) for the manufacture of wood fiberboard, which wood fibers are supplied dispersed in a carrier gas from a distribution means (6), where the separation means (9) comprises a rotary roll (12) and means (8) for supplying the carrier gas with dispersed fibers substantially tangentially to said roll (12). The essential feature of the invention is that the carrier gas and wood fibers are separated from each other in that said roll (12) rotates at a speed substantially exceeding the speed of the supplied carrier gas, that the wood fibers are discharged through an opening (16), and that the carrier gas is recycled through a return line (11).

Description: Device for distributing particles This invention relates to a device for separating particles, preferably wood fibers dispersed in a carrier gas from a distribution means for distributing the particles on a running web, for example for the manufacture of wood fiberboard, where a separation means comprises a rotary roll and means for supplying the carrier gas with dispersed particles substantially tangentially to said roll. In a forming station for the manufacture of wood fiberboard there is today a demand for distributing glue-coated wood fibers on a wire or belt to a layer of a certain definite thickness. The layer of wood fibers is transported by said wire or belt to a press installation, in which the wood fibers by the effect of pressure and temperature are pressed to coherent board. Through SE 457 729 a device of the kind described above is previously known, the object of which is to bring about a material web with a uniform material distribution. This is achieved in that a carrier gas containing wood fibers is supplied tangentially to a convex surface, where fine grained fibers by the action of the so-called Coanda- effect follow along with the carrier gas along the convex surface to a first outlet, which opens to an endless permeable web, while coarse grained fibers and lumps follow a substantially straight path to a second outlet, which is connected to a line for re-circulation of the fibers. In connection to the endless web a suction box is located for collecting and recycling the carrier gas. Although this arrangement has operated satisfactorily, it was found at certain applications that the carrier gas has caused eddy formation with non-uniform material distribution as a result thereof. The present invention has the object to separate the particles from the carrier gas and to produce a homogenous layer with uniform distribution of particles across the width of a material web. 2 This object is achieved according to the invention by a device of the kind described above, which is characteristic in that the carrier gas and particles are separated from each other in that said roll rotates at a speed which substantially exceeds the speed of the supplied carrier gas, that the particles are discharged through an outlet and that the carrier gas is recycled through a return line. The invention is described in greater detail in the following with reference to the accompanying drawings, where Fig. 1 is a schematic view of a forming station for wood fiberboard, Fig. 2 is a more detailed perspective view of a device according the invention. Fig. 1 in the drawings shows a forming station for wood fiberboard comprising a schematically shown preparation station 1 for glue-coated particles, such as wood fibers. The wood fibers are transported by a carrier gas, such as air, by means of a fan 2 via a line 3 to a schematically shown coarse separator 4. The coarse separator 4 has means 5 for discharging great lumps of wood fibers and the like. After the coarse separator 4 the wood fibers pass through a distribution means 6, which can be designed in accordance with the disclosure in SE 457 729 and comprise a zigzag- shaped channel 7 with successively increasing width. At the opening of the channel 7 means 8 are located to supply the carrier gas with dispersed fibers to a separation means 9 provided according to the invention. The separation means 9 spreads out the wood fibers on a running web 10, such as a wire or belt, for transport to a press station (not shown). The carrier gas is recycled after the separation means 9 via a return line 11. In Fig. 2 the separation means 9 is shown, which comprises a rotary roll 12, which partially is enclosed in a first case 13 located in connection to the distribution means 6, and a second case 14, located in connection to the return line 11 for the carrier gas. Between the first case 13 and the second case 14 upwardly a partition wall 15 substantially sealing against the upper portion of the rotary roll 12 is located, and 3 downwardly an opening 16 is defined by the lower edges of the first case 13 and the second case 14. The opening 16 opens freely to a subsequent space and is located in the direction to the running web 10, which is located beneath the separation means 9. A means 8 in the form of an inclined wall or the like is provided for supplying the carrier gas with dispersed particles substantially tangentially to said roll 12. In operation the roll 12 rotates at a speed substantially exceeding the speed of the supplied carrier gas. The speed preferably is about 2 to 10 times higher than the speed of the carrier gas, whereby a speed gradient of the carrier gas closest to the roll 12 causes the particles to be separated from the carrier gas. The carrier gas follows along around the roll 12 and is recycled via the return line 11. The inlet to the return line 11 can comprise a high-speed nozzle, which preferably is located in the opening of the return line 11 in direction connection to the roll 12 and as far upstreams as possible of the same. In order that as great a portion as possible of the carrier gas shall be recycled and at the same time fine particles shall not be taken along together with the carrier gas, the speed can be chosen to be 5 to 8 times the speed of the supplied carrier gas. Particles, thus, tend by the centrifugal force to get away from the roll 12 and be separated from the carrier gas. Depending on the mass of the particles and on the speed of the roll 12, different particles will be separated from the carrier gas at different occasions, before they are slung out through the opening 16 in order thereafter freely in the subsequent space to fall down to the running web 10. The carrier gas, however, substantially entirely will follow along about the roll 12 to the partition wall 15, where it is separated and moved into the return line 11 to be recirculated to the preparation station 1.

Claims: CLAIMS 1. A device for separating particles, preferably wood fibers, dispersed in a carrier gas from a distribution means (6), for distributing the particles on a running web (10), for example for the manufacture of wood fiberboard, where a separation means (9) comprises a rotary roll (12) and means (8) for supplying the carrier gas with dispersed particles substantially tangentially to said roll (12), characterized in that the carrier gas and particles are separated from each other in that said roll (12) rotates at a speed, which substantially exceeds the speed of the supplied carrier gas, that the particles are discharged through an opening (16), and that the carrier gas is recycled through a return line (11). 2. A device as defined in claim 1, characterized in that said opening (16) opens freely to a subsequent space in the direction to the running web (10). 3. A device as defined in claim 2, characterized in that the roll (12) partially is enclosed in a first case (13) located in connection to the distribution means (6), and a second case (14) located in connection to the return line (11) for the carrier gas, and that between the first case (13) and second case (14) a substantially sealing partition wall (15) is located to the upper portion of the rotary roll (12). 4. A device as defined in claim 3, characterized in that the lower edges of the first case (13) and second case (14) define said opening (16). 5. A device as defined in anyone of the claims 1-4, characterized in that the roll (12) rotates at a speed about 2-10, preferably 5-8, times the speed of the carrier gas. device as defined in any one of the claims 1-5, characterized in that the return line (11) is located in direct connection to the roll (12), and that its opening is located as far upstreams of the roll (12) as possible.

Inventors: JOHANSSON LARS-ERIK, JONASSON STELLAN, SALO HEIKKI, JOHANSSON, LARS-ERIK, JONASSON, STELLAN, SALO, HEIKKI
Applicants: JOHANSSON LARS ERIK, JONASSON STELLAN, SALO HEIKKI, SUNDS DEFIBRATOR IND AB, JOHANSSON, LARS-ERIK, JONASSON, STELLAN, SALO, HEIKKI, SUNDS DEFIBRATOR INDUSTRIES AB
Application year: 1999
Main classification: B27N3
IPC codes: B27N3