ARTIFICIAL SEASONING OF TIMBER

• US 3,744,147 A
• Filed: 09/08/1969
• Issued: 07/10/1973
• Est. Priority Date: 09/06/1968
• Status: Expired due to Term

• Current Assignee: John Henry Pless
• Original Assignee: John Henry Pless
• Inventors: Pless, John Henry
• Primary Examiner(s): Sukalo, Charles
• Application Number:
  US04/855,880
• Time in Patent Office: 1,401 Days
• Field of Search: 34/1
• US Class Current: 34/259
• CPC Class Codes: F26B 15/00 Machines or apparatus for drying objects with progressive movement; Machines or apparatus with progressive movement for drying batches of material in compact form F26B13/00, F26B17/00 take precedence; conveyors in general B65G
• CPC Class Codes: F26B 2210/16 Wood, e.g. lumber, timber

Abstract

The invention relates to an improved method of preventing bowing, cupping twisting or springing of boards or planks of lumber. During the latter portion of the timber drying schedule i.e. after the lumber has reached its fibre saturation point, the boards or planks are passed between spaced pairs of rollers arranged to hold the lumber in a fixed plane. The lumber is therefore held in this plane while it is setting. Preferably the drying schedule includes intermittent exposure of the lumber to microwave radiation in an electronic kiln dryer.

Claims

1. A method of drying wooden boards in which the wood is heated to reduce the moisture content to the desired final level, including:

passing the boards between fixed pairs of rollers arranged to hold the boards in a fixed plane for at least that part of the drying process after the fibre saturation point of the wood has been reached, the unsupported length of boards between adjacent pairs of rollers being not more than five feet, and the spacing between the rollers in each pair being such that substantially no compressive force is applied to the correctly sawn boards moving between the rollers, whereby the boards set in a straightened condition and cupping, bowing twisting or springing of the boards is substantially prevented.

2. The method of claim 1 in which the boards are alternately passed through heating sections between adjacent pairs of rollers to expose said boards to heat and through control sections in which said rollers hold said boards and said boards are exposed to controlled drying conditions.

3. The method of claim 2 in which said boards are exposed for a longer time in said control sections than in said heating sections.

4. The method of claim 3 including the step of spraying the boards with water as they pass through said control sections.

5. The method of claim 4 including the step of maintaining temperatures of 120* C and a relative humidity of at least 35 percent in said control sections.

6. A method of drying boards in which the boards are heated to reduce the moisture content to the desired final level, including:

the step of passing the boards between pairs of rollers arranged to hold the boards in a fixed plane during that part of the drying process after the fibre saturation point of the boards has been reached, the unsupported length of boards between adjacent pairs of rollers being not more than 5 feet, each pair of the rollers being resiliently biased toward one another, the biasing force urging the rollers together being such that substantially no compressive force is applied to the correctly sawn boards moving between the rollers, whereby the boards set in a straightened condition and cupping, bowing, twisting or springing of the lumber is substantially prevented.