Lumber Cover

This invention relates to lumber covers for covering stacks of lumber.

Lumber covered with a lumber cover having no air holes results in poor seasoning, while lumber closely wrapped within the cover rots due to the formation of dew at night. Thus, a cover must provide sufficient ventilation. Side portions of the cover must resist such natural external moisture conditions as rain and snow.

An object of the invention is to provide a lumber cover which is formed by laminating a strong base sheet with a film, providing the lamination with both bending marks along opposite longitudinal bending lines and a number of small holes along these lines, and applying as a nailing seat bonded tapes, obtained by cutting the laminated structure, to side portions of the lamination outside the rows of the small holes.

A fuller understanding of the above and other objects of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a plan view showing the lumber cover according to the invention, with the lamination film partly removed to expose the base sheet;

FIG. 2 is a sectional view taken along line II--II in FIG. 1;

FIG. 3 is a perspective view showing a lumber cover according to the invention;

FIG. 4 is a plan view showing another embodiment of the lumber cover; and

FIG. 5 is a perspective view showing a lumber stack covered with the lumber cover according to the invention.

FIGS. 1 and 2 show the basic structure of the lumber cover according to the invention. Designated at a is a base sheet (having a width of, for instance, 2.5 meters), which is woven from wrap and weft flat yarns 1 and 2 obtained by rolling a polyolefin resins, such as polyethylene and polypropylene, and which is laminated on one side or on opposite sides with a polyolefin film 3. This cover structure A is provided with bending indicia, in the illustrated embodiment marks 4, which are printed on the structure along longitudinal bending lines defining opposite side portions of the cover, as shown in FIG. 3. The cover is also formed with a number of air holes 5 of an adequate size arranged in rows extending parallel to and on the outer side of the bending lines by perforating the laminated structure A between the indicia 4 and the side edges of the laminated structure. Further, tapes 7 obtained by cutting the aforementioned cover structure A are bonded as nailing seats to portions of the structure on the outer sides of the rows of the air holes.

FIG. 4 shows a modification of the embodiment of FIG. 3. In this case, in lieu of forming the aforementioned air holes 5 by perforating the structure A, strip-like portions of the base sheet a corresponding in position and width to the rows of air holes 5 are not laminated with the polyolefin film but are exposed, as indicated at 8, so asto utilize the exposed interstices or pores of the base sheet a as ventilating holes. The remaining elements of the structure are substantially the same as the previous embodiment.

To use the cover according to the invention, lumber 10 is stacked on base supports 11 provided on ground and is tied together by wire bands 15, providing a stack having a width m, a height n and a length l, as shown in FIG. 5. Then the cover is cut, as indicated at S, to exceed the longitudinal dimension l of the stack as in FIG. 3 and provide side flaps and end flaps. The cover is laid over the lumber stack as shown in FIG. 5. Then, its side flaps are downwardly bent along the bending marks 4, and are secured to the lumber by driving staples 14 into the nailing seats 7. Then, its end flaps which extend beyond the lumber stack are folded down and secured by staples 14 to the lumber. In this way, it is possible to neatly cover the lumber 10 and protect it from snow, while permitting ventilation of moist air through the ventilation openings 5.

As has been shown, the lumber cover according to the invention is very strong since its base sheet is woven from rolled flat yarns, is capable of preventing penetration of rain by virtue of the laminated waterproof film, and is further capable of preventing rotting of covered lumber by permitting evaporation of internal moisture through the ventilation holes.

Results of tests on the lumber cover according to the invention are as follows:

Lumber covers used for the test were of the type shown in FIG. 3, but without the bottom film, with their cover structure A consisting of a base sheet woven from 1,000-denier colorless polyethylene flat yarn warps and wefts at an interval of seven warps and wefts per inch and laminated on one side with 0.003 cm thick colorless polyethylene film. The air holes had a diameter of one cm and were arranged both in a single row and in two rows for each side at intervals 10, 20, 30, 40 and 50 cm in case of both single-row and two-row arrangements.

Lumber used for the test was square pine-tree timber 10 cm on one side and 360 cm in length l. These pieces of timber were stacked in 10 columns each of 10 timbers, as shown in FIG. 5. The lumber stack support had a height of 50 cm above the ground and a structure as shown in FIG. 5. The lumber stacks were exposed to weather, with a dew surface or supporting pad constituted of concrete, for a test period from September 1 until August 31 of the next year.

The dimensions of the lumber cover were 560 cm by 310 cm, the width of the nailing tape was 5 cm. The first air hole row was spaced 5 cm from the row of bending marks 4, and where a double row of holes were provided the second air hole row was spaced 10 cm from the first one. Table 1 shows the results of this text.

It will be seen from the results of the test that with lumber covers having fewer air holes more dew was formed, resulting in rotting of a large number of timbers at the top of the stack. In the case of lumber cover No. 2 having many air holes, however, rotting was extensive due to the intrusion of rainwater through the air holes to a somewhat greater extent, and such moisture was sufficiently dispersed. More rainwater intruded in the case of two-row air hole arrangement covers. The above facts show that it is necessary to select the number of air holes by taking into consideration the formation of moisture from lumber, the dew formation at night and the intrusion of rainwater. In this test, covers having 30-30 air holes in the cover length of 560 cm, and having 20-40 cm air-hole spacing in each row, that is, covers numbers 3, 5, 6 and 8 proved to be most suitable.

Lumber covers used for this test were of the type of FIG. 4, with their cover structure consisting of a base sheet woven from the same 1,000-denier colorless polyethylene flat yarn warps and wefts at the same interval as in Test 1 and laminated with film in the manner as described in Test 1. The ventilation bands 8 were 10, 20 and 30 cm in width and spaced 5 cm away from the associated row of bending marks. The dimensions and methods of stacking of lumber used for the test were the same as in Test 1.

The dimensions of the lumber cover were 560 cm by 310 cm. Table 2 shows the results of the test. It will be seen that the ventilation band consisting solely of the flat yarn warps 1 and wefts 2 is inferior in dew dispersing capacity to the air hole system, resulting in rotting of a slightly greater number of timbers. Among the ventilation bands of various widths, a band having a width of 20 cm gave the best results.