CA1278071C - Lumber moisture content sorter - Google Patents
Lumber moisture content sorterInfo
- Publication number
- CA1278071C CA1278071C CA 528216 CA528216A CA1278071C CA 1278071 C CA1278071 C CA 1278071C CA 528216 CA528216 CA 528216 CA 528216 A CA528216 A CA 528216A CA 1278071 C CA1278071 C CA 1278071C
- Authority
- CA
- Canada
- Prior art keywords
- wood
- mass density
- piece
- lumber
- computer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
- B07C5/04—Sorting according to size
- B07C5/12—Sorting according to size characterised by the application to particular articles, not otherwise provided for
- B07C5/14—Sorting timber or logs, e.g. tree trunks, beams, planks or the like
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
- B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
- B07C5/00—Sorting according to a characteristic or feature of the articles or material being sorted, e.g. by control effected by devices which detect or measure such characteristic or feature; Sorting by manually actuated devices, e.g. switches
- B07C5/16—Sorting according to weight
- B07C5/28—Sorting according to weight using electrical control means
Abstract
LUMBER MOISTURE CONTENT SORTER
ABSTRACT OF THE DISCLOSURE
A method and apparatus determining the moisture content of the piece of wood by sensing the volume of the piece of wood, measuring its weight and based on its species determining the percent moisture. Preferably, the pieces of wood will then be sorted on the basis of mois-ture content and dried using drying cycles keyed to moisture content.
ABSTRACT OF THE DISCLOSURE
A method and apparatus determining the moisture content of the piece of wood by sensing the volume of the piece of wood, measuring its weight and based on its species determining the percent moisture. Preferably, the pieces of wood will then be sorted on the basis of mois-ture content and dried using drying cycles keyed to moisture content.
Description
~ Z7~
LUMBER MOISTURE CONTENT SORTER
Field of the Invention -Present invention relates to the measurement of lumber moisture content, more particularly the present invention relates to the measuring of the moisture content of lumber and sorting the lumber based on moisture content.
Background of the_Present Invention The idea of sorting lumber based on moisture content so that one may operate a kiln more efFiciently by tailoring the drying cycle more accurately with the known moisture content of the wood has been known for a number of years, however, no effective means for properly sensing the moisture content of the wood having a moisture content of above about 30% moisture has been available.
It has been proposed to sense moisture content based on infrared reflections. This technique seems to work reasonably well with veneer but is not particularly effective with thick sections as normally found in lumber, ~; particularly following storage after sawing.
It is known to measure the dimensions of elements by sensing reflected light or other means such as reflected infrared light or by means of x-rays so that the physical dimensions of an article can be determined.
It is also known to utilize load cells to deter-mine the weight of any given object.
Brief Descriction of the Present Invention It is an object of the present invention to provide a new technique for sensing the moisture content of wood elements such as lumber pieces.
:
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It is a further object of the present invention to provide a system for sensing the moisture or percent moisture of pieces of lumber and to sort the lumber in accordance with the moisture or percent moisture content.
Broadly, the present invention comprises means for sensing at least the major dimension of the lumber article, means for sensing the weight said lumber article, means for determining the density of said lumber article and means for comparing the determined density with a pre-selected mass density for determining the percent moisture in the said wood element or sorting the wood elements.
In many cases the means for sensing the ma~or dimension will comprise means for sensing the length of the lumber article and wherein the width and thickness dimensions will be preset (i.e. when the moisture content of reasonably accurate dimensional lumber is being deter-mined) so that the volume of the element can be calculated based solely on the measurement of its length. Also in - some case the thickness dimension will vary significantly and must be sensed while the widths remain substantially constant, in these cases the volume of the element can be calculated based solely on the measurement of its thick-ness and length.
Preferably the wood articles will then be separ-ated on the basis of moisture content with those wood articles having a percent moisture above a preset limit being collected in one area and those with a moisture content below said preset limit being collected in another area.
Brief Description of the Drawinqs Further features, objects and advantages will be evident from the following detail description of the pre-ferred embodiments of the present invention taken in conjunction with the accompany drawings in which:
~7~
Figure 1 is a schematic illustration of the various elements forming the present invention.
Figure 2 is a schematic arrangement illustrating the sensing devices feeding the microprocessor.
Figure 3 is a graph of number of lumber pieces versus mass density (percent moisture) to indicate the distribution of lumber pieces having various moisture contents O
Description of the Preferred Embodiments An investigation of clear lumber substantially free of knots or rot proved conclusively that for a given species the mass density based on green volume and oven dry weight of the wood was substantially more uniform than that of normal run of the mill wood from that species.
Based on this finding, it was concluded that the mass density moisture content relationship for a given species is reasonably constant for clear lumber.
Based on this observation, a moisture meter was produced for lumber wherein the dimensions of each lumber piece were sensed and the individual lumber pieces were weighed to find their weights and based on these values the volume and the density for each piece of lumber was calculated. Based on this calculated mass density and the predetermined mass density of the clear oven dry wood, the percent moisture could be calculated for each wood piece.
- Obviously once the mass density for a selected moisture content is known to separate on moisture content, one need only determine the mass density of the lumber and compare that with the mass density for the selected moisture content.
Such a device is shown in Figure 2 wherein a thickness measuring means 10 is used to determ~ne the thickness of each lumber element 12, a width measuring ~ 35 device 14 senses the width of the lumber and a length ; - 3 -, ~
:`
:
.
~278~7 ~
measuring device 16 senses the length of each lumber element 12. The output of all of these sensors is sent to a computer or microprocessor 18 which deterrnines the -volume of each lumber element 12. These dimension sensors 10, 14 and 16 may be selected from any of a number of well known sensors.
Load cells 20 (two shown) sense the weight of each lumber piece 12. This sensed weight is fed to the microprocessor 18 which then calculates the density of the lumber element 12, compares this density with a preset value for density for the preselected moisture content for that particular species of lumber and based thereon gener-ates a signal to operate the sorter 22 in accordance with the mass density (moisture content) determined by pro-cessor 18. If the moisture content of each piece is desired the calculated mass density may be compared with the predetermined mass density for clear lumber of that ; species with difference being attributable to moisture differences and moisture content calculated. Normally the invention will be used for sorting and the moisture content of individual pieces need not be determined.
In many cases it will be unnecessary to sense the thickness and width since for nominal sized lumber these dimensions are reasonably accurately known and the size of the lumber particularly the width and thickness can be assumed from the nominal size being produced. In such cases, only length need be measured. In some mills, only length and thickness need to be sensed, i.e. where the mill run has significant variations in thickness but width is uniform.
Figure 1 shows a layout of a typical installa-tion incorporating the present invention. As shown lumber elements 12 are removed from a stack 24 onto a conveyor 26 having spaced lugs 28 adapted to move the lumber elements along with the conveyor with the lumber elements being at ~ ~ .
~"
:
,"", , ~27~ L
uniformly spaced intervals therealong. If it is desired to sense the thickness of the lumber a suitable thickness sensor 10 will be provided, simllarly if it is desired to sense the width of the lumber a suitable sensor such as the sensor 14 may be used. The length is sensed by the sensor as schematically indicated at 16. In some install-ations, a single sensor instrument may be used to deter-mine all the required dimensions of the lumber pieces.
Discreet lumber elements 12 move off the end of the conveyor 26 onto a roller chute 30 and the weight of each element 12 is sensed by the sensor which in the arrangement in Figure 2 is comprised of a pair of load cells 20. The discreet lumber elements 12 are then elevated by a conveyor 32 having spaced lugs 39 which ~5 engage and elevate the various lumber pieces 12 in spaced regimented relationship up to the sorter bin generally indicated at 22.
In the schematic arrangement shown in Figure 1, the bin 22 includes a gate 36 that is pivoted between a close position as illustrated and an open position as shown by the dotted line. The position of this gate 36 is determined by the microprocessor 18 which determines the mass density of each lumber element which, as above described, provides a sufficiently accurate indication of the moisture content of each of the lumber pieces 12. The location oF each of these lumber pieces is accurately known since each lumber piece is carried by the lugs up the conveyor 32 and it is known which lugs pick up each lumber piece. The gate 36 is activated depending on the mass density of the lumber element 12 such that if the lumber element is to proceed into the top bin 38 the gate 36 is closed when the lumber element 12 is deposited in the bin 22 and the lumber element slides over the gate 36 into the bin 38. On the other hand, if the mass density (moisture content) is significantly different, i.e. on the :
~ - 5 -~278~7.~
opposite side of a preset mass density cut of-f point, then the microprocessor 1~ controls the mechanism to open the gate 36 to the dotted line position and permit the element 12 of this moisture content to pass into bin section 40 of the sorter 22.
The control or cut off point for the separation in the illustrated arrangement is a single selected mas density (cut off point) so that lumber with a mass density (moisture content) higher proceeds to one bin while lumber elements with a lower mass density (moisture content) proceed to a second bin. It will be apparent that more than one cut off point may be set, i.e. there may be an intermediate range so that all lumber in an intermediate range of mass density (moisture content) falls into a third bin with lumber elements of higher and lower mois-ture contents going into their own separate bins. However, since the degree of accuracy of the moisture content determination (determination by mass density) decreases with decreasing moisture content, it is preferred to use a single cut off point at a relatively high mass density (moisture content).
. .
In Figure 3, a preselected cut off point has been indicated by the line AA. This cut off point is pre-set into the microprocessor 18 so that all the lumber pieces having a mass density to the left of the line AA
would be sorted into one bin and the high moisture content lumber indicated by that portion of the curve to the right ~ 30 of the line AA would be received in a second bin.
:.
Generally, if a single separation line is to be used that line should coincide with a speciFic moisture content that generally will be in the range of 80%-110%, preferably 90%-100% moisture and as above indicated lumber ~;~7~7.~
pieces with a moisture content above the prescribed limit will be separated from lumber below that level. It has been found that for western red cedar 100% moisture coin-cides with a mass density of about 620 kilograms/cubic meter. Obviously this does not provide a precise measure-ment of 100% moisture but is sufficiently accurate such that separation of pieces with mass density above or below the selected density results in a very significant improvement in drying efficiency. For hemlock which includes what is called sinker stock and contains wood with very high moisture two separation lines may be used, one in the range of 160%-190%, preferably 170%-180% and the other in the range described above for a single separ-ation line.
15It will be apparent from the position of line AA
in Figure 3 that by far the majority of the lumber falls to the left of AA, however, the lumber to the right though small in quantity would in a conventional system govern the drying cycle. This small quantity of lumber having moisture above the cut off point when dried together with the rest of the lumber controlled the drying cycle for all the lumber. This drying cycle, in some cases, caused ' damage to those lumber pieces having low moisture content.
With the present invention, the high mass density (moisture content) material will be dried separ-ately from the major portion of the lumber, each portion will be kiln dried using a selected drying cycle specific to that particular portion of the lumber. It has been found following this practice for western cedar lumber where line AA is at 100% moisture the majority of lumber, i.e. the lumber to the left of the line AA in Figure 3 can be dried in a significantly shorter period of time than if all the lumber were kiln dried simultaneously (the time to complete the drying cycle has been reduced by almost 50%
35 in some cases1. It has also b;en found that i~ the portion .
.
1;~7~7:1 above the separation line AA, i.e. to the right of the separation line AA, is separately kiln dried, its drying cycle can also be keyed to its particular moisture content and the time for drying this portion also reduced signifi-cantly relative to when all of the lumber was driedsimultaneously.
While it is possible to separate into more than two groups it is been found that the single separation provides a very significant improvement and further separ-ations while they can be used to advantage probably are not economically justified.
Having described the invention modifications will be evident to those skilled in the art without departing from the spirit of the invention as defined in the Claims.
,
LUMBER MOISTURE CONTENT SORTER
Field of the Invention -Present invention relates to the measurement of lumber moisture content, more particularly the present invention relates to the measuring of the moisture content of lumber and sorting the lumber based on moisture content.
Background of the_Present Invention The idea of sorting lumber based on moisture content so that one may operate a kiln more efFiciently by tailoring the drying cycle more accurately with the known moisture content of the wood has been known for a number of years, however, no effective means for properly sensing the moisture content of the wood having a moisture content of above about 30% moisture has been available.
It has been proposed to sense moisture content based on infrared reflections. This technique seems to work reasonably well with veneer but is not particularly effective with thick sections as normally found in lumber, ~; particularly following storage after sawing.
It is known to measure the dimensions of elements by sensing reflected light or other means such as reflected infrared light or by means of x-rays so that the physical dimensions of an article can be determined.
It is also known to utilize load cells to deter-mine the weight of any given object.
Brief Descriction of the Present Invention It is an object of the present invention to provide a new technique for sensing the moisture content of wood elements such as lumber pieces.
:
::
..~
~7~l~7:~
It is a further object of the present invention to provide a system for sensing the moisture or percent moisture of pieces of lumber and to sort the lumber in accordance with the moisture or percent moisture content.
Broadly, the present invention comprises means for sensing at least the major dimension of the lumber article, means for sensing the weight said lumber article, means for determining the density of said lumber article and means for comparing the determined density with a pre-selected mass density for determining the percent moisture in the said wood element or sorting the wood elements.
In many cases the means for sensing the ma~or dimension will comprise means for sensing the length of the lumber article and wherein the width and thickness dimensions will be preset (i.e. when the moisture content of reasonably accurate dimensional lumber is being deter-mined) so that the volume of the element can be calculated based solely on the measurement of its length. Also in - some case the thickness dimension will vary significantly and must be sensed while the widths remain substantially constant, in these cases the volume of the element can be calculated based solely on the measurement of its thick-ness and length.
Preferably the wood articles will then be separ-ated on the basis of moisture content with those wood articles having a percent moisture above a preset limit being collected in one area and those with a moisture content below said preset limit being collected in another area.
Brief Description of the Drawinqs Further features, objects and advantages will be evident from the following detail description of the pre-ferred embodiments of the present invention taken in conjunction with the accompany drawings in which:
~7~
Figure 1 is a schematic illustration of the various elements forming the present invention.
Figure 2 is a schematic arrangement illustrating the sensing devices feeding the microprocessor.
Figure 3 is a graph of number of lumber pieces versus mass density (percent moisture) to indicate the distribution of lumber pieces having various moisture contents O
Description of the Preferred Embodiments An investigation of clear lumber substantially free of knots or rot proved conclusively that for a given species the mass density based on green volume and oven dry weight of the wood was substantially more uniform than that of normal run of the mill wood from that species.
Based on this finding, it was concluded that the mass density moisture content relationship for a given species is reasonably constant for clear lumber.
Based on this observation, a moisture meter was produced for lumber wherein the dimensions of each lumber piece were sensed and the individual lumber pieces were weighed to find their weights and based on these values the volume and the density for each piece of lumber was calculated. Based on this calculated mass density and the predetermined mass density of the clear oven dry wood, the percent moisture could be calculated for each wood piece.
- Obviously once the mass density for a selected moisture content is known to separate on moisture content, one need only determine the mass density of the lumber and compare that with the mass density for the selected moisture content.
Such a device is shown in Figure 2 wherein a thickness measuring means 10 is used to determ~ne the thickness of each lumber element 12, a width measuring ~ 35 device 14 senses the width of the lumber and a length ; - 3 -, ~
:`
:
.
~278~7 ~
measuring device 16 senses the length of each lumber element 12. The output of all of these sensors is sent to a computer or microprocessor 18 which deterrnines the -volume of each lumber element 12. These dimension sensors 10, 14 and 16 may be selected from any of a number of well known sensors.
Load cells 20 (two shown) sense the weight of each lumber piece 12. This sensed weight is fed to the microprocessor 18 which then calculates the density of the lumber element 12, compares this density with a preset value for density for the preselected moisture content for that particular species of lumber and based thereon gener-ates a signal to operate the sorter 22 in accordance with the mass density (moisture content) determined by pro-cessor 18. If the moisture content of each piece is desired the calculated mass density may be compared with the predetermined mass density for clear lumber of that ; species with difference being attributable to moisture differences and moisture content calculated. Normally the invention will be used for sorting and the moisture content of individual pieces need not be determined.
In many cases it will be unnecessary to sense the thickness and width since for nominal sized lumber these dimensions are reasonably accurately known and the size of the lumber particularly the width and thickness can be assumed from the nominal size being produced. In such cases, only length need be measured. In some mills, only length and thickness need to be sensed, i.e. where the mill run has significant variations in thickness but width is uniform.
Figure 1 shows a layout of a typical installa-tion incorporating the present invention. As shown lumber elements 12 are removed from a stack 24 onto a conveyor 26 having spaced lugs 28 adapted to move the lumber elements along with the conveyor with the lumber elements being at ~ ~ .
~"
:
,"", , ~27~ L
uniformly spaced intervals therealong. If it is desired to sense the thickness of the lumber a suitable thickness sensor 10 will be provided, simllarly if it is desired to sense the width of the lumber a suitable sensor such as the sensor 14 may be used. The length is sensed by the sensor as schematically indicated at 16. In some install-ations, a single sensor instrument may be used to deter-mine all the required dimensions of the lumber pieces.
Discreet lumber elements 12 move off the end of the conveyor 26 onto a roller chute 30 and the weight of each element 12 is sensed by the sensor which in the arrangement in Figure 2 is comprised of a pair of load cells 20. The discreet lumber elements 12 are then elevated by a conveyor 32 having spaced lugs 39 which ~5 engage and elevate the various lumber pieces 12 in spaced regimented relationship up to the sorter bin generally indicated at 22.
In the schematic arrangement shown in Figure 1, the bin 22 includes a gate 36 that is pivoted between a close position as illustrated and an open position as shown by the dotted line. The position of this gate 36 is determined by the microprocessor 18 which determines the mass density of each lumber element which, as above described, provides a sufficiently accurate indication of the moisture content of each of the lumber pieces 12. The location oF each of these lumber pieces is accurately known since each lumber piece is carried by the lugs up the conveyor 32 and it is known which lugs pick up each lumber piece. The gate 36 is activated depending on the mass density of the lumber element 12 such that if the lumber element is to proceed into the top bin 38 the gate 36 is closed when the lumber element 12 is deposited in the bin 22 and the lumber element slides over the gate 36 into the bin 38. On the other hand, if the mass density (moisture content) is significantly different, i.e. on the :
~ - 5 -~278~7.~
opposite side of a preset mass density cut of-f point, then the microprocessor 1~ controls the mechanism to open the gate 36 to the dotted line position and permit the element 12 of this moisture content to pass into bin section 40 of the sorter 22.
The control or cut off point for the separation in the illustrated arrangement is a single selected mas density (cut off point) so that lumber with a mass density (moisture content) higher proceeds to one bin while lumber elements with a lower mass density (moisture content) proceed to a second bin. It will be apparent that more than one cut off point may be set, i.e. there may be an intermediate range so that all lumber in an intermediate range of mass density (moisture content) falls into a third bin with lumber elements of higher and lower mois-ture contents going into their own separate bins. However, since the degree of accuracy of the moisture content determination (determination by mass density) decreases with decreasing moisture content, it is preferred to use a single cut off point at a relatively high mass density (moisture content).
. .
In Figure 3, a preselected cut off point has been indicated by the line AA. This cut off point is pre-set into the microprocessor 18 so that all the lumber pieces having a mass density to the left of the line AA
would be sorted into one bin and the high moisture content lumber indicated by that portion of the curve to the right ~ 30 of the line AA would be received in a second bin.
:.
Generally, if a single separation line is to be used that line should coincide with a speciFic moisture content that generally will be in the range of 80%-110%, preferably 90%-100% moisture and as above indicated lumber ~;~7~7.~
pieces with a moisture content above the prescribed limit will be separated from lumber below that level. It has been found that for western red cedar 100% moisture coin-cides with a mass density of about 620 kilograms/cubic meter. Obviously this does not provide a precise measure-ment of 100% moisture but is sufficiently accurate such that separation of pieces with mass density above or below the selected density results in a very significant improvement in drying efficiency. For hemlock which includes what is called sinker stock and contains wood with very high moisture two separation lines may be used, one in the range of 160%-190%, preferably 170%-180% and the other in the range described above for a single separ-ation line.
15It will be apparent from the position of line AA
in Figure 3 that by far the majority of the lumber falls to the left of AA, however, the lumber to the right though small in quantity would in a conventional system govern the drying cycle. This small quantity of lumber having moisture above the cut off point when dried together with the rest of the lumber controlled the drying cycle for all the lumber. This drying cycle, in some cases, caused ' damage to those lumber pieces having low moisture content.
With the present invention, the high mass density (moisture content) material will be dried separ-ately from the major portion of the lumber, each portion will be kiln dried using a selected drying cycle specific to that particular portion of the lumber. It has been found following this practice for western cedar lumber where line AA is at 100% moisture the majority of lumber, i.e. the lumber to the left of the line AA in Figure 3 can be dried in a significantly shorter period of time than if all the lumber were kiln dried simultaneously (the time to complete the drying cycle has been reduced by almost 50%
35 in some cases1. It has also b;en found that i~ the portion .
.
1;~7~7:1 above the separation line AA, i.e. to the right of the separation line AA, is separately kiln dried, its drying cycle can also be keyed to its particular moisture content and the time for drying this portion also reduced signifi-cantly relative to when all of the lumber was driedsimultaneously.
While it is possible to separate into more than two groups it is been found that the single separation provides a very significant improvement and further separ-ations while they can be used to advantage probably are not economically justified.
Having described the invention modifications will be evident to those skilled in the art without departing from the spirit of the invention as defined in the Claims.
,
Claims (6)
1. A method of determining the moisture content of a piece of wood comprising sensing at least one dimension of said piece of wood and automatically determining the volume of said piece of wood in a computer, sensing the weight of said piece of wood and feeding the sensed weight to said computer, calculating the mass density of said piece of wood in said computer, and comparing in said computer the calculated mass density of said piece of wood with a previously determined mass density calculated based on wet volume an oven dry weight of the wood for the species to which said piece of wood belongs pre-programmed in said computer thereby to determine the moisture in said piece of wood.
2. A method of segregating wood pieces into groups of different moisture contents comprising, sensing at least the major dimension of each said wood piece to provide sufficient data to automatically determine the volume of each piece in acomputer to which a signal indicating the sensed dimension is transmitted, sensing the weight of each wood piece and feeding the sensed weight to said computer, calculating the mass density of each wood piece in said computer and controlling the segregation of said wood pieces into different groups depending on sail calculated mass densities with said computer
3. Method as defined in claim 2 further comprising segregating said wood to groups, the first group having a mass density higher than a preset value and the second group having a mass density less than said preset value and wherein said preset volume of mass density corresponds with a moisture content of between about 80% and 110%.
4. Method as defined in claim 2 further comprising segregating said wood to groups the first group having a mass density higher than a preset value and the second group having a mass density less than said preset value and wherein said preset volume of mass density corresponds with a moisture content of between about 90% and 100%.
5. An apparatus for separating wood pieces into groups of different moisture contents comprising means for sensing at least the maximum dimension of each of said wood pieces to permit determination of the volume of each of said wood pieces, means for weighing each of said wood pieces, computer means for calculating mass density of each of said wood pieces based on said volume determined from said sensed dimension and weight of each of said wood pieces as determined by said means for weighing, said computer means comparing said calculated mass density with a predetermined mass density and means for separating said wood pieces into groups based on said calculated and said preselected mass densities for each of said wood pieces.
6. An apparatus as defined in Claim 5 further comprising means for sensingthe thickness of each of said wood pieces to provide data to determine said volume of said wood pieces.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 528216 CA1278071C (en) | 1987-01-27 | 1987-01-27 | Lumber moisture content sorter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 528216 CA1278071C (en) | 1987-01-27 | 1987-01-27 | Lumber moisture content sorter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1278071C true CA1278071C (en) | 1990-12-18 |
Family
ID=4134832
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 528216 Expired CA1278071C (en) | 1987-01-27 | 1987-01-27 | Lumber moisture content sorter |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1278071C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112403927A (en) * | 2020-11-12 | 2021-02-26 | 梁金 | Wood moisture detection device in high-frequency vacuum wood drying process |
-
1987
- 1987-01-27 CA CA 528216 patent/CA1278071C/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112403927A (en) * | 2020-11-12 | 2021-02-26 | 梁金 | Wood moisture detection device in high-frequency vacuum wood drying process |
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