Title:
Fork assembly for lumber stackers
Kind Code:
A1


Abstract:
The fork assembly for lumber stackers includes a plurality of mechanized arms. Each mechanized arm includes a biasing assembly that provides a movable carrying surface onto the arm upper surface Such movable carrying surface is for example in the form of an endless belt, that biases an object deposited onto the arm towards a distal end thereof. The fork assembly according to the present invention prevents smaller pieces of lumber to rise when the fork assembly is retracted above a lumber stacker elevator during deposition of the lumber from the fork assembly to the elevator's platform. The present invention further allows creating stack of lumbers having different configurations.



Inventors:
Piche, Guy (Quebec, CA)
Laprise, Rene (Quebec, CA)
Truchon, Sylvain (Quebec, CA)
Application Number:
10/119135
Publication Date:
05/15/2003
Filing Date:
04/09/2002
Assignee:
PICHE GUY
LAPRISE RENE
TRUCHON SYLVAIN
Primary Class:
International Classes:
B65G57/18; (IPC1-7): B65H29/26
View Patent Images:



Primary Examiner:
KRIZEK, JANICE LEE
Attorney, Agent or Firm:
IP GROUP OF DLA PIPER LLP (US) (PHILADELPHIA, PA, US)
Claims:

What is claimed is:



1. A mechanized arm for a lumber stacker comprising: a body; a longitudinal arm mounted to said body and having a proximate end and a distal end and generally extending from said body from said proximate end along a longitudinal axis; a biasing assembly mounted on said longitudinal arm; said biasing assembly defining a carrying surface on said longitudinal arm; said carrying surface being movable along said longitudinal axis, and a biasing assembly actuator in operative relation with said biasing assembly for moving said carrying surface; whereby an object deposited onto said longitudinal arm is biased towards said distal end of said arm by actuating said biasing assembly using said biasing assembly actuator.

2. A mechanized arm as recited in claim 1, wherein said longitudinal arm includes a belt-receiving portion and said biasing assembly includes a drive pulley so mounted to said body as to be complementary aligned with said belt-receiving portion, and an endless belt rotatably mounted to said drive pulley and said belt-receiving portion.

3. A mechanized arm as recited in claim 2, wherein said biasing assembly further includes at least one of an upper guide pulley mounted to said body near said proximate end of said longitudinal arm and a bottom guide pulley mounted to said longitudinal arm below said belt-receiving portion.

4. A mechanized arm as recited in claim 3, wherein said biasing assembly is so position relatively to said drive pulley as to define an upward slope portion of said belt.

5. A mechanized arm as recited in claim 2, wherein said biasing assembly further includes a belt idler assembly.

6. A mechanized arm as recited in claim 1, wherein said longitudinal arm has a generally triangular profile defining a downward slope from said proximate end to said distal end of said longitudinal arm.

7. A fork assembly for a lumber stacker comprising: a plurality of mechanized arms as recited in claim 1, each of said mechanized arms being mounted to the lumber stacker as to be movable along each of said mechanized arm longitudinal axis; said plurality of mechanized arms being so positioned in a parallel relationship as to generally yield said mechanized arms carrying surfaces in a first plane; and at least one drive system mounted to the lumber stacker and coupled to said mechanized arms for causing translation movements of said plurality of mechanized arms along its respective longitudinal axis.

8. A fork assembly as recited in claim 7, further comprising a controller connected to both said at least one drive system and each of said biasing assembly actuator for operating said at least one drive system and each of said biasing assembly actuator.

9. A fork assembly as recited in claim 8, wherein said controller further allows determining a relative speed between each of said carrying surface of said plurality of mechanized arms and said plurality of mechanized arms.

10. A fork assembly as recited in claim 7, further comprising a carriage so mounted to said at least one drive system as to be movable along said longitudinal axis; said plurality of mechanized arms being mounted to said carriage; whereby, operation of said at least one drive system causing translation of said plurality of mechanized arms along said longitudinal axis.

11. A fork assembly as recited in claim 10, wherein said plurality of mechanized arms being pivotally mounted to said carriage.

12. A fork assembly as recited in claim 10, wherein said longitudinal arm includes a belt-receiving portion and said biasing assembly includes a drive pulley so mounted to said body as to be complementary aligned with said belt-receiving portion and an endless belt rotatably mounted to said drive pulley and said belt-receiving portion.

13. A fork assembly as recited in claim 12, wherein said biasing assembly actuator includes a motor and at least one drive assembly for transmitting the energy of said motor to said biasing assembly.

14. A fork assembly as recited in claim 13, wherein said plurality of mechanized arms being mounted to said carriage via a rotatable mounting shaft positioned generally perpendicular to said longitudinal axes; said at least one drive assembly including a first drive assembly for transmitting the energy of said motor to said rotatable mounting shaft, and a second drive assembly for transmitting the energy of said rotatable mounting shaft to said biasing assembly; whereby actuation of said motor causes the actuation biasing assembly via said first and second drive assembly.

15. A fork assembly as recited in claim 14, wherein said first drive assembly includes a first drive wheel mounted to a drive shaft of said motor, and a first driven wheel fixedly mounted to said rotatable mounting shaft and being coupled to said first drive wheel for rotation in unison; said second drive assembly includes a second drive wheel fixedly mounted to said mounting shaft and rotatably mounted to said body, a second driven wheel rotatably mounted to said body and coupled to said second drive wheel for rotation in unison, and a shaft mounted to said body and coaxially mounted to said second driven wheel and said drive pulley.

16. A lumber stacker comprising: a mounting structure; a lumber transfer apparatus mounted to said mounting frame structure for receiving wood lumbers, aligning wood lumbers parallel to a second axis, in a second plan, and for moving wood lumbers, in said second plan, in a second direction perpendicular to said second axis; said lumber transfer apparatus including a series of parallel spaced conveyor belts; an elevator mounted to said mounting structure positioned adjacent said lumber transfer apparatus and including a platform movable along an axis perpendicular to both said second plan and said second direction; a fork assembly as recited in claim 2 mounted to said mounting structure, said fork assembly being so configured and sized and so positioned relative to said lumber transfer apparatus and said elevator as to be movable between a first position wherein said arms of said fork assembly generally overlap said belts of said lumber transfer apparatus, to a second position wherein said arms extend above said elevator; a first stop mounted to said mounting structure so as to allow passage of lumbers from said lumber transfer apparatus to said fork assembly when said fork assembly is in its second position and to force lumbers on said fork assembly from said fork assembly to said platform of said elevator when said fork assembly is moved from said second position to said first position; and a second stop so mounted to said mounting structure opposite said first stop relatively to said elevator as to be positioned in a moving path of said fork assembly

Description:

FIELD OF THE INVENTION

[0001] The present invention relates to lumber stackers. More specifically, the present invention is concerned with a fork assembly for a lumber stacker.

BACKGROUND OF THE INVENTION

[0002] Lumber stacker apparatuses allowing stacking rows of wood lumbers are well known in the art of wood processing. A conventional lumber stacker 10 is described in FIG. 1 of the appended drawings.

[0003] The lumber stacker 10 comprises a lumber transfer apparatus 12 mounted on top of a mounting frame structure 14, an elevator 16 mounted to said mounting frame structure 14, adjacent said lumber transfer apparatus 12, and a fork assembly 17, so mounted to said mounting frame structure 14 as to reciprocate between a retracted position and an extended position.

[0004] The lumber transfer apparatus 12 is in the form of a conveyor belt that includes conventional drive means 18 and a controller (not shown) that allows moving distanced parallel belts 20 (only one showed) in both forward and backward direction (see arrows 22 and 24)

[0005] The lumber transfer apparatus 12 allows aligning, side-by-side in a parallel relationship, wood lumbers 26 incoming from the distal end 28 of the lumber transfer apparatus 12. The wood lumbers are positioned parallel to a first axis 30 and then moved by the belts 20 towards the elevator 16 (see arrow 24) in a direction perpendicular to the axis 30.

[0006] The lumber transfer apparatus 12 includes liftskids 32 to help separate the lumbers 26 into rows 34 having predetermined width. The liftskids 32 allow accumulating lumbers onto the lumber transfer apparatus belt 20 during the addition of a row of lumbers onto the platform 40 of the elevator 16. The lumbers 26 may be positioned in rows according to different needs and criteria. For example, the longest and widest pieces of lumber may be positioned at both longitudinal ends of the row as can be seen in FIG. 1.

[0007] The proximate end 38 of the lumber transfer apparatus 12 is provided with an angled portion 36 to facilitate the transfer of wood lumbers from the lumber transfer apparatus 12 to the fork assembly 17 as it will be explained hereinbelow.

[0008] The elevator 16 includes a platform 40 vertically movable along a second axis 42 perpendicular to the plan of the belts 20. The platform 40 is dimensioned to accommodate a row of lumbers from the row forming apparatus 17.

[0009] The fork assembly 17 comprises a carriage 44, provided with driven wheels 46 or another drive means such as rails, and a plurality of spaced arms 48 (only one shown) extending from the carriage 44 in a parallel relationship. The arms 48 are so configured, sized and spaced as to generally provide a surface for supporting and carrying a row of lumbers 26 incoming from the lumber transfer apparatus 16. A conventional drive system 49 drives the carriage 44. Since drive systems for fork assemblies are believed to be well known in the art, they will not be described herein in more detail.

[0010] The fork assembly 17 is so movably mounted to the support frame structure 14 under the transfer apparatus 16 and so configured and sized that its arms overlap the belts 20 of the transfer apparatus 12 with the arm and the belts 20 generally disposed in a common plan. Of course, the relative width and interspaces of the both the arms 48 of the fork assembly 17 and the belts 20 of the lumber transfer apparatus 12 are both so chosen as to allow the overlapping relationship.

[0011] The carriage 44 and the drive system 49 allow reciprocal movement of the fork assembly 17 between an extended position, wherein the arms are positioned above the platform 40 of the elevator 16, to a retracted position, wherein the arms of the fork are completely removed from above the platform 40.

[0012] In operation, lumbers of wood 26, usually incoming from a wood mill (not shown), are first aligned in rows 34 on the lumber transfer apparatus 12. Translation of the belts 20 causes an aligned row 34 of lumbers 26 to be transferred to the fork assembly 17, which is then in its extended position over the platform 40 of the elevator 16. The fork assembly 17 is then translated in the direction of arrow 22 from its extended position to its retracted position under the lumber transfer apparatus 12. During the translation of the fork assembly 17, the lumbers 26 are prevented from translating back to the lumber transfer apparatus 12 by a retractable mechanical stop assembly 50 and therefore are forced to fall onto the platform 40.

[0013] The mechanical stop assembly 50 is mounted to the mounting frame structure 14 near the distal end 38 of the lumber transfer apparatus 12 so as to block the path of the first lumber of the row when the fork assembly returns in its retracted position. The mechanical stop 50 is made retractable so as to allow the passage of the lumber when the fork assembly 17 is moving from the retracted position to the extended position.

[0014] The mounting frame structure 14 can be any structure or body allowing to adequately position the lumber transfer apparatus 12, the elevator 16, the fork assembly 17 and the retractable stop 50 relatively to each other in an operative relation.

[0015] Even though, the conventional lumber stacker 10 has been described with its elements assembled to a mounting frame structure 14, other structures are known to be used to correctly position the elements so as to provide a lumber stacker.

[0016] Of course, conventional lumber stackers in general, and more specifically the lumber transfer apparatus 12, the elevator 16 and/or the fork assembly 17, may take many other forms according to the prior art.

[0017] Since conventional lumbers stackers are believed to be well known in the art, they will not be described herein in more detail.

[0018] A drawback of such lumber stackers from the prior art, and more specifically to conventional fork assemblies, is that relatively narrow pieces of lumber may rise among other pieces in a row and overlap the deposited row during the retraction of the fork apparatus.

[0019] Another drawback is that fork assemblies from the prior art do not allow complex arrangement of lumbers stacking.

OBJECTS OF THE INVENTION

[0020] An object of the present invention is therefore to provide an improved fork assembly for lumber stackers.

SUMMARY OF THE INVENTION

[0021] More specifically, in accordance with the present invention, there is provided a mechanized arm for a lumber stacker comprising:

[0022] a body;

[0023] a longitudinal arm mounted to the body and ***having a proximate end and a distal end and generally extending from the body from the proximate end along a longitudinal axis;

[0024] a biasing assembly mounted on the longitudinal arm; the biasing assembly defining a carrying surface on the longitudinal arm; the carrying surface being movable along the longitudinal axis; and

[0025] a biasing assembly actuator in operative relation with the biasing assembly for moving the carrying surface;

[0026] whereby an object deposited onto the longitudinal arm is biased towards the distal end of the arm by actuating the biasing assembly using the biasing assembly actuator.

[0027] According to a second aspect of the present invention, there is provided a fork assembly for a lumber stacker comprising:

[0028] a plurality of mechanized arms according to the present invention; each of the plurality of mechanized arms being mounted to the lumber stacker as to be movable along each of the mechanized arm longitudinal axis; the plurality of mechanized arms being so positioned in a parallel relationship as to generally yield the mechanized arms carrying surfaces in a first plane;

[0029] at least one drive system mounted to the lumber stacker and coupled to the plurality of mechanized arms for causing translation movements of the plurality of mechanized arms along its respective longitudinal axis; and

[0030] a controller connected to both the at least one drive system and each of the biasing assembly actuator for operating the at least one drive system and each of the biasing assembly actuator.

[0031] According to a final aspect of the presenting invention, there is provided a lumber stacker comprising:

[0032] a mounting structure;

[0033] a lumber transfer apparatus mounted to the mounting frame structure for receiving wood lumbers, aligning wood lumbers parallel to a second axis, in a second plan, and for moving wood lumbers, in the second plan, in a second direction perpendicular to the second axis; the lumber transfer apparatus including a series of parallel spaced conveyor belts;

[0034] an elevator mounted to the mounting structure positioned adjacent the lumber transfer apparatus, and including a platform movable along an axis perpendicular to both the second plan and the second direction;

[0035] a fork assembly according to the second according to the present invention mounted to the mounting structure; the fork assembly being so configured and sized and so positioned relative to the lumber transfer apparatus and the elevator as to be movable between a first position wherein the arms of the fork assembly generally overlap the belts of the lumber transfer apparatus, to a second position wherein the arms extend above the elevator;

[0036] a first stop mounted to the mounting structure so as to allow passage of lumbers from the lumber transfer apparatus to the fork assembly when the fork assembly is in its second position and to force lumbers on the fork assembly from the fork assembly to the platform of the elevator when the fork assembly is moved from the second position to the first position; and

[0037] a second stop so mounted to the mounting structure opposite said first stop relatively to the elevator as to be positioned in a moving path of the fork assembly.

[0038] Other objects, advantages and features of the present invention will become more apparent upon reading the following non restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In the appended drawings:

[0040] FIG. 1. which is labeled “Prior Art” is a side elevational view of a conventional lumber stacker;

[0041] FIG. 2 is a perspective view of a fork assembly according to a preferred embodiment of the present invention;

[0042] FIG. 3 is a side elevational view of a mechanized arm of FIG. 2;

[0043] FIG. 4 is a bottom view of the mechanized arm of FIG. 3,

[0044] FIG. 5 is a reverse perspective view of the mechanized arm of FIG. 3;

[0045] FIG. 6 is a side elevational view of a lumber stacker according to an embodiment of the present invention;

[0046] FIGS. 7a-7d are partial side elevational views of the lumber stacker of FIG. 6, illustrating different stack configuration obtained using the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0047] Turning now to FIG. 2 of the appended drawings, a fork assembly 100 according to a preferred embodiment of the present invention is shown.

[0048] The fork assembly 100 comprises a carriage 102, a drive system 104 for the carriage (see FIG. 6), a plurality of mechanized arms 106 (nine shown) pivotally mounted to the carriage 102, an a controller (not shown).

[0049] The carriage 102 is in the form of a metal frame provided with four wheels 108 that allow the carriage 102 to be freely moved along the axis 110.

[0050] Turning now briefly to FIG. 6, the drive system 104 allows translating the carriage 102 along the axis 110. The drive system 104 includes a motor 103 and a drive mechanism 105 that transforms a rotating movement of the motor into an axial one according to known methods. The drive system 104 is commanded and controlled by the controller (not shown), which is in the form of programmable logic controller (PLC) or a computer. Numerous control mechanisms are placed on the machine as to know the positions, speeds and status of the different parts of the stacker 200.

[0051] The mechanized arms 106 are pivotally mounted to the carriage 102 via a shaft 112. More specifically, the shaft 112 is rotatably mounted to the carriage 102 via shaft receiving brackets 114, while each mechanized arm 106 is mounted to the shaft 112 via a mounting assembly 116.

[0052] It is to be noted that the pivotally mounting of the mechanized arms 106 to the carriage 102 is advantageous since it allows the arms 106 to rise, and therefore be protected against breakage, when a loaded platform underneath reach beyond the operational level for loading.

[0053] The shaft receiving brackets 114 include an aperture to receive the shaft 112 and are secured to integral mounting blocks 118 of the carriage 102 via screws 120 or other securing means such as welding.

[0054] Turning now to FIGS. 3 to 5, a mechanized arm 106 of the fork assembly 100 will be described in more detail.

[0055] The mechanized arm 108 comprises a body 122, a longitudinal arm 124, a biasing assembly 126, and a biasing assembly actuator 128.

[0056] The body 122 includes a first aperture 130 to receive the shaft 112, and therefore allows to pivotally mounting the mechanized arm 106 to the carriage 102. The body 122 is preferably made of CHT 360 steel that provides stiffness to the body 122. Of course, other metal or materials may alternatively be used.

[0057] The longitudinal arm 124 extends from the body 122 from a proximate end 132 to a distal end 134 generally along a longitudinal axis 136. The longitudinal arm 124 includes a longitudinal belt-receiving portion 138 extending laterally from the body 122. The distal end of the belt-receiving portion 138 includes a groove (not shown) that helps aligning the belt 144.

[0058] The longitudinal arm 124 advantageously has a triangular profile defining a downward slope from the proximate end 132 to the distal end 134 to ease the unloading of lumbers as it will be explained hereinbelow.

[0059] The biasing assembly 126 includes a drive pulley 140 mounted to the body 122 on the lateral side 142 of the belt-receiving portion 138 so as to be complementary aligned therewith as it will be explained hereinbelow and an endless belt 144 rotatably mounted to the belt-receiving portion 138 of the arm 124 and to the drive pulley 140. The biasing assembly 126 also includes an upper guide pulley 146 and two bottom guide pulleys 148.

[0060] Finally, the biasing assembly 126 includes a belt idler assembly 150 to tighten the belt 144 about the belt-receiving portion 138 and prevent slipping. Many belt idler assemblies can be used without departing from the spirit and nature of the invention. The belt idler assembly 150 may be of the manual-adjusting type or of the self-adjusting type. Since belt idler assemblies are believed to be well known in the art, they will not be described further in.

[0061] The belt-receiving portion 138 on the longitudinal arm 124 defines a carrying surface that is movable along the longitudinal axis 136.

[0062] It is to be noted that the body 122 includes a slope portion 152 and that the drive and upper guide pulleys 140 and 146 are so dimensioned and positioned relatively to the longitudinal arm 124 and the slope portion 152 as to provide an upward slope portion 154 of the belt 144. This optional slope portion 154 allows helping loading lumbers onto the longitudinal arm 106.

[0063] The pulleys 140, 146 and 148 and the belt idler assembly 150 are provided with resilient belt contacting surface such as urethane to increase friction with the belt 144.

[0064] As it will now become apparent to a person skill in the art, rotation of the drive pulley 140 allows biasing the carrying surface from the proximate end 132 to the distal end 134 of the longitudinal arm 106 or vice-versa.

[0065] The longitudinal arm 126 is advantageously in a material that is lightweight, such as aluminium. Of course, other materials such as steel can also be used.

[0066] Returning to FIG. 2, the biasing assembly actuator 128 includes a motor 156 connected to the controller, a first drive assembly 158 for the transmission of the energy of the motor 156 to the shaft 112, and a second drive assembly 160, for transmission of the energy of the shaft 112 to the drive pulley 140.

[0067] The first drive assembly 158 includes a drive sprocket wheel 162, a driven sprocket wheel 164 and a first drive chain 166 therebetween to coupled the drive and driven sprocket wheel for rotation in unison The drive sprocket wheel 162 is fixedly mounted to the shaft of the motor 156. The driven sprocket wheel 164 is fixedly mounted to the shaft 112 so as to be generally aligned with the first sprocket wheel 162.

[0068] The second drive assembly 160 includes a drive sprocket wheel 168 fixedly mounted to the shaft 112 and rotatably mounted to the body 122, and a driven sprocket wheel 170 rotatably mounted to the body 122 and connected to the drive sprocket wheel 168 via a second drive chain 172 for rotation in unison.

[0069] Rotational movement of the driven sprocket wheel 170 is transmitted to the drive pulley 140 via the dumb-bell shaft 174 mounted to body 122 so as to be coaxially mounted to both the driven sprocket wheel 170 and the drive pulley 140.

[0070] Of course the use of sprocket wheels, gears and pulleys are interchangeable in the transmission and drive assemblies, and so is the use of drive chains and belts Other transmission means or drive assembly may also alternatively be used. The motor 156 may be electric, hydraulic, pneumatic or mechanical.

[0071] Since the configuration and operation of drive assemblies and of transmissions are believed to be well known in the art, they will not be described herein in more detail.

[0072] In operation, when the carrying surfaces of the mechanized arms 106 have to move in either a forward or a backward direction, a command signal is sent from the controller to the motor 156 that is energized. The rotation of the drive shaft of the motor 156 causes the rotation of the shaft 112 via the first drive assembly 158. The rotation of the shafts 112 then causes the rotation of the drive pulleys 140 via the second drive assemblies 160 of all the mechanized arms 106, which in turn, cause rotation of the belts 144 and therefore translation of the carrying surfaces.

[0073] As it will now become more apparent, any object (not shown) deposited onto the longitudinal arms 106 is biased towards the distal ends 134 of the fork assembly 100 by actuating the biasing assemblies 126 using the biasing assembly actuators 128.

[0074] The controller is advantageously configured so as to detect the speed of the belts 144 and therefore, indirectly the speed of the carrying surface.

[0075] Alternatively, a chain may replace the belt. Also the complete belt system of the biasing assembly may be replaced, for example, by a series of adjacent toothed wheels (not shown) that can be driven by an actuating system such as the one described hereinabove.

[0076] Of course, the carriage 102 may have other configurations allowing supporting and translating the arms 106.

[0077] It is to be noted that the mechanized arms 106 are so mounted to the carriage 102 in a parallel relationship as to yield their carrying surfaces in a common plane.

[0078] The drive system 104 allows for causing translation movements of the mechanized arms 106 along the axis 120.

[0079] Alternatively, each mechanized arm 106 may be independently motorized by a plurality of drive systems. For example, independent rail systems (not shown) may be used A single or a plurality of motors could power such rail systems. An evener system (not shown) may however be required to ensure that all mechanized arms extend simultaneously.

[0080] In addition to the management and operation of the biasing assemblies 126 of the mechanized arms 106, the controller also advantageously commands the operation of the drive system 104.

[0081] As it will be explained hereinbelow in more detail, by varying the relative speed of the carriage 102 and of the biasing assemblies 126, it is possible to obtain different configurations of stacks.

[0082] A lumber stacker 200 according to a preferred embodiment of the present invention will now be described with reference to FIG. 6. Since, the lumber stacker 200 is very similar to the conventional lumber stacker 10 described hereinabove, with the major exception of the incorporation of a fork assembly 100 according to the present invention, only the major differences will be discussed. Those differences will be enlightened in the course of the description of the operation of the lumber stacker 200.

[0083] In operation, the lumbers 26′, 26 and 26″ arrive side by side on the lumber transfer apparatus 12. The pieces of lumber 26 are then positioned perpendicular to their travelling direction. When the number of lumbers 26′, 26 and 26″ is sufficient to form a row, the liftskids 32 stop new incoming pieces of lumber. The platform 40 of the elevator 16 then lowers sufficiently to allow room for a new row of lumbers 26 and to ensure that the mechanized arms 106 of the fork assembly 100 will not contact the top of the stack 202 taking form on the platform 40. It is to be noted that the fork assembly 100 is then in its retracted position.

[0084] The carriage 102 then moves forward in the direction of the elevator 16 and the pieces of lumber fall one by one of the carrying surface formed by the mechanized arms 106 since the proximate end 38 of the lumber transfer apparatus 12 includes a slope portion 39. When the carriage 102 is at the end of its course, the fork assembly 100 is in its extended position, as illustrated in FIG. 6. The elevator platform 40 then raises until the last row of the stack 202 contact the mechanized arms 106.

[0085] Turning now to FIGS. 7A to 7D, four different ways to deposit a row from the fork assembly 100 to the platform 40, and therefore to achieve different stack configurations, are shown.

[0086] In FIG. 7A, the mechanical stop assembly 50 is positioned at a short lateral distance from the mounting frame structure 14. The controller is programmed and set to begin withdrawal of the fork assembly 100 from above the elevator 16 by commanding the drive system 104 of the fork assembly 100. The controller detects when the first piece of lumber 26′ contact the mechanical stop 50, and then commands the biasing assembly actuators 128 to move the belts 144 of the fork assembly100 in a direction opposite the direction of withdrawal of the fork assembly 100 (see arrow 204 on FIG. 7A), with a speed slightly inferior to the speed of the carriage 102. Since the pieces of lumber 26, 26′ and 26″ are biased towards the distal end 134 of the mechanized arms 106, the pieces of lumber 26, 26′ and 26″ are prevented from raising under the pressure caused by the movement of the carriage 102 and the abutment of the row of lumbers onto the stop 50 when the fork assembly 100 is moved to its retracted position. The pieces of lumber 26′, 26 and 26″ are then gradually deposited onto the stack 202. This mode of operation of the fork assembly 100 allows creating a solid stack near the first mechanical stop assembly 50.

[0087] In FIG. 7B, the formation of a solid stack near the side of the platform 40 opposite the first mechanical stop 50 is illustrated.

[0088] According to this second mode of operation of the fore assembly 100, the controller commands the biasing assembly actuators 128 so as to move the belts 144 in the direction of second mechanical stop 206, opposite the first mechanical stop 50. The pieces of lumber 26′, 26 and 26″ are then biased towards the second mechanical stop 206. The controller detects the contact of the last pieces of lumber 26″ with the stops 206 commands the drive system 104 to move the fork assembly 100 to its retracted position and the biasing assembly actuators 128 to move the belts 144 of the fork assembly 100 in a direction opposite the direction of withdrawal of the fork assembly (see arrow 204 on FIG. 7A), with a speed slightly superior to the speed of the carriage 102.

[0089] Since the pieces of lumber 26′, 26 and 26″ are biased towards the distal end 134 of the mechanized arms 106, this ensure that the pieces of lumber 26, 26′ and 26″ are again prevented from raising under the pressure caused by the movement of the carriage 102 and the abutment of the row of lumber onto the stop 206 when the fork assembly 100 is moved to its retracted position. The pieces of lumber 26′, 26 and 26″ are then gradually deposited onto the stack 202.

[0090] The third mode of operation allows creating a square stack as illustrated in FIG. 7C.

[0091] The third mode of operation is similar to the second mode with the following differences: at one point when the fork assembly 100 moves towards its retracted position, the controller commands the biasing assembly actuators 128 to stop biasing the pieces of lumber 26″, 26 and 26″, until the leftmost piece of lumber 26′ contacts the first mechanical stops 50. Then, the controller commands the biasing assembly actuators 128 so as to move the belts 144 of the fork assembly 100 in a direction opposite the direction of withdrawal of the fork assembly 100, with a speed slightly inferior to the speed of the carriage 102. The pieces of lumber 26′ and 26 still remaining on the mechanized arms are then deposited onto the stack 202. It is to be noted that in order to solidify the stack 202, it has been found advantageous to vary the time where the controller commands the biasing assembly actuators 128 to stop biasing the pieces of lumber 26′ and 26.

[0092] Turning finally to FIG. 7D, a fourth mode of operation of the fork assembly 100 will be described.

[0093] The fourth mode of operation is similar to the second mode of operation, with the following differences: when the controller detects the contact of the last pieces of lumber 26″ with the stops 206, it commands the drive system 104 to move the fork assembly to its retracted position and the biasing assembly actuators 128 to move the belts 144 of the fork assembly 100 in a direction opposite to the direction of withdrawal of the fork assembly 100 with a speed slightly inferior to the speed of the carriage 102.

[0094] This fourth mode of operation allows creating interspaces 208 between the lumber 26′, 26 and 26″ deposited onto the stack 202.

[0095] In operation, the controller detects the position of the lumbers 26′, 26 and 26″ relative to the mechanical stops 50 or 206 by detecting the position and speed of the carriage 102 or the speed of the belts 144. Alternatively, sensors (not shown) may be appropriately positioned so as to detect the position of the pieces of lumbers 26, 26′ and 26″.

[0096] Of course, the fork assembly 100 may be operated in a mode that emulates a conventional fork assembly 17 by applying no tension onto the motor 156 and therefore not actuating the biasing assemblies 126.

[0097] Although the present invention has been described in reference to the stacking of lumber, it can also be used to stack other generally rectangular objects such as veneer, boxes and board sheets to name a few.

[0098] The present invention may optionally be used with a lumber stacker equipped with a sticker placer (not shown) that allows inserting stickers 210 in the stack 202 perpendicularly to the rows of lumbers 26 (see for example FIGS. 7A-7D). Since sticker placer apparatuses are believed to be well known in the art, they will not be described herein in more detail.

[0099] Of course, a plurality of interconnected controllers may alternatively be used in place of the single controller described, each controlling a specific element of the lumber stacker 200. Of course, one of this plurality of controllers is then configured to manage the overall operation of the lumber stacker.

[0100] Although the present invention has been described hereinabove by way of preferred embodiments thereof, it can be modified without departing from the spirit and nature of the subject invention, as defined in the appended claims.