Abstract:
A wood-edger for cutting away irregularities left on the edges of wood products, such as planks or boards, comprises a succession of different transferring mechanisms cooperating to regulate the flow of wood products to be processed and to properly position the same for the ultimate edging operation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to handling of elongated elements and, more particularly, pertains to a material-handling system which is suitable for use in sawmill operations. 
     2. Description of the Prior Art 
     A log entering a sawmill is initially sawed into lumber pieces(hereinafter referred to as cants) having flat and parallel top and bottom surfaces but unfinished longitudinal side surfaces or wanes. The wanes of a cant maybe very irregular and are usually oblique to the top and bottom surfaces thereof. Accordingly, the cants have to be run through an edger to trim the wanes thereof such as to produce wood pieces having parallel side surfaces which are planar and perpendicular to the top and bottom surfaces thereof. 
     Conventional edgers generally comprise various transfer mechanisms which are adapted to transversally transport successive cants through a scanning station which is adapted to ascertain the profile of the cants. In accordance with calculations made on the basis of the profile data, the cants are conveyed and positioned on an infeed table of an edging station where the cants are longitudinally accelerated. Typically, the infeed table comprises a series of driven rollers disposed at regular intervals along the longitudinal axis of a frame for supporting and moving the cants and a series of overhead pressing rollers adapted to engage the top surface of the cants. The overhead pressing rollers are displaceable between inoperative and operative positions by means of hydraulic cylinders. Brackets are provided to connect the hydraulic cylinders to the overhead pressing rollers. 
     Although the conventional mechanisms used to transfer the cants from an intake station, through a scanning station and then onto an infeed table of an edging station perform satisfactorily, it has been found that there is a need for new and simpler transfer mechanisms which are adapted to enhance the productivity of an edging apparatus. 
     For instance, conventional cant transfer mechanisms do not allow to fill unwanted gaps between successive cants resulting from problems during the loading thereof on an entry conveyor of the edger. 
     Moreover, actual cant transfer mechanisms do not permit changing the speed of the production line according to the length of each incoming successive cant, although shorter cants require less time to be processed. Accordingly, this limitation results in a lost of productivity. 
     Another problem associated with the actual cant transfer mechanism is the premature wear of the hydraulic cylinders of the overhead pressing rollers of the edger infeed table. This is mostly attributable to the vibrations transmitted to the rollers when the same are in contact with the top surface of the cants. Furthermore, according to the above-described construction of the pressing rollers, the traveling speed of the rollers is limited, since relatively severe impacts of the rollers against the top surface of the cants can damage the cylinders. 
     SUMMARY OF THE INVENTION 
     It is therefore an aim of the present invention to provide an apparatus which is adapted to feed elongated elements. 
     It is also an aim of the present invention to provide such an apparatus which is adapted to feed elongated elements at a substantially uniform rate. 
     It is a further aim of the present invention to provide such an apparatus which is well adapted to cooperate with a scanning station and an edging station of a wood edger. 
     It is still an aim of the present invention to provide transfer mechanisms which are adapted to enhance the productivity of an edger. 
     It is still an aim of the present invention to provide a means for increasing the service life of an overhead pressing roller. 
     Therefore, in accordance with the present invention, there is provided an apparatus for feeding elongated elements at a substantially uniform rate comprising a frame having a longitudinal axis, multiple axially extending conveying means disposed in laterally spaced relationship on said frame means and adapted to be selectively driven at various speeds to move successive incoming transversally extending elongated elements along said longitudinal axis such as to provide a regular feeding rate, and means for controlling operation of said conveying means. 
     In a more specific construction, said multiple conveying means are independently and successively driven to convey one incoming elongated element at a time, thereby allowing the accumulation of one elongated element per conveying means at a delivery end of said apparatus. 
     In accordance with another general aspect of the present invention, there is provided an apparatus for transferring and orienting successive cants on an infeed table of an edging station. The apparatus comprises a frame having a longitudinal axis and at least two axially extending conveying means disposed in lateral spaced-apart relationship on said frame for moving successive incoming cants in a direction transversal to longitudinal axes thereof. Each conveying means includes first and second endless driving members. The first and second endless driving members are respectively provided with at least one first engaging means. and with at least one second engaging means. The first and second engaging means are adapted to cooperate to convey successive incoming cants along said longitudinal axis of said frame. The first and second engaging means each have opposed pushing and abutment sides. The apparatus further comprises reversible motor means for selectively driving said first and second endless driving members of said conveying means in a forward direction and a backward direction, and control means adapted to control the operation of said conveying means such as to transport successive incoming cants to the infeed table of the edging station by alternately wedging the same between said pushing side of said first, engaging means and said abutment side of said second engaging means, and between said pushing side of said second engaging means and said abutment side of said first engaging means. 
     In a further construction in accordance with the present invention, the pushing side of each said first and second engaging means is provided with compressible means, whereas said abutment side thereof is substantially rigid. 
     In accordance with a further aspect of the present invention, there is provided a method of transporting successive elongated elements transversally of respective longitudinal axes thereof. The method comprises the steps of: detecting a first incoming elongated element, positioning first engaging means adjacent a longitudinally extending upstream side of the first incoming elongated element, wedging the first incoming elongated element between said first engaging means and second engaging means located on a downstream side of the first incoming elongated element, moving said first and second engaging means in unison so as to transport said first incoming elongated element to a delivery location, moving said first and second engaging means away from said first incoming elongated element such as to position said first and second engaging means on the downstream and upstream sides of a second incoming elongated element, respectively, whereby said first and second engaging means alternately serve to push and retain the successive incoming elongated elements. 
     In accordance with a further aspect of the present invention there is provided an infeed table of an edging station adapted to cut away unfinished lengthwise extending wane surfaces of a cant to produce a dimensioned product as the cant is displaced therethrough along a prescribed edging path. The infeed table comprises infeed conveyor means for longitudinally displacing the cant into the edging station along the edging path, said infeed conveyor means including a supporting surface and a plurality of overhead roller pressing units, each said overhead roller pressing unit including first and second frame members pivotally mounted on a common pivot, said first frame member supporting a roller adapted to roll on the top surface of the cant, damping means disposed between said first and second frame members to absorb vibrations transmitted to said roller, and means for acting on said second frame member to displace said roller between an inoperative position wherein said roller is out of engagement with the cant and an operative position wherein said roller engages a top surface of the cant. 
     In accordance with a further aspect of the present invention there is provided an apparatus for feeding one element at a time, comprising frame means defining a longitudinal axis, a series of conveyors supported by said frame means and adapted to move incoming elements in a feeding direction parallel to said longitudinal axis, sensing means for detecting the space between successive incoming elements, and control means coupled to said sensing means and adapted to operate said conveyors to create a differential of speed between said conveyors such as to provide a desired spacing between the elements. 
     In accordance with a further aspect of the present invention there is provided a method for feeding one element at a time, wherein the elements are conveyed along a feeding direction by a series of conveyors, comprising the steps of: ascertaining the spacing between successive incoming elements, generating related spacing data, and on the basis of said spacing data, creating a differential of speed from one conveyor to another to provide a desired spacing between the elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus generally described the nature of the present invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which: 
     FIG. 1 is a schematic top plan view of a wood edger in accordance with the present invention; 
     FIG. 2 is a schematic side elevational view of the wood edger of FIG. 1; 
     FIG. 3 is a schematic top plan view of a scanner delivery station of the wood edger of FIG. 1; 
     FIG. 4 is a top plan view of one module of a positioning apparatus of the wood edger; 
     FIG. 5 is fragmentary cross-sectional view taken along lines  5 — 5  of FIG.  4  and showing the construction of a cant engaging member thereof; 
     FIG. 6 is a simplified end elevational view of the module of FIG. 4, showing the disposition of two rollers of an edger infeed table with respect thereto; 
     FIGS. 7 a  to  7   d  are schematic side elevational views of the positioning apparatus, illustrating the sequence of operations thereof; 
     FIGS. 8 a  and  8   b  are side elevational views of an overhead pressing roller of the edger infeed table respectively shown in an inoperative position and an operative position thereof; and 
     FIG. 9 is a top plan view of the pressing roller of FIGS. 8 a  and  8   b.   
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now referring to the drawings, and in particular to FIGS. 1 and 2, a wood edger in accordance with the present invention and generally designated by numeral  10  will be described. 
     The wood edger  10 , as will be explained hereinafter, is adapted to cut away the irregularities or flaws left on the longitudinal side surfaces of elongated wood pieces or cants C cut from debarked logs. Accordingly, cants C having flat and parallel top and bottom surfaces and unfinished lengthwise extending wane surfaces may be converted into finished pieces having parallel side surfaces which are plane and perpendicular to the top and bottom surfaces thereof. 
     Basically, the wood edger  10  comprises a number of transfer or feeder mechanisms which are adapted to transversally transfer successive cants C from an intake station  12 , through a scanning station  14 , and then onto an infeed table  16  of an edging station  18  where the cants C are longitudinally accelerated. 
     The scanning station  14  detects the profile of the cants C and generates related data that are processed by a control system (not shown) to determine the position of the circular saws (not shown) of the edging stations  18  and to adjust the orientation of the cants C on the infeed table  16  before being fed through the edging station  18 . This permits minimizing the amount of material to be trimmed so as to produce the largest possible product. 
     As seen in FIGS. 1 and 2, the intake station  12  includes two consecutive inclined multiple chain conveyors  20  and  22 . The multiple chain conveyor  20  comprises a number of parallel endless chains  24  which are driven in unison by means of driving sprockets engaged with the endless chains  24  at the delivery end of the first multiple chain conveyor  20 . Similarly, the multiple chain conveyor  22  is provided with a number of parallel endless chains  28  which are driven by means of driving sprockets  30  engaged with the chains  28  at the delivery end of the multiple chain conveyor  22 . The cants C to be processed are transversally dragged one by one along the supporting surfaces of the inclined multiple chain conveyors  20  and  22  by attachments inserted at intervals in the endless chains  24  and  28 . Lateral guide plates  32  are also provided along the sides of the multiple chain conveyors  20  and  22  to keep the cants C from running off. 
     The cants C are then successively transferred to an aligning station  34  where an operator may intervene to remove non-desired cants and properly position the same, if need be. The aligning station  34  consists of a horizontal multiple chain conveyor that is composed of a plurality of parallel endless chains  36  driven in unison by sprockets  38  mounted on a driving shaft  39  disposed at a delivery end of the aligning station  34 . fit an Driven spiral rolls (not shown) are mounted in the endless chains  36  and are driven in synchronism therewith. A driven endless chain  40  engaged at opposed ends thereof with sprockets  42  mounted on vertical shafts is provided along one side of the aligning station  34  to cooperate with the spiral rolls (not shown) in aligning one end of the cants along a common reference line extending in the feeding direction on the opposed side of the aligning station  34 . It is noted that, according to the illustrated embodiment, the driven endless chain  40  forms and angle of about 6° with the feeding direction of the cants C. 
     From the aligning station  34 , the successive cants C are discharged to a spacing station  46  which includes a series of three multiple chain conveyors  48 ,  50  and  52  independently driven by respective motors  54 ,  56  and  58  to move the cants C transversally of their longitudinal axes. The multiple chain conveyors  48 ,  50  and  52  each comprise a plurality of parallel endless chains  60  disposed in a laterally spaced-apart relationship on a frame structure  62 . The spacing station  46  further includes a sensing system (not shown) which is coupled to the control system (not shown) to analyse the space between the cants C. Accordingly, for two successive cants, the control system computes the distance existing between the cants C and consequently increases or reduces the feeding speed of the conveyor on which the upstream or second cant is supported such as to provide a desired space between the two. More generally, it can be said that based on the sensing data, the control system. creates a differential of speed through the conveyors so as to obtain a desired spacing between the cants C. It is understood that different numbers of conveyors may be provided to obtain the intended result. 
     In the event that two cants C overlap, the operator can reduce the speed of the preceding conveyor in order to create a required space for the cant C in excess. Then, the operator may place the excess cant behind the first cant. Therefore, this permits to maintain a substantially uniform space between the cants. 
     It is also noted that, since the movement of the cants C is continuous, it is possible to reduce the average speed of the multiple chain conveyors  48 ,  50  and  52 , thereby facilitating the transportation of the cants C and the work of the operator. 
     Moreover, another advantage of the present invention resides in the fact that the empty spaces, due to loading problems that occurred at the intake station  12  and to rejections of deficient cants by the operator, may be filled by adjusting the relative speed of the multiple chain conveyors  48 ,  50  and  52 . 
     The cants C are then transferred one by one from the spacing station  46  to a scanner infeed station  64 . The scanner infeed station  64  consists of a feeding apparatus comprising a frame  65  on which a plurality of parallel endless chains are disposed in a laterally spaced-apart relationship. Referring now more specifically to FIG. 3, it can be seen that the endless chains are grouped in five sets of three chains identified by reference numerals  66 ,  68 ,  70 ,  72  and  74 , the chains of a same set being driven in unison by a common motor. Accordingly, the sets of chains  66 ,  68 ,  70 ,  72  and  74  are driven by respective motors  76 ,  78 ,  80 ,  82  and  84 . The motors  76 ,  78   80 ,  82  and  84  are coupled to respective driving shafts  86 ,  88 ,  90 ,  92  and  94  extending transversally of the longitudinal axis of the chains. The driving shafts  86 ,  88 ,  90 ,  92  and  94  are provided with respective sets of three sprockets  96 ,  98 ,  100 ,  102  and  104  distributed along the length thereof such as to engage the set of chains associated therewith. The chains are provided with attachments  106  for engaging and moving the cants C forward. The cants C are, transported above the chains on a plurality of longitudinal rails  108  extending along the sides of the chains. 
     A sensing system (not shown) adapted to detect the space between the cants C emanating from the last multiple chain conveyor  52  of the spacing station  46  commands, through the control system, the successive activation of the sets of chains  66 ,  68 ,  70 ,  72  and  74  to transport one cant at a time in front of the scanning station  14 . Each set of chains  66 ,  68 ,  70 ,  72 ,  74  accumulates one cant. The sensing system is further adapted to ascertain the. width of the incoming cants in order to control the relative position of the attachments  106  of the sets of chains  66 ,  68 ,  70 ,  72  and  74 . Accordingly, a uniform space between adjacent cants accumulated on the upstream side of the scanning station  14  is provided. As the set of chains  66 ,  68 ,  70 ,  72  and  74 . are independently driven, it is possible to vary the speed thereof according to the number of cants waiting in front of the scanning station  14 . The scanner infeed station  64  also optimises the productivity of the wood edger  10  in that it increases the rate at which shorter cants are fed. Indeed, it is advantageous to be able to vary the advancing speed of the cants, as shorter cants require less time to be processed. 
     FIG. 3 illustrates two successive cants C and C′ which are moved transversally of their longitudinal axes toward the scanning station  14  by the first set of chains  66  and the second set of chains  68 , respectively. The chains of the first set  66  are driven in unison to cooperate in transporting the cant C by means of their attachments  106   a.  Similarly, the chains of the second set  68  are driven in unison to cooperate in transporting the cant C′ by means of the attachments  106   b.  The attachments  106  of the first and second sets of chains  66  and  68  are respectively engaged at three spaced-apart locations on a longitudinally extending upstream surface of the cants C and C′ to push the same forward. The relative speed of the first and second set of chains  66  and  68  is controlled so as to provide a uniform feeding rate, as explained hereinbefore. Indeed, the cant C and C′ may be simultaneously supported on the snapper infeed station  64 , while not being advanced at the same speed. 
     It is understood that the number of sets of chains and the quantity of chains per set may vary in accordance with the length of the cants and the number of cants to be accumulated in front of the scanning station  14 . It is noted that the sets of chains  66 ,  68 ,  70 ,  72  and  74  could be replaced by corresponding sets of endless belts. 
     From the scanner infeed station  64 , the cants C are transferred onto a conveyor  110  extending through the scanning station  14 . The conveyor  110  is composed of at least two laterally spaced-apart parallel endless chains or belts driven in unison. The speed of the conveyor  110  may be adjusted in accordance with the desired number of cants to be processed per minute. 
     The cants C carried by the conveyor  110  through the scanning station  14  are optically scanned to detect the profile thereof. As mentioned hereinbefore, the data obtained during scanning are processed by the control system (not shown) to establish the orientation of the cants and the position of the circular-saws (not shown) of the edging station  18 . 
     Once a cant has been scanned, it is positioned onto the edger infeed table  16  by an edger positioning apparatus  112 . As seen in FIG. 1, the edger positioning apparatus  112  comprises three modules  114  which are disposed in lengthwise parallel laterally spaced relation to one another on a downstream side of the scanning station  14 . It is noted that depending on the length of the cant emanating from the scanning station  14 , only the two modules  114  that are nearest to the ends of the cant may be operated by the control system (not shown) to position the cant on the edger infeed table  16 . 
     Referring now more specifically to FIG. 4, it can be seen that each module  114  includes first and second side by side extending conveyors  116  and  118  which are driven by respective reversible motors  120  and  122 . Each module  114  further includes a supporting member  123  disposed between the first and second conveyors  116  and  118  to fill the gap between the delivery end of the conveyor  110  and the edger infeed table  16 . The first conveyor  116  includes an endless belt  124  having three cant engaging members  126   a,    126   b  and  126   c  secured at regular interval thereon. Similarly, the second conveyor  118  includes an endless belt  128  having three cant engaging members  130   a,    130   b  and  130   c  secured at regular intervals thereon. Each cant engaging member  126 ,  130  has a front pushing side  132  and a rear abutment side  134 . 
     In operation, as shown in FIG. 7 a,  a sensor (not shown) disposed in the area of the delivery end of the conveyor  110  and the receiving end of the edger positioning apparatus  112  detects the presence of a cant C and then sends a signal to the control system (not shown) to activate the first conveyor  116  of at least two modules  114  such as to position the front pushing side  132  of the cant engaging member  126   a  thereof adjacent an upstream longitudinal surface of the cant C. The cant C is then pushed by the cant engaging members  126   a.    
     At this time, the second conveyor  118  of each elected module  114  is not activated and thus the cant engaging member  130   a  is immobile at a certain distance downstream of the cant C. As the control system (not shown) has already obtained and analysed the profile data of the cant C, it can control the speed and the advancement of the second conveyors  118  such as to properly wedge the cant C between the front pushing side  132  of the cant engaging member  126   a  of each operated first conveyor  116  and the rear abutment side  134  of the cant engaging member  130   a  of each operated second conveyor  118 , as illustrated in FIG. 7 b.  It is noted that the wedging operation of the cant C is effected while the first conveyors  116  are driven to move the cant C toward the cant engaging member  130   a  of the second conveyors  118 . 
     Once the cant C is properly held in position between the cant engaging members  126   a  and  130   a,  the first and second conveyors  116  and  118  are driven in unison to transversally transport the cant onto the edger infeed table  16 , as illustrated in FIG. 7 c.  The alignment and the position of the cant C with respect to the circular-saws (not shown) of the edging station  18  are controlled by the control system which positions the first and second conveyors  116  and  118  of the elected modules  114 . 
     For the sequence illustrated in FIGS. 7 a  to  7   c,  the cant engaging members  126   a  serve as pushing members behind the cant C, whereas the cant engaging members  130   a  serve as abutment members in front of the cant C. 
     Once the cant C has been positioned on the edger infeed table  16 , the first conveyors  116  are driven backward, while the second conveyors  118  are driven forward, as illustrated in FIG. 7 d.  At this stage, the cant engaging members  126   a  will serve as abutment members for the next incoming cant C′, whereas the cant engaging members  130   a  will eventually return to the receiving end of the edger positioning apparatus  112 ′ to push an incoming cant. 
     The cant engaging member  130   c  of the second conveyors  118  and the cant engaging member  126   a  of the first conveyors  1116  will then cooperate to move the next incoming cant C′ as per the way described hereinbefore. 
     Accordingly, it can be said that the cant engaging members  126  and  130  alternately serve to push and retain the cants. 
     FIGS. 5 and 6 illustrate, in greater detail, the construction of the cant engaging members  126  and  130 . More particularly, each cant engaging member  126 ,  130  includes a base portion  136  and an upwardly protruding portion  138  extending substantially at right angle therefrom. A sleeve member  140  fitted over the upwardly protruding member  138  is normally urged in a forward position relative thereto by two compression springs  142  extending from two vertically spaced-apart horizontal bores  144  defined in a front surface of the upwardly protruding portion  138 . 
     This construction provides a front pushing side  132  which is compressible to compensate for inaccurate positioning of the cant engaging members  126  and  130  by the control system, while still having a rigid rear abutment side  134  to retain the cant. 
     The first and second conveyors  116  and  118  are provided with lateral guides  146  which extend on the sides of the belts  124  and  128  to laterally restrain the motion of the cant engaging members  126  and  130 . The lateral guides have a L-shaped configuration and include a portion which extends above the base portion  136  of the cant engaging members  126  and  130  to limit upward movements thereof. 
     It is understood that the number of modules  114  of the edger positioning apparatus  112  may be different than three and that the first and second conveyors  116  and  118  thereof may consist of chain conveyors instead of belt conveyors. Furthermore, the number of cant engaging members per conveyor could be less or more than three. 
     As seen in FIGS. 4 and 6, the edger infeed table  16  includes a number of retractable cant supports  148  which are adapted to receive the cants from the edger positioning apparatus  112 . The retractable cant supports  148  are disposed near the modules  114  of the edger positioning apparatus  112  and are rockable between raised and lowered positions about axes which are parallel to the feeding direction of the edger positioning apparatus  112 . The retractable cant supports  148  enable to temporarily maintain the cant above a conveying surface  150  of the edger infeed table  16 . 
     The conveying surface  150  of the edger infeed table  16  is composed of a number of driven rollers  152  which are disposed between the modules  114  of the edger positioning apparatus  112  for longitudinally accelerating the cants in a direction transversal thereto. 
     As seen in FIG. 2, the edger infeed table  16  further includes a series of overhead pressing rollers  154  which are adapted to engage an upper surface of the cants C to guide the same into the edging station  18 . 
     Referring now more specifically to FIGS. 8 and 9, each overhead pressing roller includes first and second frame members  156  and  158  which are pivotally mounted on a common pivot  160 . The first frame member  156  supports at a first end thereof a roller  162  which is adapted to roll on the top surface of the cants. 
     A pair of pneumatic bladders  164  are disposed between the first and second frame members  156  and  158  of each overhead pressing roller  154  to act as a damping member in order to absorb vibrations transmitted to the roller  162 . The pressure inside the bladders may vary to adjust the pressure of the roller  162  on the cants C. The damping member could also be other means, such as hydraulic and pneumatic cylinders, springs and resilient links. 
     As seen in FIGS. 8 a  and  8   b,  each overhead pressing roller  154  includes a pneumatic or hydraulic cylinder  166  which is pivotally mounted to a main frame structure  168  of the infeed table  16  to act on the second frame member  158  such as to selectively raise and lower the roller  162  in an inoperative position wherein the roller  162  is out of engagement with the cant and an operative position wherein the roller  162  engages a top surface of the cants. 
     The first and second frame members  156  and  158  are provided with cooperating abutment members  170  and  172  which are adapted to assist the cylinder  166  in maintaining and displacing the roller  162  in the inoperative position thereof. 
     In operation, the cant is maintained above the driven rollers  152  by the retractable cant supports  148  to permit the cant engaging members  126  and  130  to move away from the cant and the overhead pressing rollers  154  to reach their operative position. Then, the retractable cant supports  148  are pivoted to their lower position to permit the engagement of the cant C by the driven rollers  152 . 
     The cant C is then longitudinally translated through the edging station  18  where circular-saws (not shown) trim the unfinished longitudinal wane surfaces of the cant C. 
     The edged cant can then be transferred to a discharge table  174  where it can be conveyed to an appropriate storing facility. 
     It is noted that the present invention has been described in the context of a sawmill, since the transfer and orientation of a wood cant particularly exemplifies the problems to which the present invention is directed. However, it is understood that the invention is applicable to workpieces other than wood cants, such as, for instance, elongated steel elements produced during rolling mill operations.