Patent Application
20120198669
The present disclosure generally relates to apparatus used in forming engineered wood products. More particularly, the present disclosure relates to an apparatus for compressing a fibrous mat to achieve a uniform density.
Processing the trees into engineered products involves a number of steps. One of the steps is crushing young trees (stripped of branches) to obtain loose bundles of fibrous strands. The bundles of fibers are formed into mats of crushed fibers with the fibers being generally parallel. Resin is added as well as other binding agents and the mat is dried under pressure to eventually reach a target moisture content and density. After the fibers are formed into mats and before resin is added the mats must be processed to provide a uniform density of fibers across the width W (i.e., perpendicular to the direction of the fibers, see
It is important for the mat to have a uniform density of fibers across the entire mat width W so that the resulting wood product has uniform and predictable strength. Density variation can cause failure of the wood product in use, which can have disastrous effects where the wood product is load bearing.
Old growth unprocessed wood generally has been more desirable for making engineered wood products than new growth unprocessed wood or pulpwood, in part because of the lower moisture content of older trees. Pulpwood is commonly defined as wood that is about 12-60 years of age or of a certain diameter (to be distinguished from veneer or dimension lumber). Old growth trees are rapidly vanishing as forests are depleted. New “immature” tree farms are increasing in development to provide a nearly limitless source of such wood. Such farms can grow trees at a faster rate using modern technology. Immature trees can be harvested at a younger age than old grow trees, however, there is a greater variation of fiber density in immature trees than in old growth trees, resulting in a need for improved methods of producing uniform density mats.
One type of conventional apparatus which attempts to create a uniform density mat of fibers utilizes a pair of parallel vertical opposing plates between which is inserted a mat coming off, for example, a scrim line, to be compressed (also referred to as “densified”). One or both plates are connected to a reciprocating drive mechanism which drives the plates toward each other, compressing the fibrous mat therebetween. A challenge with this apparatus is that the compressive force is applied to the front and rear edges (4, 6 in
It would be desirable to have an apparatus which could densify a fibrous mat uniformly across the mat and improve the resulting strength characteristics. It would also be desirable to use density to control moisture content.
In one exemplary embodiment of the present disclosure an apparatus is provided for uniformly densifying a fibrous mat. A densifying assembly includes a set of parallel bars each having a row of pins extending downward therefrom which can engage the mat fibers, a plurality of shafts along which the bars slide so as to maintain the bars parallel, a plurality of extendable accordion linkages connecting the set of bars, and a linear positioning assembly having a reciprocating drive mechanism coupled to one of the bars which can move the bars in response to an actuation signal. As the drive mechanism retracts the bar to which it is coupled the spacing between the rows of bars is decreased uniformly and the rows of pins draw the fibers together and compress them uniformly across the width of the mat.
In another exemplary embodiment an apparatus is provided including a carriage frame having front and rear rails, left and right side rails, a plurality of downwardly extending brackets, each bracket having a roller mounted thereon by a bearing. The apparatus further includes a densifier assembly comprising a plurality of generally parallel elongated bars comprising a plurality of passive bars disposed between a drive bar and a static bar, the static bar being connected to the carriage frame, a plurality of pins associated with and extending downward from the drive bar and each of the passive bars; a plurality of extendable and retractable accordion linkages arranged generally parallel to each other and generally perpendicular to the bars, each accordion linkage being associated with at least one point on each bar, the accordion linkages being adapted to maintain each row of elongated bars in a generally parallel relationship to each other and permitting the distance between the bars to expand or contract proportionately so that the spacing between the rows of bars is equal while the overall spacing between adjacent bars increases or decreases, and a plurality of shafts slidingly associated with the passive bars and the drive bar and fixedly associated at one end with the static bar; at least one linear positioning assembly having a reciprocating drive member having a first and a second end, the first end being attached to the carriage frame, a coupler for coupling the second end of the reciprocating drive member to the drive bar, and, a motor operatively associated with the reciprocating drive member; a vertical positioning assembly including at least one support plate connected to the frame, and at least one reciprocating drive mechanism connected to the at least one support plate for raising and lowering the bars; a main frame having at least four legs, a pair of front and rear members, a pair of opposing side members, the densifier assembly and carriage frame being slidingly positioned and the rollers resting on the pair of side members, a conveyor, and a reciprocating drive mechanism connected to the main frame and to the carriage assembly; a weight detector for weighing the mat to obtain weight data; a surface area sensor for detecting the surface and edges of the mat to obtain square footage data; and, a processor in communication with the weight detector and the surface area sensor for calculating a densification value based on the weight and square footage data indicating the distance the drive bar must travel in order to provide a desired densification. The drive bar is reciprocatingly slidable in response to actuation by the linear positioning assembly motor and drive shaft. The rows of pins are insertable in the mat and when the drive bar is urged toward the static bar the passive bars move so as to decrease the distance between rows of bars and cause the pins which are inserted into a mat to compress the mat in a direction across the face of the mats and generally uniformly along the length of the mat.
In another embodiment of the present disclosure, the apparatus described hereinabove further includes a stripper assembly for removing fibrous material which may adhere to the pins after removal of the pins from the mat when the densification has been achieved. The stripper subassembly assembly includes a frame; a plurality of stripper members associated with the frame; a plurality of gaps defined in the stripper members, a pin being insertable into and removable from a gap; a positioning mechanism for raising and lowering the frame and stripper members with respect to the pins such that the stripper members are proximate to the pins and strip the pins of fibers or other material when the pins pass through the gaps.
In another embodiment of the present disclosure, an apparatus is provided for densifying a mat having fibers aligned in a generally parallel direction and having a front edge and a rear edge parallel to the direction of the fibers whereby the distance between the front and rear edges defines the width of the mat, the apparatus including means for providing a uniform compressive force to the mat, the compressive force being applied at a plurality of points throughout the mat and substantially the entire width of the mat so as apply substantially the same compressive force to substantially all the fibers at the same time so as to achieve a substantially uniformly densified mat.
Another embodiment of the present disclosure provides a method for increasing the density of a fibrous mats, the mat having a grain defined as the direction of the face of the mat, comprising (a) weighing a mat to obtain weight data; (b) scanning the mat with a detection device to obtain square footage data; (c) determining from the weight and square footage data a densification value indicating how much the mat is to be compressed; (d) actuating an apparatus for increasing the density of the mat, the apparatus being as described hereinabove; and, (e) moving the rows of pins so as to compress the mat substantially uniformly across the grain of the mat. The method may also include a step (f) moving the compressed mat of step e) away from the linear positioning apparatus and toward a location for stacking a plurality of compressed mats. The method may also include a step (g) resetting the rows of pins to accommodate another mat. The method may also include a step (h) assembling a plurality of sets of compressed mats and cutting the sets of mats to a desired length.
Another embodiment of the present disclosure provides a mat formed by the method disclosed herein. The mat has a substantially uniform density. The mat also has substantially uniform moisture content.
A feature of the apparatus of the present disclosure is that by controlling densification of the mat during processing, the moisture content can be controlled.
The invention is illustrated in the drawings in which like reference characters designate the same or similar parts throughout the figures of which:
Overall Apparatus
Steam press scrim lumber (“SPSL”) is composed of processed mats of fibers obtained by crushing and processing logs of generally small diameters. A conventional mat 1 (see
The main assemblies include a main frame, carriage frame assembly, and densifier assembly. The densifier assembly includes a densifying subassembly and a stripper subassembly.
Main Frame
It is to be understood that in the present disclosure reference to air cylinders, pistons, actuators or other linear motion-inducing devices is intended to include other drive mechanisms, such as, but not limited to, pneumatic, hydraulic, belt, ball screw, chain drive, and the like. Such devices are also intended to include (if not specifically mentioned) associated valves, actuators, motors, PLC communication connections and the like normally associated with such devices for ordinary functioning. It is also to be understood that reference to a particular number of such devices is intended to include at least that number and the scope of the present disclosure include additional (or possibly fewer) units, unless otherwise specifically excluded.
The main frame 100 is divided into two main areas, a densification area 126 and a mat gathering area 127 (see
Carriage Frame Assembly
The carriage frame assembly 21 has mounted to it a pair of vertical raising and lowering actuators 95 and associated mechanism for raising and lowering the densifier assembly 20 in response to an electronic signal from the processor 140 (discussed in more detail hereinbelow). The carriage frame assembly 21 has also mounted to it a pair of actuators 66 and associated air valves for raising and lowering a stripper assembly 21. Thus, the densifier assembly 20 is raised and lowered with respect to the carriage frame assembly 21 so that a mat 1 can be positioned under the densifier assembly 20. The stripper subassembly 60 The carriage frame assembly can move horizontally on the main frame 100.
Densifier Assembly
The densifier assembly 20 consists generally of a densifying subassembly 19 and a linear stripper subassembly 60.
Densifying Subassembly
The densifying subassembly 11 also includes a number of elongated passive densifying bars 22 (see
The densifying subassembly 20 has at least one, and, in one exemplary embodiment, a plurality of extensible accordion linkages (also known as extensible scissors linkages) 42 spaced across the bars 22, 28, 30. In one embodiment the accordion linkages 42 are mounted on top of the bars 22, 28, 30. Each accordion linkage 42 is attached via at least one pin 44 to each bar 22, 28, 30. The accordion linkages 42 function to maintain the bars 22, 28, 30 in a generally equal spaced relationship; in other words, as the passive and drive bars 22, 30 are moved along the shafts 26 the accordion linkages 42 maintain the same relative distance between each bar 22, 30.
The densifying subassembly 11 includes at least one (two are shown in the drawings) stop assemblies 15 (see
The passive and drive bars 22, 30 are moved along the shafts 26 by means of a linear positioning actuator 50 (see
Stripper Subassembly
The apparatus 10 may also include a stripper assembly 60 (see
In an alternative embodiment, rather than being L-shaped plates, the strippers may be generally flat elongated plates which have holes or openings in which the pins 40 may be inserted or removed. The holes are sized to be close in diameter to the diameter of the pins 40 so that when the pins are removed from the densified mat the pins 40 pass through the holes and the edge of the hole scrapes extraneous matter (e.g., fibers and resin) from the pins 40. Alternatively, other configurations of stripper devices can be used, such as doctor blades, spring mounted flexible pieces of materials (e.g., metal), brushes, scrapers or the like.
The stripper subassembly 60 can be vertically raised and lowered and guided by vertically mounted shafts 65 and bearings which are attached to the top of the carriage frame assembly rails 86, 88 and driven by a pair of actuators 66 mounted on the carriage frame assembly 21.
As shown in
During the densification process mat fibers may stick to the pins 40. The stripper subassembly helps to remove mat fibers from the pins 40 when the pins 40 are removed from a densified mat 9. When the pins 40 are withdrawn from a mat they pass through the stripper surfaces 62, which scrape off the fibers from the pins 40. The densifying subassembly 11 and stripper subassembly 60 can be raised and lowered independently of each other. The stripper subassembly 60 is mounted on the carriage frame assembly 21 and the densifying subassembly 11 is mounted above the stripper subassembly 60 on the carriage frame assembly 21.
The relative movement of the assemblies and subassemblies with respect to the main frame 100 is described as follows. The carriage frame assembly 21 itself can move horizontally on the main frame 100. The densifier assembly 20 can be raised and lowered with respect to the carriage frame assembly 21 so that a mat 1 can be positioned under the densifier assembly 20. The stripper subassembly 60 can be raised and lowered independently of the densifying subassembly 11 so that the pins 40 can be stripped of extraneous material.
Measuring Sensors and Logic Control
An infeed conveyor assembly 128 (see
A programmable logic controller (“PLC”) 140 (not shown) is in electronic communication with the linear positioning drive motor 58, densifier assembly vertical positioning cylinders 95, the linear positioning assembly drive motor(s) 58, the stripper subassembly actuators 66, the carriage drive motors 116, and/or various other components. The PLC 140 is also in communication with the weight sensor 130 and the surface area detector 132. Preferably, the PLC 140 includes a user interface control panel 142 (not shown) for programming and operating the PLC 140.
Exemplary Method
One exemplary method of densifying a mat 1 using the apparatus 10 of the present disclosure is now described, with reference to the flow diagram shown in
The mat 1 is introduced by the infeed belt 129 and is weighed by the weight sensor 130 and scanned (for surface area) by the surface area detector 132. From this information the PLC 140 calculates the amount of densification needed to achieve the desired mat density. The PLC 140 determines the distance the linear positioning screw 54 must travel and the distance the drive bar 30 must travel to compress the mat 1.
The mat 1 is fed to the densification area 127 underneath the densifier assembly 20 by the introduction conveyor 128. The mat 1 is oriented on end with the fibers 2 being in a direction generally parallel to the bars 22. The mat 1 may have variable fiber density across the mat prior to densification, such as lower fiber density areas 7 and higher fiber density areas 8. The densifier assembly 20 is initially configured so that the distance between the drive bar 30 and the static bar 28 is roughly the width W of the mat 1. The densifier assembly 20 is raised and lowered by the vertical actuators 95 so that the pins 40 are pushed into or removed from the fibers 2.
The linear positioning actuator 54 is actuated by the PLC 140 and the drive bar 30 is drawn toward the stop block. The passive bars 22 move simultaneously, with the accordion linkages 42 maintaining the same relative spacing “Sp” between the bars 22 as the distance between the bars decreases. The pins 40 push and compress the individual fibers (or bundles of fibers) together uniformly.
One feature of the presently described apparatus and method is that the result of having all the pins 40 on all the passive bars 22 and drive bar 30 moving the same proportionate distance at the same time is that substantially the entire mat 1 (from the front edge 4 to the rear edge 6) is compressed by the same amount. Thus, the density of the densified mat 90 is now essentially uniform across the width W of the mat. This is in contrast to prior densification apparatus, which typically sandwich the mat between two external plates which drive the front edge toward the rear edge.
After the mat 1 (now identified as densified mat 9) is compressed to the desired width, the carriage frame assembly 21, with densifier assembly 20 (and a mat 9 with the pins 40 still inserted therein), rolls on the main frame side rails 106, 108 in response to actuation of the main frame side rail pistons 114 and away from the densification area 127 and onto the exit conveyor 120. The stripper subassembly 60 is raised just prior to raising the pins 40. The densifier assembly 20 is raised by the actuators 95 and the pins 40 are removed from the mat fibers 2. The carriage frame assembly 21 is moved horizontally back to the densification area 126 for processing of the next mat 1. The densified mat 9 is conveyed toward the back stop 118 which has a gathering area 127 at the end of the conveyor 120. Densified mats 9 are crowded together and accumulated in this gathering area 127. These sets of mats 9 can be further processed, such as cut and stacked. The process is repeated with the next mat 1 being fed into the densification area 126.
The following describes one nonlimiting example of the method described above using an example of measurements and calculations to illustrate the densification determination. The surface area detector 132 scans the surface area of the mat 1. The square footage determines the “starting” width of the mat 1. The PLC 140 actuates the linear positioning actuator 50 and sets the initial spread of the pins 40 so that all the rows of pins 40 are in the fibers 2. The PLC 140 is programmed and preset for a given mat width or density.
A 30 inch wide by 9 foot long mat (22.5 sq ft) may weigh about 65 lbs. The PLC 140 calculates the starting density from these numbers as being 3.0 lb/sq. ft. A desired end density, e.g., 3.4 lb/sq. ft, is programmed into the PLC 140. Accordingly, the surface area needs to be compressed from 22.5 sq. ft down to 19.1 sq. ft to achieve this density. The width W needs to be compressed 4.5 inches, i.e., from 30 inches wide to 25.5 inches wide. The PLC 140 actuates the linear positioning actuator 50 to move the drive bar 4.5 inches. The accordion linkage 42 retracts and pins 40 drive and compress the fibers 2 substantially evenly across the mat 1 to achieve the desired width and thus the desired density. It is to be understood that compression, while occurring substantially evenly, may still result in areas of small density variation across the width of the mat.
A feature of the presently described densification method and apparatus is that the densified mat 9 stays densified after the pin force is released. If the mat had been compressed only by squeezing the front and rear mat edges 4, 6 toward each other, the mat 9 would tend to decompress because it was not compressed uniformly.
The densified mat 9 formed by the apparatus and method of the present disclosure has a more uniform density and moisture content across the width W of the mat than has been achievable by other known techniques. The density of the mat to be formed by the apparatus and method described herein can be selected by the apparatus operator. The density variation can be
The apparatus and method of the present disclosure can be adapted for use with materials other than crushed wood mats and the densifier assembly can be used to increase the density of any of a variety of materials which can accommodate the pins 40. The densifier assembly 20 can be adapted to have the pins 40 be marking “fingers” and used to create a set of rows of marks across a mat or sheet of material. Alternatively, rather than pins, lasers, cutters or drill bits can be substituted so that a set of uniform and controllable width rows of holes can be created in a sheet of material, such as steel, by having the hole-creating devices lowered onto the sheet of material from above. The apparatus 10 can be adapted for creating a uniform density of large foam or cotton particles in creating mattresses or other articles requiring a uniform density of material and where the pins 40 can be inserted into and removed from the material to be densified.
Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims.
Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect.
As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.
The headings of various sections are used for convenience only and are not intended to limit the scope of the present disclosure.
Throughout the description and claims of this specification, the word “comprise” and variations of the word, such as “comprising” and “comprises,” means “including but not limited to,” and is not intended to exclude, for example, other additives, components, integers or steps. “Exemplary” means “an example of and is not intended to convey an indication of a preferred or ideal embodiment. “Such as” is not used in a restrictive sense, but for explanatory purposes.
Disclosed are components that can be used to perform the disclosed methods, equipment and systems. These and other components are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc., of these components are disclosed that while specific reference of each various individual and collective combinations and permutation of these may not be explicitly disclosed, each is specifically contemplated and described herein, for all methods, equipment and systems. This applies to all aspects of this application including, but not limited to, steps in disclosed methods. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific embodiment or combination of embodiments of the disclosed methods.
It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope or spirit. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit being indicated by the following inventive concepts.
It should further be noted that any patents, applications and publications referred to herein are incorporated by reference in their entirety.
