WO2006034594A1

WO2006034594A1 - Face gluing apparatus and method

Info

Publication number: WO2006034594A1
Application number: PCT/CA2005/001499
Authority: WO
Inventors: Eric Cable
Original assignee: Eric Cable
Priority date: 2004-09-30
Filing date: 2005-09-29
Publication date: 2006-04-06

Abstract

A method and apparatus (10) for assembling, gluing and clamping wood pieces (90) to produce an engineered wood product. A glue application system (30) connected to a frame applies glue to a wood lath (90) being conveyed onto a retractable lath support (25, 26), which then retracts in order to drop the lath onto an assembly surface wherein a clamping system (50, 60) operably connected to the frame applies a perpendicular clamping pressure to the assembly surface to form a glued wood product.

Description

FACE GLUING APPARATUS AND METHOD

FIELD OF THE INVENTION

The present invention relates generally to the field of wood product assembly. More particularly, the present invention relates to an apparatus for assembling, gluing, and clamping wood pieces to produce an engineered wood product.

BACKGROUND OF THE INVENTION

In the lumber industry, various applications or projects may require a specific size or strength of wood product. As is known, the wood product may be a solid board cut to a specific size, or an engineered product created by joining together wood blocks or pieces in a specific orientation. For example, small blocks of lumber may be assembled end to end using a glued fingerjoint, and fingerjointed or natural lumber may be glued edge to edge or face to face into a panel or beam.

In the assembly of engineered products, there are two generally types of glue used in wood product assembly, slow curing and fast curing glues. Slow curing glues provide the user with substantial working time prior to curing of the glue, but require the assembled product to be held or clamped for a relatively long time (often several hours) during the curing process to ensure proper bonding between adjacent pieces of wood.

This lengthy clamping time reduces manufacturing efficiency by limiting the flow of products through a manufacturing facility. Faster setting glues, such as polyurethane glues, require substantially shorter clamping times, but also cure quickly upon exposure to air or water, thereby providing limited time for manipulation of the pieces into an assembled product which results in handling complexities. As a result, the industry generally favors slower curing glues despite the manufacturing inefficiency of using such glues.

Several methods are known for edge-gluing and clamping together fingerjointed or natural lumber. For example, US 6,779,576 (issued to Eric Cable) describes an apparatus for maintaining consistent interjoint clamping pressures across an edge glued panel of boards as the panel is assembled and the glue begins to cure. This consistent clamping pressure, even during the addition of new boards, permits a fast curing glue to be used, enabling the rapid production of structural grade engineered products. Furthermore, methods are known by which individual boards may be face glued and clamped to produce an engineered wood product. However, and again, fast curing glues are generally not used in such applications, as it is difficult to properly position and align large boards within the limited curing time provided by fast setting glues. This difficulty is particularly exacerbated when long and/or wide panels are to be assembled and face glued as such boards require increased handling speeds to ensure satisfactory glue coverage within the shorter setting times. Generally, slower curing glues are used which, as noted above, significantly reduces the productivity of the assembly process, and requires a large number of clamping stations to hold the assembled products during curing.

There is, therefore, a need in the art to improve the efficiency of assembling boards for face gluing. SU]VIMARY OF THE INVENTION

It is an object of the present invention to obviate or mitigate at least one disadvantage of previous systems and methods.

In accordance with a first embodiment of the invention, there is provided a method for face gluing wood laths within a clamping system comprising the steps of: a) applying glue to a wood lath while conveying the wood lath onto a retractable lath support; b) retracting the lath support to allow the wood lath to drop onto an assembly surface; c) repeating steps a) and b) as required with or without glue application for at least one subsequent lath wherein prior to step b) the lath support is reset; and d) applying a clamping pressure perpendicular to the assembly surface to form a glued wood product.

In accordance with another embodiment of the invention, there is provided an apparatus for gluing and clamping wood laths comprising: a frame; a glue application system operably connected to the frame for selectively applying glue to a wood lath; a conveyor system for conveying the wood lath onto a retractable lath support operably connected to the frame, the retractable lath support operable between an extended position for supporting a lath and a retracted position for allowing a wood lath to drop onto an assembly surface; and, a clamping system operably connected to the frame for applying a perpendicular clamping pressure to the assembly surface to form a glued wood product.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:

Fig. 1 is a schematic front view of an apparatus in accordance with one embodiment of the invention;

Figs. 2A, 2B, and 2C are schematic plan views of an apparatus and conveying system during various stages of product assembly; Figs. 3 A and 3B are schematic side views of an apparatus in accordance with one embodiment of the invention during various stages of product assembly;

Fig. 4A and 4B are front views of an apparatus in accordance with one embodiment of the invention, with the side door shown in both open and closed positions; and, Fig. 5 is a schematic diagram of two adjacent clamping systems in accordance with one embodiment of the invention.

DETAILED DESCRIPTION

Generally, the present invention provides a method and system for gluing, assembling, and clamping wood pieces (laths, panels or boards) into an assembled engineered wood product. As shown in the Figures, a system 10 is provided that allows for rapid assembly of individual laths, panels or boards (hereinafter laths) into a multi-board/panel wood product. With reference to Figure 1, the front of the apparatus 10 generally includes a loading area 20 for receiving laths or panels 90, a glue application system 30 for applying glue onto laths 90 as they are loaded lengthwise into the loading area 20, an elevator 40 for adjusting the vertical position of the loaded laths 90 such that each newly introduced lath comes to rest on the glued surface of the previously loaded lath. When all of the laths are assembled in the apparatus, a press plate 50, actuated by hydraulic presses 60, clamps the assembled wood product together during curing of the glue. The apparatus also includes a side door 70 and chain transfer system 80 for removing the assembled wood product from the apparatus IO upon release of the clamping pressure.

Loading Laths into the Apparatus

As shown in Figures 2A, 2B and 2C, an individual lath B is conveyed on rollers 110 to a position proximal to and in line with the loading area 20 of the apparatus 10. A previously loaded lath A is supported by the elevator 40 with the surface to which glue has been applied facing upwards. A number of retractable board supports 25 are slidably mounted on board support shafts 26 within the loading area 20. As the lath B is advanced into the loading area 20, glue is applied by the glue application system 30 onto the upper surface of the lath B.

The lath B will be received within the system 10 by the board supports 25 and will be advanced until it abuts an upwardly extending stop 41 at the dowπnstream end of the system as shown in Figure 2B.

As shown in Figure 2C, once the received lath B is properly positioned, the board supports 25 are retracted over the support shafts 26, to drop the lath B onto the glued surface of lath A, with the glued surface of lath B exposed. At this stage, the board may be manipulated by an optional positioning system (shown schematically as arrows 45) to adjust the orientation of the board, as necessary to ensure alignment of successive laths. Simultaneously, a new lath C is advanced towards the loading area 20 by the rollers 110. The elevator is subsequently lowered by the thickness of one lath and the board supports are again extended to prepare for loading of the next lath C.

This process is repeated until the desired number of laths has been loaded, at which time the board supports will remain retracted and the elevator will drop to its lowermost position as shown in Figure 3A. The hydraulic presses 60 are then activated, lowering the press plate 50 to clamp the assembled boards against the elevator or an appropriate lower support system as shown in Figure 3B, applying pressure for a sufficient amount of time to provide sufficient glue penetration for effective curing. In further embodiments, as explained in greater detail below, the press plate 50 may be segmented and matched with single or paired hydraulic presses 6O enabling the individual control of various segments of the press plate for increased flexibility in the clamping process.

When the curing process is complete, the hydraulic presses and press plate are retracted from the wood product, and the side door 70 is opened. A transfer system 42 engages the underside of the wood product and removes the assembled product dfrom the apparatus through the open side door as shown in Figures 4 A and 4B.

Curing Time

In order to ensure an even glue curing for each lath, it is desirable to load the laths into the apparatus as quickly as possible in order that a) the glue on each board is exposed to the air for roughly the same time and b) each board is subjected to roughly the same clamping pressure time. However, given that the glue on the first lath is applied earlier that the glue on the second last lath, the glue on the first lath will always be resting in the apparatus without the high clamping pressure being applied as successive laths are being introduced into the system. Within the system, this effect is at least partially offset by the steadily increasing pressure being applied to the glue on the first lath as the weight of subsequent laths increases. Thus, as each lath is introduced, the weight of each lath initiates the glue penetration process, thus minimizing the exposure of the glue to the air and atmospheric moisture.

Rapid Lath Advancement As noted above, it is preferred to load boards into the apparatus as quickly as possible both to speed production, and to minimize the time each glued surface is exposed to air.

Rapid advancement of laths into the apparatus is accomplished by the roller system 110, which in current embodiments can advance laths at a rate of 1200 feet/minute. At this rate, each lath is advanced into the apparatus with significant force and inertia and an appropriate stop system 41 should be provided to reduce or eliminate any lcick-back of each board. It is contemplated that significantly higher rates may be achieved in the order to 2500 feet/minute.

Glue Compositions

Operationally, glue curing times are balanced against the time required to fully load the system and clamping times. Thus, in a system where 25 laths are being loaded at a rate of approximately 3 seconds/lath, the total loading time will be in the order of 75 seconds. The glue applied to the first lath must not cure before the clamping system has been engaged. Similarly, the clamping time must be long enough to ensure that the glue on the second last lath is fully cured before release. Accordingly, in this exiample, the glue must provide a minimum working time in the order of 75-100 seconds. Thus, the total clamping time is determined by the minimum working time plus the cure time (ie the time from when the glue begins to set up until it is acceptably cured). Glues with faster cure times will improve the overall speed of production provided they have sufficiently long working times. Glue compositions can be formulated wherein the total clamping time is in the range of 2-5 minutes.

While faster curing glues are generally preferred, it is understood that the apparatus and method may be used with slow curing glues as equally well.

The efficiency of the system can be further improved by associating more than one apparatus 10 with each roller/conveyor system such that almost continuous production can be achieved. That is, by successively loading parallel systems X and V as shown in Figure 5, a manufacturing facility can be made to load one side X while trie other side Y is clamping. For example, if it takes approximately 75-100 seconds to load one side and total clamping time is in the range of 2-5 minutes, each side will be discharging product roughly every 3.5 to 7 minutes. In order to achieve this parallel efficiency;, a lath delivery system 80 would selectively deliver individual laths to either the X or Y side of the facility. For example, the Y side may be provided with a stop 81 that would selectively prevent lateral travel of a lath A to the X side when programmed to advance. Thus, by selective advancement and retraction of stop 81, laths would be positioned for loading the Y and X sides of the system respectively. Furthermore, in this configuration, wood product may be removed from alternate sides of the system 10. Board Support System

In a preferred embodiment and as shown in Figures 2A through 2C, retractable board supports 25 are slidably mounted around board support shafts 26. It is preferable that the board supports retract over the support shafts, as glue may drip over the side of a lath and make contact with the board supports 25. Retraction over the support shafts 2.6 will therefore decrease the likelihood of glue contacting the support shafts and thus, minimizes the risk of glue contacting the moving parts.

Furthermore, while the embodiment shown in the Figures details board supports 25 and shafts 26 in a staggered configuration on either side of the apparatus, it is understood that board supports need not be staggered, and may be present only on one side of the loading area 20.

Control System

The apparatus and associated parts are controlled by an electronic system to control and monitor the advancement, gluing, assembly, and clamping of the laths, and removal of the product from the apparatus. The control system may include various processors, logic, and sensors for determining the position of laths and for detecting problems during assembly as understood by those skilled in the art. For example, the system could be preset to assemble particular products by controlling the glue application system 30, hydraulic presses 60, transfer system, roller system 110, and extension and retraction of the board supports 25 as appropriate.

In a still further embodiment, the positioning system 45 (shown schematically by arrows) may also be enhanced to laterally clamp the laths during the main clamping phase. In particular, lateral clamping is beneficial to ensure accurate alignment of the boards which will minimize or reduce the degree to which the product will ha_~ve to be dressed post clamping.

As noted above, it is contemplated that the clamping system may be modified to enable a cambered wood product to be created. That is, during the assembly and main clamping phases, the supports for the laths may be adjusted thus permitting a non-linear support surface to be created. Accordingly, through adjustment of the position of individual hydraulic presses (or pairs), the hydraulic pressures can be made to apply an appropriate clamping pressure against the non-linear support surface thus creating a cambered or curved product.

The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention which is defined by the claims appended hereto.

Claims

What is claimed is:

1. A method for face gluing wood laths within a clamping system comprising the steps of: a) applying glue to a wood lath while conveying the wood lath onto a retractable lath support; b) retracting the lath support to allow the wood lath to drop onto an assembly surface; c) repeating steps a) and b) as required with or without glue application for at least one subsequent lath wherein prior to step b) the lath support is reset; and d) applying a clamping pressure perpendicular to the assembly surface to form a glued wood product.

2. The method of claim 1 further comprising a step (e) of removing the clamping pressure and transferring the glued wood product from the assembly surface.

3. The method of any one of claims 1-2 wherein assembled laths are lowered prior to step b).

4. The method of any one of claims 1-3 wherein first and second clamping systems are provided wherein the first clamping system applies a lateral force perpendicular to the clamping pressure during step d) and the second clamping system applies the clamping pressure.

5. The method of any one of claims 2-4 wherein the glued wood product is removed from a first side of the clamping system.

6. The method of any one of claims 2-5 wherein the individual laths enter the clamping system at a first end of the clamping system and the glued wood product is removed from a second end of the clamping system opposite to the first end.

7. The method of any one of claims 2- 6 wherein the assembly surface is non-linear and the method includes the step of applying a clamping pressure against the non¬ linear assembly surface.

8. An apparatus for gluing and clamping wood laths comprising: a frame; a glue application system operably connected to the frame for selectively applying glue to a wood lath; a conveyor system for conveying the wood lath onto a retractable lath support operably connected to the frame, the retractable lath support operable between an extended position for supporting a lath and a retracted position for allowing a wood lath to drop onto an assembly surface; a clamping system operably connected to the frame for applying a perpendicular clamping pressure to the assembly surface to form a glued wood product.

9. The apparatus of claim 8 further comprising an elevator for adjusting the vertical position of the assembly surface.

10. The apparatus of any one of claims 8-9 further comprising a control system.

11. The apparatus of any one of claims 8- 10 further comprising a stop operably connected to the frame for retarding forward linear movement of a lath being conveyed into the apparatus.

12. The apparatus of any one of claims 8-1 lwherein the lath support includes a lath support surface mounted over a support shaft.

13. The apparatus of any one of claims 8-12 wherein the frame includes a side door for removing a wood product from the side of the frame.

14. The apparatus of of any one of claims 8-13 wherein the assembly surface is adjustable for providing a non-linear assembly surface and wherein the clamping system is adjustable for providing a clamping pressure against the non-linear assembly surface.

15. The apparatus of any one of claims 8-14 further comprising a second apparatus for gluing and clamping wood products, the first and second apparatus including a loading system adapted for alternate loading of the first and second apparatus.