CA1325096C - Laminated veneer round pole - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A tubular pole and method of making same from laminated wood veneer is disclosed. The pole is constructed from two or more equal length and transversely curved pole sections which have been joined together along their longitudinal edges to form the pole. Each pole section is comprised of a molded and transversely curved wood veneer laminate which is further characterized by having the wood grain in each layer of the laminate extending in a direction parallel to the longitudinal extent of the pole section.
Each pole section is formed from a lay-up of layers of wood veneer which have been coated with an uncured adhesive and wherein the wood grain of the veneer in each layer is orientated in the longitudinal direction of the pole section to be formed. The lay-up together with its support plate is transversely curved and the adhesive cured in a molding press, after which the edges of the molded pole section are trimmed so that two or more pole sections can be joined together along their trimmed edges to form the tubular pole.
Further, the coating of uncured adhesive can be applied in a discontinuous manner in order to promote penetration of a wood preservative across adjacent layers of veneer and all or selected layers of veneer and be incised for the same purpose.

Description

1 3250~6 . ~ ' ACRGROUND OF ~E INVENTION

FIELD OF THE INVENTION
This invent~on relates to tubular poles which have been cor.structed from laminated wood veneer and the method of their manufacture. ;

DESCRIPTION OF T~E PRIOR ART
Solid wooden poles have been widely used as utility poles ~or many decades. ~owever, as the old ~rowth large diameter soft woods are gradually disappearing, the ava~lability of suitable long solid wooden poles is becomln~
more scarce and the cost of same has increased dramatically.
Indeed, man-made laminated wood and composite wood materials have been constructed and successfully used as substitutes 16 ~or solid wood utility poles as reported in, for example, "Proceeding~ of the 6th Wood Pole Institute", 1965, page 65 - Bob McKa~n, and at page 69 of the same publication - ~d Hockaday, and in the 1981 proceedings of the American Wood-;, .~
Preservers Association entitled "Compole - The Composite Wood Material Utility Pole".
~hile solid or hollow laminated wood poles as well as wood chip composite poles are known in the art, at least hitherto it has not been possible to successfully produce ~ ~
tubular poles of laminated wood construction. In Unlted ~ -:- :
, .
~ ';.,'-" ': ~

" ' . ' ' . " ' , . ',',": ',, " ,' , ' ., ''. ', ' ' , . '- ,' . ' ' 1 3250~6 States Patent 1,058,701 issued April 8, 1913 - Mutter, and in United States Patent 2,543,901 - Dunne, which issued on March 6, 1951, hollow tubular laminated poles constructed from wood veneer are disclosed. Tn these prior art forms of construotion, the tubular laminated wood veneer pole so produced includes reverse spiraled wood veneer which extending the length of the pole, no doubt to impart additional strength to the side wall of the pole since the use of an expansible fluid bag internally of the pole is re~uired to impart sufficient outward pressure to achieve proper adhesion of the adhesive between the laminates.
Needless to say, tubular poles constructed in the manner are labor intensive, as well as being slow and difficult to produce on a commercial scale and at a reasonable cost.
1 have found that laminated wood veneer poles which have been constructed in accordance with my invention are easy and faster to produce, and involve limited labor requirements, when compared to the aforesaid pole construotions of Mutter and Dunne.
Further, from an eng{neer~ng standpo$nt, the poles constructed in accordance with the present invention exhibit greater resistance to external loads imparted thereon over the principal stress axis (the longitudinal axls of the pole~. It should be noted that the tensile and compression strengths of wood markedly decrease with increasing the grain '' ' 1 32~096 - 3 - ~
~ , ', angle to e~ternal load dtrection from O to 90 degrees. The effect of ~rain angle on tensile and compression strengths ,~ can be e~pressed by the following formula - known as Hankinson's formula.

al3 - __ a~ o, _ a" sinn~ + a~, coonl3 " ~' ':.
Where ~ and $ are the strength parallel and perpendicular to gra~n directions, respectively, is the angle between the load direction and grain direction, i8 the strength at the grain angle , and n is the constant (e.g. 1.5 to 2 for tensile strength and 2.5 for compression strength).
Although it is obvious that it is much easier to treat veneer sheets with a presensitive made-up laminated pole, the use of preservatives is of great environment concern. It ls not easy to dispose of the heavily preservative-treated veneer sheets which are pre-treated prior to the course of pole manufacture. On the other hand, it is not easy to treat, after fabrication, the laminated veneçr pole with a preservative. This is because the veneer ~n the laminated pole is normally coated with an ex.terior adhesive between the veneer layers, and the adhesive therebetween forms a continuous lmpermeable film after curin~.

~.- i - , ~ : -~''' ' ~ ' ', ' , ' ' . ' ' , ' ' ' " ' , ,, . " ''. ' '' ' 1 3250q6 I have found that the preservative treatability of ; made-up laminated veneer poles or laminated veneer pole sections can be dramatically improved if the adhesive used between the layers of veneer does not form a continuous film after curing thereby enabling the preservative to pass therethrough. Improved permeability can also be accomplished, w~thout impairing the performance in terms of strength properties, by mechanically perforating in the pole or pole section prior to treating same with a preservative.
Moreover, not only does my tubular pole possess similar characteristics of solid wooden utility poles, but it also has several advantages thereover. Natural defects such as knots, holes and slop of grain common in solid wooden poles are randomly found in my pole constructlon and thus are advantageously dispersed among many piles of veneer.
Further, my tubular poles can be readily engineered as to slze and propertie~ ln order to con~orm with the re~uirements of various end use appllcations.
When compared to polygonal laminated wood poles, tubular or rGund poles are easier to climb and, when constructed in two pole half sections glued together, which is one preferred form of construction, the likelihood of glue-line failure is reduced. Polygonal wood chip composite poles suffer the same shortcomings; and being harder, are ,. . .

more d~fficult to climb. They are also heavier, and more difficult to handle.

SU~MARY OF TKE INV~NTION
The novel tubular pole of my invention is constructed from two or more co-linear, elongate and transversely curved, laminated wood veneer pole sections which are ~oined together along their abutting edges to ~orm the pole. Two pole sections are prefexred, as this results 0 in only two glue lines being exposed to the environment. It will be appreciated, however, that three and possibly four pole sections can be used although the prospect of failure at the ~oints given the increased number of glue lines, can result. Where three or ~ore pole sections are used in the assembly, they can all be identical or substantially alike, and certain portions of a pole section can be made larger than the remainder when measured along the transverse curvature whlch each pole section describes.
In constructing a pole section, a predetermined number of layers of wood veneer coated w~th an uncured adhes~ve i8 'llayed-upll on a support plate, with the wood grain of the veneer in each layer or~entated in the longitud~nal direction of the pole sectlon to be formed therefrom.

Optionally, and in order to improve the depth penetration for a preservative applied to a pole or pole section a~ter fabrication, the adhesive between the layers o veneer may be coated in such a way that the cured adhesive will not form a continuous film and which thus enables the preservative to pass from one veneer layer to the next through the voids in the discontinuous film of adhesive.
This may be achieved, for example, by using a foam adhesive having abundant bubbles. The bubbles will collapse and leave a discontinuous film after the veneer lay-up is pressed and the adhesive is cured. Alternatively, the adhesive may ~e applied to the veneer in random spacing, such as in strips or s~nuously in order to permit migration of preservative between Joined together layers of veneer. All or ~ust the lnterlor layers of veneer may also be incised or perforated prior to molding, again to promote penetration of the veneer layers by a wood preservative.
once the laying up has been completed, it or it and its supportlng plate is transversely curved in a press which simultaneously effects curin~ of the adhesive. The longitudinal edges of the curved and cured (now molded) lay-up, are then trimmed so that the requisite number of pole sections, each functioning a longitudinal pole segmen~, as required to create the tubular pole, can be ~oined together at their abutting trimmed edges.

~ 1 325096 T~e number of layers of wood veneer in each lay-up is predetermined as it represents the wall thickness of the mclded pole section. The support plate on which the layerfi of wood veneer are initially layed up, in addition to being used as a carrier or vehicle for positioning the lay-up in the molding press, can also usefully serve as a sliding interface between the female pres~ face and the layer of veneer abutting it and which, once molded, becomes the large ~0 radius side of the transversely curved pole section. The bendable support plate which assists in positioning the lay-up above the female mold during pressing, al~o assists in mlnimlzing cracking or splintering of the veneer in each layer during curve mold~ng, particularly with respect to those veneer layers undergoing large radius curvature where relative sliding mot~on between ad~acent layers is most acute. Thin metal sheet, wlre mesh or a substitute such as Teflon ~a trade mark), has been found to be suitable as a support plate.
The need for bending the carrier plate with the lay-up in the press may be dispensed with, provided the molds, and particularly the upper edyes of the female mold are rounded in order to facilitate ease of entry and minimize cracking or splinterlng of the layer of wood veneer in contact with it.

, 13250q6 ,: ,, , .:As the tubular pole may be of substantial length, two or more lengths of wood veneer sheet which are of substantially the same thickness can be arranged in end-to-end relationship in any given layer. These sheets can either be joined together prior to lay-up, or physically joined during the curving and curing press operation. The ~oints themselves can be any one of scarf, lap and butt joints, and when ~oints are required, the ~oints in any given layer can be offset to those appearing in the remaining layers in order to reduce the likelihood of stress failure during field use. Additionally, and in instances where the fabricated pole is of a substantial extent, each pole section may be made up of two or more pole section lengths which have been joined together in end-to-end relationship. In ~uch a case, the joints between two lengths in a given pole section should be off~et relative to any similar Joints in the corresponding pole section.
Where two pole section~ are employed in the pole assembly, as indicated above, they are preferably substant$ally alike meaning they are effectively trimmed 80 that two pole sections can be joined ~ogether into a tubular pole. Where t~ree pole sections are utilized in making up the tubular pole, alike pole sectlons can again be advantageously employed. If two or more pole sections used in forming the tubular pole have butt joints, the trimmed .-g pole sections can be identical, and can otherwise be substantially alike if scarf, tongue and groove, splined or other types of joints as known in the art are employed.
The number of layers utilized in the lay-up depends on the density of the formed pole and the wall thickness of the pole section to be formed and necessarily the spacing between the press faces. ~he radius of curvature of the female face determines the outer diameter of the pole, and the male press face radius determines the inner diameter of the pole; the difference therebetween determ$ning the thickness of the pole wall. These press face~ can be either uniformly transversely curved along their longitudinal extent at a constant spacing for the purpose of producing an uniform curvature, or tapered along their longitudinal extent if it is desired to produce tapered pole sections and a resultant tapered tubular pole.
The uncured resin used in coating the layers of wood veneer is preferably a pressure or a pressure and temperature curing exterior grade wood adhesive such as phenol-formaldehyde resin, resorcinol-phenol-for~aldehyde resin and isocyanat. Any suitable glue to best suit a given application, can be e~ployed when ~oinin~ pole sections together. These joints can be further reinforced using other suitable ~eans such as strapplng or the like, as $s known ln the art.
; .

,'.'"

'.

. .'~ ~ .

1 3250~6 The assem~led pole itself may be made from the same or different wood species. Sapwood or heartwood may be utilized as desired, in order to facilitate preservation uptake. It w~ll also be apparent that the pole can be treated with preservative to improve its durability or a softening agent to improve its cllmbability.
The bottom portion of the pole may also be specially treated or overlaid to increase its durability, or to reinforce same in order to impart to it improved performance in terms of strength. In this respect, by relatively minor changes to the lay-up technique and the spacing between the male and female faces of the press, the wall thickness of the pole can be varied along its length, such as making it thinner at the top o~ the pole and thicker at the pole bottom. Further, different wood species can be grafted into eaFh layer in strateyic locations along each pole section, if thls type of wood species is regarded as an attr~bute in the overall pole construction.

BRI~F DESCRIPTION OF T~E D~AWINGS
In the accompanying drawings which lllustrate one working embodiment of my invention:
~igure 1 ~llustrates a cut-away view of an elongate male press component as used when constructing circular pole half sections;

1 3250q6 ..
Figure 2 illustrates a cut-away view of the corresponding female press component used in producing a half section with a molded half section therein; and Figure 3 i5 a sectional view taken lonsitudinally of the molded layers of wood veneer in a pole section and which illustrates the offsetting of veneer sheet ~oints in each layer from the sheet joints in the remaining layers; and Figure 4 is a cut-away view of a laminated wood veneer pole when constructed from two alike half sections.

DETAIL~D DESCRIPTION OF T~ DRAWINGS
With reference to Figures 1 and 2, the elon~ate male press component 1 and elongate female press component 2 as illustrated i8 used for forming longitudinal wood veneer pole half sections 4 which are made from a lay-up of laminated wood veneer. As depicted, the press components are designed for press~ng a lay-up of a half pole section having a uniform thickness throughout its length. The pole half section may have a un~form radius along its length, or it may be tapered along its length.
With reference to Figure 1, the male press component 1, at one end has a radius of curvature rl from point 10 and at its other end, a radius of curvature r2 taken from point 11. If the pole section to be formed is of uniform radius along its length, r1 equals r2. However, if the pole is to be tapered, r2 is made greater than rl.
The female press component 2, at one end, has a radius of curvature R1 from point 10 as illustrated, and at -~
its other end, a radius R2 from point 11 as illustrated.
Again, for c1rcular poles R1 is equal to R2: but where the pole is to be tapered, R2 i8 made greater than R1. Thus, for a pole section of uniform thickness, the spacing between press face 20 of male press component 1 and press face 22 of female press co~ponent 2 is uniform along the length of these components; the spacing therebetween being represented by the thickness o~ the laminated wood veneer 4 and its carry plate 3 as seen 1n situ in Pigure 2.
IS it is desired to laminate pole half sections which are thicker at one end than the other, the spacing between face 20 and face 22 of press components 1 and 2 is not uniform, but rather the ~pacing therebetween increasec toward the end which is to become the thick end of the :
finished pole. ~: :
The upper portion of male press component has a -: -diameter 2r1 which corresponds to the 2r1 diameter of the laminated pole section 4 shown in Figure 2. It will be observed that the axis of revolution taken through points 10 and 11 lies below the back~ng face 30 of male component 1, and also below the upper longitudinal edges 32 of laminated -~

: .. , :: ,: : - ., ~ . - , , . . ,., - .... . ~

:
1 3250q6 ' ' pole section 4. The distance therebetween represents the amount of the laminated wood which may be cut off or trimmed from the formed pole half section.
Carry plate 3 undergoes deformation with the wood -veneer laminate and in addition to supporting the lay-up during its posltioning in the press, serves to avoid breakage or splitting of the layers of wood veneer and particularly, those layers adjacent plate 3 which otherwise can occur as the lay-up ic pressed into female component 2. As indicated above, the grain of wood in each layer is or~entated longitudinally of the pole half section.
Typically, tubular pole half sections of uniform inner and outer radii along their length can be malded in a press, where the radius rl e~uals r2 and R1 equals R2 which renders a wall thickness of R1 ~ r1 minus the thicXness of the carrier plate 3.
.: .
The longitudinal cross-sect10n v~ew of the pole wall 18 seen in Figure 3 as laminate 4 overlying carrier plate 3. Scarf joints 40 interconnect adjacent veneer sheets in each layer, and these joints are offset relative to the joints of sheets found in other layers of the la~inate. As ment~oned previously, the woo~ grain in ea~h layer of ~eneer is aligned and extends in the same direction of the pole or pole section.

.' ~ -1 3250q6 The assembled pole 50 as seen in F~gure 4 is of - uniform thickness and has the same inner and outer diameter along its length. The pole i8 formed from two alike pole sections 51 and 52. Pole sections 51 and 52 have been formed in a press as above described, and have had their edges trimmed 80 that each pole section describes an arc of 180 such that they are thereafter joined together along butt ~oint 56 and glue line 53.
~0 Optionally, and if desired, the glue ~oints can be supported or strengthened using strapping rings 55 positioned thereabout in a manner as is well-known in the art. Fur'her, and as indicated above, the connecting ~oint can be any sultable type of joint such as a butt, scarf, tongue and groove or spline, as i8 known in the art, and thus two pole sections can be the same s~ze, or of slightly dif~erent size.
As indicated above, the adhesive film bstween the layers o~ veneer may be discontinuous, or the adhesive can be randomly applied so as to permit a wood preservative to pass through ad~acent layers of veneer of the molded pole or pole section. In order to also promote the migration of preservative into the interlor of the molded pole or pole section, the molded veneer can also be incised or its interior veneer layers perforated.

Claims (22)

1. A method of manufacturing a tubular pole from two or more collinear, elongate and transversely curved laminated wood veneer pole sections, comprising, for each of said pole sections, laying-up a predetermined number of layers of wood veneer which have been coated with an uncured adhesive on a support plate of dissimilar material with the wood grain of the veneer in each layer oriented to the longitudinal direction of the pole section to be formed, transversely curving said support plate and said lay-up simultaneously, curing said adhesive to form an untrimmed pole section separating said support plate from said untrimmed pole section, trimming the longitudinal edges of said untrimmed pole section, and thereafter joining two or more of said trimmed pole sections together along their abutting trimmed edges to form said tubular pole.

2. The method as claimed in Claim 1, wherein said support plate is transversely curved along the large radius side of said transversely curved lay-up.

3. The method as claimed in Claim 2, wherein the wood veneer in a given layer comprises at least two lengths of wood veneer sheet of substantially the same thickness and which are arranged in end-to-end relationship.

4. The method as claimed in Claim 3, wherein said sheets in each layer are joined together prior to laying up.

5. The method as claimed in Claim 3, wherein said sheets in each layer are joined together during curing of said adhesive.

6. The method as claimed in Claim 3, 4 or 5, wherein the joints of end-to-end sheets in a given layer are offset relative to the joints of end-to-end sheets in the remaining layers.

7. The method as claimed in Claim 3, 4 or 5, wherein said end-to-end sheets are interconnected by means of at least one of a scarf, lap and butt joint.

8. The method as claimed in Claim 1, 2 or 3, wherein said tubular pole is circular in cross-section and is manufactured from two substantially alike pole sections.

9. The method as claimed in Claim 1, 2 or 3, wherein said tubular pole is circular and is manufactured from three substantially alike pole sections.

10. The method as claimed in Claim 1, 2 or 3, wherein said adhesive is a pressure curing resin and said trimmed pole sections are glued together.

11. The method as claimed in Claim 1, 2 or 3, wherein the lay-up is uniformly transversely curved along its longitudinal extent in an elongate press having opposed male and female press faces.

12. The method as claimed in Claim 1, 2 or 3, wherein the lay-up is transversely curved in a taper along its longitudinal extent in a press-having opposed and tapering male and female press faces.

13. The method as claimed in Claim 1, 2 or 3, wherein said layers of wood veneer are coated with an uncured adhesive in a random manner so as to provide voids in each cured coating of adhesive, and said pole section is treated with a wood preservative.

14. The method as claimed in Claim 1, 2 or 3, wherein said layers of wood veneer are coated with an uncured adhesive foam and said tubular pole is treated with a wood preservative.

15. The method as claimed in Claim 1, 2 or 3, wherein at least the interior layers of said predetermined number of layers of wood veneer are perforated or incised and said tubular pole is treated with a wood preservative.

16. The method as claimed in Claim 1, 2 or 3, wherein each pole section is incised and treated with a wood preservative.

17 17. The method as claimed in Claim 1, 2 or 3, wherein the exterior of said tubular pole is incised and treated with a wood preservative.

18. A method of manufacturing a tubular wood pole, comprising laying-up a predetermined number of layers of wood veneer, which have been coated with an uncured adhesive, on a support plate of dissimilar material with the wood grain of the veneer in each layer orientated in the longitudinal direction of the pole to be formed therefrom, locating the support plate and veneer lay-up between opposed male and female faces of a press with the support plate adjacent said female face, forcibly bending the support plate and layers of wood veneer into the female face, curing said adhesive while said support plate and said layers are in the forcibly pressed condition to form an untrimmed pole section, separating said support plate from said untrimmed pole section, trimming the longitudinal edges of said untrimmed pole section, and joining trimmed edges of so formed pole sections together thereby providing said tubular pole.

19. The method as claimed in Claim 18, wherein the wood veneer in a given layer comprises at least two lengths of wood veneer sheet of substantially the same thickness and which are arranged in end-to-end relationship.

20. The method as claimed in Claim 19, wherein said tubular pole is circular in cross-section and is manufactured from two or more substantially alike trimmed pole sections, the trimmed edges of which have been joined together to form said tubular pole.

21. The method as claimed in Claim 20, wherein said adhesive is a pressure curing resin and said trimmed pole sections are glued together.

22. The method as claimed in Claim 1, 18 or 19, wherein two or more pole lengths are each constructed in the same manner as said pole sections, and wherein said lengths are joined together in end-to-end relationship to form a pole section.