Hollow veneered pole

A hollow light weight pole like structure suitable for use as a utility pole, column or log building member is made of a plurality of wood strips glued edge to edge forming a hollow interior core, with at least one layer of high strength veneer material glued to the exterior of the wood strips with the veneer grain running parallel to the length. The layer of veneer increases the strength, distributes bending stresses uniformly, provides greater decay resistance than ordinary glued hollow poles, and increases the service life. The veneer can be made in several layers forming a continuous overwrap without longitudinally extending gaps that expose the interior wood strips to weather or splitting.

BACKGROUND OF THE INVENTION 
This invention relates to a hollow pole made up of a core of wood strips 
that are glued along mating edges and forming an enclosure around a 
central axis, with one or more layers of high strength veneer tightly 
wrapped and glued to the exterior of the core to provide a high strength 
pole. Power companies that require poles have tried to find a satisfactory 
substitute for a solid wood pole. Trees that will provide a long, solid 
pole are becoming unavailable and that means that costs are increasing. 
Likewise, more efficient use of wood has been recognized as a way of 
obtaining greater strength than a solid wood pole of similar dimensions. 
Several efforts have been made to make a suitable hollow wood pole that is 
formed with a plurality of staves or strips that are glued together along 
their mating side edge surfaces around a central axis. For example, a 
hollow, wood stave pole made by using vacuum on the interior during gluing 
is shown in U.S. Pat. No. 4,468,273. Sealing caps are used for sealing the 
ends of the hollow pole so the interior vacuum can be created for gluing. 
U.S. Pat. No. 4,428,792 shows a column made up of preformed multiple layers 
of glued veneer panels that can be wrapped around a solid core of wood. 
International publication WO80/02709 also shows a multiple stave, glued 
pole. 
Other patents of general interest show pole structures that are hollow, 
such as the pole structure in U.S. Pat. No. 3,200,554 and a column used 
for construction shown in U.S. Pat. No. 4,387,546, which is similar to 
U.S. Pat. No. 4,428,792. Another pipe shaped structure is shown in U.S. 
Pat. No. 4,897,140. 
U.S. Pat. No. 5,150,557 shows a column that is formed of two sections glued 
together. However, none of the patents illustrate a hollow stave pole core 
having a high strength, permanently mounted overwrap at the outer 
periphery, where the greatest contribution to bending strength is 
achieved. 
SUMMARY OF THE INVENTION 
The present invention relates to a hollow, wooden pole that is light weight 
and has high bending strength in relation to its weight and size. The pole 
comprises a core made of a plurality of longitudinally extending wood 
strips or staves that are glued edge to edge, and formed around a central 
axis to provide a hollow pole. The staves are generally trapezoidal shaped 
in cross section, with side edges abutting the next stave and intimately 
adhered thereto to form a rigid tubular pole core. 
The staves can be tapered along their longitudinal length so that the pole 
has a generally conical shape, and after the staves are glued together 
with techniques that are known to form a core, the outer periphery can be 
smoothed so that the shape is generally circular at any cross section 
along the pole. This would mean removing some material at the exterior 
corners at the junctions between adjacent staves. Alternatively the staves 
can be machined prior to core formation to make the outer surface of the 
stave convex and with the right radius of curvature. 
The pole core is then tightly wrapped with an overwrap of high strength, 
thin material, such as a wood veneer, or a suitable synthetic, glueable 
material that would have the ability to wrap tightly around the outer 
periphery of the pole core, taking into account the diameter of the pole. 
The overwrap of veneer is glued into intimate contact with the outer 
peripheral surface of the pole core. The veneer layers extend around the 
entire periphery, and the longitudinal seam of each veneer layer is 
positioned so that it does not coinside with the seams of the veneer 
sheets in the previous layers so that the outer peripheral surface of the 
staves forming the pole core are protected by the veneer layer or layers. 
If desired, several layers of overwrap veneer can be wrapped around the 
pole core, and preferably there would be at least three wrap layers. 
The veneer layers are at the outer edge or surface of the pole, where the 
greatest contribution to bending strength is achieved. It is accepted that 
about 90% of the bending strength of a pole comes from the outer 22% of 
the pole diameter. The high strength veneer is at this location. The 
contacting, glued surfaces of adjacent staves are protected from weather 
elements; the staves themselves are protected from weather, and a great 
increase in strength is achieved by having the high strength outer veneer 
wrap integrally formed to the pole core. The grain of the veneer, if the 
veneer is wood, will be oriented parallel to the longitudinal axis of the 
pole. 
A rigid, bend resistant pole made of staves of readily available wood and 
veneer is produced. The wood staves can be chemically treated faster, 
cheaper, and more thoroughly than conventional solid poles. The weight of 
the finished pole is reduced so that the erection of the pole is 
simplified. The poles can be made up with staves that are of a selected 
length so there are pole core sections of selected length which can be 
assembled for forming a full length pole. The individual staves also can 
be shorter than the core length, with the shorter staves interfitted with 
ends of other staves using finger joints. Thus, full length staves can be 
formed. Care is taken to stagger any end joints in the staves from end 
joints of adjacent staves. 
The wood strip or stave cores can be joined end to end by the use of male 
and female threads, or other suitable junction members. The veneer 
wrapping provides the majority of the bending strength, and the edge and 
butt joints of the veneer sheets are staggered so that when using multiple 
layers no single joint extends all the way to the staves.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A utility pole or structural column indicated generally at 10 is made, 
according to the present invention, of a plurality of elongated wood 
staves or strips 12, that are generally trapezoidal in shape as shown in 
FIG. 3, and have side edge surfaces 14 and 15, an outer surface 16, and an 
inner surface 17. When glued with the side edge surfaces 14 abutting or 
contiguous with the edge surface 15 of an adjacent stave 12 as shown in 
FIG. 2, the assembly is a hollow, generally conical pole shaped core 22 
generated around a central axis 20. The side edge surfaces 14 and 15 are 
at acute included angles relative to each other. Each stave is permanently 
adhered to the adjacent staves to form a continuous, elongated pole core 
of the desired length. The pole core 22, comprising the staves 12 joined 
together around the central axis 20, could be made in suitable lengths, 
which then can be joined end to end for making a pole 10 of adequate 
length and diameter. 
The wood staves 12 can be made of any suitable wood, preferably 
underutilized species of hardwood. The staves 12 can be chemically treated 
for rot, insect infestation and the like before being glued together, or 
the entire pole can be treated after its manufacture. The lengths of the 
staves can be selected by using finger joints to join stave sections end 
to end. 
Once the pole core 22 has been formed, preferably the exterior corner 
portions indicated generally at 24 (FIG. 2) between the adjacent staves 12 
are removed by sanding or cutting to form a surface that is along the 
lines indicated at 26 and thus generally circular in cross section at any 
given cross section along the core 22 of the pole 10. 
After the operation of removing the projecting exterior corner portions of 
the trapezoidal staves and forming a smooth circular cross section conical 
exterior surface, the core 22 is overwrapped with one or more layers of a 
suitable laminate or veneer, such as layers 26, 28, and 30, as shown. The 
first wrap layer 26 of veneer is in intimate contact with the outer 
peripheral surface 32 of the pole core 22, and is wrapped so that it is 
substantially encompasses the entire outer peripheral surface of the pole 
core and is glued to the outer peripheral surface. The veneer, if it is a 
wood veneer, generally is in the range of about 3/16 inch in thickness, 
and has its grain oriented to be parallel to the longitudinal axis 20 of 
the pole. High strength soft woods can be used for the veneer. Subsequent 
veneer layers 28 and 30 are also then intimately wrapped around the next 
adjacent inner layer and tightly glued or otherwise adhered with a 
suitable adhesive to the surface of the next interior veneer layer. Butt 
joints between the edges of the veneer, such as that shown at 34 on layer 
30, are staggered longitudinally relative to the other veneer layers and 
with respect to other sheets in the same layer. The veneer layers have 
longitudinally extending joints which are annularly staggered so that the 
veneer layer joint does not overlie the junctions or seams between 
adjacent staves, or rather in the mid part of a stave outer surface, and 
also the joints of outer veneer layers do not directly overlie the 
longitudinal joint of another layer. 
It is also possible to have a continuous wrapping of the veneer layers, 
with present machines. The layers would be a continuously wrapped sheet 
with only a beginning edge on the core, and an outer edge on the exterior. 
When the veneer layers have been tightly adhered into position, the pole 
core 22 is sealed effectively from the weather, and the high strength 
veneer material layers, which can be a high strength wood, a polymer wrap, 
or a combination of the two, or other easily wrapped and relatively easily 
adhered materials, such as high strength synthetics sold under the 
trademark "FORMICA", or material known as KEVLAR will provide for a great 
increase in pole bending strength over that of unwrapped pole cores 22 of 
glued wood staves. 
It has been accepted that about 90% of the bending strength comes from the 
outer 22% of the total pole diameter. The outer 2.2 inches of diameter of 
a 10 inch pole contributes 90% of the bending strength. 
The composite pole of the present invention has numerous advantages. The 
wood contained is 50% or less compared to solid wood poles, and it can be 
engineered for strength requirement by selection of the materials, the 
thickness (number of layers) of overwrap and the material used for the 
veneer overwrap. 
The energy intensive (and inadequate) drying for solid wood poles is 
eliminated. The weight of the pole is reduced substantially, for equal 
strength and size, and it is less energy intensive to manufacture than 
poles of concrete or steel, which are also quite heavy and form 
substitutes for wood poles. The cost of production of the pole of the 
present invention is in the range of one-half to perhaps two-thirds of 
that of an equal sized solid wood pole. 
The staves 12 can be glued up using known machinery as illustrated in the 
prior art cited or using other known techniques. The strength of the 
veneer overwrap greatly increases the strength of the wood pole, as well 
as protecting it from the environment. The veneer overwrap may be clamped 
with band clamps or full length clamps during gluing to insure a good, 
strong glue joint. The clamps are removed after the glue has set, and 
additional veneer layers are added as desired. The glue used should be 
waterproof and compatible with the veneer material. The glue is permitted 
to fully cure before use of the pole. 
The pole length can be selected as needed. Veneer layers are usually in 8 
foot lengths in the grain direction, which are oriented with the 8 foot 
lengths along the pole with butt joints between lengths of veneer. The 
butt joints are staggered between successive veneer layers. 
While the description has dealt with a "pole" or column, the structure of 
the present invention can be used as a log for log homes or as a conduit 
or pipe as well as a support for power lines or the like. If the structure 
is used for a log home, the outer veneer would have the desired grain or 
knotty appearance, and the pole could be made without a taper. 
Although the present invention has been described with reference to 
preferred embodiments, workers skilled in the art will recognize that 
changes may be made in form and detail without departing from the spirit 
and scope of the invention.