Composite beam

A composite beam has round timber sections joined by nail plates, each timber section being edged in accordance with the conical contour of the tree trunk from which it is formed. The timber sections are joined by the nail plates with their tapered ends pointed in the same or in opposite directions, depending on the load requirements. Each nail plate has a front edge, a rear edge and a pair of longitudinal edges, and rows of nails are formed of tongue-shaped punch-outs in the nail plate, with each punch-out being parallel to the longitudinal edges. A step pattern is provided on the front edge and/or the rear edge.

BACKGROUND OF THE INVENTION 
The invention involves a composite beam, including edged, round timber 
sections connected by nail plates. 
Existing composite beams of this type consist of rectangular or square 
prismatic beams trimmed on all sides. Manufacture of these beams starts 
from the smaller diameter at the top or head of the trunk. This makes the 
diameter at the base relatively greater, depending on the length of the 
beam, resulting in an increase in the bearing cross-section at the base. 
The diameter per running meter can increase or decrease by 1 cm. Due to 
this taper or conicity, a tree trunk 10 meters long can thus have a 
diameter differential of about 10 cm between head and base. 
The existing nail plates used for joining the beams have been found to be 
in need of improvement, since it has been shown that vibration and peak 
loads cause the nails to loosen, thereby reducing the bearing strength of 
the composite beam. 
SUMMARY OF THE INVENTION 
A purpose of the present invention is to produce composite beams consisting 
at least partly of round timber sections which are edged according to the 
taper of the trunks and joined, depending on static load requirements, 
with converging or opposing taper, to provide exceptional bearing strength 
and extended service life. 
The present invention resolves this task by edging the round timber 
sections according to the taper of the trunks and joining them, depending 
on load requirements, with converging or opposing taper by means of nail 
plates. These nail plates have punched-out, tongue-shaped nails in 
parallel rows along the longitudinal edge of the plate. The front and/or 
back edge of the plates is designed in a stepwise pattern. 
An advantage of the invention is to permit exceptionally economical 
manufacture of composite beams with exceptional bearing capacity. This 
advantage is firstly based on the use of conically edged beams. This 
minimizes the amount of timber waste because the beams are edged according 
to the natural shape of the trunks. These beams therefore provide a 
greater bearing mass than beams trimmed to a constant diameter. 
The advantage of exceptionally high, as well as exceptionally durable, 
load-bearing capacity is also realized by use of the specially designed 
nail plates. The rows of nail bases are not parallel to the grain of the 
beams joined by the nail plates. If these nail plates are placed for 
example with their lateral edges approximately parallel to the joint or 
seam between two beams, the rows of nail bases arranged across the nail 
plate, as well as the rows of nail bases arranged parallel to the 
longitudinal sides of the nail plate, will run diagonally to the seam 
between the two beams. Also, the broad side of each individual, flat nail 
will be diagonal to the seam. The tacking effect of the row of nails is 
thus increased, while the risk of the joint loosening upon oscillation or 
at peak load is significantly reduced. 
An additional advantage is that these nail plates have significantly better 
tacking ability than existing nail plates, because nails are punched out 
over the entire surface of the plate, thus providing a greater number of 
nails to achieve the tacking effect. A final advantage to be mentined is 
that these nail plates themselves can be manufactured most economically, 
further enhancing the production of the entire composite beam. 
One type of construction type according to the invention is a composite 
beam made of round timber sections, edged on four sides to form 
frustrum-shaped beams with a rectangular or square cross-section. These 
beams are joined along their taper, for example with converging conicity 
in the same direction. 
Another construction type according to the present invention involves 
composite beams made of round timber sections which are edged according to 
the conicity of the trunk on those sides intended as matching surfaces 
where the beams being joined contact each other, while by contrast the 
sides used for the nail plates are trimmed to form surfaces parallel to 
each other. This allows the round timber sections to be joined with 
opposing taper, that is, with the head of one section or beam lying 
against the base of the other. 
The composite beam may consist of conically edged round timber sections 
joined to a prismatic beam having a rectangular or square cross-section 
and a uniform width for example to make equal the distance between 
opposing parallel surfaces of the round timber sections. 
The front and rear edges of the nail plate can each be designed to form a 
series of rising or falling steps, with each step having edges extending 
in parallel in between the longitudinal edges of the nail plate. This 
design has the advantage of giving the nail plate a rhomboid external 
form, which has an inherently advantageous shape. 
In another design variant of the invention, the relative distance between 
steps at the front edge of the nail plate is equal in each case to the 
relative distance between steps at the rear edge. This design variant 
firstly has the advantage of permitting economical production of the nail 
plate, because the stepped cuts in each case can be made with the same 
tool. An additional advantage is that these nail plates can be placed 
directly end-to-end, without any gap therebetween, when desirable or 
necessary. 
A further development according to the invention is to alternate the 
direction of laterally adjoining punch-outs in the nail plate. This 
improvement has the advantage of maintaining maximum stability in the nail 
plate itself. 
it is expedient to provide a distance greater than the length of the punch 
hole, between the base points of a transverse row of nails being punched 
out between the lateral edges of the plate, and the opposite row of nail 
base points. This invention design also contributes to maintaining maximum 
stability in the nail plate. An additional advantage is thereby 
maintained, permitting the nail plate to be made of relatively thin sheet 
metal, once again reducing the cost of the nail plates. 
An equal distance is in each case maintained between rows of punch-outs 
aligned in the same direction. 
The base points of a given row of punch-outs is always placed between two 
rows of base points aligned in the opposite directions. This maximizes the 
number of nails on the nail plate surface, while simultaneously 
maintaining maximum stability.

DESCRIPTION OF PREFERRED EMBODIMENTS: 
The invention is described in detail for the following embodiments, with 
reference to the drawings. 
FIG. 1 shows a tree trunk 3, edged on four sides according to its conical 
or tapered contour to form a timber 1. Sections of such a timber with 
rounded edges, which attains a frustrum shape, can be joined by means of 
nail plates 2 to form a supporting beam unit as shown in FIG. 2. The most 
tapered or top ends are aligned according to the load requirements of a 
roof construction. 
In the design shown in FIG. 3, the composite beam has a uniform 
cross-section. Here the edged, round timber beams 1 are positioned with 
opposing conicity, the tapered top end of one beam being placed against 
the base end of the other, and the tapering contact areas 4 are joined by 
means of nail plates 10. The surfaces 5 held by the nail plates 10 are 
edged to be parallel to each other, thus providing the rectangular 
cross-section. 
FIG. 4 shows a composite beam (nail plates 10 not shown) made of edged, 
round timbers 1 arranged with top ends opposed, as shown in FIG. 3. 
Between these round timber sections 1, a prismatic beam 6 of rectangular 
or square cross-section has been placed. The width of this beam 6 
establishes the distance between the facing parallel surfaces of the 
edged, round timber sections 1. FIG. 5 provides a top view of a composite 
beam as described above for FIGS. 3 and 4 (not showing the nail plates 
10). 
FIG. 6 shows a top view of a nail plate 10, as described in the invention. 
The punch-outs 12 are parallel to the longitudinal edges 16 and 18 of the 
plate 10, and bent out to form nails. Every row of punch-outs 12 is 
parallel relative to the lateral edges 16 and 18, while the direction of 
alignment alternates with each row. The punch-outs are laid out so that 
the points 20 of a given row of punch-outs fall between two punch-outs 
aligned in the opposite direction. However, a sufficient distance is 
maintained between the bases 24 of punch-outs in alternating rows and the 
bases 26 of the oppositely oriented punch-outs, to ensure that the head or 
points 20 do not extend between the pairs of similarly-oriented bases. 
This ensures that the area between pairs of base points in alternate rows 
remains intact from any punch-out. The nail plate is thus given 
exceptionally high stability. 
The front edge 30 and rear edge 32 of the nail plate have a stepped design, 
extending from bottom left to upper right. This design of the invention 
has the desired effect of giving the nail plate 10 an approximately 
rhomboid external form. 
FIG. 7 illustrates a composite beam consisting of two beams 34 and 36, 
joined by the nail plates 10 according to the invention. Wedges 38 show 
two supports on which the two ends of the composite beam are resting. 
As shown in FIG. 7, the nail plates 10 of the invention are nailed into the 
two beams in such a way that the stepped front and rear edges 30 and 32 of 
the nail plates are aligned approximately parallel to the seam 33 between 
the two connected beams 34 and 36. By this arrangement, the rows of nails 
parallel to the longitudinal sides 16 and 18 of the nail plate run 
diagonally to the seam 33. In this way an exceptionally strong tacking 
effect is achieved. 
As is furthermore evident from both FIGS. 6 and 7, the total surface area 
of the nail plate 10 is available for the application of nails. This 
provides the composite beam with exceptionally good tacking effect. 
FIG. 8 shows a roof rafter construction using a joist 40 and two rafters 42 
as well as two diagonal supports 44. The joist 40 and rafters 42 are 
joined by means of the nail plates 10 of the present invention. The joist 
40 is also tightly joined to the diagonal supports 44 using the described 
nail plates 10. As shown in this diagram, the nail plates 10 of the 
invention can also be used together with other nail plates 46 for the 
purpose of such composite constructions. 
The present invention allows for a number of modifications in nail plate 
designs and numerous advantageous applications, as would be apparent to a 
skilled worker in the art in possession of the present disclosure.