U.S. patent application number 10/572972 was filed with the patent office on 2007-07-19 for log-made truss structural material.
Invention is credited to Masumi Fujimoto, Noriyuki Fujita, Hiroko Fukutome, Katsuhiko Imai, Masanori Inada, Atsuo Takino, Shizuo Tsuzioka, Kozo Wakiyama.
Application Number | 20070163199 10/572972 |
Document ID | / |
Family ID | 34372966 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070163199 |
Kind Code |
A1 |
Imai; Katsuhiko ; et
al. |
July 19, 2007 |
Log-made truss structural material
Abstract
The invention is a log-made member for a large-scale truss
structure. A truss structural member 1 comprises a log 2 cut so as
to form flat surfaces on butt ends 2A thereof. A connector 4
slidably holds a shank 6m of a fastening bolt 6 and holds the
periphery of the butt ends. Large lag screws 5 fix the connector 4
to the butt end 2A of the log. The connector 4 is disposed between
the joint device 3 and the log 2, and is composed of a first
element 4A and a second element 4B which engage with the portion of
a counter-node side of the first element 4A. The first element 4A
is provided with an axial symmetrical shell accommodating an
elastic element 10 for biasing the fastening bolt 6. The second
element is 4B is fixed to the log 2 by plural lag screws 5 so as to
hold the butt end by using an annular thorn 4c so that the portion
of the counter-node side thereof contacts the butt end 2A without
any clearance.
Inventors: |
Imai; Katsuhiko; (Osaka,
JP) ; Takino; Atsuo; (Hyogo, JP) ; Fujita;
Noriyuki; (Osaka, JP) ; Wakiyama; Kozo;
(Osaka, JP) ; Tsuzioka; Shizuo; (Fukui, JP)
; Fujimoto; Masumi; (Osaka, JP) ; Inada;
Masanori; (Hyogo, JP) ; Fukutome; Hiroko;
(Osaka, JP) |
Correspondence
Address: |
WILLIAM J. SAPONE;COLEMAN SUDOL SAPONE P.C.
714 COLORADO AVENUE
BRIDGE PORT
CT
06605
US
|
Family ID: |
34372966 |
Appl. No.: |
10/572972 |
Filed: |
September 21, 2004 |
PCT Filed: |
September 21, 2004 |
PCT NO: |
PCT/JP04/13728 |
371 Date: |
September 13, 2006 |
Current U.S.
Class: |
52/633 |
Current CPC
Class: |
E04B 2001/196 20130101;
E04B 2001/1945 20130101; E04C 2003/026 20130101; E04C 3/16
20130101 |
Class at
Publication: |
052/633 |
International
Class: |
E04C 3/02 20060101
E04C003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2003 |
JP |
2003-329668 |
Claims
1. A truss structural member for providing screw type joint devices
on both ends of a log, which have a fastening bolt engaged with a
screw hole of connector nodes, comprising: a log cut so as to form
flat surfaces on butt ends thereof, a connector having a supporting
hole which slidably holds the shank of said fastening bolt at the
end of a node side thereof and a contacting surface which is seated
on said butt end at the end of a counter-node side thereof, lag
screws advanced against the log to fix said connector to the butt
end of the log; said connector having a first element with said
supporting hole, occupying one half of a node side thereof, and a
second element with said contacting surface, occupying another half
of the node side thereof, which engage with each other; said first
element having an axial symmetrical part making a space to
accommodate a part of said fastening bolt retractable through the
supporting hole on the side of the counter-node thereof and a
connecting threaded portion formed at the end of the counter-node
side of said axial symmetrical part; said second element being a
metallic seat provided with bores as large as the threaded portion
of said lag screw passable therethrough, which has a threaded part
engaged with said connecting threaded portion on the node side
thereof and one or plural annular thorns driven into the butt end
under a pressure load on the counter-node side thereof; and said
screw type joint device having said fastening bolt and a sleeve for
covering the fastening bolt, the bolt having a fastening threaded
portion on the node side thereof and a stopper contacting an
internal end surface of said first element on the counter-node side
thereof and the sleeve has a sleeve hole for transmitting
rotational torque to the fastening bolt and for sliding the bolt in
an axial direction thereof.
2. The truss structural member according to claim 1, further
comprising: an auxiliary thorny ring disposed to surround the neck
of a lag screw on the contacting surface of the second element and
the butt end of the log.
3. The truss structural member according to claim 2, wherein: said
auxiliary thorny ring is a dowel independent of said second
element.
4. The truss structural member according to claim 2, wherein: an
auxiliary annular thorn and said auxiliary thorny ring are formed
on the contacting surface of the second element in one united
body.
5. The truss structural member according to any claim of 1 to 4,
wherein: said screw type joint device has a fastening bolt provided
with a polygonal boss on the node side of the shank thereof away
from said first element so as to transmit the rotational torque
from the sleeve to the fastening bolt owing to inserting said boss
into the sleeve hole.
6. The truss structural member according to claim 5, wherein: a
standard high tensile bolt is used as said fastening bolt, the bolt
head being said stopper.
7. The truss structural member according to claim 6, wherein: said
boss is formed by bonding a polygonal cylinder having a round bore
in the center thereof, manufactured as a sole part, around the
shank of said high tensile bolt.
8. The truss structural member according to claim 6, wherein: said
boss is formed by bonding a polygonal cylinder having a threaded
aperture in the center thereof, manufactured as a sole part, around
the threaded end of the counter-node side of said fastening
threaded portion after engaging with each other.
9. The truss structural member according to any of claims 5 to 8,
wherein: the sleeve covering said boss is provided with a pin for
preventing the sleeve from coming off a fastening bolt by
contacting the pin to the end of the counter-node side of the
boss.
10. The truss structural member according to any of claims 1 to 4,
wherein: said screw type joint device has a sleeve provided with a
slit extending along the longitudinal axis thereof and a fastening
bolt provided with a rod extending in the radial direction thereof
through said slit for transmitting rotational torque from the
sleeve to the fastening bolt.
11. The truss structural member according to any of claims 1 to 10,
further comprising: an elastic element biasing said fastening bolt
toward a screw hole of the connector node disposed in the space for
accommodating a part of the fastening bolt retracted through the
supporting hole.
Description
TECHNICAL FIELD
[0001] The present invention relates to a log-made truss structural
member and, more particularly, to a structural member made of a log
which is also applicable to a large-scale truss structure, so that
a log may be joined as a truss member to connector nodes with high
accuracy in spite of the fact that the main body of the member is
made of wood.
BACKGROUND
[0002] A structural member made of a log is much less than one made
of steel on the characteristics of strength, toughness and
durability over a long period of time. Moreover, it substantially
cannot be manufactured exactly in length, which is different from
steel-made products.
[0003] A screw type joint device for joining a truss structure to
connector nodes is disclosed in German Patent No. 901,955 and in
U.S. Pat. No. 4,872,779. However, such joint devices are shown as
metallic products applied to hollow steel pipes only, with no
consideration of the application to solid logs.
[0004] A hard kind of wood with a high density is generally used to
manufacture wooden structural members. It is especially required
that wooden structural members used in a truss structure and/or
brace structure do not deform easily under any load, so the wood
should be well-dried and/or large in diameter, and further,
homogeneous, so as to deform as impartially as possible. The
construction of a truss structure with high precision in length has
always forced the use of metallic joint devices of the screw
type.
[0005] In constructing roofs and/or walls of a gymnasium, large
hall and the like by using a truss structure, a large number of
structural members are required. However, it is not often possible
to use only thick wood with high density as well as high strength
and rigidity from the viewpoint of the quantity and the costs. This
results in attempting to use comparatively thin logs, such as the
structural member with high joining strength found in
JP2003-74125A1.
[0006] The wooden structural member mainly comprises a log 2, a
screw type joint device 30, a connector 4 and lag screws 5 as shown
in FIG. 9 which is a sectional view of one side part thereof. The
joint device 30 for joining the member to connector node 8 is
almost the same as the one disclosed in U.S. Pat. No. 4,872,779
mentioned above.
[0007] A connector 4 comprises a first element 4A occupying one
half of a node side thereof and a second element 4B which engages
with the former, occupying another half of a counter-node side
thereof. The connector is fixed not only to the joint device 30 for
joining a truss structural member 31 to the connector node 8 but
also tightly to a butt end 2A of a log 2 by several big and thick
lag screws 5 though one lag screw only is shown in FIG. 9. The
connector and the joint device have enabled constructing
large-scale roofs and large-scale walls having wooden truss
structures.
[0008] A projection 2B like a truncated cone is shaped on both butt
ends 2A of the log 2 by machining on a lathe. A tapered portion 2m,
whose diameter is designed to be smaller to the end of a node side,
is formed around the projection 2B so as to be covered by the
connector 4. Not only undersized holes 9 for advancing lag screws
are bored in the butt ends 2A before hand but oversized passage 4f
for the lag screws are drilled through the second element 4B.
[0009] The first element 4A has a supporter for holding slidably
the shank 6m of the fastening bolt 6 at the end of the node side
thereof and an annular projection 4n engaging tightly with the
projection 2B at the end of a counter-node side thereof. Pressing
the butt end 2A in both radial and circumferential directions
thereof, owing to the end of a counter-node side of connector 4,
restrains the butt end from cracking and expanding while a lag
screw advances and stays in the log, resulting in facilitating a
strong engagement of lag screws with the log so as to maintain a
durable connection of connector 4 to log 2. Large and/or plural lag
screws improve the reliability and the stability of wooden
structures and contribute to the continued development of
large-scale wooden truss structures.
[0010] The connectors can be manufactured to desired shapes and
size with high accuracy because they are made of metal which can be
easily machined. However, it is almost impossible to cut a log
exactly in size. Manufacturing a log with high accuracy requires
lots of working time, great technical skill, complicated working
and high quality, making it nearly impossible to make truss
structural members economically by using ordinary logs that are
easy to obtain.
[0011] In the structural member of FIG. 9, it is important to make
a projection 2B of a circumference which is held by the annular
projection 4n exactly in size. However, the provisional center
established on the basis of the whole of a log often results in
giving not only the projection 2B a slightly wrong position and an
incorrect contour but the tapered portion 2n a wrong shape, being
different from an exact center established in metallic machined
products. An undesirable clearance appears between the
circumference of projection 2B and the connector 4 even if the
latter is manufactured with high accuracy in size. Therefore, the
engagement of the connector with the butt end becomes weak in the
radial and circumferential directions thereof.
[0012] The annular projection 4n mentioned above can prevent cracks
occurring around the lag screws 5 from extending toward the
periphery of the butt end. Since the circumference of projection 2B
is held by it, however, there are no obstacles for stopping cracks
before they reach the annular projection 2B. The higher the number
of lag screws used, the more serious the cracks tend to become on
the butt ends. Therefore, the butt ends result in a decrease in
strength.
[0013] The joint device 30 shown in FIG. 9 has a coiled spring 32
installed on the shank 6m of the fastening bolt 6, so that the
coiled spring can project from the end of fastening threaded
portion 6a from the sleeve 7, since it biases the fastening bolt
whenever it is retracted toward the connector. The sleeve 7
inconveniently comes off the fastening bolt, depending on an
attitude of a truss structural member 31 because it only covers a
fastening bolt 6. Such a behavior will be avoided if a pin 11 for
preventing the sleeve from coming off a fastening bolt is disposed
on the sleeve in the direction of a radius thereof. However, the
pin is inapplicable in consideration that a head of the pin will
disturb the expansion and contraction of the coiled spring 32.
[0014] A complicated fastening bolt 6 provided with a hexagonal
boss 6p for the above-mentioned joint device is not an ordinary
bolt found on the market as a standard industrial product.
Accordingly, such a fastening bolt will become remarkably expensive
since a stopper 6s, a shank 6m, boss 6p and a fastening threaded
portion 6a must be formed by machining an original bar of
steel.
[0015] The first object of the present invention relating to a
log-made truss structural member is to propose a structural member
not only having high size performance but keeping the original
strength of the log even if the log is just cut off on both ends
thereof. The second object is to restrict the deterioration and
weathering of the butt ends where a screw type joint device is
fitted. The third object is to enable a big axial force to be
introduced into a structural member by using a large-diameter lag
screw and/or plural screws to install joint devices on a log, and
the fourth object is to improve the reliability and stability of a
large-scale wooden truss structure.
[0016] More particularly, in the present invention it is important
to decrease the complicated machining procedures and highly precise
machining necessary to suppress the cracks occurring on the butt
ends and their progress, i.e., to propose a new connector not only
for installing a joint device to the butt end with high accuracy
but holding the butt end tightly without any clearance.
[0017] A further object is to prevent as many cracks occurring on
the butt ends as possible even when plural lag screws are used.
This is aimed at restraining the progress of cracks bridging
between lag screws close to each other under the state that the
butt end is already held at its periphery.
[0018] Furthermore, another three objects are as follows; the first
is to propose a connector also available to the screw type joint
device having another transmission mechanism for rotating the
fastening bolt even when the device is applied to a log. The second
is to propose mechanisms not only for preventing a sleeve from
coming off the fastening bolt but for automatically restoring the
bolt being pushed into the sleeve. The third is to enable a screw
type joint device to be made at a low price by using an ordinary
bolt already on the market as a standard industrial product as the
fastening bolt.
SUMMARY OF THE INVENTION
[0019] The present invention as applied to a truss structural
member provides screw type joint devices on both ends of a log,
which have a fastening bolt engaged with a screw hole of connector
nodes. Referring to FIG. 1, the truss structural member 1 comprises
a log 2 cut so as to form flat surfaces on butt ends 2A thereof, a
connector 4 having not only a supporting hole 4a which slidably
holds the shank 6m of the fastening bolt 6 at the end of a node
side thereof but a contacting surface 4b which is seated on the
butt end 2A at the end of a counter-node side thereof, and lag
screws 5 advancing against the log 2 to fix the connector 4 to the
butt end 2A of the log. The connector 4 is composed of a first
element 4A with said supporting hole 4a, occupying one half of a
node side thereof, and a second element 4B with said contacting
surface 4b, occupying another half, which engage with the first
element 4A. The first element 4A is provided with an axial
symmetrical part making a space 4s to accommodate a part of said
fastening bolt 6 retracted through the supporting hole on the side
of counter-node thereof and a connecting threaded portion 4d formed
at the end of counter-node side of said axial symmetrical part
making the space 4s. The second element as 4B is a metallic seat
provided with bores 4f as large as the threaded portion of said lag
screw which passes through, which has not only a threaded part 4g
engaged with the connecting threaded portion 4d on the node side
thereof but one or plural annular thorns 4c driven into the butt
end 2A under a pressure load on the counter-node side thereof. The
screw type joint device 3 is provided with said fastening bolt 6
and a sleeve 7 for covering the fastening bolt 6. The former has
not only a fastening threaded portion 6a on the node side thereof
but a stopper 6s contacting the internal end surface of said first
element 4A on the counter-node side thereof and the latter has a
sleeve hole 7a not only for transmitting rotational torque to the
fastening bolt 6 but for sliding the bolt 6 in the direction of
axis thereof.
[0020] The neck of a lag screw is surrounded by an auxiliary thorny
ring 12 on the contacting surface of the second element 4B and the
butt end 2A of the log. The auxiliary thorny ring 12 can be made as
a sole part independent of the second element 4B or an auxiliary
annular thorn as an auxiliary thorny ring may be formed on the
contacting surface 4b of the second element 4B as shown in FIG.
5.
[0021] Referring to FIG. 1 again, the screw type joint device 3 has
a fastening bolt 6 provided with a polygonal boss 6p on the node
side of the shank 6m thereof away from the first element 4A so as
to transmit the rotational torque from the sleeve 7 to the
fastening bolt owing to inserting the boss 6p into the sleeve hole
7a.
[0022] As shown in FIG. 3, a high tensile bolt 6A already on the
market is used as the fastening bolt 6 and its bolt head is
assigned to the stopper 6s.
[0023] As shown in FIG. 2(a), the boss 6p is formed by bonding a
polygonal cylinder 13 having a round bore 13a, manufactured as a
sole parts, around the shank 6m of the high tensile bolt 6A. Or as
shown in FIG. 2(b), the boss is formed by bonding a polygonal
cylinder 13 having a threaded aperture 13b, manufactured as a sole
part, around the threaded end of counter-node side of the fastening
threaded portion 6a after engaging with each other.
[0024] The sleeve 7 covering said boss 6p is provided with a pin 11
shown in FIG. 1 for preventing the sleeve 7 from coming off a
fastening bolt 6 by contacting the pin to the end of counter-node
side of the boss 6p. Referring to FIG. 7, a screw type joint device
3B has a sleeve 7A provided with a slit 7b extending along the
longitudinal axis thereof and a fastening bolt 6 provided with a
rod 7c extending in the radial direction thereof through the slit
for transmitting rotational torque from the sleeve to the fastening
bolt.
[0025] As shown in FIG. 1, an elastic matter 10 (see 10B in FIG. 7)
for biasing the fastening bolt 6 toward a screw hole of the
connector node is disposed in the space 4s of the first element 4A
for accommodating a part of the fastening bolt retracted through
the supporting hole.
[0026] According to the present invention, a connector comprises a
first element slidably holding a shank of a fastening bolt and a
second element engaged with the end of a counter-node side of the
first element under the state that it is tightly fixed on the butt
end of a log by lag screws disposed at the end of the log, so that
a screw type joint device which was used with a steel pipe
structural member can be used with wooden structural members such
as a log as well. The connector can be also installed on the screw
type joint device having a different transmission mechanism for
rotating the fastening bolt as long as the device has a fastening
bolt supported by the first element.
[0027] Driving an annular thorn formed on a contacting surface of
the connector into the butt end of a log protects the butt end from
deformation in the direction of the radius and circumference
thereof since the end of a log is held by the thorn. There is no
clearance left between the butt end and the annular thorn driven
therein, so that the deformation of the butt end can be avoided
perfectly and a strong connection of the connector to a log can be
kept for quite a while. Big lag screw and/or plural screws
available for wooden members facilitate a wooden truss structure on
a large-scale.
[0028] A log having non-constant sections, which is kept as an
original figure with a little bend, is also applicable to a truss
structural member as well as a machined log having a constant round
section. Contacting the contacting surface of the second element to
the butt end introduces an axial force uniformly into the whole of
section of a log. The present invention is applicable to not only a
bar having a round section but a bar having a square section that
is sawn because wooden bar is available for a structural member as
long as the thorn can advance into the butt end of the bar.
[0029] The second element of the connector independent on the first
element can be fixed alone to the butt end of a log by lag screws,
then, the first element never obstructs the rotation of a lag screw
and an operational load necessary for a lag screw is lightened in
the free space.
[0030] Removing a part of the circumference on the node side of any
second member fixed on both ends of a log owing to machining
assigns the log to an exact overall length easily. Accordingly,
assembling the first member machined into the second member makes a
log-made truss structural member with high accuracy by contacting
the first element to the circumference on the node side of the
second member. Changing the amount of the engagement of the first
element with the second one can not only absorb the error occurred
during the manufacture but can give another length to a truss
structural member intentionally.
[0031] The center of the log is not required to be in exact
alignment with two connectors fixed to both sides of the log. The
alignment with the connectors only is necessary, which can be
processed easily in a well-equipped factory. As the butt ends of a
log can be formed by just cutting them off, the woodworking does
not essentially need high technique and great skill aiming at high
precision.
[0032] Disposing an auxiliary thorny ring between the second
element and the butt end of a log so as to surround the neck of lag
screws makes the cracks caused by the advance of lag screw against
the log and the stay therein end up inside an auxiliary thorny
ring, so that the cracks will not spread on the whole butt end of
the log. The auxiliary thorny ring independent of the second
element is driven into the butt end before the second element is
carried to the butt end. The auxiliary annular thorn formed on the
contacting surface of the second element can be driven into the
butt end while the lag screw advances into the log.
[0033] A screw type joint device, wherein a polygonal boss is
equipped on the fastening bolt so as to transmit rotational torque
by covering the sleeve thereon, having been generally applied to a
structural member made of steel pipe, comes to be applicable to a
truss structural member made of log by introducing a connector,
which comprises a first element and a second one, into the joint
device.
[0034] The fastening bolt may be a high tensile bolt already on the
market, being resistible for a big axial load, in the case that it
is made of standard products. Not only a portion of the screw may
be used as a fastening threaded portion but a bolt head may be used
as a stopper which reacts against the fastening force occurred
during the engagement of the fastening bolt with a connector node.
Use of high tensile bolts on the market contributes to lower the
manufacturing cost of fastening bolts.
[0035] Bonding a sole-made polygonal cylinder provided with a round
bore around the shank of a high tensile bolt can easily supply a
fastening bolt equipped with a boss made of a bolt on the market. A
polygonal cylinder provided with a threaded aperture can be easily
mounted and bonded around the threaded end of the counter-node side
of the fastening threaded portion. The coating of an adhesive agent
covering both sides of screw threads generates twice the uniting
force as strong as the coating covering a cylindrical surface
around the shank, for the former results in having a bonding area
more than twice as wide as the latter.
[0036] The pin provided on the sleeve covering the boss can prevent
the sleeve from coming off the fastening bolt by contacting the end
of the counter-node side of the boss.
[0037] A screw type joint device, having a sleeve is provided with
a slit extending along the longitudinal axis thereof and a
fastening bolt is provided with a rod extending in the radial
direction thereof through the slit for transmitting rotational
torque to the sleeve, and having been applied to a structural
member made of steel pipe in general, also becomes applicable to
log-made truss structural member by introducing a connector
comprising a first element and a second one into the joint
device.
[0038] An elastic element biasing the fastening bolt toward a screw
hole of the connector node and being disposed in the space of the
first element for accommodating a part of the fastening bolt
retracted through the supporting hole, does not require a coiled
spring to be disposed inside the small sleeve, which consequently,
allows to mount the pin mentioned above on the sleeve.
BRIEF DESCRIPTION OF DRAWINGS
[0039] FIG. 1 is a sectional view of one side of an example of the
log-made truss structural member according to the present
invention.
[0040] FIG. 2 contains two sectional views of the assembly
comprising a high tensile bolt, a boss made of a polygonal cylinder
and sleeve covering the boss; (a) is a case that includes a
polygonal cylinder provided with a round bore therein and (b) is
another case that includes a polygonal cylinder having a threaded
aperture therein.
[0041] FIG. 3 is a view for explaining the procedures to assemble
the log-made truss structural member shown in FIG. 1.
[0042] FIG. 4 is a sectional view showing the progress of cracks at
the butt end reinforced by an annular thorn; (a) is a case without
auxiliary thorny ring and (b) is another case with auxiliary thorny
rings.
[0043] FIG. 5 is two sectional views in vicinity of a butt end
reinforced by a metallic seat integrated with thorns.
[0044] FIG. 6 is two sectional views in vicinity of a butt end
reinforced by rings.
[0045] FIG. 7 is a sectional view of a log-made truss structural
member using a joint device and a connector of another
configuration.
[0046] FIG. 8(a) is a sectional view of a log-made truss structural
member using a joint device and (b) is a conical shell of
furthermore different configuration.
[0047] FIG. 9 is a sectional view of a log-made truss structural
member having butt ends reinforced by a mechanism belonging to
prior art.
BEST MODE FOR CARRYING OUT THE INVENTION
[0048] A log-made truss structural member according to the present
invention is disclosed referring to the drawings showing some
examples, as follows. FIG. 1 is a sectional view of one side of a
truss structural, wherein a screw type joint device having a
fastening bolt engaged with the screw hole of a connector node is
provided at both ends of a log. The truss structural member 1
mainly has a log 2, a screw type joint device 3, a connector 4 and
lag screws 5 advancing against the log so as to fix the connector
to the butt end 2A of the log.
[0049] The joint device provided at both ends of the log 2 is a
screw type device, having the fastening bolt 6 provided with a
fastening threaded portion 6a and the sleeve 7 covering the
fastening bolt so as to transmit rotational torque thereto and so
as to slide the bolt in the axial direction thereof. The joint
device 3A has the same mechanism of transmitting rotational torque
as the joint device indicated in U.S. Pat. No. 4,872,779, wherein a
coiled spring (Referring to 32 in FIG. 9) is not installed on a
shank of the fastening bolt 6, being different from the joint
device of the U.S. patent.
[0050] The connector 4 comprises a first element 4A occupying one
half of a node side thereof and a second element occupying another
half, which engages with the first element. The connector is fixed
to the joint device 3A which joins a truss structural member 1A to
the connector node 8, and also is fixed tightly to the butt end 2A
of the log 2 by means of a big lag or plural lag screws 5, enabling
wooden truss structural members to be used in the construction of
large-scale roofs and large-scale walls.
[0051] As mentioned above, the connector 7 comprises the first
element 4A occupying one half of a node side thereof and the second
element 4B occupying another half thereof, so that the screw type
joint device used with steel pipe structural members can also be
installed on logs, further, it can be installed on a screw type
joint device 3B shown in FIG. 7 described later as long as the
first element 4A can support the fastening bolt 6 of the device
3.
[0052] Even a log 2 only cut off e.g., 2 to 4 meters in length, is
usable for a wooden structural member as long as both butt ends 2A
are parallel to each other. Undersized holes 9 were drilled to
advance lag screws 5 into the butt end 2A of such a log 2
previously. Though the holes result in generating a reduction of
sectional material in the log 2, the engagement of the lag screws
with the log promotes the integration with each other, resulting in
filling the reduction of sectional material with lag screw and in
recovering the original strength of the log.
[0053] All of a round machined bar, a barked log and an original
log with a little bend may be used as a structural member. However,
it is required that the joint devices 3A and 3A be installed on
both ends of the log by using the connectors 4 and 4 and these
should just be in alignment.
[0054] The screw type joint device 3 is explained as follows. A
fastening bolt 6 has not only a fastening threaded portion 6a at
the end of a node side thereof but a stopper 6s contacting the
internal end surface of the first element 4A on the counter-node
side thereof. The rotational torque is transmitted to the fastening
bolt 6 by covering the hexagonal boss 6p formed on the shank of the
bolt with the sleeve 7, which is provided with the sleeve hole 7a
so as to slide the fastening bolt 6 in the direction of axis
thereof.
[0055] The stopper 6s reacts on the fastening force by preventing
the fastening bolt 6 from advancing more, resulting in achieving
the tight fastening of the joint devise and a connector node. A
high tensile bolt on the market is used as a fastening bolt 6, and
bolt head thereof is assigned to the stopper 6s mentioned before as
shown in the drawing. The fastening bolt is obtained by using a
bolt on the market is as follows.
[0056] The joint device 3A is provided with an elastic element 10
disposed in the space 4s mentioned below to bias the fastening bolt
6 toward a screw hole of the connector node 8. The pin 11 for
preventing the sleeve 7 from coming off a fastening bolt 6 by
contacting the end of counter-node side of the boss 6p can be
equipped on the device because the coiled spring 32 disposed inside
the sleeve 7 shown in FIG. 9 is not applied to the present
embodiment. The pin 11 is inserted into a small hole drilled into
the sleeve beforehand after covering the boss 6p with the sleeve
7.
[0057] A spring plate 10A is used as the elastic element mentioned
above, always pushing the stopper 6s. This plate 10A deforms as
shown by the broken line when being pressed toward the counter-node
side by pushing the projecting part of the fastening threaded
portion 6a into the sleeve 7 so as to dispose the structural member
into the un-expansible space between two connector nodes occupying
the final positions, thereby, automatically restoring the spring
plate 10A owing to the release of the force acting on the fastening
bolt 6a staying in the sleeve 7 making the initial engagement of
the fastening threaded portion 6a with a screw hole 8a of the
connector node very easy after meeting each other. The truss
structure that is equipped with the joint devices without elastic
elements, see the device 3C shown in FIG. 8 explained later, is
inexpensively usable when disposing the structural member into
expansible space between movable connector nodes.
[0058] The connector 4 holds not only the fastening bolt 6 slidably
at the end of a node side but in the vicinity of a periphery of the
butt end 2A at the end of a counter-node side, because of having a
hole 4a for supporting the fastening bolt 6 on the node side and a
contacting surface 4b which is seated on most of the butt end 2A on
the counter-node side. An annular thorn 4c formed near the
periphery of the contacting surface reinforces both sides of the
log 2 by being driven into the butt end, resulting in preventing
the butt end from cracking and chipping for quite a while. The
reinforcement according to the connector becomes effective against
the butt end in the direction of not only radius but circumference
as well, resulting in restraining the butt end from cracking and
expanding during the advance of lag screws thereinto and in
contributing to a tight and long-lived connection of the connector
and the log. Big lag screw and/or plural screws are available for
wooden members and facilitate a wooden truss structure of
large-size.
[0059] The first element 4A of the connector 4 is provided with the
supporting hole 4a which enables the shank 6m of the fastening bolt
to move slidably at the end of a node side, and with a conical
shell having an opening widely expanding toward the counter-node
side thereof as a whole, wherein a space 4s for accommodating a
part of the fastening bolt 6 retracted through the supporting hole
on the side of counter-node thereof is formed, and a connecting
threaded portion 4d is formed at the inside of the axial
symmetrical part regulating the space on the counter-node side.
[0060] Holes 4e may be formed on the conical shell 4A for
lightening itself under the condition that the joint device 3A is
not exposed to moisture and/or raindrop. The spring plate 10A
mentioned above is welded to the inner surface of the axial
symmetrical part regulating the space after inserting the fastening
bolt 6 into the first element 4A.
[0061] The second element 4B, which is engaged with the conical
shell 4A, has not only a contacting surface 4b which is seated on
the butt end 2A but an annular thorn 4c driven into the butt end at
the circumference thereof. The annular thorn, being about 2
millimeters high, can be shaped easily by slightly digging the
contacting surface 4b during manufacturing of metallic seats 4B.
The annular thorns 4c for preventing the butt end from being
damaged advance into the log easily owing to pressing the second
element 4B to the butt end 2A by a hydraulic press. Since no
clearance remains between the annular thorns and the log, the butt
end can be held perfectly. The annular thorns may be driven into
the log by using the force occurred during the advance of the lag
screws 5. The fastening force generated by the propulsion of the
lag screw 5 always prevents the annular thorns 4c from loosing.
[0062] A threaded part 4g engaging with the first element 4A is
formed on the shrunk periphery occupying a half part of the
original periphery of the second element 4B provided with bores 4f
for positioning the lag screws 5. The axial force introduced into
the first elements 4A through the connector nodes 8 and joint
devices 3A is transmitted to the butt ends 2A through the second
elements 4B having the flat contacting surfaces seating on the butt
ends 2A under the constant and uniform distribution.
[0063] Since plural bores 4f of the second element 4B may accept
the number of the lag screws 5 selected in response to the
difference of characteristics of the log within the number thereof,
many of the connectors 4 are usable for logs with different size,
resulting in a decrease of cost according to the mass production.
Keeping the adjustable portion 4h between the shrunk periphery and
original one mentioned above may compensate to assign the exact
length L2 to the main body of a structural member if increasing the
size of the shrunk periphery by machining in the state that the
second elements 4B is fixed to both ends of log 2, so that the
log-made structural member 1A is assigned to the overall length L1
with high accuracy because both the first element 4A and the sleeve
7 are, of course, machined products.
[0064] A cutting error margin of a log may be compensated by the
adjustment of engagement of the first element 4A with the second
element 4B, which is different from the above-mentioned. The length
of a truss structural member can also be changed on purpose by
adjustment owing to the same procedures. The inevitable errors
occurring during the manufacture of wood products can be absorbed
depending on the process to assemble metallic parts which can be
produced with accurate size. Since the screw type connection is
applied to all parts except a log, the deterioration and the change
in dimension of the installation portion of the joint device can be
avoided. In addition, the assembling work becomes much easier.
[0065] In FIG. 1, auxiliary thorny rings 12 are used with an
annular thorn, which reinforces the circumference of every neck of
lag screw 5 on the butt end 2A individually. If the auxiliary
thorny ring is a single part, a pipe of e.g., 0.6 millimeters thick
can be used by cutting 4 millimeters wide, the ring driven into the
portion around the opening of hole 9 for the lag screws 5 by a
hydraulic press, as discussed above.
[0066] Since bolts on the market do not come with a polygonal boss,
a high tensile bolt will require the polygonal boss in the case
that adoption of standard industrial products are desired for
manufacturing the fastening bolts 6. Bonding the polygonal cylinder
13 having a round bore 13a as shown in FIG. 2 (a), which is
manufactured as a sole part, around the shank 6m of the fastening
bolt with adhesive agent 14 integrates a polygonal boss 6p with the
bolt. A polygonal cylinder 13 provided with a threaded aperture 13b
as shown in FIG. 2 (b), can be easily mounted and bonded around the
threaded end of counter-node side of the fastening threaded portion
6a. The coating of adhesive agent covering both sides of the screw
threads generates twice as strong of a uniting force as the coating
covering a cylindrical surface around the shank, resulting in
improved bonding durability.
[0067] The truss structural member 1A mentioned above is assembled
as indicated in FIG. 3. The log 2 is cut so as to form flat
surfaces on butt end 2A thereof, and is drilled so as to make the
undersized bores 9 in the butt end, the hole threaded by a tapping
screw if necessary. The auxiliary thorny rings are driven into the
butt end 2A to surround the opening of the undersized holes. The
second element 4B is carried to the butt end, simultaneously, to
engage the annular thorn 4c with the butt end 2A by a hydraulic
press. The lag screws 5 advancing against the undersized bore 9
through the hole 4f press the metallic seat 4B toward the butt end
2A, so as not to loosen the annular thorn as well as the auxiliary
annular thorny rings 12 by means of the contacting surface 4b. The
adhesive agent may be applied to the lag screws before they advance
into the log.
[0068] The head of lag screw 5 occupies a part of the open space
15, as shown in FIG. 5(a), for instance, as described later, so as
not to interfere with each other while driving the screws, even if
plural screws 5 are used since the conical shell 4A of the first
element is still not installed on the metallic seat 4B when driving
the lag screw 5. The adjustment of the length of the member is
performed by cutting the adjustable portion 4h, see FIG. 3, if
necessary, after the second elements 4B are fixed to both ends of
log 2.
[0069] The high tensile bolt 6A is inserted into the supporting
hole 4a of the first element 4A, and a polygonal cylinder 13 is
bonded around the threaded portion 6a or the shank 6m of the bolt,
which are projected from the sleeve toward the node side as shown
in FIGS. 2(a) and (b). The pin 11 is driven into the sleeve 7 after
the fastening bolt 6 with the boss 6p is covered with the sleeve.
Finally, the threaded portion 4d of the first element 4A is engaged
with the threaded part 4g of the second element 4B, resulting in
obtaining a truss structural member 1 made of a log as shown in
FIG. 1.
[0070] The introduction of the annular thorn into the joint device
not only allows the log to be cut off easily without high accuracy
but allows to use a big lag screw or plural lag screws. As a
result, a structural member becomes strong in resisting the large
axial force in spite of the fact that the main body of the member
is just made of a log. Beside, great technical skill for installing
the screw type joint device on the log is not required, and the
process for reinforcing the butt end owing to an annular thorn
merely depends on the driving, resulting in holding the butt end
tightly due to the annular thorn without slack.
[0071] Holding the butt end 2A by the annular thorn 4c restrains
the cracks 16 from growing around the hole 9 as shown in FIG. 4
(a). Even if the cracks reach the annular thorn 4c, further growth
will be restricted to the region surrounded by the annular thorn.
As shown in FIG. 4(b) drawn corresponding to FIG. 1 the expansion
of cracks 16 stay only around the lag screw 5, resulting in
restraining the cracks from progressing as possible according to
dual-barrier system consisting of the annular thorn 4c and the
auxiliary thorny ring 12.
[0072] The threaded portion 4d and the threaded part 4g, see FIG.
1, may be engaged tightly with each other by bonding. Also, the
direction of threaded spiral assigned to such portion and part may
be opposite to that assigned to the fastening threaded portion 6a
and screw hole 8a of a connector node engaging with each other.
Joining truss structural members 1 to connector nodes 8 facilitates
the engagement of the threaded portion with the threaded part,
resulting in elimination of the slack occurring between the
threaded portion and the threaded part.
[0073] Using the mechanism where the direction of spiral of the
connector at one side of the log is opposite to that at the other
side enables the length of the truss structural member to be
adjustable to match with the pitch of two connector nodes to be
joined. Only rotating a log can continuously change the distance
between the connector nodes of both right and left sides, similar
to a movement of a well-known turnbuckle, even if the length of the
truss structural member is different from the distance between two
connector nodes.
[0074] A small screw 4p threaded as shown in FIG. 1 may prevents
the connector from slacking. Releasing the small screw allows the
disconnection of connector 4, enabling the reuse not only of the
joint devices but of the connectors, even when replacing the
logs.
[0075] In FIG. 1, the annular thorn 4c is formed on the contacting
surface 4b of the second element 4B. The auxiliary thorny ring 12
is a dowel independent of the second element 4B. As shown in FIG.
5(a), however, an auxiliary annular thorn 12c, corresponding to the
auxiliary thorny ring, may be formed on the contacting surface 4b.
These two kinds of thorns are driven into the butt end 2A. In
addition, as shown in FIG. 5(b), the auxiliary annular thorn 12c
may only be equipped on the connecting surface 4b.
[0076] FIG. 6 contains two examples where only auxiliary thorny
rings are used instead of an annular thorn. FIG. 6 (a) is an
example including a large thorny ring 17 holding the whole butt end
and small thorny rings 18 surrounding each lag screw and FIG. 6(b)
is an example having a large thorny ring 17 only. Any thorny ring
would be a sole or unitary part, therefore, any ring having a
proper width in response to the required driven depth can be
selected as necessary.
[0077] FIG. 7 is an example where the truss structural member 1B is
equipped with a joint device 3B having another composition. The
joint device 3B has the same mechanism of transmission of
rotational torque as the joint device described in German Patent
No.901,955. However, this is different in that the coiled spring
10B biasing the stopper 6s is installed in the conical shell 4C.
With regard to the details of the joint device, this has the slit
7b extending along the longitudinal axis on the sleeve 7A and a rod
7c for transmitting rotational torque is mounted on the fastening
bolt 6 through the slit. Accordingly, a polygonal boss is not
required on the fastening bolt 6, and a high tensile bolt 6A
already available on the market can be used without modification.
Furthermore, the coiled spring 10B can be also be used in the
device shown in FIG. 1, instead of a spring plate 10A.
[0078] In FIG. 1, the threaded portion 4d engaging the first
element 4A with the second element 4B is an internal thread. On the
other hand, in FIG. 7, the threaded part of the second element 4D
is an internal thread 4g and the threaded portion of the first
element 4C is an external thread 4d, so that a groove which
receives the tip of conical shell 4C is formed in the second
element 4D. Either configuration of the connector for integrating
the first element with the second element may be used.
[0079] FIG. 8 is an example of the log-made truss structural member
1C provided with the joint device 3C having fastening bolt 6 which
can not automatically restore, wherein the joint device is the same
kind as the joint device 3A in FIG. 1 except for the absence of an
elastic element. The characteristic of such a truss structural
member is that the base part 4j of the cylindrical second element
4F is kept flat to contact tightly the butt end 2A. Also, the
threaded part 4g engaging with the first element 4E is formed at
the end of the inner wall of the cylindrical part 4F opening at the
end of a node side.
[0080] Also, in the case where the second element 4F is
cylindrical, this can be fixed to the log 2 easily if the lag
screws 5A with a head 5a having hexagonal hole 5b are applied to
the element. Of course, the hexagonal hole is not necessary when
the cylindrical space 4t is large enough to use a socket
wrench.
* * * * *