Note: Descriptions are shown in the official language in which they were submitted.
1131S~9
MULTIPLE BLADE SPLlTTING DEVICE
T}~s invention relates to methods and apparatus for splitting
substantially straight grained lignocell~osic material. More particularly,
this invention relates to methods and apparatus for splitting wood sections
or whole logs substantially along the wood grain into slabs.
Long wood strands with longitudinal grain extending along their
lengths are reguired for the production of adhesively bonded structural
lumber products. An example of one type of structural lumber product
is disclosed in our U.~. Patent 4,061,819 issued December 6, 1977. One
method of producing the long wood strands for a structural lumber
product
describes the logs being first split
substantially along the grain into sector shaped segments, further split
into a plurality of slabs, and then îinally split into wood strands with
the grain generally extending along their length. Inasmuch as the logs
are split along the grain line, the side faces of the slabs are not
perfectly ~at, but tend to be irregular. When wood is split into narrow
strips or slabs) there is often a tendency for the strips to curl which
damages the strips or slabs and in some cases they may even break.
Thus, the present invention provides methods nnd apparatus for splitting
a wood section such as a sector shaped segment substantially along the
wood grain into slabs, and which do not cause excessive curling of the
slabs as they lesve the apparatus.
Although reîerence is made throughout the specification to splitting
wood sections, whole logs could also be split into slnbs on an apparatus
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of the present invention. Furthermore, any substantially strsight grained
lignocellulosic material may be split into slabs on the present apparatus.
When wood is pressure split, as opposed to being impact split,
the cutting edge of a tapered metal blade is pressed into the wood
until the wood on each side of the blade parts and a crack or split
commences along the grain. Once the wood has commenced splitting,
the cutting edge of the blade need not touch the wood, as the crack
or spIit extends in front of the blade and tends to follow the grain in
the wood. lf the grain is twisted, then the split tends to follow the
twist.
In one embodiment, the present invention provides an apparatus
~or splitting substantially straight grained lignocellulosic material
substanffally along grain lines into slabs, comprising: means for advancing
such material along a direction of travel, a plurality of splitter blades,
said blades being spaced along the direction of travel, and being laterally
spaced apart in a stepped row from a first splitter blade located to
commence splitting at one side of the material, to a last splitter blade
located to finalize splitting at the opposite side of the material, and
support means to support the material when advancing the material in
the direction of travel and past said splitter blades, said apparatus
permitting the split slabs to separate away from the remainder of said
ma~erial.
In another embodiment, the present invention provides an apparatus
~or splitting substantially straight grained lignocellulosic material
substantially along grain lines into slabs, comprising similar material
advancing means and splitter blades, but wherein the support means to
support the material is compressible, said apparatus permitting the
material to move laterally away from the splitter blades and from the
slabs being split therefrom in response to lateral forces created during
splitting.
An additional embodiment of the invention comprises the
combination of the features of the two above embodiments.
In a further embodiment, a method is provided for splitting
substantially straight grained lignocellulosic material substantially along
grain lines into slabs, comprising: adYancing such material along a
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direction of travel past a plurality of splitter blades, said blades being
spaced along the direction of travel, and being lsterally spaced apart
in a stepped row from a first splitter blade located to commence
splitting at one side of the material, to a last splitter blade located
to finalize splitting at the opposite side of the material, and permitting
the spIit slabs to separate away from the remainder of said material.
ln a still further embodiment, a method is provided for splitting
substantiaUy straight grained lignocellulosic material substantially along
grain lines into slabs, comprising similarly advancing such material along
a direction of travel past a similar plurality of splitter blades while
permitting the material to move laterally away from the splitter blades
and from the slabs being split therefrom in response to lateral forces
created during splitting.
Another embodiment of the invention comprises the combination
of the features of the two above-detailed methods.
ln drawings which illustrate embodiments of the invention,
Fig. 1 is a side elevational view of one embodiment of an apparatus
according to the present invention, with a wood section passing through
the splitter blades.
Fig. 2 is a side elevation of the apparatus shown in Fig. 1 with
the wood section split into slabs.
Fig. 3 is a perspective view of a sector shaped wood section.
Fig. 4 is a perspective view of a sector shaped wood section split
into substantially parallel slabs.
Fig. 5 is a detailed elevational view of a splitter blade splitting
a slab from a wood section.
Fig. 6 is a partial side elevational view of the splitting device
shown in Fig. 1.
Fig. 7 is a partial plan view of the splitting device shown in
Fig. L
Fig. 8 is a partial sectional elevational view of the carriage of
the splitting device shown in Fig. 1.
Fig. 9 is a sectional view taken at line 9-9 of Fig. 8.
Fig. 10 is a sectional Yiew taken at line 10-10 of Fig. 8.
One embodiment of an apparatus for splitting substantially straight
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gr~ned lignocellulosic material into slabs is shown in Figs. 1 and 2,
wherein a wood section 15 is pushed from a first stationary support 16
by a ram 17 operated from a hydraulic cylinder 18 through a stepped
row of splitter blades 19 to commence splitting the wood section 15 into
slabs 20. The ram 17 pushes the wood section 15 from the first stationary
support 16 onto a secondary support platform 21 which comprises a series
o~ support plates 22 linked together. The second support platform 21
rests on a carriage 23 which in turn is moved along a track 24 by a
second hydraulic cylinder 25. At the trailing edge of the carriage 23
is a vertical movable thrust member 26 which is raised to replace the
rsm 17 and complete the splitting of the wood section as the carriage
23 is moYed along the track 24 so that the slabs 20 are split from the
wood section 15.
Preferably, the apparatus is operated in a horizontal position so
that the splitting proceeds in a substantially level fashion. However,
the entire apparatus may be tipped at one end or toward one side. For
example, the apparatus may be placed in a vertical position so that the
force of gravity assists in the splitting. The only limitation on the
orientation of the appsratus is that it should be operated to produce
splits in wood in the desired fashion, along the grain thereof.
Hence, while the invention is discussed in the context of
substantially horizontal operation, this is merely done for purposes of
illustration and to avoid confusion.
Means may be placed below one end of a log being split so that
the end is elevated with respect to the other end in the direction of
travel during the splitting. This is particularly useful when splitting a
log wherein the grain proceeds in general from one.end of the log to
the other, but where the grain centers of the log are at substantially
different locations at the respective ends of the log.
When wood is to be split into slabs, it is preferred to split directly
across the annular growth rin~s of a tree. Fig. 3 shvws a wood section
15 in the form of a sector shaped segment which has been radifllly split
from a log. Fig. 4 shows the wood section 15 split into slabs 20. The
splits are substantislly parallel to each other and to the radius which
bisects the sector shaped segment. Thus, the slabs 20 have substantially
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parallel sides. ~urthermore, the splits occur across the growth rings of
the tree.
An example of splitting is illustrated in Fig. S wherein a splitting
blade 19 has a lower face 30 substantially parallel to the direction of
travel of the wood section lS, a cutting edge 31 at the front of the
splitting blade 19, and a first upper wedge face 32 extending upwards
from the cutting edge 31 joining into a second upper wedge face 33
which is preferably at an angle of approximately 3~ to the direction
o~ travel, and acts to force the split slab 20 away from the remainder
of the wood section 15 and extends the commencement of the split or
crack 34 in advance of the cutting edge 31 of the blade 19. Although
the first upper wedge face 32 is illustrated in Fig. 5, it will be apparent
thst this is not an essential part of the splitting blade 19, and the
splitting blade 19 may be formed with merely one upper wedge face.
When wood is split in such a fashion that a slab 20 is removed
from the remainder of a wood section 15, the slab 20 bends as it passes
by the blade 19, which res~ts in stresses near the splitting point. These
stresses tend to cause the slab 20 to becom e progressively thinner.
These stresses may also result in the occurence of internal cracks in
the slab which may weaken the grain structure therein. This tendency
during splitting may be minimized if the slab 20 is permitted to freely
split away from the remainder of the wood section 15, rather than being
constrained to bend around the blade 19 and rest under tension directly
against the unsplit portion of the wood section 15. In one embodiment
of the present invention, splitting is conducted such that no heavy
pressure is applied by the apparatus to force or retain together the
wood section with slabs during splitting. Light downward pressure may
be applied to guide the slabs as they are removed from the wood section
15, but the primary pressure pushing down on the slabs being split comes
merely from the weight of the slabs above them.
Some progressive reduction in the thickness of slabs produced
often occurs. The remaining unsplit portion or "block" of the wood
section lS yet to be split by the blades correspondingly becom es
progressively more acutely wedg~shaped. The variation in thickness of
such a block of m~terial from one end to the other, which Mock must
1131S49
be ~orced through the chamber of the splitter, may result in stresses
within the splitter. These stresses may become suficiently grest to
cause breakdown of the splitting operation, as by jamming of the wood
section or by bending or breakage of blades. These problems are avoided
by an embodiment of the present invention, wherein the support means
~or the wood section as it is moved past the blades is compressible.
By this provision, the unsplit portion of the wood section being split
may move away from the splitter blsdes and from the slabs being split
therefrom, when pressure in the splitter becomes excessive. For example,
if the apparatus of Figs. 1 and 2 is operated so that the carriage 23
moves horizontally from right to left, the unsplit portion of the wood
section 15 being split may move downward as necessary to relieve stress.
The two above embodiments of the invention may be employed
either alone or together as needed. The decision to utilize one or both
may readily be made by one sldlled in the art.
Details of one specific embodiment of the splitting device are
illustrated in Figs. 6-10. The first stationary support 16 is in three
sections as il~ustrated in Fig. 7. Each section has three plates 40 which
are vertical when the support 16 is in a horizontal plane as illustrated
by chain-dotted lines in Fig. 9. The plates 40 in each section are
attached to support arms 41 which in turn are pivoted about shaft 42
as illustrated in Fig. 9. A single hydraulic cylinder 43 is Yertically
positioned beneath a horizontal bar 44 which raises the support arms 41
so they pivot about shaft 42 and thus vary the angle of the support
plane from the horizontal plane. Thus, any shape of segment may be
positioned on the three support plates 40, the hydraulic cylinder 43 is
then activated to raise the support arms 41 so that the angle of the
support plane changes and the wood segment 15 is positioned such that
when it is split into slabs the splits occur as close as possible to being
substantially perpendicular to the grain lineO If one side face of a
segment 15 was allowed to remain resting on a horizontal plane, then
splitting would not occur perpendicular to the annular growth rings,
which would result in poor quality strands. A side plate 45 as seen in
Fig. 9 is pro~/ided to hold the wood section 15 on the first stationary
support 16 snd prevent sideways movement when the wood section is
1131S49
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being forced through the splitter blades. As is also illustrated in Fig.
9 the ram plate 17 which is an extension of the irst hydraulic cylinder
18 ~or pushing the wood section IS through the splitter blades has cut-
outs 46 to allow the support plates 40 to be pivoted to any angle of
the support plane.
The first hydraulic cylinder 18 is mounted on a main frame 50
which extends beyond the first stationary support in the direction of
trsvel to provide structure for supporting the splitter blades 19 and
supporting the split slabs. The frame 50 has two rigid cross frames
51, one at each end of the row of splitter blades 19, which support an
interior frame 52 having two side plates 53 which have a series of ~lots
~4 to hold the splitter blades 19. The slots 54 are located in a stepped
row as illustrated in Fig. 8. The two side plates 53 have the slots 54
directly opposite each other so that each blade 19 may be slid through
a pair of slots and supported at each end. Each blade has a locator
in the form of a peg (not shown) which holds it in place so that it
cannot slide out of the pair of slots during the splitting step. The
blades may be changed by merely sliding them out of the slots 54 and
inserting new blades. Thus, if blsdes become bent or need sharpening,
they can easily be replaced. I
A carriage track 24 is located beneath the interior frame 52
which supports a carriage 23. The carriage track 24 extends downstream
to the end of the frame 50. The carriage 23 has support rollers 62
and side rollers 63 which run in the track 24. A second hydraulic
cylinder 25 has a ram 64 to move the carriage 23 back and forth along
the track 24. The frame of the carriage 23 has a plurality of structural
stands 65 on which are mounted pneumatic air bags 66. On top of
each air bag is a support plate 22, each support plate 22 having a link
arm 68 and a pivot pin 69 so that the adjacent support plates are
joined together in a long line to form a single movable support platform
21. Vertical arms 70 extend down from each side of the support plates
22 and have guide rollers 71 at their base, which are fitted below the
horizontal nange of a guide track 72 supported on each side of the
main frame 50. The guide tracks 72 prevent any upward movement of
the guide rollers 71 and hence of the support plates 22. However, the
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guide tracks 72 do not prevent downward movement of the support
pl~tes 22, which is restricted only by air pressure within the pneumatic
a~r bags 66. Thus some downward movement of the support plates 22
may occur due to downward pressure on the support plates 22 from the
splitting action of the wood section lS passing through the splitting
blades 19. The guide tracks 72 commence by being horizontal and then
have a downward sloping section 73 extending into a further horizontal
section 74. Thus when the carriage 23 moves on the carriage track
24 the support plates 22 are initially free to move in a horizontal plane;
subsequently they are depressed so that the air bags 66 are compressed
as the guide rollers 71 traverse the downwards sloping section 73 of the
track ~2. As illustrated in Fig. 8 the support plates 22 are depressed
downwards to miss the splitting blades 19, specifically the last five
splitting blades in the row of splitting blades 19.
At the trailing edge of the carriage 23 is located a thrust member
26 for advancing the wood section lS from the row of splitter blades
19. The thrust plate 26 moves vertically upwards and downwards in
guides by means of a hydraulic cylinder 80. Guide rollers 81 are provided
on each side of the thrust plate 26, which engage on the lower edges
82 of the side plates 53. -The lower edges 82 are sloped downwards in
the direction of travel so that when the carriage 23 moves along the
track 24, the guide rollers 81 engage on the edges 82 and the thrust
plate 26 slowly moves downwards so that the top of the thrust plate
26 just clears each splitting blade 19. The movement of the carriage
23 is such that the thrust plate 26 moves beyond the last splitting blade
19 but the guide roller 81 does not leave the edge 82 of the side plates
53 and, therefore, when the carriage 23 returns to the starting position,
the thrust plate 26 always clears the splitting blades 19.
In operation, a wood section 15 is placed on the stationary support
16. If the wood section 15 is a segment similar to that shown in Fig.
3 then the pivot arm 41 holding the individual support plates 40 is
pivoted about the pivot position 42 until the wood section 15 is arranged
so that splitting occurs substantially radially By the term "radially" is
meant splitting such that at least one split in the center of the segment
is substantially radial, and that the others are all substantially parallel
11315~9
_ 9
to the center split such as that shown in Fig. 4. When the section 15
has been positioned on the stationary support 16 the hydra~ic, cylinder
18 is operated and the ram 17 pushes the wood section 15 into the
plurality of splitting blades 19. Before this pushing step commences the
carriage 23 is located directly beneath the splitting blades 19 so that
there is support for the wood section 15 as it is pushed through the
blades 19 to control bending or movement downwards of the wood section
15 and to ensure that splitting occurs.
The splitting action of the blades 19 is illustrated in Fig. 5. The
tapered portion 33 of each blade l9 forces the slab 20 upwards and the
split generally ~ollows the grain line. However, wood generally does
not have straight grain lines and, therefore, splits do not always extend
either straight or parallel to each other. Some play is taken up by
the compressed air bags 66 to allow depression of the support plates
22. It is preferable to allow a split to follow the grain line, but if
the line is at a steep angle then the splitting blade has to cut across
grain lines.
When the ram 17 comes to the end of its stroke the wood section
15 is well into the splitting blades 19 and the ram 17 then returns to
its original position. At this point the second thrust plate 26 is raised
by the hydraulic cylinder 80 as can be seen in Fig. 8. The second
thrust plate 26 is raised behind the location of forward approach of the
ram 17. The hydraulic cylinder 25 is activated and slowly pushes the
carriage 23 along the carriage track 24. As the carriage progresses,
the guide rollers 81 from the thrust plate 26 engage with the underneath
edges 82 of the two side plates 53 and as these edges are sloped
downwards the thrust plate 26 slowly moves down as the carriage 23
progresses along the track 24. Thus the top of the thrust plate 26
~lears each splitting blade 19 but still pushes the unsplit portion of the
wood section 15. As the sloped edges 82 are substant;ally in line with
the stepped row of blades 19 the top of the thrust plate 26 moves in
n line substantially parallel to the stepped row of blades 19.
The last few splitting blades 19 are located below the initial
po6ition of the support plates 22. ` The compressed air bags 66 allow
for downward movement of the support plates 22. The forces to cause
1131549
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U~s downward movement arise from the natural tendency for splitting
to cause the split section to move away from the splitting blade 19.
These forces may be enhanced if the split does not extend in a plane
parallel to the support plates 22. Additionally, when the guide rollers
71 for each support plate 22 reach the sloped section 73 in the guide
r~il 72, each support plate 22 moves downwards compressing the air bag
66 so that the support plate 22 clears the last few splitting blades 19.
Pig. 2 illustrates the carriage 23 st the end of its movement with the
thrust plate 26 shown at a location below the last blade 19 in the
stepped row of blades. The wood section lS has been split into slabs
20 which are ready for further splitting into strands.
The stepped row of splitting blades 19 may be varied according
to the thickness of slabs 20 required from a wood section 15.
Purthermore, the configuration of the splitting blades 19 may also be
varied. Fig. 5 illustrates one embodiment having two angles of tapered
section. It will be apparent that one single angle of tapered section
could also be used. Whereas hydraulic cylinders are defined herein,
these cylinders may be pneumatic, and other mechanical types of
advancing mechanisms such as chain drives may be used. Furthermore,
the air bags illustrated in the drawings may be replaced by other
compressible means such as springs. Various other changes may be made
in the details of the splitting device without departing from the scope
of the present invention which is limited only by the claims.
