Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROIJND OF THE INVENTION
The invention relates to a log feed conveyor particularly suited
for feeding logs through chipping cantors and high speed bandmills.
Conveyor chains and power transmission chains have been used
for many years to feed logs through twin circular saws as well as tWiZI bandmills
to produce sguared timbers or cants. The chain passes between the two saws, so
the minimum thickness of the cant is limited by the width of the chain. The
10 chain must be substantially narrower than the thickness of the cant so the chain
will not contact the saws during the cutting operation. Because of the relatively
narrow chains required to permit, for example7 the cutting of four inch nominsl
c~nts, the standard manufacturing tolerance and design of these chains and
carrier systems have not previously incorporated a high degree of lateral
15 stability. The lack oE late~al stability in the chain resulted in lateral instability
in the log, causing sawing inaccuracies. Additional allowances had to be m~de
because of these inaccuraeies to avoid undersized lumber, resulting in underutili
zation of valu~ble lumber fiber.
In an attempt to overcome the lack of lateral stability, ex-
pensive high precision chains and chainways have been prod~ced, such as those inUnited States Patent #3,8S8,713 to Allen This system provides increased lateral
stability by providing downwardly extended guiding side bars on the chain.
However, such chains do not adequately cope with the torsional forces acting on
25 ~ log during transport ~nd sawing. Because the center of gravity of the log
rarely coincides with the center line of the chain, gr~vity, together with the
cutting forces, exert a torsional moment acting about the longitudinal ~xis of the
conveying ch~in. Because chains as disclossed in the Allen patent ride on the top
o~ chainw~ys, these torsional forces cause pivotting of the chain about the top
30 surface. The reactive force is directed to the unsupported edge of the extended
side link at the most extreme cantilever position from the chain barrel or othercross member which provides the resisting moment. Such twisting of the chain
results in movement of the log during the CUttiDg operation and consequent
s~wing inacCurQCy and w~ste of lumber.
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SUMMARY OF THE INvENrrIoN
According to one aspect of the invention, a conveyor chain is
provided for running on an elongate chainway of a log feed conveyor. The
5 chainway comprises a longitudinally extending central portion with a top. A pair
of longitudinal running surfaces are spaced-apart by the central portion. The
running surfaces are generally horizontal when the conveyor is positioned for use.
A pair of longituc3inal side walls, each side wall being on one side of the central
portion, extends generally vertically between one of the running surfaces and the
10 top of the central portion when the conveyor is positioned for use. The conveyo r
chain comprises a plur~lity of interconnected links. Each of the links has flanges
to each side thereof which straddle the central portion Oe the chainway. ~ach ofthe flanges has an inner face and ~ bottom face. As the chain runs on the
chainway, the inner faces slidably contact the side WQllS of the chainway to
15 provide lateral stability for the chain. The bottom faces slidably contact the
runnin~ surf~ces of the chainway, providing vertical support for the chain and
clearance between the ehain and the top of the central portion ancl resist axialrotation of the chain about the chainway.
According to another aspect s)f the invention, a log feed con-
veyor comprises the elongate chainway and a complementary conveyor chain for
running on the chainway.
Dis~dvantages of prior art devices; such as that found in United
States Patent #3,858,713, are accordingly overcome by providing the relatively
wi~stanc~d support of the bottom edges of the flanges. The reactive forces
resisting .otation OI the chain are accordingly at the maximum distance ~rom thecenter line of the chain. Rotation of the chain is therefore less likely than with
prior art chains where the only support is from the central portion of the
30 chainway. ~urthermore, because rotation tends to occur about a pivot point atthe outside of the link, the angular rotQtion and hence lateral motion of the top
of the chain will be much less than thflt of ~ chain which tends to pivot about an
interior point. There is also a greater chance that the center of gravity of thelog and CUttiJlg forces will occur between the two outer extremities of the chain.
35 In this situation, there will be no torsional pivotting. The result is a torsionQlly
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more stable chain without loss in lateral stability.
5 13RIEF DESCRIPTICN C)E~ THE DRAWINGS
Figure l is a side elevational view showing a longitudinal segment of a
log feed conveyor according to an embodiment of tl~e invention;
,
10 Figure 2 is an enlarged sectional view taken along line 2-2 of Figure l;
and
F;gure 3 is an isometric view, partly broken away, of a segment of an
alternative chain for the log feed conveyor.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
~0 Referring firstly to Figures 1 and 2 of the drawings, ~ log feed
conveyor l comprises an elongate chainway 2 and a complementary conveyor
chain 4 for running on the chainway. The chain 4 is continuous and only a r~
presentative number of links are shown with a corresponding length of the chain-way 2. With reference to the chain and chainway, longitudinal directions and
25 dimensions are defined as being along central axis fi of the chainway cr parallel
thereto. Tr~nsverse directions and dimensions are perpendicular to axis ~ such as
transverse axis 9 of the chRin shown in Figure 2i
Chainway 2 has a longitudinally extending central portion 8 with
30 a top 10. The chainway has steps on each side of the central portion 8 which
form a pair of longitudinal side walls 16 and 18 and a pair of longitudinal running
surfaces 20 and 22.
Running surfaces 20 and 22 are spaced-apart by central portion
35 8. The running surfaces are ~lat and coplanar and are generally horizontal when
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the conveyor is positioned for use as shown in Pigures 1 anci 2. Eaclh of the side
walls 16 and 18 is on one side of the ~entral portion 8 and extends generally
vertically between running surfaces 20 and 22, respectively, and the top 10 of the
central portion when the conveyor is positioned for use as shown.
Chainway 2 has a longitudinal spline 24 received within the
complementary keyway 26 of cradle 28. Cradle 28 is mounted on top of a box-
section member 30, only the upper portion of which is shown in Figures 1 and 2.
A plurality of central, vertical bores 32 are spaced-apart along the length of
10 chainway 2. Each of the bores 32 is aligned with a tapped bore 34 in cradle 28
and a similar tapped bore 36 in the top of member 30. A counter bore 37 at the
top of bore 32 is sized to received hend 3fi of a bolt 38. Bolt 38 passes freelythrough bore 32 and is threadedly received by bores 34 and 36 in cradle 28 and
member 30 respectively. Accordingly, a plurality of bolts 3~ along the length of15 the chainway serves to conneet together the chainway, cradle 28 and member 30.
;
The eonveyor 1 also includes the conveyor chain 4 which com-
prises a plurality of first links 40 interconnected by a plurality of second links 42
and a plurality of pins 44. Each o~ the first links 4n comprises a space~apart
20 pair of side bars 46 and 4~ to each side of the centrnl portion 8 of the ehainway
as seen best in Figure 2. Side bars 46 and 48 have bottom portions comprising
flanges 50 and 52 which are shown in Figure 2. The ~langes straddle central
portion 8 of the chainway 2. Flanges 50 and 52 have inner faces 54 and 56,
respectively, and bottom fnces 58 and 60, respectively. As may be seen, as the
25 chain runs on the chainway, inner faces 54 and 5~ slidably contact side walls 16
and 18 of the chainwa~ and provide lateral stability for the chain. The bottom
faces 58 and 60 of the first links are planar and have coextensive widths with the
running surfaces 20 and 22 of the chainway as shown in ~igure 2. The~ widths of
the bottom edges of the links and of the running surfaces are sufficient to
30 provide bearing surfaces for the chain 4 and for logs carried on the chain as described below.
Each of the first links 40 has a first end 62 and a second end 6~
which overlap ends 66 and 68 of the adjacent second links 42. The second links
35 are generally block-shaped and alternnte with the first links. ~nch of the second
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links extends longitudinally between two of the first links as seen in Figure 1 and
ex$ends transversely between the side bars 46 and 48, as seen in Pigure 2, spaced
above the top 10 of the central portion 8 of the chainway. Accordingly, the
flanges 50 and 52 not only provide vertical support for the chain, but also provide
5 vertical clearance 70 between second links 42 and the top 10 of the central
portion.
Each of the first links 40 has a pair of transverse bores 7~ and
74 extending through both side bars near ends 62 and 64. The second links 4
have bores 76 and 78 of similar diameters near ends 66 and 68 as shown in Figure2 and Figure 1. The bores in the overlapping ends of links 40 and 4~ are
transversely aligned and receive one of the pins 4~. Pins 44 are rotatably re-
ceived within bor~es 76 and 78 in links 42 and are welded at the outer ends to side
bars 46 and 48 to provide a hinged connection between adjacent ends OI the firstlS and second linksO
The side bars 46 an~ 48 have upwardly projecting shalp teeth 80
and 82, respectively, on the tops thereof. These teeth are adapted to penetrate
and hold a log carried on top of the ehain 4 as the chain runs longitudinally along
20 the chainway 2. Forces, such as force F shown in Figure 2, caused by curvature
of the log and the sawing operation tend to cause rotation of chain 4 about
longitudinal axis ~ or a parallel axis. In the log feed conveyor disclosed in United
States Patent #3,&58,713 to Allen, such rotation is countered only by wear blocks
contacting the upper wall oP the chainway which is equivalerlt to the top 10 of the
25 central portion 8 of the present invention. By comparison, as illustrated in
Figure 2, the reactive force RF for log Peed conveyor 1 is ~t the outside of thechain, increasing the ~noment resisting rotation. Unlike the Allen p~tent, the
side bers of the present invention slidably contact running surfaces 20 and 22 of
the chainway, providing wid~stanced vertical ~upport. The clearance 7 0
30 between the chain and the top 10 of the central portion 8 o~ the chainway, means
th~t there is no tendancy for the chain to rotate about the central portion as
occurs in the Allen patent. At the same time, the present invention retains the
lateral stability brought about by the sliding contact of inner Pa~es 54 and 56
with the side walls 16 and 18 of centrQl portion 8.
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Figure 3 shows a chain 4.1 which is a variation of chain 4 of
Figures 1 and 2 and runs on a similar chainway 2. Ch~in 4.1 is adapted to hold ~log 84 which has a spline 86 formed along the bottom thereof by chipping prior to
the sawing operation. This method of log sawing is used on log sallving machinery
5 sold under the trade rnark CHIP-N-SAW. C:hain 4.1 is similar to chain 4 in most
respects with chain ~ having second links 42.1 with bores 76.1 and 78.1 at each end
thereof. Links 42.1 are hingedly connected to first links 40.1 by a plurality of pins
44.1. The bottom portions of first links 40.1 are similar to those of links 40 in
Figures 1 and 2. Howeverg in lieu of teeth 8û and 82 of the first embodiment,
10 slde bars 46.1 and 48.1 are extended upwardly to form top flanges 88 and 90. As
may be seen in the figure, the top flanges form a complementary channel for
receiving spline 86 of the log 8~1.
Both embodiments OI the invention offer significant advantages
15 when compared with chains such as those in United States Patent #3,858,713.
Since rotation tends to occur about a pivot point at the outside of the side bars,
the angular rotation and hence lateral motion of the top of the chQin will be
much less than that of a chain which tends to pivot about a point between the
side bars. This means that there is less lateral deviation of the log whether it is
20held by the teeth of the first embodiment or between the top flanges oP the
second embodiment. It will also be appreciated that, due to the wider stance of
the improved chain, there is a greater chance that the center of ~ravity and of
the cutting forces will occur between the two outer extremities of the side bars.
In this case, there will` be no torsional pivotting occurring. The result is a
25 torsionally more stable chain without loss in lateral or vertical stability.
