CONVOYEUR INCLINE

INCLINE CONVEYOR

Abrégé français

Un convoyeur incliné pour une utilisation dans le transport de grumes à partir d'une première élévation vers une deuxième élévation dans une scierie. Le convoyeur comprend un châssis de support et une pluralité d'arbres rotatifs montés sur le châssis de support à des positions espacées entre les première et deuxième élévations. Des leveurs de grumes comportant au moins une partie de réception de grume sont montés sur les arbres rotatifs. Chacun des arbres est entraîné par un moteur séparé monté sur le châssis de support. Les leveurs montés sur les arbres peuvent ainsi être mis en rotation à des vitesses variables pour faire en sorte que les grumes sont déchargées du convoyeur à une vitesse constante (ce qui évite ainsi les écarts entre les grumes successives sur la bande convoyeuse de décharge). Les moteurs sont actionnés et contrôlés par des capteurs de position qui détectent la position des grumes entre les première et deuxième élévations.

Abrégé anglais

An incline conveyor for use in transporting logs from a first elevation to a second elevation in a sawmill. The conveyor includes a support frame and a plurality of rotatable shafts mounted on the support frame at spaced-apart positions between the first and second elevations. Log lifters having at least one log receiving portion are mounted on the rotatable shafts. Each of the shafts is driven by a separate motor mounted on the support frame. The lifters mounted on the shafts may thus be rotated at variable speeds to ensure that logs are discharged from the conveyor at a constant rate (thereby avoiding gaps between successive logs on the discharge conveyor belt). The motors are actuated and controlled by position sensors which detect the position of the logs between the first and second elevations.

Revendications

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WHAT IS CLAIMED IS:
1. An incline conveyor for moving an elongated workpiece from
a first elevation to a second elevation, comprising:
(a) a frame;
(b) a plurality of shafts rotatably coupled to said frame at
spaced-apart locations between said first elevation and said second
elevation; and
(c) a plurality of lifters coupled to said shafts and rotatable
therewith, each of said lifters having at least one workpiece
receiving portion.
2. The conveyor of claim 1, wherein the speed of rotation of each
of said shafts is independently controllable.
3. The conveyor of claim 2, further comprising a plurality of
motors mounted on said frame, wherein each of said motors drives one of
said shafts.
4. The conveyor of claim 3, wherein each of said motors is
controlled by a position sensing means identifying the position of said
workpiece between said first and second elevations.

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5. The conveyor of claim 1, wherein said frame comprises first
and second sections spaced apart a distance greater than the length of said
workpiece and wherein said connector shafts extend between said first and
second sections.
6. The conveyor of claim 5, wherein first and second lifters are
mounted on each of said connector shafts proximate end portions thereof,
wherein said lifters are adapted to support said workpiece such that a
longitudinal axis thereof extends parallel to longitudinal axes of said
connector shafts.
7. The conveyor of claim 6, wherein each of said lifters comprise
opposed first and second workpiece receiving portions.
8. The conveyor of claim 5, wherein said connector shafts are
spaced between a front end and a rear end of said frame such that a plane
intersecting said connector shafts is non-vertical.
9. The conveyor of claim 5, wherein said lifters are mounted on
said connector shafts at staggered longitudinal positions, whereby the
rotation of one of said lifters will not obstruct the rotation of another one
of said lifters mounted on an adjacent one of said shafts.
A modular incline conveyor for moving logs one at a time
from a first elevation to a second elevation, comprising:
(a) a frame;

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(b) a plurality of shafts coupled to said frame at spaced-apart
locations between said first elevation and said second elevation; and
(c) a plurality of rotatable lifters coupled to said shafts, each of
said lifters having at least one log receiving portion,
wherein each of said logs is moved in stages between said lifters mounted
on a lowermost one of said shafts extending at said first elevation and said
lifters mounted on each of shafts extending above said lowermost shaft.
11. A method of moving a log between a first elevation and a
second elevation comprising the steps of:
(a) providing a frame for supporting a plurality of rotatable shafts
extending at spaced-apart locations between said first and second
elevations, each of said shafts having log lifters mounted thereon;
(b) delivering said log to said log lifters mounted on one of said
shafts;
(c) actuating rotation of said one of said shafts to move said log to
approximately the elevation of a next-in-sequence one of said shafts;
(d) sensing the position of said log at the elevation of step (c);
(e) actuating rotation of said next-in-sequence shaft to cause the
transfer of said log from said log lifters mounted on said one of said

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shafts to said log lifters mounted on said next-in-sequence one of
said shafts; and
(f) repeating steps (c) - (e) until said log has been transferred
between said first elevation and said second elevation.

Description

CA 02239534 1998-06-03
INCLINE CONVEYOR
Field of the Invention
This application relates to an improved conveyor for
conveying logs up an incline in a sawmill production line. The conveyor
minimises the gaps between successive logs to enhance sawmill efficiency.
Background of the Invention
to
In sawmill production lines it is often necessary to move logs
from one elevation to a higher elevation. For example, debarked logs may
be conveyed from a storage bin up an incline to a discharge conveyor belt
which delivers the logs one at a time to the cutting saws. Various devices
are known in the prior art for transporting logs up inclines of this sort in
a controlled manner.
For example, some incline conveyors employ chains driven
by a head shaft, each of the chains having carriers welded thereon for
2 o preventing logs from rolling down the incline. However, quite often the
logs will not line up properly on the carriers and the misaligned logs will
slide back into the storage bin. This results in a gap between logs on the
discharge conveyor, resulting in less efficient log processing.
2 5 Other more sophisticated step feeders are also in common use.
United States Patent No. 5,257,688, Fridlund, dated 2 November, 1993
discloses a step feeder for feeding logs up a rising support path. The logs
are moved one step at a time up the incline at a constant rate. It is
therefore not possible to selectively vary the transfer speed of one log

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relative to the other logs on the conveyor. Some step feeders include
photocell sensors to measure the leading and trailing edges of successive
logs. This log position information is used to control the timing of
discharge of the logs from the step feeder onto the saw conveyor belt,
thereby reducing gaps between logs on the conveyor.
Quadrant feeders are also installed in many sawmills.
Quadrant feeders comprise a large rotating frame having a log receiving
portion which picks up a single log with each rotation and delivers it to
1 o the discharge conveyor. Quadrant feeders suffer from the limitation that,
if a log is missed on any cycle of the frame, a gap between successive logs
will result on the discharge conveyor.
Another limitation common to conventional prior art incline
z 5 conveyors is that they are bulky in size and therefore difficult to
install in
existing sawmills without dismantling walls or buildings.
The need has therefore arisen for an incline conveyor which
is modular in construction and is adapted for transferring logs at variable
2 0 speeds to achieve optimum production line performance.

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Summary of the Invention
In accordance with the invention, the applicant's incline
conveyor is adapted for moving an elongated workpiece, such as a log,
between a first elevation and a second elevation. The conveyor comprises
a frame; a plurality of shafts rotatably coupled to the frame at spaced-apart
locations between the first elevation and the second elevation; and a
plurality of lifters coupled to the shafts and rotatable therewith, each of
the
lifters having at least one workpiece receiving portion. The speed of
1 o rotation of each of the shafts is preferably independently controllable.
In
particular, the conveyor may include a plurality of motors mounted on the
frame, each of the motors driving one of the shafts and being controlled by
one or more position sensors identifying the position of the workpiece
between the first and second elevations.
The application also describes a method for conveying an
elongated workpiece, such as a log, between a first elevation and a second
elevation. 'The method includes the steps of (a) providing a frame for
supporting a plurality of rotatable shafts extending at spaced-apart
2 0 locations between the first and second elevations, each of the shafts
having
log lifters mounted thereon; (b) delivering the log to the log lifters
mounted on one of the shafts; (c) actuating rotation of said one of the
shafts to move the log to approximately the elevation of a next-in-sequence
one of the shafts; (d) sensing the position of the log at the elevation of
step
2 5 (c); (e) actuating rotation of the next-in-sequence shaft to cause the
transfer of the log from the log lifters mounted on said one of the shafts
to the log lifters mounted on the next-in-sequence one of the shafts; and (f)

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repeating steps (c) - (e) until the log has been transferred between the first
elevation and the second elevation.
Brief Description of the Drawings
In drawings which illustrate a preferred embodiment of the
invention, but which should not be construed as restricting the spirit or
scope of the invention in any way,
1 o Figure 1 is an isometric view of the applicant's incline
conveyor;
Figure 2 is a side elevational view of the incline conveyor of
Figure 1;
Figure 3 is an end elevational view of the incline conveyor of
Figure 1; and
Figure 4 is a side elevational view of a rotary log lifter
2 o component of the incline conveyor of Figure 1.
Detailed Description of the Preferred Embodiment
This application relates to an incline conveyor 10 for
2 5 conveying elongated workpieces, such as logs, from one elevation to a
higher elevation. Conveyor 10 is particularly adapted for the efficient
transport of logs in a sawmill.

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As shown in Figure 1, conveyor 10 includes a support frame
14 consisting of spaced-apart support members 16 preferably constructed
from metal tubing. A plurality of rotatable connector shafts 18 are
mounted on frame 14 at different elevations. The ends of each shaft 18 are
supported in bearings. 20 mounted on a respective support member 16.
Rotation of each shaft 18 is driven by a corresponding variable speed drive
motor 22 mounted on a support member 16. Each motor 22 is coupled to
one end of a corresponding shaft 18 by means of a bearing 20, a coupling
24 and a gearbox 26 preferably having a 60:1 gear ratio.
A pair of rotary lifters 28 are coupled to end portions of each
connector shaft 18. Lifters 28 are keyed and timed to rotate at the same
speed as the respective shaft 18. As shown best in Figure 2, the
longitudinal positions of lifters 28 are staggered so that all of the lifters
28
may rotate simultaneously at variable speeds without obstruction. Each
lifter 28 has first and second blades 30 having curved end edges 32 (Figure
4). 'The side edges 34, 36 of blades 30 taper inwardly to form a pair of
opposed log receiving portions 38. Lifters 28 are preferably fabricated by
machining a circular metal wheel having the desired diameter and cutting
2 o first and second wedge-shaped segments from the wheel to define the log
receiving portions 38.
As should be apparent to someone skilled in the art, the
spacing between each pair of lifters 28 may be adjusted to suit the length
of the logs 12 to be transported. For example, for 8 foot logs, lifters 28 are
preferably spaced about 6 feet apart.

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Conveyor 10 is modular in nature. Thus, two or more
conveyors may be aligned side-by-side to accommodate logs 12 of any
desired length. The modular nature of conveyor 10 also allows for easy
installation into existing sawmills without dismantling any walls or
s buildings.
In use, conveyor 10 is adapted for transporting logs 12 up an
incline in stages from an input elevation 40 to an outlet elevation 42
(Figure 3). For example, in many sawmill operations logs are transferred
1 o to a storage pit after debarking. The logs must then be conveyed one at
a time from the storage pit to a discharge conveyor belt which delivers the
logs to the saws. In this example, the log storage pit is the input elevation
40 and the discharge conveyor belt 42 is the output elevation 42. For
optimum sawmill performance, logs 12 must be delivered to the discharge
15 conveyor belt in a controlled manner with no gaps between successive
logs.
As shown in Figure 3, logs 12 are delivered to the first stage
of conveyor 10 at an elevation approximating that of the lowermost
2 o connector shaft 18. Logs 12 are oriented so that their longitudinal axis
is
parallel to the longitudinal axis of shafts 18. As the first log 12 approaches
the lowermost connector shaft 18, a first photo cell or cam switch control
(not shown) triggers a motor 22 to drive rotation of the lowermost shaft 18.
The spaced-apart lifters 28 mounted on the lowermost shaft 18 rotate with
2 5 the shaft to receive the first log 12 in one of the log-receiving portions
38.
The remaining shafts and lifters 28 comprising conveyor 10 remain parked
in a stationary position. As the lowermost shaft 18 rotates, the first log 12

CA 02239534 1998-06-03
is moved upwardly to the second stage of conveyor 10 where it is
deposited into the lifters mounted on the next highest or second stage
shaft 18 (Figure 3). The second stage shaft 18 and the lifters 28 mounted
thereon are triggered to rotate when a second photo cell sensor or cam
s switch control signals to the corresponding drive motor 22 that the first
log
12 has reached a height sufficient to be received by the second stage lifters
28. The first log 12 is then conveyed upwardly to the third stage of the
conveyor 10 in a similar manner, and so on, until the log 12 is ultimately
discharged on to the saw conveyor at outlet elevation 42.
to
The next-in-sequence logs 12 are transported upwardly by
conveyor 10 from input elevation 40 to output elevation 42 in a similar
manner (Figure 3). Each lifter arm 28 is configured so that as one log is
deposited from one of the log-receiving portions 38 to the next stage in the
15 conveyor, the next-in-sequence log is received by the opposite log-
receiving portion 38. Accordingly, each full rotation of the uppermost
shaft 18 deposits two successive logs onto the discharge conveyor at
output elevation 42.
2 o The speed of rotation of shafts 18 may be selectively varied to
ensure that gaps between logs 12 on the discharge conveyor are
~inimi~ed. For example, if the conveyor 10 fails to pick up a log 12 from
the storage bin due to production line malfunctions or the like, this is
detected by the conveyor's log position sensors which are interfaced with
2 s a microprocessor. 'The microprocessor in turn sends a "catch-up" signal to
the motors 22 driving the lower shafts 18 to cause such shafts 18 to rotate
at an increased rate in comparison to the upper shafts 18. This ensures

CA 02239534 1998-06-03
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that the gap between successive logs on the conveyor 10 (caused by the
production line malfunction) will be reduced or eliminated as the logs 12
move toward the upper stages of conveyor 10. Thus the time lost by the
missing logs) 12 will effectively be recovered, thereby avoiding a
degradation in sawmill performance. It is anticipated that the top speed
of conveyor shafts 18 will be on the order of 20 revolutions per minute.
Another advantage of selectively controllable drive motors 22
is that shafts 18 and attached lifters 28 may be "parked" in a stationary
l0 position when not required. This results in enhanced energy efficiency.
For example, immediately following start-up only the lowermost shaft 18
will be triggered to rotate; the upper shafts 18 will remain stationary until
logs) 12 have been moved to the corresponding upper stages of the
conveyor 10. Conversely, if the delivery of logs 12 to conveyor 10 stops,
this will be sensed by log position sensors and the lowermost lifters 28 will
be parked in a stationary position.
As will be apparent to those skilled in the art in the light of
the foregoing disclosure, many alterations and modifications are possible
2 o in the practice of this invention without departing from the spirit or
scope
thereof. Accordingly, the scope of the invention is to be construed in
accordance with the substance defined by the following claims.

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