ELECTRIC DRIVE SYSTEM FOR PLANER MILL INFEED AND OUTFEED ROLLS

SYSTEME D'ENTRAINEMENT ELECTRIQUE DES CYLINDRES D'ENTREE ET DE SORTIE DE RABOTEUSES

English Abstract

A method and apparatus for converting a conventional mechanical or hydraulic system for driving the infeed and outfeed rolls of a planer mill or a similar conveyor to variable frequency electric power. The method involves disconnecting the roller shafts from pre-existing mechanical and hydraulic drive components housed within the conveyor gearbox or other support frame. The electric motors are mounted at fixed positions on a panel rigidly connected to the gearbox or other support frame at a location spaced-apart from the roller shafts. Each motor is coupled to a corresponding roller shaft by means of a connector drive shaft having universal joint couplers at each end thereof. This arrangement permits displacement of the roller shafts during normal operation of the conveyor without transferring torque forces to the electric motors. The speed of each motor and hence each roller may be independently controlled by a frequency inverter which is operable by remote control.

French Abstract

Une méthode et un appareil pour convertir un système mécanique ou hydraulique conventionnel pour faire fonctionner les cylindres d'entrée et de sortie d'une raboteuse ou d'un convoyeur similaire à une puissance électrique de fréquence variable. La méthode consiste à déconnecter les axes des cylindres des composants d'entraînement mécanique et hydraulique préexistants logés dans la boîte d'engrenages du convoyeur ou dans tout autre châssis de support. Les moteurs électriques sont montés en des positions fixes sur un panneau rigidement raccordé à la boîte d'engrenages ou à l'autre châssis de support à un emplacement éloigné des axes des cylindres. Chaque moteur est couplé à un axe de cylindre correspondant au moyen d'un arbre de transmission de connexion ayant des coupleurs joints universels à chaque extrémité de celui-ci. Cet agencement permet un déplacement des axes des cylindres durant le fonctionnement normal du convoyeur sans transférer les forces de couple aux moteurs électriques. La vitesse de chaque moteur et donc de chaque cylindre peut être commandée indépendamment par un variateur de fréquence qui est opérable par télécommande.

Claims

9
WHAT IS CLAIMED IS:
1. An electric drive mechanism for a conveyor comprising rotatable rollers
comprising:
(a) a plurality of roller shafts loosely coupled to a support frame to permit
limited displacement of said shafts relative to said support frame;
(b) a plurality of electric motors supported in a stationary position at a
location
removed from said support frame, wherein each motor independently drives
rotation of one of said roller shafts; and
(c) a plurality of displaceable connector drive shafts each having universal
joint
couplers at first and second ends thereof,
wherein said first end of each drive shaft is operatively coupled to one of
said
roller shafts and said second end of said drive shaft is operatively coupled
to
one of said motors.
2. The drive mechanism of claim 1, wherein said motors are mounted on a panel
rigidly connected to said support flame at a spaced location from said roller
shafts.
3. The drive mechanism of claim 2, further comprising a reduction gearbox
mounted on said panel for coupling said motor to said connector drive shaft
second end.
4. An electric drive mechanism for a conveyor comprising rotatable rollers,
each
of the rollers having a rotatable roller shaft coupled to a support frame to
permit limited displacement of said shaft relative to said support frame, said
drive mechanism comprising:
(a) a plurality of electric motors, wherein each motor independently drives
rotation of one of said roller shafts; and
(b) a plurality of displaceable connector drive shafts each having couplers at
first and second ends thereof, wherein said first end of each connector drive

10
shaft is pivotably coupled to one of said roller shafts and said second end of
said drive shaft is operatively coupled to one of said electric motors.
5. The drive mechanism of claim 4, wherein said motors are mounted at a fixed
location spaced apart from said support frame and wherein said roller shafts
are displaceable
relative to said support frame without transfer of substantial torque forces
to said motors.
6. The drive mechanism of claim 4, wherein each of said motors is operably
coupled to an electronic controller to enable variable frequency operation of
said drive
mechanism.
7. An electric drive mechanism for a conveyor comprising rotatable rollers,
each
of the rollers having a vertically displaceable roller shaft, said drive
mechanism comprising:
(a) a plurality of electric motors supported in a stationary position at a
location
removed from said roller shafts, wherein each motor independently drives
rotation of one of said roller shafts; and
(b) a plurality of displaceable connector drive shafts each having couplers at
first and second ends thereof, wherein said first end of each connector drive
shaft is pivotably coupled to one of said roller shafts and said second end of
said drive shaft is operatively coupled to one of said electric motors.

Description

CA 02230227 1998-02-20
ELECTRIC DRIVE SYSTEM FOR PLANER MILL
INFEED AND OUTFEED ROLLS
Technical Field
This application relates to a method and apparatus for converting
a conventional mechanical or hydraulic system for driving the infeed and
outfeed rolls of a planer mill to variable frequency electric power.
B_ ack~,round
Sawmill production lines typically employ rotating press roller
assemblies to convey lumber at a. controlled rate through saws, planers or
other wood processing equipment. The rollers rotate about shafts which are
connected to sprockets housed within a gearbox. Rotation of the sprockets
and hence the roller shafts is driven by a long serpentine drive chain usually
powered by a single electric motor. This type of mechanical drive system
requires relatively costly maintenance. For example, the drive chain and
sprocket system must be maintained in an oil bath for optimum performance.
:?0
Some planer mill infeed and outfeed rolls may alternatively be
driven by hydraulic power to allow for variable frequency operation.
Variable frequency operation is desirable, for example, for optimum
processing of lumber pieces of different sizes (smaller pieces may require
less
;?5 planin;~ and may be fed through the mill at a faster rate). Various
hydraulic
drive systems are in use. According to one existing system, a relatively small
hydraulic motor is mounted on each roll shaft and is driven by a remote
hydraulic pump. A torque arm is provided for counteracting rotation of the

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roller shafts. Such hydraulic drive systems are also relatively expensive to
maint~~in and may result in environmental contamination and increased fire
danger due to oil leaks from hydraulic pumps, motors, hoses, fittings or the
like.
One strategy for overcoming the shortcomings of conventional
mechanical and hydraulic drive systems is to couple each roller shaft directly
to an electric motor. However, during normal operation planer mill roller
shafts are deflected up and down depending upon the size and position of
lumber passing through the mill. Previous attempts to mount electric motors
directly on the ends of roller drive shafts have failed due to the weight of
the
motors and mechanical problems arising from periodic roller deflection.
The need has therefore arisen for a method and apparatus for
economically converting a planer mill drive system from conventional
mechanical or hydraulic power to variable frequency electric power.
Summary of Invention
In accordance with the invention, a method of converting a pre-
existing conveyor drive mechanism to electric power is disclosed, the pre-
existing drive mechanism comprising at least one rotatable roller shaft having
a drive end coupled to a mechanical gearbox or hydraulic motor housed
'? 5 within a support frame. The conversion method includes the steps of (a)
dis-
consenting the roller shaft from the mechanical gearbox or hydraulic motor

CA 02230227 1998-02-20
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assembly; (b) removing the mechanical gearbox or hydraulic motor assembly
from the support frame; (c) rigidly connecting a supplementary mounting
panel to the support frame at a location spaced apart from the roller shaft
drive .end; (d) mounting at least one electric motor on the supplementary
mounting panel at a fixed location; (e) providing a connector drive shaft
having universal j oint couplers at first and second ends thereof; and (f)
operatively coupling the drive shaft first end to the roller shaft drive end
and
the drive shaft second end to the motor. The method may also include the
step of operatively coupling the motor to a fi equency inverter operable by
remote control. Optionally, the method may further include the step of
mounting a reduction gearbox on the supplementary panel for coupling the
motor to the connector drive shaft second end.
An electric drive mechanism for a conveyor comprising rotatable
rollers is also disclosed. The drive mechanism includes a plurality of roller
shafts loosely coupled to a support frame to permit limited displacement of
the shafts relative to the support frame; a plurality of electric motors,
wherein
each motor independently drives rotation of one of the roller shafts; a
plurality of displaceable connector drive shafts each having universal joint
0 couplers at first and second ends thereof, wherein the first end of each
drive
shaft is operatively coupled to one of the roller shafts and the second end of
the drive shaft is operatively coupled to one of the motors. Preferably, the
motors are mounted on a panel rigidly connected to the support frame at a
spaced location from the roller shafts.

CA 02230227 1998-02-20
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A kit for converting a pre-existing drive mechanism for a
conveyor to electric power is also disclosed, the pre-existing drive mecha-
nism comprising at least one rotatable roller shaft displaceably coupled to a
support frame. The kit includes a mounting panel rigidly connectable to the
support frame at a location spaced-apart from the roller shaft; an electric
motor securable in a fixed position on the mounting panel; a connector drive
shaft having universal joint couplers at first and second ends thereof,
wherein
the fir~~t end of each drive shaft is operatively connectable to the roller
shaft
and the second end of the drive shaft is operatively connectable to the motor.
Brief Description of Drawings
In drawings which illustrate the preferred embodiment of the
invention but which should not be construed as restricting the spirit or scope
of the invention in any way,
Figure lA is an isometric view of a conventional prior art
mechanical drive system for driving rotation of the infeed and outfeed rolls
of a planer mill;
Figure 1B is an isometric view of a conventional prior art
hydrau~.lic drive system for driving rotation of the infeed and outfeed rolls
of
a planar mill;

CA 02230227 1998-02-20
Figure 2 is an isometric view of the drive system of Figure 1 A
or 1B .after it has been converted in accordance with the invention to
variable
frequency electric power;
Figure 3 is a partially fragmented, cross-sectional view of the
convened drive system of Figure 2;
Figure 4 is an end elevationa.l view of the converted drive system
of Figure 2.
Descri. tp ion
Figure 1 illustrates a mechanical drive mechanism for the infeed
rolls 1 n and outfeed rolls 12 of a conventional lumber processing mill. In
the
illustr~~ted embodiment two pairs of infeed rolls 10 and one pair of outfeed
rolls 1:~ are shown. Each pair of rolls 10, 12 includes an upper roller 14 and
a lower roller 16. Lumber fed between rollers 14,16 is conveyed down the
mill production line through wood processing equipment, such as planing
tools. The invention may used, for example, in conjunction with a Stedson
Ross f> 14D planer.
Each roller 14, 16 comprises a rotatable shaft 17 displaceably
couplf;d to a front panel 19 of gearbox 18 (Figure 3). In Figure 1 the rear
panel of each gearbox 18 has been removed to expose a conventional
mechanical drive mechanism comprising a plurality of sprockets 20
operatively connected to an endless belt or serpentine chain 22. Chain 22 is

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driven by a single electric motor 24, either directly or indirectly through a
reduction gearbox 26.
As should be apparent to someone skilled in the art, rollers 14,
16 ma:y alternatively be driven by a hydraulic drive system to permit variable
frequency operation. A conventional hydraulic drive system is illustrated in
Figure' 1B. In this embodiment, a DC electric motor 25 is connected to a
hydravic pump 28 which draws hydraulic fluid from a reservoir 30. Pump 28
propels hydraulic fluid through an adjustable valve 31 to a hydraulic motor
32 shown mounted on a manifold 33. Motor 32 controls the speed of rotation
of rollers 14,16.
In operation, lumber passing through the mill is fed between
rotating rollers 14, 16 and is conveyed to or through wood processing
machinery. The relative vertical spacing between rollers 14, 16 varies
depending upon the size, orientation and position of the lumber pieces. For
example, when a large piece of lumber is fed between rollers 14, 16, the
upper rollers 14 will ordinarily deflect upwardly to accommodate the
diameter of the lumber piece and will deflect downwardly to the rest position
after the lumber piece has passed therethrough. The roller shafts 17 are
loosely coupled to gearbox 18 to permit such vertical displacement.
Figure 2 illustrates a planer mill drive system after it has been
conve rted to electric power in accordance with the subj ect invention. In
order t:o achieve the conversion, the mechanical drive assembly comprising
sprockets 20 and chain 22 (or any hydraulic equivalents) is removed together

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with tree rear panel of the existing gearbox 18 (or other support frame
housing
the drive mechanism). A supplementary frame 34 is rigidly connected to each
gearbox 18. Supplementary frame 34 includes a vertical panel 36 which is
maintained in spaced relation from gearbox 18 by means of braces 3 8 and 40 .
A plurality of electric motor assemblies each comprising an electric motor 42
and a reduction gearbox 43 are mounted on panel 36 at fixed locations for
driving; corresponding rollers 14, 16. General Electric XSD motors (25 HP,
18001ZPM) are suitable for this purpose.
Each electric motor assembly is connected to a respective roller
14, 16 by means of a connector drive shaft 44. Spicer 1550 heavy duty drive
shafts available from Dana Corporation of Toledo, Ohio are suitable for this
purpose. Universal joint couplers 45 are provided at either end of connector
drive shaft 44 for coupling each drive shaft to a respective roller shaft 17
and
reduction gearbox 43. When the converted drive mechanism of Figure 2 is
in use, vertical displacement of rollers 14 and 16, as lumber is fed through
the
mill, will result in some corresponding deflection of connector drive shafts
44. However, motors 42 and reduction gearboxes 43, which are rigidly
mounted to panel 36, remain fixed in place. Torque forces resulting from
deflection of roller shafts 17 are therefore effectively absorbed by connector
drive shafts 44 and are not transferred to motors 42.
As should be apparent from Figure 2, each roller 14, 16 is
independently driven by a separate motor 42 for optimum control. The motor
speed may be controlled by a frequency inverter which may be remotely
controlled by a manual switch or a computer processor. This arrangement

CA 02230227 1998-02-20
g _
enables better roller control at variable speeds and temperatures than
conventional mechanical or hydraulic drive mechanisms. Optimization of
roller speeds results in more efficient mill operation and lower energy costs.
Moreover, the converted electric drive mechanism of Figure 2 requires very
little on-going maintenance as compared to conventional designs.
As shown in Figure 4, drive shafts 44 may be enclosed within
a housing having a top panel 50 and side doors 52 which swing about hinges
54. 'the existing gearbox 18 and vertical panel 36 of the supplementary
frame :34 form the end portions of the housing. Although not essential to the
functionality of the invention, an enclosed housing is recommended for safety
reasons. Parts 56 shown in Figure 4 do not form part of the invention, but
rather indicate reinforced portions of the gearbox 18 where sprockets 20 were
mounted prior to the retrofit.
As will be apparent to those skilled in the art in the light of the
foregoing disclosure, many alterations and modifications are possible 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.

Representative Drawing