U.S. patent application number 12/699430 was filed with the patent office on 2011-02-10 for concrete finishing trowel with speed control.
This patent application is currently assigned to BARTELL MORRISON. Invention is credited to Jeff Gao, Rob Leggitt.
Application Number | 20110033235 12/699430 |
Document ID | / |
Family ID | 43534936 |
Filed Date | 2011-02-10 |
United States Patent
Application |
20110033235 |
Kind Code |
A1 |
Leggitt; Rob ; et
al. |
February 10, 2011 |
CONCRETE FINISHING TROWEL WITH SPEED CONTROL
Abstract
A concrete finishing trowel includes a frame, a power source
supported on the frame and having an output shaft, at least one
rotor assembly supported on the frame. Each rotor assembly
comprises a driven rotor shaft with a plurality of trowel blades
extending outwardly therefrom so as to rest on a surface to be
finished and to rotate with said driven rotor shaft to finish a
respective circular area. A transmission system operably couples
the power source output shaft to the driven rotor shaft of the at
least one rotor assembly. The transmission system includes a
variable driving pulley operable coupled directly or indirectly to
the power source output shaft and including a resiliently
deflectable portion that is movable to change the effective drive
diameter of the variable driving pulley, and a variable driven
pulley operably coupled to the variable driving pulley with a belt.
The variable driven pulley in turn is operably coupled directly or
indirectly to the driven rotor shaft of the at least one rotor
assembly. A rotor speed control system permits an operator to
adjust the center-to-center distance between the pulleys, thereby
to cause the drive diameter of the variable driven pulley to change
resulting in an adjustment of the speed of the driven rotor
shaft.
Inventors: |
Leggitt; Rob; (Halton Hills,
CA) ; Gao; Jeff; (Toronto, CA) |
Correspondence
Address: |
SIM & MCBURNEY
330 UNIVERSITY AVENUE, 6TH FLOOR
TORONTO
ON
M5G 1R7
CA
|
Assignee: |
BARTELL MORRISON
Brampton
CA
|
Family ID: |
43534936 |
Appl. No.: |
12/699430 |
Filed: |
February 3, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61149563 |
Feb 3, 2009 |
|
|
|
Current U.S.
Class: |
404/112 |
Current CPC
Class: |
E04F 21/247
20130101 |
Class at
Publication: |
404/112 |
International
Class: |
E01C 19/22 20060101
E01C019/22 |
Claims
1. A concrete finishing trowel comprising: a frame; a power source
supported on the frame and having an output shaft; at least one
rotor assembly supported on the frame, each rotor assembly
comprising a driven rotor shaft with a plurality of trowel blades
extending outwardly therefrom so as to rest on a surface to be
finished and to rotate with said driven rotor shaft to finish a
respective circular area; a transmission system operably coupling
the power source output shaft to the driven rotor shaft of the at
least one rotor assembly, comprising: a variable driving pulley
operable coupled directly or indirectly to the power source output
shaft and including a resiliently deflectable portion that is
movable to change the effective drive diameter of the variable
driving pulley; and a variable driven pulley operably coupled to
the variable driving pulley with a belt, and operably coupled
directly or indirectly to the driven rotor shaft of the at least
one rotor assembly; and a rotor speed control system for permitting
an operator to adjust the center-to-center distance between the
pulleys, wherein a change in the center-to-center distance causes
the drive diameter of the variable driven pulley to change thereby
to adjust the speed of the driven rotor shaft.
2. The concrete finishing trowel as defined in claim 1, wherein
said power source comprises an internal combustion engine.
3. A concrete finishing trowel as defined in claim 1, wherein said
transmission system further comprises a gearbox from which said
driven rotor shaft extends and which tilts relative to said frame
during a steering operation, said gearbox having an input shaft
which is operatively coupled to said variable driven pulley via a
U-joint drive shaft.
4. A concrete finishing trowel as defined in claim 1, wherein each
of the at least one rotor assembly further comprises a plurality of
support arms which extend radially outwardly from said driven shaft
and on which said trowel blades are mounted, and wherein said
trowel blades are mountable on multiple axial locations on said
support arms so as to alter the diameter of said circular area.
5. A concrete finishing trowel as defined in claim 4, wherein said
finishing trowel is a riding trowel comprising at least two rotor
assemblies each for finishing a respective circular area.
6. A finishing trowel as defined in claim 5 and further comprising:
a deck mounted on the frame; an operator's pedestal positioned on
said deck; and an operator's seat supported by said pedestal;
wherein said pedestal and said seat are hingedly attached to said
deck to permit access to components of said finishing trowel
located thereunder.
7. The concrete finishing trowel of claim 1, further comprising: a
shear pin hub associated with the variable driven pulley, the shear
pin hub adapted to receive a shear pin for mechanically coupling
the at least one rotor assembly to the power source, wherein a
shear pin is designed to break under predetermined conditions
thereby to mechanically decouple the at least one rotor assembly
from the power source with little damage.
8. A concrete finishing trowel comprising: a frame; a power source
supported on the frame and having an output shaft; at least one
rotor assembly supported on the frame, each rotor assembly
comprising a driven rotor shaft with a plurality of trowel blades
extending outwardly therefrom so as to rest on a surface to be
finished and to rotate with said driven rotor shaft to finish a
respective circular area; a transmission system operably coupling
the power source output shaft to the driven rotor shaft of the at
least one rotor assembly; a steering system comprising a steering
column operably coupled to the rotor assembly and operable to tilt
the rotor driven shaft relative to the frame thereby to effect a
steering operation, the steering system comprising a steering
assistance subsystem operable to provide mechanical assistance to
aid an operator when moving the steering column away from a neutral
position.
9. The concrete finishing trowel of claim 8, wherein the
transmission system comprises: a variable driving pulley operable
coupled directly or indirectly to the power source output shaft and
including a resiliently deflectable portion that is movable to
change the effective drive diameter of the variable driving pulley;
a variable driven pulley operably coupled to the variable driving
pulley with a belt, and operably coupled directly or indirectly to
the driven rotor shaft of the at least one rotor assembly; the
concrete finishing trowel further comprising: a rotor speed control
system for permitting an operator to adjust the center-to-center
distance between the pulleys, wherein a change in the
center-to-center distance causes the drive diameter of the variable
driven pulley to change thereby to adjust the speed of the driven
rotor shaft.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to concrete finishing
trowels, and more particularly to a concrete finishing trowel
having a rotor speed control system and a concrete finishing trowel
having a steering force assistance system.
BACKGROUND OF THE INVENTION
[0002] Various machines are available for smoothing or otherwise
finishing wet concrete. Of the known varieties of such machines,
self-propelled finishing trowels, and particularly riding finishing
trowels, are particularly useful for finishing large sections of
concrete more rapidly and efficiently than, for example, their
manually-pushed counterparts.
[0003] Riding concrete finishing trowels typically include a mobile
frame including a deck, with two or more rotor assemblies mounted
on an underside of the deck. Each rotor assembly includes a driven
rotor shaft extending down from the deck and a plurality of trowel
blades mounted on and extending radially out from the bottom end of
the driven rotor shaft. The trowel blades are supported on the
surface to be finished. The driven rotor shafts of the rotor
assemblies are driven by one or more engines that also mounted on
the frame of the finishing trowel. The one or more engine is
typically coupled to a respective driven rotor shaft via at least a
gearbox. The weight of the finishing trowel and the operator is
transmitted frictionally to the concrete by the rotating blades,
thereby smoothing the concrete surface.
[0004] The individual blades usually can be tilted relative to
their supports, via operation of a suitable mechanical lever and
linkage system accessible by an operator seated on an operator's
platform in order to alter the pitch of the blades. When this is
done, the pressure applied to the surface to be finished by the
weight of the machine is altered. This blade pitch adjustment
permits the finishing characteristics of the machine to be
adjusted. For example, during a finishing operation, the operator
may first perform an initial "floating" operation in which the
blades are operated at low speeds (on the order of about 30 rpm)
but at high torque. Then, the concrete is allowed to cure for
another 15 minutes to one-half hour, and the machine is operated at
progressively increasing speeds and progressively increasing blade
pitches up to the performance of a finishing or "burning" operation
at the highest possible speed. It is known to perform the burning
operation at preferably above about 150 rpm and up to about 200
rpm.
[0005] In order to provide for steering of a power finishing
trowel, the driven rotor shafts of the rotor assemblies are
typically also tiltable relative to the frame. By tilting the
driven shafts of the rotor assemblies, the operator can cause the
forces imposed on the concrete surface by the rotating blades to
propel the vehicle in a direction extending perpendicularly to the
direction of driven shaft tilt. For example, tilting at least the
driven shaft of the rotor assembly from side-to-side and
fore-and-aft steers the vehicle in the forward/reverse and the
left/right directions, respectively. Whereas the driven rotor
shafts of both rotor assemblies should be tilted for
forward/reverse steering control, it is known that only the driven
shaft of one of the rotor assemblies needs to be tilted for
left/right steering control.
[0006] It is known to drive rotor assemblies of the typical riding
finishing trowel by a drive train that is connected directly to
input shafts of the assemblies' gearboxes via a centrifugal clutch
and a system of shafts, belts or chains, and other torque transfer
elements of constant speed ratio. The drive trains typically
require universal joints to accommodate tilting of the gearbox
relative to the remainder of the drive train during a steering
control operation. Alternatively, a flexible shaft may be employed,
as discussed in U.S. Pat. No. 6,250,844 to Sartler et al., the
contents of which are incorporated entirely herein by
reference.
[0007] Various other proposals for drive trains in riding finishing
trowels include variable ratio transmissions, such as that
disclosed in U.S. Pat. No. 5,967,696 to Allen et al. In the patent,
Allen et al. discuss a variable gear drive unit comprising a
variable ratio pulley driven by a motor. A second pulley drives the
gear box input shaft, with a drive belt entrained between the
pulleys. A linear actuator causes the linear displacement of
portions of the variable ratio pulley to change the effective
pulley diameter.
[0008] In known concrete finishing trowels, operators achieve
variations in rotor speed by adjusting the speed of the engine.
While indeed rotor speed is adjustable in this way, there is the
significant problem that the reduction in engine speed brings about
a concomitant reduction in delivered power. This results in
insufficient torque at the trowel blades. Therefore, improvements
in the transmission of power from the engine to the driven rotor
are desired.
[0009] Another issue known to those familiar with the concrete
finishing trowel industry is that, after having used riding
finishing trowels for an extended period of time, an operator can
become physically fatigued. One cause of such physical fatigue is
the requirement to repeatedly push and pull the steering handles
against frictional forces so as to tilt the driven rotors thereby
to steer the machine. As such, improvements in steering control and
comfort are therefore also desired.
[0010] It is therefore an object of the present invention to
provide a novel concrete finishing trowel.
SUMMARY OF THE INVENTION
[0011] Accordingly, in one aspect there is provided a concrete
finishing trowel comprising:
[0012] a frame;
[0013] a power source supported on the frame and having an output
shaft;
[0014] at least one rotor assembly supported on the frame, each
rotor assembly comprising a driven rotor shaft with a plurality of
trowel blades extending outwardly therefrom so as to rest on a
surface to be finished and to rotate with said driven rotor shaft
to finish a respective circular area;
[0015] a transmission system operably coupling the power source
output shaft to the driven rotor shaft of the at least one rotor
assembly, comprising: [0016] a variable driving pulley operable
coupled directly or indirectly to the power source output shaft and
including a resiliently deflectable portion that is movable to
change the effective drive diameter of the variable driving pulley;
[0017] a variable driven pulley operably coupled to the variable
driving pulley with a belt, and operably coupled directly or
indirectly to the driven rotor shaft of the at least one rotor
assembly; and
[0018] a rotor speed control system for permitting an operator to
adjust the center-to-center distance between the pulleys,
[0019] wherein a change in the center-to-center distance causes the
drive diameter of the variable driven pulley to change thereby to
adjust the speed of the driven rotor shaft.
[0020] The concrete finishing trowel described herein provides
advantages over prior devices due at least in part to its ability
to provide both automatic torque response and operator-adjustable
speed control. Whereas prior concrete finishing trowels required
the operator to achieve variable speeds by adjusting the speed of
the engine itself, the concrete finishing trowel described herein
permits rotor speed control while maintaining a level of engine
speed that delivers sufficient power and thus torque for the rotors
to operate effectively during finishing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Embodiments will now be described more fully with reference
to the accompanying drawings in which:
[0022] FIGS. 1a to 1d show various views of a concrete finishing
trowel according to an aspect of the invention;
[0023] FIG. 2 is a perspective view isolating portions of the
engine, transmission and rotor assembly portions of the concrete
finishing trowel of FIG. 1;
[0024] FIG. 3 is a perspective view isolating portions of the
transmission and rotor assemblies portions of the concrete
finishing trowel of FIG. 1;
[0025] FIGS. 4 is a perspective view isolating portions of the
steering system and portions of the rotor assemblies of the
concrete finishing trowel of FIG. 1;
[0026] FIGS. 5a and 5b are a perspective views isolating portions
of the steering system including a steering assistance subsystem of
the concrete finishing trowel of FIG. 1; and
[0027] FIG. 6 is a perspective view isolating the steering
assistance subsystem shown in FIG. 5.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0028] Turning now to FIGS. 1a to 1d (hereinafter referred to as
FIG. 1 for brevity), a riding concrete finishing trowel in
accordance with a preferred embodiment of the invention is shown.
The riding concrete finishing trowel comprises a rigid frame, an
upper deck mounted on the frame, an operator's platform or pedestal
provided on the deck, and right and left rotor assemblies. The
right and left rotor assemblies respectively extend downwardly from
the deck and support the finishing trowel on the surface to be
finished. The rotor assemblies rotate towards the operator, or
counterclockwise and clockwise, respectively, to perform a
finishing operation.
[0029] A conventional ring guard is positioned at the outer
perimeter of the finishing trowel and extends downwardly from the
deck to the vicinity of the surface to be finished. The pedestal is
positioned longitudinally centrally on the deck at a rear portion
thereof and supports an operator's seat. Preferably, the pedestal
and operator's seat can be pivoted via hinges (not shown) to permit
access to components of the machine located thereunder, such as the
machine's engine. Vibration damping means are provided for reducing
the vibration imparted to the operator's seat. An operator presence
switch is mounted beneath the operator's seat. A fuel tank is
disposed on the deck, beside the pedestal. On the opposite side of
the pedestal is a fluid tank for an integral retardant spray
system. An electrical system, including four headlights for easing
nighttime operation of the concrete finishing trowel at the site,
is protected against the unwanted ingress of water and dust in
accordance with the IP55 qualification set by International
Electrical Standards (IEC).
[0030] Each rotor assembly is coupled to a respective worm-drive
gearbox. The driven rotor shaft of each rotor assembly extends
downwardly from its gearbox, and a plurality of
circumferentially-spaced trowel blades are supported on the driven
rotor shaft via radial support arms. The trowel blades extend
radially outwardly from the bottom end of the driven rotor shaft so
as to rest on the concrete surface. As can be seen, in this
embodiment the trowel blades are mountable on multiple axial
locations on the support arms, so as to enable an operator to alter
the diameter of the circular area covered by each rotor assembly
between finishing operations. The circular areas may be made to
overlap by selective placement of the trowel blades on the support
arms. Each gearbox is mounted on the undersurface of the deck but
is tiltable relative to the deck for steering, as will be
described.
[0031] The pitch of the trowel blades of each of the right and left
rotor assemblies can be individually adjusted by a dedicated blade
pitch adjustment assembly. The pitch blade adjustment is preferably
electrically actuated. Alternative blade pitch adjustment systems
are described in the above-noted U.S. Pat. No. 6,250,844 to Sartler
et al., and U.S. Pat. No. 2,887,934 to Whiteman, the contents of
which are incorporated entirely herein by reference.
[0032] Both rotor assemblies, as well as other powered components
of the finishing trowel, are driven by a power source such as a
gasoline powered internal combustion engine that is mounted under
the operator's seat. It will be understood that the size of the
engine will vary with the size of the machine and the number of
rotor assemblies powered by the engine. For example, the
illustrated two-rotor, 48'' machine typically will employ an engine
of about 25 hp. A catalytic converter system is coupled to the
engine exhaust and supported on the frame.
[0033] The rotor assemblies are operably connected to the engine
via a unique transmission system and, along with their respective
gearboxes, can be tilted for steering purposes via a unique
steering system as will be described.
[0034] FIG. 2 is a perspective view isolating portions of the
engine mounted on the frame, the transmission and the rotor
assembly portions of the concrete finishing trowel of FIG. 1. FIG.
3 shows the various isolated portions without the engine. The
output shaft of the engine is coupled to a clutch, which in turn is
coupled to a driven pulley via a belt. The driven pulley is
rotatably mounted on a jack shaft that is supported within the
subframe of the concrete finishing trowel. The other end of the
jack shaft is connected to a variable driving pulley which, via a
variable driving belt, is coupled to a variable driven pulley. A
U-joint drive shaft is coupled to the variable driven pulley via a
shear pin hub, and extends to the tiltable right rotor assembly via
its respective tiltable worm gearbox. The shear pin hub receives a
shear pin which acts as a mechanical fuse of sorts to mechanically
couple the rotor assemblies to the power source. As would be
understood, the shear pin is designed to break under predetermined
conditions such as overload or impact, thereby to impart little or
no damage through the transmission system to the engine. A broken
shear pin is easily replaced by an operator in the field and thus
is a simple, inexpensive and effective way by which certain
components of the concrete finishing trowel can be shielded from
costly damage.
[0035] Another U-joint drive shaft extends from the variable driven
pulley to another tiltable worm gearbox which is, in turn, coupled
to the left driven rotor. During a steering operation, the tiltable
worm gearboxes move in unison with their respective rotor
assemblies, as permitted by the U-joint drive shaft.
[0036] In operation, rotational power is transmitted via the driven
pulley to the variable driving pulley, then to the variable driven
pulley via the variable driving belt, via the U-joint drive shafts
to respective worm gearbox and finally to the respective rotor
driven shafts of the rotor assemblies.
[0037] The variable driving pulley includes a resiliently
deflectable portion that is automatically movable to change the
effective drive diameter of the variable driving pulley in response
to changes in torque. In this embodiment, the resiliently
deflectable portion is one half of the pulley that is biased to a
"home" position relative to the other half of the pulley. When the
deflectable pulley half moves away from its other half, the
variable driven pulley belt traverses a smaller pulley diameter,
thus causing the variable driven pulley, and accordingly the driven
rotor, to turn slower. A spring biases the deflectable pulley half
back towards its home position. As the deflectable pulley half
moves back towards the home position, the variable driven pulley
belt traverses a larger pulley diameter, thus causing the variable
driven pulley and accordingly the driven rotor, to turn faster.
[0038] The resiliently deflectable portion will move automatically
as the operating conditions fluctuate, accordingly widening the
space between the pulley halves. Thus, such changes permit the
engine speed to remain constant through changes in the rotational
speed of the rotors.
[0039] Advantageously, the concrete finishing trowel is provided
with a rotor speed control system that permits an operator of the
machine to adjust the speed of the driven rotors without
necessarily adjusting engine speed. In order to decrease the driven
rotor speed of rotation, the operator turns a speed control handle
(shown as item 1 in FIG. 3) clockwise. Turning the speed control
handle clockwise causes a yoke end to move upwards. This
counterclockwise turns a front control shaft to which the yoke end
is connected (when viewed from the right of the machine in FIG. 3).
Turning of this front control shaft causes the tie rod to which it
is connected to shift to the left (again, when viewed from the
right of the machine) causing in turn the rear control shaft to
which the tie rod is connected to rotate counterclockwise. As the
rear control shaft is rotated counterclockwise, the shaft supporter
that supports the shaft connecting the driven pulley and the
variable driving pulley is moved upwards. As the shaft is moved
upwards, the variable driving pulley is accordingly caused to move
away from the variable driven pulley. More particularly, the center
to center distance between the variable driving pulley and the
variable driven pulley is increased. At this point, the tension on
the variable driving belt increases so as to cause it to force
itself between the two pulley halves of the variable driving
pulley. As a result, the deflectable pulley half is pushed away
from its other half, and the effective pulley diameter is
decreased. This decrease leads to a decrease in the speed of the
variable driving belt and accordingly a decrease in the speed of
the driven rotors.
[0040] In order to increase the driven rotor speed of rotation, the
operator turns the speed control handle (shown as item 1 in FIG. 3)
counterclockwise. Turning the speed control handle counterclockwise
causes the yoke end to move downwards. This clockwise turns the
front control shaft to which the yoke end is connected (when viewed
from the right of the machine in FIG. 3). Turning of this front
control shaft causes the tie rod to which it is connected to shift
to the right (again, when viewed from the right of the machine)
causing in turn the rear control shaft to which the tie rod is
connected to rotate clockwise. As the rear control shaft is rotated
clockwise, the shaft supporter that supports the shaft connecting
the driven pulley and the variable driving pulley is moved
downwards. As the shaft is moved downwards, the variable driving
pulley is accordingly caused to move towards the variable driven
pulley. More particularly, the center to center distance between
the variable driving pulley and the variable driven pulley is
decreased. At this point, the tension on the variable driving belt
decreases and due to the spring-influenced resilience of the
deflectable pulley half the pulley halves are moved closer
together. As a result, the effective pulley diameter is increased.
This increase leads to an increase in the speed of the variable
driving belt and accordingly an increase in the speed of the driven
rotors.
[0041] It will be understood that, at any given speed set by the
operator of the concrete finishing trowel, the transmission system
will still have automatic torque response because the deflectable
pulley half will be able to move relative to its other half in
response to changing conditions. As such, a manually adjustable
speed control with integrated automatic torque response has been
provided in a triple reduction transmission system
[0042] FIGS. 4 is a perspective view isolating portions of the
steering system and portions of the rotor assemblies of the
concrete finishing trowel of FIG. 1. The steering system comprises
a pitch sensor bracket, a limit switch adjustment bracket, a
gearmotor, a pin-block U-joint, a screw jack, a jack mount bracket,
a yoke arm, a limit switch, a pressure plate, a switch mount
bracket, and a steering control arm. The steering system is
supported on the subframe of the concrete finishing trowel.
[0043] FIGS. 5a and 5b are perspective views isolating portions of
the steering system including a steering assistance subsystem of
the concrete finishing trowel. A control panel supports operator
hand grips and gauges for giving an operator visual indications of
trowel blade speed in revolutions per minute, the relative degree
of blade pitch, the battery charging status, the fuel level, the
total run hours, a "system on" indicator lamp, and a "low oil
pressure" indicator lamp. It will be understood that other
indicators and controls can be supported on the control panel. The
control panel is supported atop a single steering column, which is
pivotable in various directions to, in conjunction with a steering
assistance system (shown in isolation in FIG. 6) change the
position of left- and right-side steering control arms in order to
accordingly tilt the driven rotors in the rotor assemblies to
effect steering. The left-side steering control arm is mounted onto
the back of the left side gearbox, while the right-side steering
control arm is mounted on the back of the right side gearbox. A
steering bracket is fixed to the vertical steering shaft within the
steering column, and there is no relative movement between the
steering bracket and the steering shaft.
[0044] In order to propel the concrete finishing trowel forward
during operation, the operator grips both hand grips and pushes the
steering column forward so as to pivot within a spherical bearing
(see item 13 in FIG. 6). The steering bracket 14 then moves forward
and the ends of the rods 26 and 27 move forward. In turn, the
steering shafts 9 and 28 are turned counterclockwise (when viewing
FIG. 5a from the left side), and the pivot plates 3 and 29 are
turned clockwise. Ends of rods 2 and 30 then move downwards and
both gearboxes are tilted so as to cause the concrete finishing
trowel forwards.
[0045] In order to propel the concrete finishing trowel backwards
during operation, the operator grips both hand grips and pulls the
steering column backward so as to pivot within a spherical bearing
(see item 13 in FIG. 6). The steering bracket 14 then moves
backwards and the ends of the rods 26 and 27 move backwards. In
turn, the steering shafts 9 and 28 are turned clockwise (when
viewing FIG. 5a from the left side), and the pivot plates 3 and 29
are turned counterclockwise. Ends of rods 2 and 30 then move
upwards and both gearboxes are tilted so as to cause the concrete
finishing trowel to travel backwards.
[0046] In order to turn the concrete finishing trowel to the left,
the operator pulls the left hand grip and pushes the right hand
grip. The vertical steering shaft accordingly is turned
counterclockwise (when viewed from the top). The rod end 26 then
moves backwards and rod end 27 moves forwards. Accordingly, the
left side steering shaft 9 turns clockwise while the right side
steering shaft 28 turns counterclockwise. When this occurs, the
left side pivot plate 3 turns counterclockwise and the right side
pivot plate turns clockwise. As this occurs, the rod end 2 moves up
and the rod end 30 moves down. The left side gearbox accordingly
tilts outside and the right side gearbox tilts inside, causing the
concrete finishing trowel to turn left.
[0047] In order to turn the concrete finishing trowel to the right,
the operator pushes the left hand grip and pulls the right hand
grip. The vertical steering shaft accordingly is turned clockwise
(when viewed from the top). The rod end 26 then moves forwards and
rod end 27 moves backwards. Accordingly, the left side steering
shaft 9 turns counterclockwise while the right side steering shaft
28 turns clockwise. When this occurs, the left side pivot plate 3
turns clockwise and the right side pivot plate turns
counterclockwise. As this occurs, the rod end 2 moves down and the
rod end 30 moves up. The left side gearbox accordingly tilts inside
and the right side gearbox tilts outside, causing the concrete
finishing trowel to turn right.
[0048] In order to move the concrete finishing trowel laterally to
the left, the operator moves both hand grips to the left. The
vertical steering shaft is thereby caused to move leftwards about
its pivot point on the spherical bearing 13, and the steering
bracket 14 accordingly moves left. The rod end 24 moves left, while
the L/R pivot plate 17 turns counterclockwise. The L/R steering
lever 8 then turns counterclockwise and the rod end 25 moves up.
Accordingly, the right side gearbox is caused to tilt backwards
(when viewed from the top), causing the concrete finishing trowel
to move left laterally.
[0049] In order to move the concrete finishing trowel laterally to
the right, the operator moves both hand grips to the right. The
vertical steering shaft is thereby caused to move rightwards about
its pivot point on the spherical bearing 13, and the steering
bracket 14 accordingly moves right. The rod end 24 moves right,
while the L/R pivot plate 17 turns clockwise. The L/R steering
lever 8 then turns clockwise and the rod end 25 moves down.
Accordingly, the right side gearbox is caused to tilt forwards
(when viewed from the top), causing the concrete finishing trowel
to move right laterally.
[0050] FIG. 6 is a perspective view isolating the steering
assistance subsystem shown in FIGS. 5a and 5b. The steering
assistance subsystem makes it easier for an operator to move the
vertical steering column from its neutral position. Springs 16 are
compressed, such compression being adjustable by way of movable
adjusting nuts 18 and lock nuts 19 being moved up- or downwards. A
cross pivot bracket 22 is pivotable about pin 32 on vertical
steering shaft 12, and pivot bracket 15 is pivotable about the pins
on cross pivot bracket 22. As a result, pivot bracket 15 can remain
parallel to the pressure plat 10 under the equal pressure of the
four springs 16, while the vertical steering shaft 12 moves in the
spherical bearing 13.
[0051] At a neutral position, the four springs are compressed, and
accordingly push the pivot bracket vertically downwards to the
centre of the spherical bearing 13. When the vertical steering
shaft is moved either backwards or forwards by the operator of the
concrete finishing trowel, the pivot bracket moves forwards or
backwards causing the springs to leave their neutral position. The
springs extend and provide a level of assisting force to push the
steering shaft in the direction in which it has been moved. As a
result, the vertical steering shaft tends to remain in the position
in which it is moved by the operator to provide assistance to the
operator. A similar operation occurs when the vertical steering
shaft is moved either backwards or forwards.
[0052] When the vertical steering shaft is twisted as described
above, the pivot bracket is turned, causing the springs to extend
and provide twisting force assistance.
[0053] While the above has been set out with reference to an
embodiment, it will be understood that alternative embodiments that
fall within the purpose of the invention set forth herein are
possible.
[0054] Although embodiments have been described with reference to
the drawings, those of skill in the art will appreciate that
variations and modifications may be made without departing from the
spirit and scope thereof as defined by the appended claims.
* * * * *