IES84790Y1 - Three-wheel forklift truck - Google Patents
Three-wheel forklift truckInfo
- Publication number
- IES84790Y1 IES84790Y1 IE2007/0379A IE20070379A IES84790Y1 IE S84790 Y1 IES84790 Y1 IE S84790Y1 IE 2007/0379 A IE2007/0379 A IE 2007/0379A IE 20070379 A IE20070379 A IE 20070379A IE S84790 Y1 IES84790 Y1 IE S84790Y1
- Authority
- IE
- Ireland
- Prior art keywords
- truck
- mode
- wheel
- rear wheel
- front wheels
- Prior art date
Links
- 230000002441 reversible Effects 0.000 claims abstract description 3
- 239000012530 fluid Substances 0.000 claims description 20
- 230000002706 hydrostatic Effects 0.000 claims description 3
- 210000000474 Heel Anatomy 0.000 abstract 1
- 230000001808 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D7/00—Steering linkage; Stub axles or their mountings
- B62D7/06—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins
- B62D7/14—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering
- B62D7/15—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering characterised by means varying the ratio between the steering angles of the steered wheels
- B62D7/1509—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering characterised by means varying the ratio between the steering angles of the steered wheels with different steering modes, e.g. crab-steering, or steering specially adapted for reversing of the vehicle
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
- B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
- B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
- B66F9/075—Constructional features or details
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
- B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
- B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
- B66F9/075—Constructional features or details
- B66F9/07568—Steering arrangements
Abstract
ABSTRACT A forklift truck comprises two driven front wheels 12L, 12R and a single driven central rear wheel 14. The truck is operable in a sideways mode (Figures 2A - 2C) in which the rear wheel is fixed at an angle substantially parallel to an axis passing through the two front w heels and the two front wheels are steerd in synchronism in opposite directions of rotation. The truck is further operable in a rotational mode in which the centre of rotation C of the truck is disposed inside a notional circle 200 passing through all three wheels. The truck enters the rotational mode from the sideways mode by automatic reversal of the dn ve direction of the rear wheel, by actuating a changeover valve 40, when the centre of rotation moves from outside to inside the notional circle.
Description
THREE WHEEL FORKLIFT TRUCK
This invention relates to a three—wheel forklift truck.
The invention provides a forklift truck comprising a
chassis having two driven, steerable front wheels and a
single driven rear wheel disposed centrally between, but
displaced rearwardly of, the front wheels, wherein the
truck is operable in a sideways mode in which the rear
wheel is fixed at an angle substantially parallel to an
axis passing through the two front wheels and the two
front wheels are steered in synchronism in opposite
and wherein the truck is operable
in a rotational mode in which the centre of rotation of
the truck is disposed inside a notional circle passing
through all three wheels, the truck entering the
rotational mode from the sideways mode by automatic
reversal of the drive direction of the rear wheel when
the centre of rotation moves from outside to inside the
notional circle.
An embodiment of the invention will now be described, by
way of example, with reference to the accompanying
drawings, in which:
Figures lA—1C are schematic plan views of a forklift
truck according to a first embodiment of the invention,
Operating in standard mode.
Figures 2A—2C are schematic plan views of the truck of
Figures 1A-1C operating in sideways mode.
Figures 3A—3C are schematic plan views of the truck of
Figures 1A-1C operating in rotational mode.
Referring to Figure 1A, a three—wheel, four-directional
forklift truck with all—wheel drive comprises a chassis
having left and right front ground wheels 12L, 12R
respectively and a single rear ground wheel 14 disposed
centrally between, but rearwardly displaced, relative to
the front wheels. All three wheels are steerable by
rotation about respective substantially vertical axes 16.
Such rotation is effected by a respective hydraulic
cylinder associated with each wheel, the
actuation/deactuation of the hydraulic cylinders being
controlled by the truck driver using a steering wheel 28.
This is well-known and is therefore not shown. rThe
chassis carries a conventional mast (not shown) and lift
forks 20.
Each wheel 12L, 12R and 14 can be driven selectively in
either one of two opposite directions of rotation by a
respective hydrostatic motor 18. Each motor has
hydraulic fluid inlet ports F and R respectively, the
application of hydraulic fluid under pressure to the
inlet port F driving the wheel in a forward direction
(indicated by the arrows in Figure 1A) and the
application of hydraulic fluid under pressure to the
inlet port R driving the wheel in the reverse direction.
The motors 18 are driven by a hydraulic circuit which
includes a pump 22 for supplying hydraulic fluid under
pressure selectively to fluid supply ports P1 and P2
respectively, the supply ports being connected to the
motors 18 by hydraulic lines 24A, 24B, 24C, 26A, 26B and
26C.
The inlet ports F, R of the right front wheel 12R are
coupled to the supply ports P1, P2 of the pump 22 via a
selectively actuable switchover valve 30. Similarly, the
inlet ports F, R of the rear wheel 14 are coupled to the
supply ports P1, P2 of the pump 22 via a selectively
actuable switchover valve 40. The inlet ports F, R of
the other front wheel 12L is non-switchably coupled to
the supply ports P1, P2 respectively.
The operation of the valve 30 is such that when the valve
is not actuated (as shown in Figures 1A-1C) the inlet
ports F, R of the right front wheel l2R are connected to
the supply ports P1, P2 respectively, whereas when the
valve is actuated (Figures 2A-2C and 3A—3C) the hydraulic
lines 24B, 26B cross over so that the inlet ports F, R of
the wheel 12R are connected to the supply ports P2, P1
respectively. Similarly, the operation of the valve 40
is such that when the valve is not actuated (as shown in
Figures 1A-1C) the inlet ports F, R of the rear wheel 14
are connected to the supply ports P1, P2 respectively,
whereas when the valve is actuated (Figures 3A-3C) the
hydraulic lines 24C, 26C cross over so that the inlet
ports F, R of the wheel 14 are connected to the supply
ports P2, P1 respectively. The valves 30 and 40 can be
actuated and de—actuated hydraulically, mechanically,
electro—magnetically or in any other suitable manner.
When the truck is configured for standard (i.e.
forward/reverse) operation, Figures 1A—1C, the valves 30
and 40 not actuated. In order to drive the truck in the
forward direction, fluid under pressure is supplied by
the pump 22 to the supply port P1 and thus to the
hydraulic lines 24A, 24B and 24C. Therefore, the fluid
pressure is applied to the inlet port F of each wheel
motor 18, and all three wheels are driven in a forward
direction. In order to drive the truck in the reverse
direction (not shown), the fluid under pressure supplied
by the pump 22 is simply switched from the supply port P1
to the supply port P2 and is thus removed from the inlet
ports F and applied to the inlet ports R via the
hydraulic lines 26A, 26B and 26C. The switchover of the
hydraulic fluid under pressure between the supply ports
P1 and P2 is effected under operator control. In
standard mode, in both forward and reverse drive
directions, the front wheels 12L, 12R of the truck are
turned parallel to one another in the front—to—rear
direction and locked in that position, and the rear wheel
14 is steered by the operator in conventional manner to
steer the vehicle, i.e. the rear wheel is rotated
clockwise (Figure 1B) or anti-clockwise (Figure 1C) about
its axis 16 as the steering wheel 28 is rotated one way
or the other. In the drawings, the dash—dotted arcs are
the paths of travel of the wheels of the truck and, when
the truck is not moving in a straight line, the point C
is the centre of rotation of the truck.
In order to configure the truck for operation in sideways
mode, Figures 2A—2C, the rear wheel 14 is turned parallel
to an axis 100 (Figure 2A) passing through the two front
wheels and locked in that position, and the front wheels
are turned inwards (i.e., in plan view the wheel 12L is
rotated clockwise about its axis 16 and the wheel 12R
anti-clockwise about its axis 16), each through 900, so
that they lie in line and parallel with the rear wheel
(i.e. substantially normal to the front—to—rear direction
of the chassis). Also, the valve 30 is actuated so that
the hydraulic lines 24B, 26B cross over whereby the inlet
ports F, R of the wheel 12R are connected to the supply
ports P2, P1 respectively. These actions may be effected
automatically by the vehicle control system (not shown)
when the operator selects sideways mode, for example, by
pressing a button located in the cab.
Now, if the hydraulic fluid under pressure is supplied to
the port P1 all three wheels, and hence the truck, will
drive to the right, as indicated by the arrows in Figure
2A. Alternatively, if the hydraulic fluid under pressure
is supplied to the port P2, all three wheels will drive
In sideways mode, in both left
to the left (not shown).
and right drive directions, the front wheels 12L, 12R of
the truck can be steered by the operator, to change the
directional course of the truck. When steering in
sideways mode both front wheels rotate in synchronism in
opposite directions, i.e. when one rotates clockwise
about its axis 16 the other rotates anti-clockwise about
(Figs. 2B & 2c).
its axis 16, and vice versa
The truck is also operable in a rotational mode (Figures
3A-3C) in which the centre of rotation C of the truck is
within a notional circle 200 (Figure 3B) passing through
all three wheels. The truck can be made to enter
rotational mode automatically from sideways mode by the
operator turning the steering wheel 28 to rotate the
front wheels 12L, 12R sufficiently to bring the centre of
rotation C within the notional circle 200. At the point
at which the centre of rotation C moves from outside to
inside the notional circle 200, Figure 3A, the switchover
valve 40 is automatically actuated to reverse the drive
direction of the rear wheel 14 (compare Figures 2C and
3A). Correspondingly, the switchover valve 40 is
automatically actuated when the centre of rotation C
moves from inside to outside the notional circle 200,
when reverting to sideways mode from rotational mode, to
restore forward drive to the rear wheel 14. The point at
which the centre of rotation C moves inside the notional
circle 200 can be detected by, for example, a sensor
attached to one of the front wheels. The sensor can be a
proximity switch, a hydraulic switch or any other
suitable mechanism for determining when the wheel has
turned to a predetermined angle.
In rotational mode, like sideways mode, steering is as
for sideways mode, i.e. both front wheels rotate in
synchronism in opposite directions. The centre of
rotation C can be anywhere along a line 300 (Figure 3C)
extending from the rear wheel to a point midway along the
axis 100.
Then, if it is desired to rotate the truck in a clockwise
direction about the axis C, Figure 3A, hydraulic fluid
under pressure is supplied to the port Pl. This fluid
pressure is applied via the lines 24A, 24B and 24C to the
inlet port F of each wheel so that the wheels are driven
in the directions indicated by the arrows.
If the truck enters rotational mode from sideways mode
when the truck is moving left to right, the truck will
rotate clockwise in rotational mode, as shown in Figures
3A-3C. However, if the truck enters rotational mode from
sideways mode when the truck is moving right to left, the
truck will rotate anti—clockwise in rotational mode.
The advantage of the above arrangement is that the truck
enters rotational mode from sideways mode automatically
by continuing to rotate the steering wheel 28 in the same
direction. other alternatives would work depending on the
steering direction of the wheels, the side of the wheel
the drive motors are mounted on, and even just coupling
the switchover valve to the left front wheel instead of
the right front wheel.
The invention is applicable to a three-wheel forklift
truck driven by one or two hydrostatic motors, or indeed
by other drive means.
The invention is not limited to the embodiment described
herein and may be modified or varied without departing
from the scope of the invention.
Claims (5)
1. A forklift truck comprising a chassis having two driven, steerable front wheels and a single driven rear wheel disposed centrally between, but displaced rearwardly of, the front wheels, wherein the truck is operable in a sideways mode in which the rear wheel is fixed at an angle substantially parallel to an axis passing through the two front wheels and the two front wheels are steered in synchronism in opposite directions of rotation, and wherein the truck is operable in a rotational mode in which the centre of rotation of the truck is disposed inside a notional circle passing through all three wheels, the truck entering the rotational mode from the sideways mode by automatic reversal of the drive direction of the rear wheel when the centre of rotation moves from outside to inside the notional circle.
2. A forklift truck as claimed in claim 1, wherein each wheel motor is a hydrostatic motor, the truck further including a hydraulic circuit for supplying hydraulic fluid under pressure to each motor.
3. A forklift truck as claimed in claim 2, wherein each motor has first and second hydraulic fluid inlet ports, the application of hydraulic fluid under pressure to the first inlet port driving the wheel in one direction and the application of hydraulic fluid under pressure to the second inlet port driving the wheel in the opposite direction, and wherein the hydraulic circuit comprises a source of hydraulic fluid under pressure having first and second fluid supply ports, the hydraulic fluid under pressure being selectively supplied at the first or second supply port.
4. A forklift truck as claimed in claim 3, wherein the first and second inlet ports of the rear wheel are coupled to the first and second supply ports via a selectively actuable switchover valve, wherein when the truck is operated in sideways mode the switchover valve is not actuated, and wherein when the truck enters rotational mode the switchover valve is automatically actuated.
5. A forklift truck as claimed in claim 4, wherein the rear wheel is also steerable and the truck is operable in a standard mode in which the two front wheels are fixed substantially parallel to one another in the front-to- rear direction of the chassis and the rear wheel is steered, and wherein the first and second inlet ports of one of the front wheels are coupled to the first and second supply ports via a further selectively actuable switchover valve, the further switchover valve not being actuated in the standard mode but being actuated in the sideways and rotational modes.
Publications (2)
Publication Number | Publication Date |
---|---|
IE20070379U1 IE20070379U1 (en) | 2008-01-23 |
IES84790Y1 true IES84790Y1 (en) | 2008-01-23 |
Family
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