[0001] The invention relates to a lift truck according to the preamble of claim 1.
[0002] US-A-3 490 633 discloses a lift truck whose upright is tiltable in forward and backward
direction and displaceable in lateral direction relative to the frame. To that end,
one end of a working cylinder is connected to the back of the upright, while the other
end is connected to the frame of the lift truck, with the working cylinder directed
approximately transversely to the upright. To enable the motions of the upright to
be followed, the points of attachment of the working cylinder to the frame and to
the upright are designed as ball-and-socket joints and it has a relatively great length.
This lift truck has such a length that it is not eligible to be taken along on a lorry
for loading and unloading that lorry.
[0003] The lift truck of the type described in the preamble does lend itself for this purpose
and is known from NL-C-165 992. This lift truck can be suspended at the back of the
lorry by inserting parts of the load carriers thereof into openings at the back of
the lorry and moving the load carrier downwards relative to the lift truck, so that
the lift truck itself is lifted. The lift truck can for instance be secured by means
of chains.
[0004] In a light-weight lift truck intended to be taken along at the back of a lorry, compact
dimensions and slight weight are of great importance. Further, the lift truck must
stick out from the back of the lorry as little as possible. A lift truck of this type
must therefore be built so as to be as short as possible rearwardly of the upright.
[0005] For these reasons, it is undesirable to use counterweights in such a lift truck so
as to prevent the lift truck from tilting in forward direction. Instead, to prevent
forward tilting of the lift truck, the frame of a lift truck of this type is provided
with two arms extending substantially in forward direction on opposite sides of the
load carrier, which arms carry front wheels spaced from the upright in forward direction.
[0006] Due to the presence of the wheels of a lorry, these arms cannot be moved to any point
under the lorry during the loading and unloading of the lorry. The upright of a lift
truck of this type should therefore be movable in lateral direction over a relatively
great distance.
[0007] In the known lift truck referred to, the means for tilting the upright forwards and
backwards are designed as a runner which is connected to the upright via an arm of
a toggle. The runner can be moved over a rail in lateral direction across the frame
of the lift truck. The other arm of the toggle is connected to an end of a working
cylinder directed upwards approximately parallel to the upright, the other end of
the cylinder being connected to the upright. By operating the working cylinder, the
toggle pivots about its point of connection to the upright and the position of the
upright is changed in forward or backward direction.
[0008] These means for tilting the upright forwards and backwards are of very compact construction
in rearward direction, which is important for obtaining the desired short construction
rearwardly of the upright, in particular because these means are connected to a rail
extending across the frame and can be moved along that rail.
[0009] However, a drawback of this known lift truck is that the construction is laborious
and relatively expensive in that it comprises a heavily loaded toggle. A further drawback
of this lift truck is that the lift truck operator's view of the load carrier is obstructed
by the working cylinder projecting from the toggle.
[0010] The object of the invention is to provide a lift truck which, in addition to being
of light construction and compact construction, in particular rearwardly of the upright,
is of simpler construction, can be manufactured at lower cost and offers a better
view of the load carrier.
[0011] This object is realized according to the present invention in that in a light truck
of the type described in the preamble the characterizing features according to claim
1 are used.
[0012] Inasmuch as the working cylinder is directed substantially transversely to the upright,
with one end of the working cylinder connected to the upright and the other end of
the working cylinder connected direct to the runner, a simple construction is obtained
in that no transmission means is required for transmitting the displacement effected
by the working cylinder. Inasmuch as the working cylinder is moreover directed approximately
in the viewing direction of a lift truck operator and transmission means such as the
toggle referred to are absent, the view of the area of the load carrier is obstructed
to a considerably lesser extent.
[0013] A further advantage of the lift truck according to the invention is that is has a
lowered centre of gravity in that the working cylinder does not project above the
runner but extends approximately horizontally from the runner.
[0014] Notwithstanding the working cylinder extending approximately transversely to the
upright, the means for tilting the upright forwards and backwards nevertheless constitute
a short construction rearwardly of the upright, in that the working cylinder is connected
to the upright adjacent the front thereof.
[0015] Hereinafter the invention will be further explained with reference to a most preferred
embodiment, shown in the accompanying drawings, in which:
Fig. 1 is a perspective view of a lift truck according to one embodiment of the invention,
and
Fig. 2 is a cutaway side elevation of a lift truck according to the invention.
[0016] The figures are overall views of the lift truck according to the invention. The lift
truck comprises a frame 1, two front wheels 2 and a driven rear wheel 4 operable by
means of a steering pole 3. Instead of a steering pole, other means for steering the
rear wheel can be used as well, such as a steering device with a steering wheel or
a joystick.
[0017] Mounted on the frame is an upright 6. The upright 6 comprises a fixed upright section
7, an upright section 8 which is movable relative to the fixed upright section 7 in
the longitudinal direction thereof and a load carrier 10 which is movable relative
to the movable upright section 8 in the longitudinal direction thereof. The movable
upright section 8 and the load carrier 10 can be moved telescopically in the direction
indicated by an arrow 9.
[0018] In the lift truck of the embodiment shown, the load carrier 10 comprises two forks
15 suspended from a fork board 16. Depending on the field of application, the load
carrier may also be shaped differently, for instance without a separate fork board
or with more or fewer and/or differently shaped forks.
[0019] The frame comprises two arms 11 extending substantially in forward direction on opposite
sides of the load carrier 10 and carrying front wheels 2 spaced from the upright in
forward direction.
[0020] Extending across the frame 1 are upper and lower rails 17 and 18, respectively, for
guiding displacement of the upright 6 in lateral direction relative to the frame 1.
[0021] The upright 6 is connected to a runner 19 guided by the upper rail 17 and to two
working cylinders 20, connected to that runner 19, for tilting the upright 6 backwards
and forwards.
[0022] For the lateral displacement of the upright 6, a double-acting working cylinder 21
is mounted between the frame 1 and a cross beam 22 of the upright 6 (see Fig. 1).
The cross beam 22 is designed as a section extending around the working cylinder 21
and the lower rail 18, so that it occupies little space, has a high rigidity and protects
the working cylinder 21.
[0023] The lift truck comprises a combustion engine 13 for driving a hydraulic pump (not
shown) for driving the different working cylinders and a hydromotor (not shown) connected
to the wheel 4. Naturally, instead of a combustion engine, an electric motor can be
used. Batteries for that purpose can be charged during driving by a dynamo which is
driven by the engine of the lorry.
[0024] The steering pole 3 is fitted with a group of control handles 5 for controlling the
vertical displacement of the load carrier 10 as well as the lateral displacement (side-shift)
and the tilt of the upright 6 in forward and backward direction. Mounted further on
the frame 1 is a control panel 14 with control means for starting and stopping the
engine 13.
[0025] If, instead of the steering pole 3, an operating means, arranged adjacent to the
control panel 14, such as a steering wheel or a joystick for steering the rear wheel
4 is arranged, the group of control handles for lifting, tilting and the side-shift
are preferably also arranged on the control panel.
[0026] The working cylinders 20 are directed approximately transversely to the upright 6.
One end of each of the working cylinders 20 is connected to the upright 6 in the area
of the front of the upright 6, and the other end of each of the working cylinders
20 is connected direct to the runner 19.
[0027] This construction of the means for tilting the upright 6 forwards and backwards is
of simple construction, can be manufactured at low cost and constitutes a minimal
obstruction of the view of the load carrier 10. Inasmuch as the working cylinders
20 are connected to the upright 6 in the area of the front of the upright 6, they
can be of sufficient length in rearward direction to obtain a sufficiently large working
range for tilting the upright 6 forwards and backwards, while still projecting in
rearward direction over only a very limited distance. Transmission means for arranging
the working cylinders parallel to the upright are therefore not necessary.
[0028] It is observed that, instead of two working cylinders, a different number of working
cylinders can be used for tilting the upright 6 forwards and backwards. It is for
instance possible to use a single working cylinder, which extends centrally between
standards of the upright and is connected to a cross beam interconnecting those standards.
It can for instance be mounted on a central portion of an Ω-shaped element, extending
between the standards of the upright, the ends of the Ω-shaped element being mounted
against the back of standards of the upright. Parts which can be displaced in longitudinal
direction of the upright, including the movable upright section, may in that case
require an adapted design, so that they can pass the working cylinder and any elements
by which it is connected to the upright.
[0029] According to the embodiment shown, the runner 19, which is connected to the working
cylinders 20, runs over the upper rail 17. It is also possible, however, to make the
lift truck according to the invention of such design that the runner runs over the
lower rail and the upright is tiltable about the upper rail.
[0030] Preferably, however, the runner 19 can be moved over the upper rail 17 because that
rail 17 can be arranged above the rear wheel 4 further to the back than the lower
rail 18 without increasing the dimensions of the lift truck rearwardly of the upright
6.
[0031] The combustion engine 13 is arranged in an area lower than the upper rail 17 and
laterally relative to the rear wheel 4. This offers the following advantages over
the conventional location of the engine above the rear wheel:
- first, above the rear wheel 4, rearwardly of the upright 6, there is more free space
for the upper rail 17 and for the passage of the runner 19;
- secondly, the view of the area of the load carrier 10 is obstructed to a lesser extent;
- thirdly, the centre of gravity of the lift truck is located at a lower point.
[0032] In this position, viewed in side elevation, the engine is disposed within the profile
of the lift truck, so that this position of the engine 13 entails no drawbacks with
regard to the extent to which the lift truck projects from a lorry at the back of
which the lift truck is suspended.
[0033] In the lift truck according to the embodiment shown, the engine 13 is located laterally
of the middle of the frame 1. In a lift truck with two rear wheels, however, the position
laterally of a rear wheel can also be obtained by arranging the engine centrally between
the rear wheels.
[0034] The engine 13 is located at a lateral distance from the rear wheel 4, such that the
rear wheel 4 can be swivelled at least into a position directed substantially transverse
to the front wheels 2. Thus, the contribution of the rear wheel 4 and the steering
pole 3 to the size of the profile of the lift truck in side elevation, can be limited
to a minimum when the lift truck is suspended behind a lorry.
[0035] For limiting the size of the profile of the lift truck in side elevation when the
lift truck has been arranged in the transit position, it is further advantageous when
steering pole 3 is located at least partly above the engine 13 when the back of the
rear wheel 4 has been swivelled towards the engine 13 into the position directed at
least substantially transverse to the front wheels 2.
[0036] Inasmuch as in the lift truck according to the embodiment shown the upper rail 17
is located above a bridge portion 24 of the frame 1 that extends upwards from the
arms 11, behind the upright 6, it is possible to arrange the rail, at a given length
of the lift truck, further backwards rearwardly of the upright 6 than in the known
lift truck, where the rail is disposed in front of this bridge portion of the frame.
Further, as a consequence thereof, the working cylinders 20 for tilting the upright
6 forwards and backwards are located at a relatively large distance from the tilting
shaft of the upright 6, so that the forces exerted thereon are relatively low.
[0037] Inasmuch as in the lift truck according to the embodiment shown two working cylinders
20 for tilting the upright 6 forwards and backwards are mounted on opposite sides
of the upright 6, an optimum view through the upright 6 is obtained and a considerably
smaller torque is exerted on the standards of the upright 6 than in the conventional
construction, where a toggle engages the upright centrally. Further, the standards
are stabilized in that the upright 6 comprises a cross beam 23 between the standards,
at the level of the points of engagement of the working cylinders 20. Owing to the
working cylinders 20 engaging the upright 6 adjacent to the standards, this cross
beam 23 can be of relatively slender and light construction, which saves weight and
is advantageous for obtaining a proper view through the upright 6.
[0038] In the lift truck according to the invention, the load on the cross beam 23 is further
limited in that it is not loaded with a force parallel to the upright for operating
a toggle as is the case in the conventional construction with a toggle and a working
cylinder parallel to the upright.
[0039] The upper rail 17, which guides the runner 19 connected to the working cylinders
20, has a cylindrical outside surface. At spaced points along its length, the rail
is connected to the frame 1. This rail 17 is easy to manufacture and can be of light
construction because it is supported by the frame at spaced points along its length.
The upper rail 17 moreover does not have a recess or the like on the outside where
dirt can accumulate and water may collect.
[0040] In order to obtain low-friction guidance of the runner 19 relative to the rail 17,
the runner 19 is fitted with rollers 25 (Fig. 2). These rollers 25 each have a tread
of concave cross-section, viewed in side elevation, and can roll over the rail 17.
The rollers 25 centre the runner 19 relative to the rail 17 and do not prevent the
runner 19 from following the tilt of the working cylinders 20. To obtain this effect,
the rail can optionally be shaped as well, with, for instance, only the part of the
outer surface that faces away from the upright being of cylindrical shape, instead
of the entire outer surface.
[0041] The runner comprises a retaining piece opposite the rollers 25, which retaining piece
is located at such a distance from the rollers 25, that, when the rollers 25 rest
against the rail in centred position, the retaining piece is disposed against the
rail 17 or located at a very minor distance therefrom. It is thus achieved that the
runner 19 embraces the rail 17 in a reliable manner, also when the working cylinders
20 are subject to a pressure load and a rearward force is exerted on the runner 19
away from the upright 6. This can for instance occur when the truck is driven backwards
with a load on the load carrier 10 and the brakes are applied abruptly. To absorb
shocks which may arise as a result of the retaining piece striking against the rail
and to prevent rattling in the case of a light load on the runner 19, the retaining
piece is made of plastics.
[0042] The lower rail 18, too, has a cylindrical outer surface and is connected to the frame
at spaced points along its length. The upright 6 comprises a tube 26 (Fig. 2) having
a slot in its longitudinal direction, which tube 26 embraces the cylindrical outer
surface of the lower rail 18 and can be shifted over it.
[0043] The lower rail 18 is simple to manufacture and can be of light construction inasmuch
as it is supported by the frame 1 at spaced points along its length. The connection
between the frame 1 and the rod 18 extends through the slot in the tube 26. The lower
rail 18 has a convex surface, so that accumulation of dirt and moisture is avoided.
The tube 26 is prevented from becoming dirty inasmuch as the slot of the tube 26 is
located at the underside of that tube.
1. A light-weight lift truck comprising
a frame (1),
an upright (6), and
a load carrier (10) on the front of the upright (6), which is guided by the upright
for upward and downward displacement, wherein
the frame (1) is provided with two arms (11) extending substantially forwards on
opposite sides of the load carrier (10), said arms (11) carrying front wheels (2)
spaced from the upright (6) in forward direction, and with upper and lower rails (17
and 18, respectively), extending across the frame (1), for guiding displacement of
the upright (6) in lateral direction relative to the frame (1), and wherein
the upright (6) is connected to a runner (19) guided by one of the rails (17) and
to at least one working cylinder (20), connected to said runner (19), for tilting
the upright (6) backwards and forwards,
characterized in that
the working cylinder (20) is directed substantially transversely to the upright
(6),
one end of the working cylinder (20) is connected to the upright (6) adjacent the
front of the upright, and
the other end of the working cylinder (20) is connected direct to the runner (19).
2. A lift truck according to claim 1, characterized by two working cylinders (20) on
opposite sides of the upright (6) for tilting the upright forwards and backwards.
3. A lift truck according to claim 1 or 2, characterized in that the runner (19) can
be displaced over the upper rail (17).
4. A lift truck according to claim 3, characterized by an engine (13) for driving at
least the working cylinders (20) for operating the upright (6), said engine being
located in an area lateral to the rear wheel (4) and lower than the upper rail (17).
5. A lift truck according to claim 4, characterized in that the engine (13) is located
at a lateral distance from the rear wheel (4), such that the rear wheel can be swivelled
at least into a position directed substantially transversely to the front wheels (2).
6. A lift truck according to claim 4, characterized by a steering pole (3) which is located
at least partly above said engine (13) when the back of the rear wheel (4) has been
swivelled towards the engine (13) into the position directed at least substantially
transversely to the front wheels (2).
7. A lift truck according to any one of claims 3-6, characterized in that the frame (1)
comprises a bridge portion (24) extending upwards from said arms (11) behind the upright
(6), with the upper rail (17) located above this bridge portion (24).
8. A lift truck according to any one of the preceding claims, characterized in that the
rail (17) which guides the runner (19) connected to the working cylinder (20) has
an at least partly cylindrical outer circumference and is connected to the frame (1)
at least at a plurality of points spaced along its length.
9. A lift truck according to claim 8, characterized in that the runner (19) comprises
at least one wheel (25) whose tread has a concave profile viewed in cross-section
and can roll over the corresponding rail (17).
10. A lift truck according to any one of the preceding claims, characterized in that the
other rail (18) has an at least partly cylindrical outer circumference and is connected
to the frame (1) at least at a plurality of points spaced along its length and the
upright (6) comprises a tube (26) having a slot extending in longitudinal direction,
which tube (26) embraces the cylindrical bar and can be shifted over said bar.