U.S. patent number 3,565,273 [Application Number 04/810,549] was granted by the patent office on 1971-02-23 for lift truck construction.
This patent grant is currently assigned to Firma Ernst Wagner Apparatebav, Reutlingen, Federal. Invention is credited to Erich Hahn.
United States Patent |
3,565,273 |
|
February 23, 1971 |
LIFT TRUCK CONSTRUCTION
Abstract
A lift truck includes a wheeled vehicle having divided
longitudinal frames which may be extended or retracted for
adjusting the longitudinal spacing between the front and rear
wheels. A forklift carried by the vehicle is arranged to actuate a
sensing device such as a dynamometer to measure the load to be
lifted and the dynamometer is connected to a system to actuate
means for shifting the divided frame elements carrying the wheels
for the purpose of extending or retracting the wheel chassis in
accordance with the value of the load to be lifted.
Inventors: |
Erich Hahn (Reutlingen,
DE) |
Assignee: |
Firma Ernst Wagner Apparatebav,
Reutlingen, Federal (N/A)
|
Family
ID: |
3555443 |
Appl.
No.: |
04/810,549 |
Filed: |
March 26, 1969 |
Foreign Application Priority Data
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Apr 18, 1968 [AT] |
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8A3788/68 |
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Current U.S.
Class: |
414/631 |
Current CPC
Class: |
B66F
9/10 (20130101) |
Current International
Class: |
B66F
9/10 (20060101); B66F 9/08 (20060101); B66f
017/00 () |
Field of
Search: |
;214/2,670--674 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1148019 |
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Jul 1, 1957 |
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FR |
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751269 |
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Jun 1, 1956 |
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GB3 |
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Primary Examiner: Gerald M. Forlenza
Assistant Examiner: Frank E. Werner
Attorney, Agent or Firm: McGlew and Toren
Claims
I claim:
1. A lifting device comprising a wheeled chassis frame having an
extensible and retractable side frame for changing the wheelbase
length, a carrier supported on said chassis and being movable to
lift a load, shifting means connected to said side frame for
extending and retracting said frame to vary the wheelbase length,
and dynamometer means connected to said carrier for actuation
thereby in accordance with the load moment acting on said carrier
and connected to said shifting means to extend and to retract said
frame in accordance with the load movement acting on said
carrier.
2. A lifting device, according to claim 1, including a carrier mast
pivotally mounted on said chassis for pivotal movement about a
substantially horizontal axis and extending upwardly from said
chassis, said lift carrier being supported on said mast, hydraulic
piston and cylinder means carried on said chassis and connected to
said mast for pivoting said mast to effect lifting of said carrier
with a load thereon, said dynamometer means comprising said
hydraulic piston and cylinder means.
3. A lifting device, according to claim 2, wherein said dynamometer
means includes switching means connected to said fluid piston and
cylinder and being responsive to the pressure in said fluid
cylinder to actuate means for moving said extensible and
retractable side frame for changing the wheelbase length.
4. A lifting device, according to claim 1, wherein said wheel
chassis includes a front wheel set having a wheel axis and a rear
wheel having a rear wheel axis, said dynamometer means being
arranged between said chassis and said front and rear wheel
axes.
5. A lifting device, according to claim 1, wherein said dynamometer
means comprises a fluid pressure cylinder, and a piston slidable in
said cylinder connected to said carrier.
6. A lifting device, according to claim 1, including means
associated with said dynamometer means for indicating the load
which is engaged by said carrier.
7. A lifting device, comprising a wheeled chassis having front and
rear wheels and two chassis portions carrying respective ones of
said front and rear wheels which are extensibly and retractably
movable in relation to one another for changing the wheelbase
length, a mast pivotally mounted on and extending upwardly from
said chassis, said mast being pivotal about a substantially
horizontal axis, a lift carrier supported on said mast and
extending outwardly therefrom, and being movable to lift a load, a
first fluid cylinder and piston combination connected between said
chassis and said mast for pivoting said mast and shifting said
carrier therewith for engaging and lifting a load and for lowering
and disengaging a load, a second fluid piston and cylinder
combination carried on said chassis and connected to said
relatively movable chassis portions for shifting them relatively to
change the wheelbase length, and dynamometer means connected to
said carrier for measuring the load moment acting on said carrier
and being connected to actuate said second fluid piston and
cylinder combination for extending and retracting said two chassis
portions in accordance with the load moment on said carrier.
8. A lifting device, according to claim 7, wherein said dynamometer
means comprises said first fluid cylinder and piston combination, a
driving circuit for controlling the movement of said movable frame
by actuating said second fluid cylinder and piston combination, and
a plurality of switches connected in said operating circuit and
being responsive to the pressure in said first fluid cylinder and
piston combination as determined by the load engaged by said
carrier to actuate said drive circuit by separate and distinct
proportional amounts.
9. A lifting device comprising a wheeled chassis having front and
rear wheels and two chassis portions carrying respective ones of
said front and rear wheels which are extensibly and retractably
movable in relation to one another for changing the wheelbase
length, a mast pivotally mounted on and extending upwardly from
said chassis, said mast being pivotal about a substantially
horizontal axis, a lift carrier supported on said mast and
extending outwardly therefrom, and being movable to lift a load, a
first fluid cylinder and piston combination connected between said
chassis and said mast for pivoting said mast and shifting said
carrier therewith for engaging and lifting a load and for lowering
and disengaging a load, a second fluid piston and cylinder
combination carried on said chassis and connected to said
relatively movable chassis portions for shifting them relatively to
change the wheelbase length, dynamometer means connected to said
carrier for measuring the load moment acting on said carrier, said
dynamometer means comprising said first fluid cylinder and piston
combination, a driving circuit for controlling the movement of said
movable frame by actuating said second fluid cylinder and piston
combination and a plurality of switches connected in said operating
circuit and being responsive to the pressure in said first fluid
cylinder and piston combination as determined by the load engaged
by said carrier to actuate said drive circuit by separate and
distinct proportional amounts, at least one of said movable chassis
portions including a blocking member preventing movement of said
switches and hence actuation of said operating circuit for said
second fluid cylinder and piston combination and to prevent
relative movement of said movable chassis portions when said
chassis portions are located at a proper orientation to produce the
desired wheelbase in accordance with the load which is engaged by
said carrier.
10. A lifting device, comprising a wheeled chassis having front and
rear wheels and two chassis portions carrying respective ones of
said front and rear wheels which are extensibly and retractably
movable in relation to one another for changing the wheelbase
length, a mast pivotally mounted on and extending upwardly from
said chassis, said mast being pivotal about a substantially
horizontal axis, a lift carrier supported on said mast and
extending outwardly therefrom, and being movable to lift a load, a
first fluid cylinder and piston combination connected between said
chassis and said mast for pivoting said mast and shifting said
carrier therewith for engaging and lifting a load and for lowering
and disengaging a load, a second fluid piston and cylinder
combination on said chassis and connected to said relatively
movable chassis portions for shifting them relatively to change the
wheelbase length, dynamometer means connected to said carrier for
measuring the load moment acting on said carrier, said dynamometer
means comprising said first fluid cylinder and piston combination,
a driving circuit for controlling the movement of said movable
frame by actuating said second fluid cylinder and piston
combination, and a plurality of switches connected in said
operating circuit and be responsive to the pressure in said first
fluid cylinder and piston combination as determined by the load
engaged by said carrier to actuate said drive circuit by separate
and distinct proportional amounts, said plurality of switches
comprising electrohydraulic switches each of said switches
including hydraulic portions connected to said first fluid cylinder
and piston combination and an electrical portion connected to said
operating device for said second fluid cylinder and piston
combination.
11. A lifting device, according to claim 10, wherein said
electrical switch portions of said switches includes a reversing
circuit for effecting a reversing movement of said movable frame
relative to said other frame.
12. A lifting device, according to claim 7, wherein said
dynamometer means includes a plurality of electrohydraulic switches
adapted to be connected to said first fluid cylinder and piston
combination for operating said first fluid cylinder and piston
combination and damping means associated with said switches.
13. A lifting device, comprising a wheeled chassis having front and
rear wheels and two chassis portions carrying respective ones of
said front and rear wheels which are extensibly and retractably
movable in relation to one another for changing the wheelbase
length, a mast pivotally mounted on and extending upwardly from
said chassis, said mast being pivotal about a substantially
horizontal axis, a lift carrier supported on said mast and
extending outwardly therefrom, and being movable to lift a load, a
first fluid cylinder and piston combination connected between said
chassis and said mast for pivoting said mast and shifting said
carrier therewith for engaging and lifting a load and for lowering
and disengaging a load, a second fluid piston and cylinder
combination carried on said chassis and connected to said
relatively movable chassis portions for shifting them relatively to
change the wheelbase length, dynamometer means connected to said
carrier for measuring the load moment acting on said carrier, said
dynamometer means including a hydraulic switch connected to said
first fluid cylinder and piston combination and being movable in
accordance with the pressure in said first fluid cylinder and
piston combination as determined by the load which is being lifted
by said carrier, said hydraulic switch including a piston arm
portion which projects outwardly in accordance with the pressure of
said first cylinder and piston combination, a hydraulic control for
said second fluid cylinder and piston combination including a
pivotal shift lever having a mounting shaft which is rotated by
movement thereof and including a blocking cam thereon, said piston
arm being movable to a position in which it blocks movement of said
lever shaft in one direction but permits movement in an opposite
direction for controlling the fluid operation of said second
cylinder and piston combination.
Description
This invention relates, in general, to the construction of lifting
and conveying trucks and, in particular, to a new and useful
forklift truck having extensible side frame members for changing
the spacing between the front and rear wheels and which includes
dynamometer means for sensing the value of the load to be lifted
and for adjusting the wheel spacing accordingly.
It is important to have an adjustable wheelbase for lift trucks
having a center of gravity which extends to the front or rear of
the vehicle when the load is engaged. Principally, it is a
prerequisite for lift trucks that are used in locations having a
minimum amount of space and also where great load moments are to be
encountered. The ability of such trucks to handle such great loads
can be achieved by varying the wheelbase but trucks having a
variable wheelbase have been used so far only to a very small
extent. This is due to the fact that the driver cannot exactly
estimate the load moment and then set the correct wheelbase.
Consequently, there is a danger that the vehicle will tip when the
wheelbase is not correctly set.
In accordance with the present invention, there is provided a truck
construction which includes an adjustable wheelbase which can be
used in practice without any difficulties because it includes a
dynamometer between the load carrier and the treads of the vehicle
wheels which can be employed for determining the size of a load to
be lifted. The driver can readily determine whether the load moment
corresponds to the respective wheelbase setting by observing the
dynamometer and he may increase the wheelbase setting if necessary.
Thus, the tipping dangers which were inherent in vehicles of this
nature is eliminated.
Preferably the dynamometer is designed as a hydraulic cylinder
having a movable piston and the hydraulic cylinder is connected
through a line to an indicator arranged in the driver's cabin.
However, the dynamometer can also be arranged, for example, between
the chassis and the wheel axles. In those lift trucks which include
a supporting frame or mast which may be tilted by a tilting device,
the dynamometer is arranged on the tilting device itself. For
example, it can be connected between the tilting device and the
mast at the center of gravity of the tilting device on the chassis.
A special simplification is obtained if the hydraulic cylinder for
tilting the mast is designed as a dynamometer.
In accordance with another feature of the invention, the
dynamometer is connected to an operating mechanism or switching
device for changing the wheelbase in accordance with the load which
is sensed and this eliminates any possible errors of judgement by
the driver. The switching mechanism is advantageously arranged so
that the dynamometer will prevent the lifting of a load at a
certain load moment when the wheel base does not correspond to the
load moment sensed or when the maximum admissible load moment is
exceeded. In this way, it is possible to adapt the wheelbase
automatically to the load to be lifted. In order to provide greater
variation possibilities, several switching devices, which act on
mechanism to move the wheelbase elements sense the position of the
relatively shiftable wheel frame portions and provide a
corresponding extension or retraction of these portions in
accordance with the load requirements.
In order to prevent a response of the switching mechanism if a
wheelbase corresponding to the load already exists, locking devices
are provided which act on one or several of the switching devices
in dependence on the orientation of the adjustable parts of the
wheelbase. In a preferred embodiment, cam strips or similar devices
designed as blocking elements are arranged on one of the mutually
displaceable chassis parts and they cooperate with the movable
switching devices arranged on the other part, for example, at a
location perpendicularly to the longitudinal axis of the truck.
Depending on the position in which the cam strips or other devices
are located relative to the respective switching devices, there
will either be a release or a blocking of the switching
devices.
The switching devices are advantageously designed as
electrohydraulic switches having a hydraulic part which is
connected with the dynamometer and having an electrical part which
is connected into the circuit of one or several drives for shifting
the relatively movable parts of the chassis. In order to prevent
the electrohydraulic switches from responding to shock pressures
during the driving operation, damping elements, particularly
chokes, are provided in the hydraulic feedlines. The
electrohydraulic switches are preferably connected with several
switches of which at least one is inserted into the circuit of the
wheelbase drive for shifting the relatively movable parts of the
wheelbase in order to achieve the automatic adjustment of the
wheelbase to the desired wheel spacing.
Accordingly, it is an object of the invention to provide a forklift
truck having an adjustable wheelbase and which includes dynamometer
means for sensing a load to be lifted for the purpose of
determining the spacing between the front and rear wheels for
adequately supporting and lifting a given load.
A further object of the invention is to provide a forklift truck
which includes a forklift portion which advantageously actuates
dynamometer means, in accordance with the size of the load being
lifted, to determine the load size; the dynamometer means being,
for example, a hydraulic drive for tilting the support mast or
frame of the truck load carrier.
A further object of the invention is to provide a forklift truck
which is simple in design, rugged in construction, and economical
to manufacture.
The various features of novelty which characterize the invention
are pointed out with particularity in the claims annexed to and
forming a part of this specification. For a better understanding of
the invention, its operating advantages and specific objects
attained by its use, reference should be had to the accompanying
drawings and descriptive matter in which there are illustrated and
described preferred embodiments of the invention.
In the Drawings:
FIG. 1 is a somewhat schematic side elevational view of a forklift
truck constructed in accordance with the invention;
FIG. 2 is a schematic side elevational view of the chassis of the
forklift truck indicated in FIG. 1;
FIG. 3 is a view similar to FIG. 2 of another embodiment of the
invention; and
FIG. 4 is a schematic representation of a circuit closer for the
wheelbase drive.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, in particular, the invention embodied
therein comprises a forklift truck having a chassis frame 1 over
which is mounted a driver's seat and motor enclosure 2. The chassis
frame 1 includes side frame members 4 and 5, which may be adjusted
relative to each other in a longitudinal direction and which are
arranged on each side of the chassis frame. The chassis frame 1 may
be elongated or contracted in the directions of the double arrow 3
in order to vary the spacing between the front wheel set 8 and the
rear wheel set 9. The side frame member 4 advantageously carries
the main drive motor below the driver's seat and it is shifted on
the frame 4 either toward or away from the lifting element or
carrier 10 at the front of the vehicle for the purposes of
providing a counter load of a size sufficient to overcome the
weight of the load being lifted. The shifting of the side frame
members 4 and 5 relative to each other is accomplished by means of
a hydraulic piston and cylinder combination comprising a cylinder 6
having a piston 7 slidable therein which are connected between the
two parts 4 and 5 to provide for the shifting thereof and the
adjustment of the spacing between the forward wheels 8 and the rear
wheels 9.
In the embodiment illustrated in FIG. 1, the forklift truck
includes a mast or lifting frame 11 having the carrier 10
associated therewith which advantageously may be raised and lowered
thereon. The mast 11 can be tilted by means of a hydraulic cylinder
12 having a piston 13 slidable therein which is connected between
the chassis and the lower end of the mast 11 to permit it to pivot
about its pivotal mounting 16. In a preferred arrangement, the
cylinder 12 is designed as a dynamometer and when the carrier 10
engages the load and the mast 11 is tilted to engage the carrier to
lift the load, the amount of the load can be readily determined by
the lifting force which is required. The dynamometer cylinder is
provided with the usual hydraulic feed and discharge lines (not
shown) and it is connected by a line 35 as indicated in FIG. 2 to a
plurality of electrohydraulic switches generally designated 14
which are arranged at spaced locations along the length of one of
the frame members, for example, the frame member 4.
A load 15 bearing on the load carrier 10, as represented by broken
lines if FIG. 1, will produce a moment of rotation about the mast
11 and its supporting pivotal mounting 16 which will be manifest in
a corresponding pressure in the hydraulic cylinder 12. The pressure
which is sensed can be used to determine the value of the load 15
and can also be used to actuate the electrohydraulic switches 14 or
an indicator (not shown) which is located adjacent the driver's
seat 2.
The position shown in solid lines in FIG. 1 is retracted state of
the chassis and the dotted line position shows the maximum extended
state. The extended state is assumed when a particularly heavy load
is to be raised.
In the embodiment indicated in FIG. 2, the switches 14 include
electrical portions or contact elements 18 which are connected to
an electrical circuit 19 which is provided for the control of the
operation of the lifting and driving cylinder 12. Each switch 14
also includes corresponding piston and cylinder arrangements 21, 22
and 23 which are set for response at different load movements. For
example, the switch cylinder 21 closer to the rear axle 20 responds
to a lower load moment and the following switches 22 and 23 are set
to the next higher values progressively. As soon as the switch 21
responds, its electrical part opens to affect the control circuit
19 which is connected to the lifting cylinder 12 and the driving
cylinder 6. If the wheelbase setting corresponds to the load which
is to be lifted, then the switch 21 is prevented from responding by
a strip or cam 24 which is carried on the frame part 5 and moves
with the frame part 5 relatively to the frame part 4 of the
chassis. The movement of the electrohydraulic switch on which the
strip 24 bears is blocked so that the electrical part 18 cannot
close the circuit 19 to effect a further drive of the cylinder 6 to
either extent or retract the frame parts 4 and 5.
In the embodiment illustrated in FIG. 3, hydraulic switches 14' are
provided which correspond to the switches 14 but which include a
reversing switch portion engageable in a circuit 26 in series with
the circuit 19' which is adapted to be connected to actuate
mechanism for the lifting cylinder 12 and the driving cylinder 6.
If the load is too low for one of the electrohydraulic switches 14'
to respond, the latter will remain in the represented bottom
position so that the lifting and driving drive to the respective
cylinders 12 and 16 is connected and the wheel drive receives its
voltage. As soon as one of the switches is actuated, the circuit
19' of the lifting and driving drive is stopped and the wheelbase
drive is connected. The chassis part 5 thus is displaced relative
to the part 4 and the strip 24 is correspondingly displaced in
respect to the switches 14' back to an original position so that
the increase of the wheelbase is completed and the lifting and
driving drive is connected again. In this construction, an
additional electrohydraulic switch 27 is provided at a location at
which it will not cooperate with the locking strip 24 and which
releases when a maximum load moment is attained which prevents the
lifting and driving of the truck. A choke 17 is connected in the
line 35 to the switches 14' to prevent actuation by impacts or
collision shocks, for example.
In the embodiment indicated in FIG. 4, there is indicated a load
dependent blocking device for the circuit closer of the wheelbase
drive (which is not represented). A gearshift lever shaft 28 of the
drive carries a shift lever 29 and it is provided with a locking
cam 30 which is adapted to cooperate with a plunger 31 of a
hydraulic switching device 32. The hydraulic switching device 32 is
connected to the pressure line 35 which is connected to the
cylinder 12, and it responds only at a pressure corresponding to a
certain load moment. When the plunger 31 is in the represented
position, that is, when the hydraulic switching device is released,
the gearshift lever 29 can only be moved in one direction, that is,
in the direction of the arrow 33. The opposite direction 34 is
blocked. In this way, it is only possible to increase the wheelbase
but not to decrease the length of the wheelbase. The embodiment of
FIG. 4 operates similar to the embodiments of FIGS. 2 and 3 and
several switching devices 32 are arranged along the length of one
of the movable frame parts. Each switching device includes a
locking cam 30 of a different length.
* * * * *