Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The purpose of this invention is to lift an object,
such as an automotive vehicle. The invention comprises an
upright mast section in which are secured: a lifting motor;
a lifting arm, the inner end of which is slidably mounted along
the mast section from which the arm freely extends outwardly;
and a lifting fork pivotably connected to the free end of the
lifting arm whereby the object to be lifted may be held by the
lifting arm and the lifting fork.
A lifting device of this type is known from Swedish
patent No. 72 13247-5 which, in comparison to other known
lifting devices having two or four upright masts, has, as its
major advantages, a safety function, s;mplicity in its design,
etc. In comparison to a lifting device constructed in accordance
with the principles of a fork lift for example, the said known
device advantageously operates as follows: its lifting arm and
lifting fork move a certain distance upwards along the upright ;-
mast in a horizontally and parallel relationship to one another
the continuous travel upwards along the upright mast is altered
by abutment means that cause the lifting fork to pivo~ at its
connection point with the lifting arm. As the lifting arm and
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the lifting fork form a V-configuration to each other with the
vehicle's under body or wheels resting on these lifting
elements, the under portion of the vehicle becomes easily
accessible. When using said known device, the pivotal movement
between the lifting arm and the lifting fork causes the vehicle
to tilt towards the mast section, which is undesirable for -
certain uses.
The object of the present invention is to overcome
this disadvantage and to provide a lifting device for lifting
a vehicle, such as an automotive vehicle, where the lifting
arms first form the V-configuration without tilting the vehicle,
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and, secondly, where the lifting arms may be lifted vertically ~ -
along the upright mast section to the desired working height.
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The lifting device in accordance with the present invention is
so constructed as to eliminate the risks of the vehicle falling
unintentionally or lowering from a lifted position. For this
purpose, the present invention includes a number of locking
devices being of, both, hydraulic and mechanical functions
which act independently of one another.
A preferred construction of the invention will herein-
after be described with reference to the accompanying drawings
in which:-
Figure 1 is a side view of a lifting device made in
- ~ccordance with the present invention with the lifting arms in
the lowermost position;
Figure 2 is a view similar to Fig. 1 with the lifting
arms in the lifted position;
Figure 3 is a cross-sectional view of the lower portion
of the mast with the respective ends of the lifting arm and of
; the lifting fork in their lowermost position;
Figure 4 is a cross-sectional view similar to Fig. 3,
but showing the lifting arm and the lifting fork after com- ;
pletion of their pivotàl movement; and
,~ Figure 5 is a cross-sectional view similar to Figs. 3
and 4, showing the lifting fork and the lifting arm in a
` 25 partial lifted position. `~
The lifting device made in accordance with the present
~' invention comprises a vertical mast section 1, a lif~ing arm 2
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which extends outwardly from the front portion of the mast 1 and
the inner ends of which are slidably mounted up and down the
30 mast, and a lifting fork 3 which is pivotably connected to the ~ -
.
~ outer ends of the lifting arm 2. The mast 1 is preferably
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constructed of two channel members or I-beams la which are
vertically arranged in opposite parallel relationship to one
another with the upper and rear portions thereof rigidly
connected cross-wise to one another and with the lower portions
thereof mounted to a bottom plate lb. At the lower portion of
the mast section la is shown a wedge-shaped portion lc that
includes tracks for rollers and a power source which will be
later described. A guiding beam (not shown) for the inner ends
of the lifting arm 2 can be located in a parallel relationship
with the two mast sections la and be connected to the upper :
end of the mast section and to the base plate lb. This guiding
beam serves to transfer the downward forces to the mast sections
and to protect the lift motor located between the mast sections.
On the lower portion of the mast is shown a number of
mounting brackets ld, into which hollow sections le,lf can be
inserted to form a solid base portion to support the upright
mast section 1. If desired, the bottom sections le and lf can
be equipped with suitable retractable wheels (not shown) in ;~
order to make the entire lifting device easily displaceable.
The lifting arm 2 consists preferably of two parallel
side beams 2a, which are connected to each other with cross-
members in order to form a rigid structure. The inner portion
of at least one (preferably two) beam 2a is equipped with a
lever 2b extending upwardly in an obtuse angle. The inner ends
of the beams are pivotably connected at point 7 to a lift motor
15 which will be later described.
At the upper free end of each lever 2b is mounted a
free wheeling roller 4. The purpose of roller 4 is to roll
along a guide rail 9-10 ;n the upright 1 when the lifting arm 2
is raised or lowered by the lifting motor 15. Each guide rail
comprises a lower portion 10 which consists o~ a welded plate
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located in each of the enlarged lower portion of upright beam
la and which extends to the inner surface of the front flanged
portion 9 of the upright beam la to which it is attached and
along which it extends longitudinally upwardly.
The angle between beam 2a and lever 2b and the angle
between the upper and lower portions of the guiding rail is set
in such a manner that, when the lifting arm 2 is in its lowest
position, roller 4 is in contact with the lower portion 10 of
the guide rail; in this position, lifting arm 2 is parallel
and close to the floor. When the pivot point of attachment 7
on the lifting arm 2 is raised, roller 4 moves upwards along
the inclined portion 10 of the guide rail while moving front- ~ -
wardly towards the front flange 9 thereby causing lever 2b and
beam 2a to pivot about point 7. When roller 4 reaches the
intersection between the inclined rail portion 10 and the
; vertical straight portion 9, beam 2a (fig. 4) maintains a ¦ -;
fixed inclined position. During the continuous upward travel ¦
of pivot point 7, roller 4 moves along the vertical portion 9
of the guide rail and lifting arm 2 is raised remaining in its -
2p inclined position. When pivot point 7 is thereafter lowered,
the lifting arm performs the same movements in reversed manner.
The lifting fork 3, which is pivotally connected to ,
the free end of lifting arm 2, consists of two parallel beams
~ 3a which are preferably connected to one another at ~heir
'~ 25 inner end by a plate 3c. The pivot connection 3b extends -
perpendicularly to the lifting arm 2 and through the center of
,
the fork-like arms 3a. At the inner end of lifting arm 3 a~e
j provided free wheeling rollers5. The rollers 5 are located
so as to contact a rail which preferably is the outer surface
of flanges 9 of the upper mast section la. When the inner end
, of the lifting arm 2 is raised, as earlier described, and when
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the lifting arm 2 simultaneously angulates downwards, the pivot
3b between the lifting arm 2 and the lifting fork 3 moves
upwards and towards the upright mast section. This results in -
that beam 3a of the lifting fork 3 pivots upwards around the -
shafts of rollers 5 which thereby act as a fixed pivot point
for the liFting fork 3. When the lifting arm 2 reaches its
final inclined position, as earlier described, and begins to
travel vertically upwards maintaining its inclined position, `
the pivot shaft 3b will follow in the same direction carrying
with it the lifting fork 3 and rollers 5 will roll upwards
contacting the guide rails 8.
It should be mentioned that the inclination of the
lifting arm 2 and the lifting fork 3 can be altered by altering
the length and/or angles of the above-mentioned members. From
the above, it may be deducted that the lifting sequence caused
by the lifting motor 15 is that, first, the lifting arm 2 and
the lifting fork 3 are moved into a V-configuration with
respect to one another and the lifting object is slightly lifted
from the floor. Thereafter, the lifting arm and the lifting ~-
20 fork are vertically raised to a desired height and the V- -
- configuration is maintained without tilting the lifted object.
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The latter is resting on support means 6a which is pivotally
mounted to the inner side of the lifting arm 2 and on support
means 6b which is pivotally and slidably mounted on the outer
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side of the lifting fork 3; the pivot shafts for these support
means are parallel to pivot shaft 3b. The distance between said
;` support means is maintained by a spacer 6c. Suppart means 6a
and 6b may be of conventional design: it can be constructed to
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support an automotive vehicle by its frame or be constructed to
` 30 support it by its wheels. Since these support means do not
constitute an innovative step of the present invention, they
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will not be described in greater detail. -
The major function of the lifting device has been
described above. What follows is a description in detail of
.
a preferred construction.
The lift motor is of the linear type and is disposed
vertically in the center between the mast beams la of the ~ -
upright mast section 1. It is preferably anhydraulic motor
with a piston and cylinder, but it may also be a rack and `
pinion motor or a worm gear motor. ~ -
As shown in the drawings, the lifting motor 15 is of
an hydraulic type and consists of a cylinder 16 in which is
displaceably mounted a primary piston arrangement 17 which
consists of a piston and a piston rod through which is drilled
a cylinder hole. A secondary piston and piston rod arrangement
` 15 18 is longitudinally displaceable in the cylinder hole of the
first piston arrangement 17. Two radially protruding shoulder
joints 19 on cylinder 16 serve as bearings for the upper
portion of two tie-rods 20 which have their lower ends
pivotally connected to the pivot connection 7 of the inner end
;-~ 20 of the lifting ar~ 2. This provision enables the pivot shaft
7 to be lowered onto the base plate lb of the upright mast
section where the lifting arm 2 is at its lowest position,
` i.e. horizontal. `
In a similar manner, there are provided on the outside
portion of the piston arrangement 17 of the cylinder, two
diametrically opposite radially extending lugs 21. At the
location closest to the upright mast section, arm 3a of the
~; lifting fork 3 is equipped with an extension element 22 which
by-passes the shaft for the rollers 5 of thè lifting fork and
forms a fork which encloses the lifting motor 15. The extension
element 22 is equipped with a groove 23 which is located in the -~
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upper portion of the extension element 22 and which receives
lugs 21 of the first primary piston arrangement 17.
The secondary displaceable piston arrangement 18 is
included within the primary piston arrangement 17 and has its
piston end resting on the bottom plate lb of the upright mast
section 1. The effective area of the secondary piston arrange-
ment 18 has less area than the corresponding area of the
primary piston arrangement 17.
When a pressurized medium is supplied by an hydraulic
pump (not shown) or by other means, through the tube-7ike piston
rod of the secondary piston arrangement into the upper closed
portion of cylinder 16, when the entire lifting device is in -
its lowest position as shown in Fig. 3, i.e. when the primary
and secondary piston arrangements are fully inserted into one
another and into cylinder 16, the pressurized medium causes a
pushing action onto the inside surfaces of the respective
pistons. Since the area of the primary piston arrangement 17
;, has a larger area than that of the secondary piston arrangement
18, a movement will first take place between cylinder 16 and
; 20 the piston arraogement 17 due to the relative distribution of
the piston areas as explained above. The secondary piston
: arrangement 18 maintains its location in the primary piston
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`~ arrangement. The primary movement causes cylinder 16 to be -
raised carrying with it via shoulder joints 19, tie-rods 20 ;~-
and pivot shaft 7, the inner end of the lifting arm 2. As
~ rollers 4 move along guide rail 10, the lifting arm 2 is thereby
; caused to be pivoted in an outward and downward inclined
position; at the same time, the primary piston arrangement 17
.
~`~' which remains stationary causes the inner end of arms 3a of
- 30 lifting fork 3 to remain at the lower portion of the upright
;~ mast section as a result of lugs 21 being engaged in extension 22
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of the lifting fork; thus, arms 3a swivel upwardly with rollers
5 acting as bearing and pivot points.
When cylinder 16 reaches the end of its predetermined
stroke length in primary piston unit 17, rollers 4 of the
lifting arm 2 reach the vertical straight portion 9 of the
guide rail 9-10 and the lifting arm 2 and the lifting fork 3
remain in a fixed inclined position. The pressurized medium
will then push the secondary piston arrangement 18 out of the
primary piston arrangement 17 whereby the primary piston
arrangement 17 and the cylinder 16 w-ill be raised unchanged
relative to one another thereby carrying with them the lifting
arm 2 and the lifting fork 3, also unchanged relative to each
other.
The relation between the areas of piston arrangements
17,18 upon which the pressurized medium acts, constitutes a
hydraulic safety function so that the above described movements
are always caused to occur in the above described sequence,
i.e. that the lifting arm and the lifting fork first form the
desired V-configuration and, thereafter, travel vertically in
.
. 20 this V-configuration. When lowering, it is evident that the
-~ ~ above-mentioned movements occur in a reversed order.
The lifting device made in accordance with the present
~; invention comprises also an hydraulic safety arrangement. As
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described above, the cylinder of the lifting motor 15 is fed
with a pressurized medium from a pump through the secondary
tube-like piston arrangement 18 causing the lifting arm 2 and
~5 the lifting fork 3 to move upwardly from their lowermost
;~ position. The lowering operation is caused by releasing the
pressurized medium from cylinder 16 through a center hole 24
in the secondary piston arrangement 18, and through said hole
.
~i 24, is arranged a release valve 25 which is so constructed that
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the volume of pressurized medium thus being released is constant
independently of the pressure in cylinder 16. The construction
of such a release valve controlling the oil flow is known to
the persons skilled in the art and should therefore not have
to be described in detail. When the supply of pressurized
medium from the pump to the cylinder 16 is stopped and a ~
mechanical safety arrangement, which will later be described, ~ . .
is manually made non-active, the lifting arm 2, the lifting fork
3 and the load carried will descend under gravitational forces
thereby pushing the pressurized medium out through hole 24 and
valve 25. Since the flow is controlled and constant independent- .
ly of the pressure in cylinder 16, the lowering speed will be
constant independently of a large or small load or if no load
` is on the lifting fork and the lifting arm. Valve 25 is
. 15 conventionally constructed so as to halt any oil flow if a
rupture in the cyllnder or pump conduits occur or if the pump
. should malfunction, whereby the lowering is automatically ~: .
stopped. The lifting device in accordance with the present
invention comprises a number of mechanical safety devices, ~ ~
` 20 which are so constructed as to allow the device to uncondition- ~.
ally function as intended. These mechanical safety devices are
entirely independent of the above described hydraulically :
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operating safety devices,.so that a multiplicity of safety
. functions are included within the present invention. ~ . .
-. 25 At the lower portion of the upright mast section 1,
:~ are provided lugs 26 which extend outwardly from the front - ~
. port;on of each beam member la of the upright mast section9 :-.
, and which engage with the inner ends of the arm 3a of the .~.
lifting fork 3 when the lifting fork is in the lowermost ~. :
.` 30 position. Lugs 26 mechanically prevent the inner ends of arms . ~ :.
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: ` 3a to move upwards when the lifting movement is initiated so : :
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that the lifting fork 3, under all circumstances will swivel
upwardly to its outward and upward inclined position. When
lifting fork 3 has reached this position, the inner ends of
arms 3a will have moved outwards from the mast section 1 a
sufficient distance to clear lugs 26 whereby the lifting fork
and the lifting arm may be raised vertically as earlier
described.
A locking rail 27 is pivotally connected to extension
element 22 of the lifting fork 3 and extends between levers 2b
of the lifting arm 2 and lifting motor 15. At its upper end,
the locking rail 27 is provided with a stopping surface 28 and
~: levers 2b of the lifting arm 2 are provided with a similar .
s~opping surface 29, preferably in the form of a cross-member
- between the free ends of levers 2b and located behind the
:. 15 levers and rollers 4. When the lifting arms and the lifting
. fork are in their lowest position, the locking rail 27 extends
. upwards in an inclined position from extension elements 22
between the lifting motor 15 and the stopping surface 29 and
is held in such position by an elastic retractable force, ::
preferably a fixed rubber cushion, between the locking rail 27
and the lifting motor 15. During the primary lifting sequence,
levers 2b of the lifting fork 2 swivel towards the front
. portion of the upright mast section 1 and the lifting motor 15,
the stopping surface 29 contacts the rearward side of the
locking rail 27 and pushes gradually the locking rail 27 to a
substantially vertical position. When the sequence of lifting ~ :
~; has reached the point where the lifting arm 2 has attained the
desired inclined position, the stopping surface 28 of the ~.
~ locking rail 27 moves under and into contact with the stopping
: 30 surface 29 of levers 2b and is held in this locking position
; under elastic force. The locking rail secures and locks a
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distance, between the inner ends of the lifting arm 2 and the
lifting fork 3, which is equal to the length of the locking
rail 27 and which is set in relation to the desired inclination
of the lifting arm 2 relative to the lifting fork 3.
The lower portion of the locking rail 27 has a
rigidly connected rearwardly extending lever 30. During the
lowering sequence, lever 30 comes into contact with the base
plate lb of the upright mast section 1 via a compression spring
mounted to lever 30. Contact with the base plate is arranged
to take place a short instance before relative pivotal movement
between the lifting arm 2 and the lifting fork 3 begins, whereby
the locking rail 27 swivels towards the lifting motor 15 which ~
causes the locking surface 28 to disengage from the locking ~ ;
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surface 29 whereby continued movement between the lifting arm 2 ;
relative to the lifting fork 3 is permitted.
The levers 2b of the lifting arm 2 are each equipped
with hingedly secured ratchets 31 which are connected with one
; another by means of a cross-member and are spring-loaded against
the rear vertical flanges 32 of the respective upright mast
~`~ 20 sections la in such a way that they will connect with any of a
- number of locking lugs 33 which are located at certain heigh~s
. from the base and fixedly secured onto the rear vertical flanges
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~-~ 32 of the mast section. By using these ratchets 31, the lifting
arm 2 and the lifting fork 3 may thereby be locked into any -
- 25 desired lifting heights, at the same time, the locking rail 27 `
; -; mechanically prevents any pivotal movement between the lifting
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~` arm 2 and the lifting fork 3 to maintain the desired V-configura-
;. tion between the members. During the lowering,ratchets 31 are
;' prevented from being engaged with the locking lugs 33 by means of
.
. 30 a manually operated handle 34. The handle 34 is preferably con-
nected to a vertical rod 35 which extends from the enlarged `~
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wedge-shaped portion lc of the upright mast section 1 to the
upper portion of the mast section between the locking lugs
and the cross-member connecting ratchets 31. The vertical rod
35 is excentrically mounted in bearings at both ends. By
swiveling handle 34, rod 35 is caused to rotate and, due to
its excentric mounting, ratchets 31 are forced out independently
of the present lifting height.
The above described lifting device has only been
described in relation to one specific form of the invention.
but it may be refined in various ways without departing from
the scope. For instance, the upright mast section 1 may be ~
fixedly secured to a wall instead of resting upon a foundation. -~ -
It is envisaged that the upright mast section may be
constructed to receive two lifting arms 2 with accompanying
lifting forks 3 extending outwards opposite each other
including their respective operative arrangement.
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