Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FLEL~ OF THE INVENTlOM
This invention relates to heavy load liftiny
equipment which is particularly adapted to -the lifting of
hea~y loads which may weigh in -the range of forty tons or
5 more.
_ACKGROUND OF THE INVENTION
A variety of forms of parallelogram type linkage
devices are disclosed for lif-ting material. Ackermann,
United States patent 3,018,011, discloses a fork lift
10 truck having a paral]elogram type linkage connected to
the forks. A lift ram is connected intermediate the
lower arm of each link to effect raising and lowering of
the linkage. The upper arm of the linkage is formed by a
hydraulic ram which controls tilting of the forks. This
15 arrangement may be satisfactory for lifting light loads.
However, with heavy loads such as in the range of 40
tons, extreme bending moments would develop in the ]ower
arm due to the lift ram being pivotally connected
intermediate the lower arm. The geometry of the
20 arrangemen-t, resulting from -the lift ram being connected
to the lower arms of the linkage, requires considerable
extension of the lift ram to elevate the forks. In orcler
to minimize sway of the lifted article, plates are
provided on each side of the vertical elements for the
25 Erames to ~ontain the vertical elements and prevent sway
of the load. This places additional side hending moment.s
on the vertical arms which could cause undue stresses in
the frame if used to lift high tonnage loads.
Carter, United States patent 2,391,224, discloses a
30 parallelogram type linkage for a tractor loader. A frame
is connected to the top of this linkage to control
lifting of the linkage. The lift cyllnder for the frame
is connected to the linkage and to the lifting Erame.
Although this arrangement may be suitable for low weigh-t
35 farm -tractor applications, due to the geometry of the
lifting frame as connected to the parallelogram linkage
for the fork results in e~treme bending moments in the
parallelogram linkage and lifting frame. Furthermore,
w:ith -the lifting frame atop -the paral:Lelogram linkage,
visibili-ty forwardly of the tractor is hampered.
United States patent 2,656,058 discloses a type of
paral.lelogram linkaye for lifting loads onto and off of a
5 truck. The frame consists of a single set of upper and
lower arms forward of the frame. The lifting ram is
positioned in a manner on the l.inkage to necessitate
considerable extension and swing angle of the ram in
lifting the forks. Such an arrangement, although
10 suitable for light loads in lifting materials onto and
off the truck, is not acceptable for lifting high tonnage
loadsO
United States patents ~,05~ 5 and 4,249,85~
disclose linkage mechanisms for lifting heavy loads.
15 ~Iowever in each arrangement, the lift cylinders are
interconnected to the linkage mechanism in a manner which
induces bending moments in the arms of the linkage when
lifting heavy loads. United States patent 2,665,017
discloses a complex arrangement :involving parallelogram
20 linkage where the lift ram is interconnected to the arms
of the parallelogram linkage. Due to its construction,
extreme bending moments in the lifting arms result if the
tractor loader is used to lift and manoeuvre hiyh tonnacJe
objects.
Altho~lyh the pr.ior art patents have contemplated in
many :Eorms the use o:E parallelogram linkages in lifting
loads, no consideration has been given to the use of a
parallelogram linkage in lifting high tonnage loads.
SUMMARY OF THE INVENTION
. .
According to an aspect of this invention, a heavy
load lifting machine for elevating a heavy object off of
and transporting the heavy object along the ~round
comprises a motorlzed mobile vehicle having a structural
load bearing frame~
The load-bearing frame has upright and base member
means fixed relative to each other. The base member
means extends forwardly of the upright member means. A
lifting linkage is secured to the frame comprising an
outwardly extending upper arm and two outwardly extending
lower arms of equal length. The upper arm has a first
3 ~3'73~
end pivo-ta:Lly connected to an upper central portion of
the upright member means and each of the lower ~rms has a
first end pivotally connected to a lower portion of the
upright member means below -the first end of the upper
5 member. Carriage means is adapted for carrying the load
comprising an upright frame to which a load-engaging
means is connected. A second end of the upper arm is
centrally pivotally connected to the carriage means frame
and a second end of each of the lower arms is pivotally
10 connec-ted to the carriage means frame below the upper arm
second end.
The lower arms include means for resisting sway in
the lifting linkage when in use for carrying heavy loads.
Two lift hydraulic rams for the lifting linkage are
15 provided. Each ram has a first end pivotally connected
to the base member means at a position intermediate the
first and second ends of the lower arm. The ram has a
second end pivotally connected to the carriage means
frame to each side of the upper arm second end and alony
20 a pivotal axis defined by the pivotal connection of the
upper member second end to the carriage means frame.
According to another aspec-t of the invent:ion, the
load bearing frame may have riyid spaced-apart members
provid:ing upright and base members fixed relative to each
25 other. The upper arm may be substitwted by two outwardly
extending arms of e~ual length disposed to each side of a
cen-tral portion of -the frame. Each of the upper arms has
a first end pivotally connected to one of the upright
members and each of the lower arms has a first end
30 pivotally connected to one of the upright members below
the first ends of the upper members. A second end of
each of the upper arms is pivotally connected to the
carriage means frame. The second end of the ram is
pivotally connected to the carriage means frame at the
35 pivotal connection of the second end of the upper memberO
According to a preferred aspect oE the invention, a
tilt hydraulic ram may be used to interconnect the first
end of the upper arm of the linkage to its pivo-t point of
pivotal connection with the upright member of the
suppor-tLrlg ~fame. Means may be included in the h~drauLic
circuit for -the rams to absorb downwarcl shock loading on
the lift:ing linkage during transport of the o~ject along
the ground.
The heavy load lifting linkage, according to an
aspect of this invention, may be mounted on a supportiny
frame which may be other than a mobile frame such as
found on a tractor body. E'or e~ample, the linkage may be
mounted on a frame which is positioned so that the load
10 lifting linkage can elevate heavy loads from a first
level to a second level on a repetitious basis.
~RIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in
drawings, wherein:
Figure 1 is a perspec-tive view of the load lifting
machine according to a preferred embodiment of the
invention;
Figure 2 is a front elevation of the machine of
Figure l;
Figure 3 is a top view of the machine of E'igure l;
Figure ~ is a side elevation Gf the machine of
Figure l;
Figure 5 is an enlarged view of the lifting linkage
as it is interconnected to the carriage frame for the
25 lift for~s;
E'igure 6 is a partial side elevation of the machine
of Figure L exen~plifyinc~ tilting of the lif-t forks; and
Figure 7 is a schematic view of the hydraulic system
for the lifting, tilting and steering rams.
30 DETAILED DESCRIPI'ION OF THE PREFERRED E~BOD~MENTS
.... .... ...
The machine 10 of Figures 1, 2, 3 and 4 provides a
system for lifting high tonnage loads, for example, in
the range of up to forty tons or more and transporting
those loads along rough terrain. The system is designed
35 in a manner to provide forward and lateral visibility at
all elevation positions of the lifting linkage. This is
accomplished by an arrangement for the linkage arms which
are raised and lowered by special positioning oE the lift
c~linders and interconnection to the lifting linkage.
~.S~J~
l-t is appreciated -that severa.L dif~erent
arrangernents for the linkage arms may be used to
accomplish the features of this invention. The machine
10, as shown in the drawings, exemplifies one embodiment
5 of the invention. The machine 10 is a mobile motorized
vehi.cle having a tractor poxtion 12 with wheels 14 and a
load bearing support frame 16 mounted on a tandem drive
wheel arrangement 18. The load lifting linkage 20 is
connected to the structural load bearing frame 16 of the
10 machlne 10 to provide for a raisiny and lowering of the
carriage frame 22 to which load lifting elements, such as
forks 24 may be connected. As shown in Figure 2, the
tractor 12 has an operator cab 26 with forward window 28
and la-tera] windows 30 and 32 to provide complete
15 visibility in operating the lifting linkage 20. The
carrier frame 22 comprises spaced-apart frame upright
members 34 and 36. These upright carrier frame members
are interconnected by cross-beams or members 38 and 40.
As shown in Figure 4, the fork 24 has a channel portion
20 42 which engages the upper ridge 41 of cross member 40.
The ].ower portion 44 of the fork 24 rests against the
lower cross member 38 to thereby support a load lifted on
the fork tangs 46.
The llfting linkage 20 of Figu,re 3 consists of two
25 upper arms 48 and S0 of eclual length and lower arms 52
and 5~ of equal l.ength. The lower arms 5Z and 5~ include
an arrangernent to resist sway from side to side during
transport. ~ccording to a preferred embodiment, the
lower arms 52 and 54 converge towards one another in the
30 direction of carriage frame 22 relative to the upper arms
48 and 50. The upper arms 48 and 50 are essentially
parallel to one another~ By arranging the lower arms so
as to converge towards one another, the arms are placed
in compression if there is a force inducing a lateral
35 sway in the lifting linkage. In turn, the lower arms
then resist this sway. It is appreciated that the lower
arms could also diverge away from one another in the
direction of the carriage frame 22 relative to the upper
arms 48 and 50. The same effect would be achieved in the
6 ~ t7~ ~ ~
lower arms dlverging for res:istiny lateral sway of the
lifting linkage. It is also appreciated that -the lower
arms may be placed paral.lel to one another and by
suitable cross bracing between the two lower parallel
5 arms, lateral sway can be resisted.
As shown in Figures 1 and 4, the structural load
bearing frame 16, as supported by the -tandem wheel
arrangement 18, has rigid spaced-apart members in the
form of base members 55 and 56 and upright members 57 and
10 58 on each side of the frame 16. The upper arms 48 and
50 are each connected at one end to the upright members
57 and 58 and at the other end to the carriage frame
uprights 3~ and 36. The upright member 58 has at its
upper portion a yoke 60 consisting of spaced-apart plates
15 62 and 64 as shown in Figure 3. The upper arm 50 at a
first end 49 has a connector portion 66 with an eye
through which connector bolt 68 extencls to provide for a
pivotal connection of a connector portion 66 of the upper
member 50 to a bearing in the upright member 58. At the
20 second end 69 of the upper member, as shown in Figure 3,
it has secured there-to a yoke portion generally
designated 70 and comprises spaced-apart plates 72 ancl
74. A pin 76, as shown in more detail in Fiyure 5,
extends through the plates 72 and 74 to complete a
25 pivotal connection to a bearing in the upr:ic~ht :Erame
member 34 oE the carriage 22. ~imi].arly, the first end
47 of the upper member 48 is pivota].ly connected to the
uprlgh-t member 57 at connector portion 67. At the second
end 71 of the upper member, it is pivotally connected to
30 the upright 36 by way of a similar yoke connector 70.
Each of the lower arms 52 and 5~ are pivotally
connected to the upright members 58 of the support frame
at a location below the point of connection of the first
ends oE the uppe~ members 48 and 50. As shown in Figure
35 4, the lower member 54 is p.ivotally connected to the
upright member 58 by way of a pin 73 extending through a
bearing in the upright member 58 and through
corresponding coupling 80 of the first end of the lower
member 5~. The lower members 5~ and 54 converge towards
7 ~ 3~
one another ~or connec-tion to the cross-member A0 of -the
carriage 22. The lower members 52 and 5~ are welded to a
common plate 82 as shown in Figure 5, and which is
pivotally connected to the cross-member 5~ by yokes 84 as
5 shown more readily in Figure 3, Each yoke 84 includes
spaced-apart plates 86 and 88. The common plate 82 has
two ou-twardly extending connectors 90 and ~2 which are
received between the respective plates ~6 and 88 and
connected thereto by the pin 9~, as shown in Figure 5.
In order to raise and lower the lifting linkage 20,
two lift rams 96 and 98 of Figure 1 are interconnected
between the vehicle frame and the linkage mechanism. A
first end of the lift ram 96 is pivotally connected at
100 to the base member 56 of the support frame 16. The
15 point of interconnection is intermediate and below the
ends 80 and 82 of the lower member 54. According to this
preferred embodiment of the invention, the point of ram
interconnection is located approximately centrally
between the :Eirst and second ends ~0, 82 o-f the
2~ respective lower member. As shown in Figure ~, the
second end 102 of the lift ram 96 is pivotally connec-ted
to the same pivot pins 76 orming the interconnection of
t.he upper arm 50 to the carriage frame upright member 3~,
Thus, the pivot axes for each second end o:E the hydraulic
25 ram are concentric with the plvot axes for the second erld
70 of each o:E the upper members ~8 and 50.
The tractor 12 is hinged:ly connected to the support
frame 16 by way of an articulation connecti.on 104 which
provides for both articulated steering of the machine 10
30 and oscillation of the tractor 12 relative to the load
bearing frame 16. The articulated steering is controlled
by a pair of hydraulic rams (not shown) in Figure ~, yet
to be discussed with respect to Figure 7. By hydraulic
controls a swinging action of the tractor 12 re]ative to
35 the load bearing frame 16 may be effected as shown by
positions 12a and 12b in Figure 3. The load lifting
linkage 20 is connected to the load bearing frame 16 of
the machine in a manner to provide a parallelogram type
linkage between the pivot points represented by pins 6~
,. .
~2~
a~d 76 of ~he upper arms ancl pins 7~ and 9~ oE the lower
arms. To provide additional strength in loading hearing
characteristics for the lower arms, cross-bracing such as
interconnecting tube 106 is provided to resist torsion
5 and lateral sway in the load lifting linkage induced by
carrying a load on the forks 24.
As shown in Figure 4, the elevation of the forks 24
may be varied as indicated by arrow 108, by either
extending or retracting the hydraulic rams 96 and 98.
10 From the position shown in Figure 4, extension of the
rams 96 and 98 to the position 96a for the ram, upper arm
position 50a and lower arm position 54a, the linkage
rotates about the pivot points of this preferred
parallelogram arrangement for the linkage system. By
15 positioning the hydraulic rams 96 and 98 with their
po:Lnts to the load bearing frame 16 intermediate the
length of the lower arms, minimal extension of the rams
is required to provide a considerable height variation oE
the fork 24 as represented by arrow 108. Due to the
20 heavy load ]iEting requirements of the carriage frame,
the less extension of the ram to provide considerable
lifting of the heavy load results in less volume of
hydraulic oil that has to be pumped into the rams 96 and
98. Furthermore, by positioning the rams in the manrler
25 shown in Eigure 4, the vert:Lcal lifting of the load is
mQre ~eacl:ily accomplished in providing less s-train on the
load bearing frame, because the rams are assuminy a more
vertical position than would be the case if the lower end
of the ram were connected more rearwardly at the upright
30 membexs 58 of the load bearing frame. According to this
preferred arrangement, by converging the lower arms 52
and 54 in the manner shown in Figure 3, sufficient space
is provided to locate the lifting rams 96 and 98 directly
below and in line with the upper arms 48 and 50 to
35 increase the lifting capacity of the linkage arrangement.
In order to pick up some heavy objects off the
ground, it is necessary to tilt the forks 24~ The upper
arms 48 and 50 of the linkage arrangement may include
tilt cylinders 108 and 11~ as shown ln Figure 3. The
.. ~
cylinders ]U8 and 11~ are connec-ted to -the arrns 48 and 50
where the rod ends 66 and 67 of the rams 108 and 11~ are
connected to the uprights 57 and 58 of the frame support
structure 16. With the rams 108 and 114 provided in -the
5 upper arms 48 and 50, the rams then function to
interconnect first ends 47 and 49 of the upper arms to
the pivot points on the upright members 57 and 58 of the
support frame. By extension and retraction of the rams
1~8 and 11~, the fork 24 may be tilted as demonstrated in
10 Figure 6 in the direction o:E arrows llU and 112 to a
position 24a. By retracting the rams 108 and 114, the
arms 50 move upwardly to the position shown at 50a. The
carrier frame 22 is tilted about pin 94 to tilt the forks
to the position 24a. During this tiltiny operation, the
15 lift ram 96 retains a constant length so -that the entire
lift linkage 20 is pivoted upwardly about the pivot
points on the frame 16. It is appreciated, however, that
in some situations where tilting of the forks is not
necessary, then the rams lU8 and 11~ are not required in
20 the upper arms 48 and 50.
The embodiment shown in Figure 6 provides a
parallelogram-t~pe linkage arrangement for the upper and
lower arms. It is understood, however, that tllting of
the forks 24 ma~ be accentuated by adapting a
25 non-parallellogram~type arrangement for the upper and
low~r arms. With reference to Figure 6, the distance
between pivot pins 68 and 78 for the first en~s of the
upper and lower arms may be less than the distance
between the pivo-t pins 76 and 94 for the second ends oE
30 the upper and lower arms. By decreasing the distance
between the pivotal pins 68 and 78, when the linkage
mechanism is elevated by extension of rams 96 and 98, the
upper arm has to swing further upwardly to permit upward
swinging of the lower arms which results in pulling back
35 pivot point 76 further and thereby accentuating the tilt
of the forks 24.
Thus by a manipulation of two sets of rams, a
versatile, mobile load lifter for heavy objects of the
forty ton range or more is provided.
r~eferriny to Figure 7, the hydraulic circuits ~or
-the tilt and 1ift rams and for the steering rams is
schema-tically shown. A master controller 1.16 is provided
to control the flow of pressurized hydraulic fluid to the
5 tilt rams 108 and 114, the lift rams 96 and 98 and the
steering rams 118 and 120. A pump 122 supplies
pressurize~ hydraulic fluid to the master controller 116.
A reservoir 124 receives pressurized hydraulic fluid
returned from the system. In accordance with standard
10 hydraulic systems, the pump 122 may withdraw fluid from
the reservoir 124 in resupplying pressurized hydraulic
fluid to the master controller 116. It is further
appreciated that the master controller 116 includes
valviny arrangements to properly control the flow of
15 hydraulic fluid in the system circuits. The valving
arrangement are operated by control knobs..
The hydraulic circuit for the lift rams 96 and 98
include fluid lines 126 and 128. In line 126 is a flow
divider 130 which ensures that all pressurized hydraulic
20 fluid, either going into the rams or being removed from
the rams, is equally divided between the lift rams to
ensure that the parallelogram linkage is always uniformly
raised at both sides. The divider 130 may be of the
standard ~ear Elow divider whi.ch splits the fluicl flow o~
2S line 1~6 and p.rovides equal fluid volume.s -to the closed
ends 132 and 134 of the lift rams. The ram rods 136 and
133 are connected to the frame uprights 34 and 36 in the
manner discussed with respect to Figure 5. When the
master control is operated to release pressurized fluid
30 from the closed ends of the rams 96 and 9~, the flow
divider 132 ensures that equal volumes of fluid flow out
o:E the rams to ensure a uniform lowering of the linkage
mechanism.
When the tilt cylinders 108 and 114 are used in
35 conjunction with the upper arms of the lifting linkage,
the hydraulic fluid in the tilt ram circuits flow through
lines 1~0 and 142. When it is desired to tilt the forks
upwardly, the tilt rams are retracted. This is
accomplished by providing pressurized hydraulic fluid in
:L:i ~2~
line :L40 as div:ided be-tween the rams 108 anc( 11~ at tee
intersection 144 to supply pressurized fluid to the rod
ends ]46 and 148 of the tilt rams. The hydraulic fluid
in the closed ends 150 and 152 flow out of the cylinders
5 to the tee 154 and return via line 142 to the reservoir
124 through the master control 116~ When it is desired to
tilt the forks downwardly, pressurized fluid is provided
in line 1~2 to extend the rams 1.08 and 114 where the
hydraulic fluid flowing out of the rod sides 146 and 1~8
10 of the eylinders is returned to the reservoir 124 through
the master controller.
Once the load is raised off of the ground and the
forks 24 tilted to -the desired angular loeation, the
wheels of the vehicle may drop into ruts or pass over
15 bumps whieh eauses a downward shoek loading on the forks
24 due to the weight of the object being earried. To
avoid over stressing the link arms of the liftlng
llnkage, a shock absorber ls provided for the rod ends
146 ancl 148 of the rams 108 and 114. The shoek absorber,
20 aecording to thls lnvention, eonsists of an aeeumulator
156 in the hydraulie eircuit 140 whieh has a eavity 158
filled with hydraulie fluid from line 1~0. ~ reclprocal
dlvlder 160 separates a eompressible gas 162 :Erom th~
hydraulic fluid in eav.ty 158. When a downward shock ls
25 applied to the carrylng frame, the gas 162 ls compressecl
due to the shock load attempting to extend the rods 162
and 16~ out of the rams 108 and 11~. However due to the
master controller bloeking off llnes 1~0 and 142, the
fluid eannot eseape so that the shoek is absorbed by
30 eompresslon of the gas 162 in the aeeumulator 156.
It is appreeiated that shoek loading of the frame
may also be aceommodated by providing a shock absorber
system in the lift rams, instead of with the tilt rams.
With referenee to Figure 7, an aeeumulator such as 156
35 used with the tilt rams can instead be placed in line 126
to absorb shoek loading by eompression of the gas
eon-tained within the aeeumulator 156. It is understood,
of eourse, that modifieation would also be have to be
macde to the c3as aeeumulator to eompensate for the
l2 ~ 3~
ad~i-tlonal load placecl on the lifting rams during raisiny
and lowering of -the heavy loads.
The articulating s-teering for the vehic:le is
effec-ted by -the steeriny rams 118 and 120 ~hich are
5 installed on both sides of the articulated connection for
-the tractor and the load bearing frame. The rams are
operated in reverse of each other so that when it is
desired to turn in one direction, ram 118 is extended and
ram 120 is retracted. Conversely when it is desired to
10 turn in the opposite direction, ram 118 is retrac-ted and
ram 120 extended. Thus the circuitry for the steering
rams is arranged to have line 166 communicate with the
rod side 168 of ram llæ and the closed end 170 of ram
120. Line 172 communicates conversely with the closed
15 end 174 of ram 118 and the rod end 176 oE ram 120.
The structure of the lifting linkage, according to
this invention, is capable of lifting very heavy loads
and transporting them over rough terrain. Due to the
articulated oscillating connection of the tractor 12 to
20 the support frame 16 and the tandem wheel arrangement 18,
the load on the forks 24 remains reasonably level during
transport. By locating the lift rams in the manner
discussed with respect to Figure ~, considerable weigh-t
can be raised and transported without placing bending
25 rnoments on the linkage arms. Instead, the members are
r?laced :in tension or cornpression therehy optimizing their
structural rigidity. As shown ln Figure 2, with the
ability to raise and lower heavy loads, the linkage
mechanism provides for unobstructed viewing forwardly of
30 the tractor cab 26 through the front windows. This is a
significant advantage in the field of raising heavy loads
due to the need to clearly see the area of opera-tion, so
that industrial accidents are minimized.
The lower arms 5~ and 5~ converge towards the
35 carriage frame 22. This not only provides room for ~he
lift rams 9~ and 98 as they extend from the base members
of the support frame to the pivots points of the carrier
upright members, but adds appreciably to the linkage
resisting sway caused by movement of heavy loads over
.
13 ~ 3~3
rouyh -terrain. By havlng the members 52 and 5~ welded -to
a common p]ate 82 and the pla-te in turn pivotally
connected to the carrier frame, sway is resisted by first
of all the converging aspec-t of the arms and secondly,
5 the use of the common plate which increases resistance -to
sway of the carrier 22 relative to the vehicle frame. To
further strengthen the lower members in resisting sway
and torsion, cross~bracing, such as at 106 as shown in
Figure 3, may be added. By virtue of placing the lower
10 arms 52 and 54 in tension or compression, very heavy
loads may be handled by the machine. At the same time,
an overall lighter structure can be provided which is
readily fabricated and easily mounted to the vehicle and
yet provide unobstructed viewing forwardly of the
15 vehicle.
It is appreciated that the liEting mechanism may be
mounted on a variety of mobile or stationary frames. For
purposes of discussing the invention, the lifting linkage
has been described with respect to a mobile frame.
20 ~Iowever in areas where it is only necessary to elevate
heavy loads from one level to another without travel, it
is possible to mount the system on some other form of
stationary supporting structure. In o-ther circumstances,
~he llftincJ mechanism may be mounted on a rotary
25 turntable for a lifting heavy load and rotating the heavy
load to a diEferent location.
It is appreciated that the upper arms for the
lifting linkage may be substituted by a single upper axm
which extends from a central region of the load bearing
30 frame to the central region of the carriage frame 2~. In
this instance, the support frame 16 would consist of a
base member means having the spaced-apart base members
56. An upright member means would include at least the
lower portion of the upright members 58 to which the
35 lower arms 52 and 54 would be pivotally connected. Above
this area, the pair of upright members 58 would be
modified to provide a central abutment central of the
vehicle and to which the first end of the single upper
arm would be pivotally connected. Similarly, centrally
1~
oE the carri.~.lge :~rame 22 a fi~ed member would be pro~ided
-to which a second end of -the single upper member wou].d be
pivo-tally connected. The upper ends of the lift rams 96
and 98 would be pivotally connected to the carriage frame
5 22 to each slde of the single upper arm. The pitoval
axes of the upper ends of the lift rams would be
coincident with the pivotal axis of the connection for
the single upper arm to the carriage frame 22. With this
arrangement of two spaced-apart lower arms and the single
10 upper arm, the lifting linkage can continue to function
in lifting heavy loads where all arms are placed in
tension or compression during raising and lowering of the
loads. A tilt cylinder, as u~ed with one of the upper
arms as shown in the drawings, could also be used with
15 the single upper arm to provide tilting of the carriage
frame 22.
It is also understood -that the lower arms may
diverge rather than converge towards the carriage frame
22. The base portions of the upright 58 would be
20 modified to provide a centrally located member to which
the first ends o~ the lower arms may be attached. The
arms wou:Ld then diverge outside of the lifting rams 96
and 98 and be pivotally connected to the carriage frame
below the pivot points oE the upper arms. Another
25 al-ternative to the arrangement for -the lower arms i5 that
t:hey may be paralle]. to one another and include cross
brac:i.ng which resists sway and torsion in -the lower arms
when the system is in use. When the lower arms are
provided parallel to one another, the lifting rams 96 and
30 98 are positioned so as to be either inside or outside of
the lower arms so that there is no interference between
the lower arms cross-bracing and the movement of the
lifting rams.
Although preferred embodiments of the invention have
35 been described herein in detail, it will be understood by
those skilled in the art that variations may be made
thereto without departing from the spirit of the
invention or the scope of the appended claims.
