Note: Descriptions are shown in the official language in which they were submitted.
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Description
Load Lifting Carriage and Mast Assembly
Technical Field
This invention relates to load lifting
apparatus and, more particularly, to a free lift
carriage and mast assembly.
Background Art
A carriage and mast assembly is commonly
used on vehicles such as fork lift trucks to pick up
and deliver loads from one area to another. The mast
usually has a pair of movable inner uprights which
can be raised vertically in relation to a pair of
fixed outer uprights. In a carriage and mast
assembly which has "free lift", the carriage is
carried on the inner uprights and can be raised or
lifted vertically without extending the inner
uprights. Furthermore, after the carriage is fully
lifted, the inner uprights and carriage can be raised
in unison along the fixed outer uprights. The
advantages of having these relative movements are
well-known and need not be discussed further.
Free lift of the carriage is accomplished
with prior carriage and mast assemblies by using lift
cylinders and lift chains. For example, an assembly
will include at least one lift cylinder having an
outer ~acket and a piston rod that can be extended
from the ~acket. At least one lift chain has one end
coupled to the carriage and extends about a sheave
connected to the piston rod, with the other end being
fixed, for example, to the outer ~acket. This lift
chain provides an indirect coupling between the lift
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cylinder and carriage. When the piston rod is
extended, the lift chain will move around the sheave
and the carriage will be lifted with respect to the
lnner uprights to produce the free lift.
A disadvantage with prior free lift
mechanisms is that the lift chains will wear over a
period of use. This means that chain failure can
occur and/or that the chains must be repaired or
replaced. Also, the weight and cost of the carriage
and mast assembly are undesirably increased due to
the need for the lift chains, together with the
mounting components such as the sheaves.
Furthermore, during the lifting of the carriage or
during movement of the lift truck, the lift chains
can flap about, thereby marring or possibly damaging
the lift cylinders.
Another disadvantage is that operator
visibllity is impaired with prior free lift
mechanisms. Typlcally, the free lift cylinders and
lift chains are disposed in the space between the
inner uprights. The use of the lift chains, and/or
this placement of the cylinders and chains, limits
operator visibility through the mast.
Yet another disadvantage with prior free
lift mechanisms is that the free lift cylinders are
exposed to damage from objects near the floor. For
example, in the lowered position, the carriage will
be near the floor with the piston rod retracted into
the cylinder ~acket and the latter also located near
the floor. The carriage, which is in front of the
cylinder, can protect the cyllnder from such ob~ects.
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However, when the carriage is raised for free lift, the cylinder jacket is
still near the floor and, thereby, exposed to damage from these objects.
Furthermore, the carriage is normally loaded in the raised position, with
the rod being extended from the jacket. This can cause the rod to bend.
The present invention is directed to overcoming one or more of the
problems as set forth above.
Summary of the Invention
In one aspect of the present invention, there is provided an apparatus
for lifting a load, comprising:
a) a mast having outer sides and having a first pair of uprights and a
second pair of uprights, said first pair being movable relative to said
second pair;
b) a load lifting carriage;
c) a pair of free lift cylinders, each of said free lift cylinders
including a jacket connected to said first pair of uprights and a free
lift piston rod connected to said carriage;
d) a pair of mast lift cylinders, each of said mast lift cylinders including
a jacket connected to said first pair of uprights and a mast lift piston
rod fixed to said second pair of uprights; and
e) first and second means for communicating fluid between one of said free
lift cylinders and one of said mast lift cylinders, respectively.
According to another aspect of the invention there is provided a
carriage and mast assembly, comprising:
a) a lift mast having outer sides, and having first and second movable
inner uprights, first and second movable intermediate uprights, and first
and second fixed outer uprights~ said first inner, intermediate and outer
uprights being nestled in one another, and said second inner, intermediate
and outer uprights being nestled in one another;
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b.) a load carrying carriage;
c) first and second cylinder means for free lifting said carriage~ each
being positioned at the outer sides of said mast, respect-.vely, and each
including a jacket having an upper end being connected to said first and
second inner uprights and a lower end having a fluid input port, and a
piston rod having a lower end being connected to said carriage;
d) first and second cylinder means for extending said first and second
inner uprights relative to said first and second intermediate uprights and
said first and second intermediate uprights relative to said first and second
outer uprightsJ each being positioned at the outer sides of said mast,
respectively, and each including a jacket ~aving an upper end having a
fluid output port and being connected to said first and second inner up-
rights, and a hollow piston rod having a fixed lower end having a fluid
input port and an upper end having a piston having a fluid passage; and
e) first and second means for communïcating fluid between said first free
lifting cylinder means and said first extending cylinder means and between
said second free lifting cylinder means and said second extending cylinder
means, respectively, each including a rigid fluid conduit having one end
heing connected to said input port of said jacket and another end being
connected to said output port of said jacket.
According to a further aspect of the invention there is provided
a carriage and mast assembly, comprising:
a) a lift mast having outer sides, and having first and second movable
inner uprights and first and second fixed outer uprights, said first inner
and outer uprights being nestled in one another, and said second inner and
outer uprights being nestled in one another;
b) a load carrying carriage;
c) first and second cylinder means for free lifting said carriage, each being
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positioned at the outer sides of said mast, respectively, and each including
a jacket having an upper end being connected to said first and second inner
uprights and a lower end having a fluid input port, and a piston rod having
a lower end b.eing connected to said carriage;
d) first and second cylinder means for extending said first and second inner
uprights relative to said first and second outer uprights, each being
positioned at the outer sides of said mast, respectively, and each including
a jacket having an upper end having a fluid output port and being connected
to said first and second inner uprights, and a hollow piston rod having a
fixed lower end having a fluid input port and an upper end having a piston
having a fluid passage; and
e) first and second means for commun;cating fluid between said first
free lifting cylinder means and said first extending cylinder means and
between said second free lifting cylinder means and said second extending
cylinder means, respectively, each including a rigid fluid conduit having
one end being connected to said input port of said jacket and another end
being connected to said output port of said jacket.
Brief Description of the Drawings
Fig. 1 is a perspective view of a lift truck having an emhodiment
of the present invention.
Fig. 2 is a section taken along lines 2-2 of Fig. 3.
Fig. 3 is a perspective view of the carriage and mast assembly of
Figs. 1 and 2 in a lowered position.
Fig. 3A is a front elevation taken along lines 3A-3A of Fig. 3.
Figs. 4-6 and Figs. 4A-6A are views, similar to Fig. 3 and Fig. 3A,
respectively, showing the sequence of operation and various positions of
the carriage and mast assembly.
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Fig. 7 is a section similar to Fig. 2 and showing an alternative
embodiment of the present invention.
Best Mode For Carrying Out The Inventi~n
Fig. 1 shows a carriage and mast assembly 10. A carriage 12,
particularly one having forks 14, is supported on a mast 16. The entire
assembly 10 is supported on, for example, a lift truck 18 in a conventional
manner.
As shown in Fig. 2, the mast 16 has a pair of fixed, U-shaped,
outer uprights 20, 22 which are coupled together by a wrap-around tie bar
24.
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A pair of movable, J-shaped, intermediate uprights
26, 28 are partially nestled within the outer
uprights 20, 22, respectively. A tie bar 30 couples
the upright 26 to the upright 28. A pair of upper
5 rollers 32, 34 are connected, respectively, to the
outer uprights 20, 22, to roll on the intermediate
uprights 26, 28, as shown. These rollers 32, 34
permit the intermediate uprights 26, 28 to move
vertically in relation to the fixed uprights 20, 22.
A pair of movable, J-shaped, inner uprights
36, 38 are partially nestled within the intermediate
uprights 26, 28, respectively. A tie bar 39 connects
the upright 36 to the upright 38. A pair of upper
rollers 40, 42 are coupled, respectively, to the
15 uprights 26, 28 and roll on the inner uprights 36,
38, as shown. These rollers 40, 42 permit the inner
uprights 36, 38 to move vertically ln relation to the
intermediate uprights 26, 28.
~he carriage 12 has a pair of roller
20 brackets 44, 45 that carry a pair of rollers 46, 47
which roll on the inner uprights 36, 38,
respectively. Consequently, carriage 12 can move
vertically in relation to the inner uprights 36, 38
to provide "free lift" capability. While Fig. 2
25 shows only pairs of upper rollers 32, 34, 40, 42, 46
and 47, the mast 16 and carriage 12 can have similar
lower rollers (not shown) to aid in the vertical
movements of the inner uprights 36, 38, the
intermediate uprights 26, 28 and the carriage 12.
Fig. 2 also shows a pair of free lift
cylinders 48, 50 and a pair of mast lift cylinders
52, 54. Cylinder 50 and cylinder 54 are disposed to
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the outer, right side R of the mast 16, while
cylinder 48 and cylinder 52 are disposed to the
outer, left side of L of the mast 16. As will be
discussed below, since the 4ree lift cylinders 48, 50
are not positioned in the space between the inner
uprights 36, 38, operator visibility through the mast
16 is improved.
Fig. 3 shows generally the mast 16 having
all the pairs of uprights shown in Fig. 2, and
specifically the fixed outer upright 22, the
intermediate upright 28 and the inner upright 38. A
top cross member 56 is fixed to the top of the inner
uprights 36, 38 and extends to the outer sides of the
mast 16 as shown by extensions 58, 60, respectively
(see also Fig. 2). The carriage 12 also is shown in
Fig. 3.
With reference to Fig. 3 and Fig. 3A, the
free lift cylinder 50 is fixedly connected at an ``
upper end 62 to the extension 60 by a connector 64.
Cylinder 50 has a lower end 66 fixed to the lower
portion of carriage 12. More specifically, cylinder
50 has an outer ~acket 68 fixed at the end 62 to the
connector 64 and a piston rod 70 fixed at the end 66
to the carriage 12. The outer ~acket 68 has a lower
fluid input port 72 through which hydraulic fluid is
received to act against a piston 74 connected to the
top end of the rod 70. Thus, cylinder 50 is
connected directly between the inner uprights 36, 38
and the carriage 12, i.e. without lift chains,
sheaves, etc., to lift the carriage 12 as will be
described.
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The mast lift cylinder 54 is fixedly
connected at an upper end 76 to the extension 60 by a
connector 78, and is fixedly connected at a lower end
80 by a connector 82 to a cross member 83
interconnecting the lower ends of the outer uprights
20, 22. More specifically, cylinder 54 has an outer
~acket 84 fixed at the upper end 76 to the connector
78 and a piston rod 86 fixed at the lower end 80 to
the connector 82. Piston rod 86 is preferably
tubular and has a fluid input port 88 at the lower
end 80 connected to a hydraulic fluid conduit 90
which can be rigid or flexible. A piston 92 is
connected to the top of rod 86 and has a fluid
passage 94 which communicates fluid between the
interior of rod 86 and an upper fluid output port 96
of the outer ~acket 84 through a cylinder area 97. A
rigid fluid conduit 98 has one end 100 coupled to the
output port 96 of the mast lift cylinder 54 and
another end 102 coupled to the input port 72 of the
free lift cylinder 50. Fixed, elongated guards (not
shown) are connected respectively between cylinder
50 and cylinder 54 and between cylinder 48 and
cylinder 52 to protect cylinder 54 and cylinder 52
when the mast 16 is extended, as will become apparent
in the discussion of Fig. 5 and Fig. 6.
Consequently, as shown by the arrows in
Fig. 3A, hydraulic fluid can flow through the conduit
90 and input port 88 to the interior of piston rod
86. From rod 86, the fluid can flow through the
passage 94, area 97, and output port 96 into the
conduit 98 and free lift cylinder 50 via the input
port 72. Free lift cylinder 50 and mast lift
cylinder 54 are sized such that hydraulic fluid
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pressure first activates cylinder 50 by fully
retracting the rod 70 to free lift the carriage 12
relative to the inner uprights 36, 38. Once the rod
70 is fully retracted, the pressure will increase in
5 the cylinder 54, i. e., in the area 97, to raise the
outer jacket 84 relative to hollow rod 86, thereby
raising the inner uprights 36, 38, cylinder 50 and
carriage 12. While not shown, free lift cylinder 48
and mast lift cylinder 52 are similarly connected to
the mast 16 and carriage 12, and hydraulically
coupled to each other, as illustrated in Fig. 3A.
Fig. 7 shows an alternative embodiment of `
the cylinder and mast assembly 10. The mast 16,
rather than having three pairs of uprights as shown
15 in the embodiment of Fig. 2, has two pairs of
uprights including the fixed outer pair 20, 22 and
the movable inner pair of uprights 36, 38. The wrap-
around tie bar 24 connects the upright 20 to the
upright 22. The roller 32 and roller 34 are
20 connected, respectively, to the upright 20 and
upright 22 to permit the inner uprights 36, 38 to
move vertically in relation to the outer uprights 20,
22. Similarly, roller 46 and roller 47 are
connected, respectively, to roller bracket 44 and
25 roller bracket 45 of the carriage 12 to permit the
carriage 12 to move vertically in relation to the
inner uprights 36, 38 for free lift purposes.
Fig. 7 also shows the pair of free lift
cylinders 48, 50 and the pair of mast lift cylinders
30 52, 54. Unlike the side-to-side positioning of these
cylinders as shown in Fig. 2, the cylinder 52 is
positioned behind and slightly to the left of the
cylinder 48, while the cylinder 54 is positioned
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behind and slightly to the right of cylinder 50. The
cylinders 48 and 52 are disposed to the left side L
of the mast 16 and the cylinders 50 and 54 are
disposed to the right side R of the mast 16 so that
5 operator visibility through the mast 16 is not
obstructed by these cylinders, similarly as in the
Fig. 2 embodiment. The embodiment of Fig. 7 also
offers greater operator visibility towards the outer
side L and outer side R over the Fig. 2 embodiment
since the mast lift cylinders 52, 54 are disposed
closer in towards the mast center. While not shown
in Fig. 7, the cylinders 48, 52 and cylinders 50, 54
are connected to the mast 16 and carriage 12, and are
hydraulically coupled to one another in the same
15 manner as shown in Fig. 3A.
While also not shown, yet another
embodiment of the invention would consist of only a
single free lift cylinder 50 and a single mast li~t
cylinder 54 disposed midway between the inner
20 uprights 36, 38. The cylinder 50 and cylinder 54
would be connected between the carriage 12 and mast
16 and hydraulically coupled to each other as already
described, with cylinder 54 being disposed behind
cylinder 50. ~his embodiment, though, would reduce
25 operator visibility through the mast 16 in relation
to the embodiments of Fig. 2 and Fig. 7. However,
increased operator visibility through the mast 16 is
obtained in relation to prior free lift mechanisms
since no lift chains are required.
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Industrial Applicability
As indicated above, the carriage and mast
assembly lO can be connected to a fork lift truck 18
which is used to pick up a load at one area and
deliver the load to another area. The operatior of
the assembly 10 is illustrated in Figs. 3-6 and Figs.
3 A-6 A .
Fig. 3 and Fig. 3A illustrate the lowered
position of the carriage 12 and mast 16. In this
lowered position, the forks 14 of the carriage 12 are
ad~acent a floor with the piston rod 70 being fully
extended from the outer ~acket 68 of the cylinder 50,
and the piston rod 86 being fully withdrawn in the
outer ~acket 84 of the cylinder 54. Also, the pair
of inner uprights 36, 38 and pair of intermediate
uprights 26, 28 are in their lowered position.
In this lowered position, the forks 14 can
be moved by the lift truck 18 beneath a load. Then,
to produce free lift of the carriage 12, i.e., to
20 lift the carriage 12 without raising the uprights of
the mast 16, hydraulic fluid is introduced into the
piston rod 86 from the conduit 90. The fluid then
flows through the piston passage 94, out the port 96
and into the conduit 98 where the fluid then flows
25 into the cylinder 50 via the port 72 to act on piston
74. Consequently, the piston rod 70 is retracted
into the outer ~acket 68 to lift the carriage 12 and
forks 14. At the end of the stroke, the carriage 12
has been lifted to the full free lift position shown
30 in Fig. 4 and Fig. 4A.
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Thereafter, to lift the inner uprights 36,
38 in relation to the intermediate uprights 26, 28,
fluid continues to be introduced into the piston rod
86. Since the piston rod 70 has been retracted its
full stroke, fluid pressure begins to rise in the
area 97 of the cylinder 54. This fluid pressure
causes the outer ~acket 84 of the cylinder 54 to be
raised in relation to the piston rod 86. As a
result, the top cross member 56 begins to rise and to
carry with it the inner uprights 36, 38, the cylinder
50 and the carriage 12.
As this movement occurs, the assembly 10
reaches an intermediate position shown in Fig. 5 and
Fig. 5h. At this intermediate position, the inner
15 uprights 36, 38 engage conventional stops (not shown)
on the intermediate uprights 26, 28. Thereafter, to
raise the intermediate uprights 26, 28 in relation to
the fixed outer uprights 20, 22, fluid continues to
be introduced into the cylinder 54. As a result, the
20 outer ~acket 84 of the cylinder 54 continues to rise
from the Fig. 5 and Fig. 5A position. Consequently,
the inner uprights 36, 38 raise the intermediate
uprights 26, 28, via the above-mentioned stops, in
relation to the outer uprights 20, 22. Fig. 6 and
25 Fig. 6A illustrate the final or fully extended
position of the assembly 10.
Note that the raising of the carriage 12
to a free-lift position and then the raising of the
inner uprights 36, 38 and intermediate uprights
30 26~ 28 occur in response to different movements of,
for example, cylinder 50 and cylinder 54. That is,
cylinder 50 is retracted in that rod 70 is retracted
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into jacket 68 while cylinder 54 is extended in that
~acket 84 is extended from rod 86.
When fluid is withdrawn from the cylinder
54 and cylinder 50 in the Fig. 6A position, the
reverse sequence of operation will occur. That is,
first the cylinder 54 will return to the Fig. 5A
position and then the Fig. 4A position to lower the
mast 16, and then cyllnder 50 will return to the
Fig. 3A position from the Fig. 4A position.
In summary, the disclosed embodiments
eliminate the need for lift chains, sheaves, etc.
by directly connecting the free lift cylinders 48,
50 to the inner uprights 36, 38 and carriage 12.
Operator visibility through the mast 16, i.e.,
between the inner uprights 36, 38, is improved by
positloning all the cylinders at the outer sides of
the mast 16.
Also, the cylinders 48, 50 are continually
protected ~rom damage due to ob;ects near the floor.
In the ~ig. 3 and Fig. 3A position, the carriage 12
protects extended rod 70, while in the Fig. 4 and
Fig. 4A position, neither the rod 70 nor the outer
~acket 68 of cylinder 50 is near the floor.
Furthermore, in the Fig. 4 and Fig. 4A
position the rod 70 is retracted into the jacket 68
and it is in this carriage position that a load
normally is carried. Since the rod 70 is retracted,
there is less likelihood of the rod being bent than
if the rod 70 were in an extended position. This also
increases operator visibility through the mast and
towards the floor.
Other aspects, objects and advantages of
this invention can be obtained from a study of the
drawings, the disclosure, and the appended claims.
