Note: Descriptions are shown in the official language in which they were submitted.
CA 02531272 2005-12-21
MULTI-SPEED DROP LEG MECHANICAL
JACK FOR USE WITH A TRAILER
FIELD AND BACKGROUND OF THE INVENTION
[0002] This invention relates generally to a multi-speed drop leg mechanical
jack, and more
particularly, to a multi-speed drop leg mechanical jack for use with a
trailer.
[0003] In the mechanical jack industry, and specifically where mechanical
jacks are used with
trailers, there is a continuing need to have user-friendly jacks that provide
a commercially
valuable balance of jack speed, lifting and lowering capabilities, ease of
cranking and overall
performance for both loaded and unloaded trailers. In mechanical jacks these
variables are best
overcome by selecting the appropriate gears by which the mechanical jack will
operate, as well
as anticipating the type of trailer that will be used with the jack.
[0004] In many instances, it is desirable for mechanical jacks to have
multiple gear ratios that not
only have the capacity to handle relatively heavy loads, but also have the
ability to handle small
and midsize loads while maintaining sufficient and commercially acceptable
cranking speeds
without excessive force required.
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[0005] In addition, it is oftentimes desirable to be able to quickly provide
elongation of the
mechanical jack, such as in a drop leg, where there is not any mechanical
cranking required in
order to have a significant amount of jack elongation or contraction in a
short amount of time,
such as at the beginning or completion of the lifting process.
[0006] Moreover, it is also desirable to provide an efficient way to change
from one operating
gear of the jack to another. To the extent that the operator of the jack can
better use the crank of
the jack to facilitate faster and smoother changes of operating gears, the
crank will be considered
to be advantageous. It is a continuing design goal to have a crank that
facilitates operator use of
the mechanical jack to which it is connected, in order to provide improved
cranking and
improved changing from one operating gear to another.
[0007] Therefore, it would be advantageous to have a mechanical jack typically
used with
trailers that has a functional combination of several working gears as well as
a drop leg feature.
It would be particularly desirable if the drop leg feature was considered when
selecting the
working gears of the jack. It would also be advantageous to have a crank or
handle for use with a
mechanical jack that assists in both effective raising and lowering of the
jack, as well as efficient
transition from one working gear to another.
BRIEF SUMMARY OF THE INVENTION
[0008] Disclosed herein is a multi-speed drop leg mechanical jack for use with
a trailer. The
jack generally comprises at least two working gears and a drop leg. More
particularly, the jack
comprises an outer tubular housing; a inner tubular housing in mechanical
engagement with the
outer tubular housing, a drop leg in non-geared sliding engagement with the
inner tubular
housing; a gearbox mounted to the outer tubular housing, the gearbox
comprising: a gear housing
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having an inner surface defined by gear housing teeth; a plurality of planet
gears, each of the
plurality of planet gears having teeth, the teeth in meshing engagement with
the gear housing
teeth; a planetary carrier connected to the plurality of plaiiet gears, the
carrier having an inner
surface defined by planetary carrier teeth; and a sun gear having sun gear
teeth, the sun gear
axially slideable between a working high gear in which the sun gear teeth are
in meshing
engagement with the planetary carrier teeth and a working low gear in which
the suri gear teeth
are in meshing engagement with the teeth of the plurality of planetary gears.
[0009] In another embodiment, a gearbox for use as part of a multi-speed drop
leg mechanical
jack for use with a trailer is disclosed. The gearbox comprises: a gear
housing having an inner
surface defined by gear housing teeth; a plurality of planet gears, each of
the plurality of planet
gears having teeth, the teeth in meshing engagement with the gear housing
teeth; a planetary
carrier connected to the plurality of planet gears, the carrier having an
inner surface defined by
planetary carrier teeth; and a sun gear having sun gear teeth, the sun gear
axially slideable
between a working high gear in which the sun gear teeth are in meshing
engagement with the
planetary carrier teeth and a working low gear in which the sun gear teeth are
in meshing
engagement with the teeth of the plurality of planetary gears; wherein the
working high gear and
the working low gear each have a turns per inch (TPI) parameter and each of
the TPI parameters
are selected at least in part to complement the drop leg.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The drawings illustrate the best mode presently contemplated for
carrying out the
invention. In the drawings:
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[0011] Fig. 1 is a schematic illustration of a multi-speed drop leg mechanical
jack having a
gearbox in accordance with one aspect of the present invention;
[0012] Fig. 1 a is an exploded perspective view of the multi-speed jack
gearbox;
[0013] Fig. 2 is a partial enlarged view of a handle for use with the multi-
speed jack;
[0014] Fig. 3 is a side sectional view of a portion of the multi-speed jack
showing the jack in a
working high gear position;
[0015] Fig. 4 is a sectional view of a gearbox of the multi-speed jack taken
along line 4-4 of Fig.
[0016] Fig. 5 is a side sectional view of a portion of the multi-speed jack
showing the jack in a
working low gear position;
[0017] Fig. 6 is a sectional view of a gearbox of the multi-speed jack taken
along line 6-6 of Fig.
5;
[0018] Fig.7 is a sectional view of the gearbox taken along line 7-7 of Fig.
5; and
[0019] Fig. 8 is a sectional view of a portion of the multi-speed jack taken
along line 8-8 of Fig.
5.
[0020] Fig. 9 is a perspective view of an alternate embodinlent of the present
invention utilizing
a motor to provide input power to the jack, where the jack is engaged by the
motor in high gear.
[0021] Fig. 10 is a perspective view of the jack of Fig. 9 wliere the jack is
engaged by the motor
in low gear.
DETAILED DESCRIPTION OF THE INVENTION
[0022] Referring to Fig. 1, a schematic illustration of a multi-speed drop leg
mechanical jack 10
having a gearbox 12 in accordance with one aspect of the present invention is
shown. The jack
can be used with a trailer 14, partially shown Fig. 1. Trailers that are
contemplated for use
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with the present invention include, but are not limited to, horse trailers,
livestock trailers, large
flatbed trailers, and construction equipment trailers.
[0023] The jack 10, in the embodiment shown, is generally a multi-speed
mechanical jack
incorporating a drop leg or "through the air" speed, and two geared working
speeds, namely a
working low gear speed that facilitates lifting of relatively higher loads,
and a working high gear
speed for faster lifting of relatively lower and medium-sized loads or
lowering relatively high
loads. As shown, gearbox 12 is connected, preferably so as to be flush
mounted, to tubular
housing 16 of jack 10. Alternatively, gearbox 12 may be mounted within tubular
housing 16 so
as to have an internal gearbox arrangement. Tubular housing 16 can generally
be referred to as a
"concentric" tubular style, and in a preferred embodiment, a concentric,
triple tubular style
housing can be used. Tubular housing includes telescoping tubular sections 18a
and 18b. Jack 10
further includes drop leg 20. Drop leg 20 is in sliding, telescoping
relationship tubular section
18b. Telescoping tubular sections 18a, 18b and 20 are supported by jack base
22. Tubular
section 18b includes pin assembly 24 having pin 26. Pin 26 is used to fix drop
leg 20 in position
relative to tubular section 18b. Gearbox 12 is connected to shaft 28. Rotation
of shaft 28
translates into linear movement of jack 10, and more particular, tubular
section 18b relative to
tubular section 18a, in order to raise and lower trailer 14. In one
embodiment, jack 10 is fixedly
connected to trailer 14, for example, via mounting tabs 27 (schematically
shown in phantom)
which can be secured to trailer channel 29 in a known fashion. The drop leg is
used to move
quickly between a retracted position and an extended position in which the
jack base is in close
proximity to the ground. The drop leg movement helps provide the necessary
clearance for the
trailer, to which the jack is attached.
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[0024] Still referring to Fig. 1, crank 30, also termed a leveraging actuator
(e.g., a handle), is used
to impart rotation as well as translation to the shaft. Crank 30 includes two
grips or handles 32,
34, which are separated by a contoured crank bar 36. The grips are used to
facilitate the
imparting of a balanced translational and/or rotation force (i.e., torque) to
shaft 28 as needed.
Contoured crank bar 36 is shown in a preferred "L"-type configuration,
however, any suitable
shape or contoured configurations are contemplated. For example, contoured
crank bar 36 can
be bent or otherwise shaped to facilitate an end user's use of crank 30.
[0025] Fig. la is an exploded perspective view of multi-speed jack gearbox 12.
Gearbox 12
provides for the necessary engagement of the gears so as to impart motion of
the shaft in two
geared positions. Planetary carrier 38 carries planet gears 39a-d, having
teeth 40a-d respectively,
via connecting pins 42a-d, carrier 38, planet gears 39a-d and connecting pins
42a-d are
positioned within gear housing 46, and more particularly, positioned such that
teeth 40a-d are in
meshing engagement with interior teeth 48 of the housing. Shaft 28 connects to
planetary carrier
38 via pin 44. Sun gear 50 includes teeth 52 and, via the teeth, meshingly
engages either teeth
40a-d of planet gears 39a-d, or alternatively, interior teeth 54 of planetary
carrier 38, with these
meshing engagements defining the two geared positions of gearbox 12. Rotation
of sun gear 50
via crank 50 (Figs. I and 2) imparts rotation and force transfer to shaft 28.
Gearbox 12 further
includes input bushing 56 and output bushing 58 and is enclosed by endplates
or cover portions
60a-b. Securing means 62 (e.g., a carriage bolt) and 64 are to fasten
(typically from inside) the
gearbox together.
[0026] Referring to Figs. 1-2, in a preferred embodiment, crank 30 is
removable, as indicated by
the phantom illustration (Fig. 1). Crank 30 includes connecting portion 65,
which extends from
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crank bar 36, and slideably engages hollow sun gear shaft portion 28a. Pin 68
is secured to crank
bar 36, and more particularly, to slideable crank bar portion 70. Both torque
and translation
forces are transmitted via pin 68 and holes 72a and 72b in connecting portion
65 and shaft
portion 28a respectively. When it is desired to remove crank 30 from shaft 28,
for exainple,
during transport of trailer 14 (Fig. 1), the following is performed: a)
raising slideable crank bar
portion 70 of crank 30 in a direction indicated by arrow 66, which in turn
raises pin 68 by
clearing the pin from holes 72a and 72b, respectively; and b) sliding
connecting portion 65 out of
shaft portion 28a, or% sungear 50, in a direction indicated by arrow 74 (i.e.,
axially along the
shaft), thereby disengaging crank 30 from shaft 28 or sungear 50. To engage
the crank with the
shaft, the above procedure is reversed. In one embodiment, the jack includes a
connecting device
to connect the crank to the shaft or may be connected directly to sungear 50.
The connecting
device may include a spring-loaded detent (not shown) or other type of catch
mechanism to
secure the coiulecting device into position. In operation, when pin 68 is
engaged, the detent
emerges to lock or prevent movement of slideable crank bar portion 70, and the
detent retreats
inside slideable crank bar portion 70 when pin 68 is disengaged to pemiit
movement of the
slideable crank bar portion.
[0027] Turning to Figs. 3-4, a side sectional view of a portion of the multi-
speed jack showing
the jack in a working high gear position, and a sectional view of a gearbox of
the multi-speed
jack taken along line 4-4 of Fig. 3 are shown, respectively. In the working
high gear position,
sun gear teeth 52 of sun gear 50 are in meshing engagement with planetary
carrier teeth 54 of
planetary carrier 38. Planetary carrier teeth 54 are formed to match the sun
gear tooth form. In
the working high gear position, sun gear 50 and planetary carrier 38 are
disposed within gear
housing 46. Sun gear 50 is driven by crank 30 to rotate, for example in a
direction indicated by
arrow 76, to drive planetary carrier 38, for example in a direction indicated
by arrow 78.
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Planetary carrier 38, in turn, causes rotation of shaft 28, for example, in a
direction indicated by
arrow 80.
[0028] Turning to Figs. 5-6, a side sectional view of a portion of the multi-
speed jack showing
the jack in a working low gear position, and a sectional view of a gearbox of
the multi-speed jack
taken along line 6-6 of Fig. 5 are shown, respectively. In the working low
gear position, sun gear
teeth 52 of sun gear 50 are in meshing engagement with planet gear teeth 40a-d
of planet gears
39-a-d. In the working low gear position, sun gear 50, planetary gears 39a-d,
and planetary
carrier 38 are disposed within gear housing 46. Sun gear 50 is again driven by
crank 30 to rotate,
for example in a direction indicated by arrow 88, and drive planet gears 39a-
d, for example in a
direction indicated by arrow 90. In addition, planet gear teeth 40a-d of
planet gears 39a-d
meshingly engage housing interior teeth 48 of housing 46, and thus, as planet
gears 39a-d rotate
in the direction indicated by arrow 90, the planet gears also revolve in a
direction indicated by
arrow 92. Planet gears 39a-d are connected, for example via pin 94 as shown,
to planetary carrier
38. Thus, as planet gears 39a-d rotate and revolve, planetary carrier 38 is
itself carried in the
direction indicated by arrow 92. Planetary carrier 38 causes rotation of shaft
28, for example, in
a direction indicated by arrow 80. It is noted that this gearing arrangement
rotates shaft 28 in the
same direction as crank 30 in both geared positions. Such an arrangement may
tend to decrease
novice operator confusion and directional errors when switching gears.
[0029] As shown in Figs. 3 and 5, crank 30 is used to shift between the
working high gear
position and the working low gear position. More particularly, a jack user can
push or pull on
crank 30 to move the crank in directions indicated by arrows 96 and 98. Since
crank 30 is
connected, for example via pin 68 (Fig. 2) to shaft 28 or sun gear 50, the sun
gear axially slides
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between the working high gear position (Fig. 4), in which sun gear teeth 52
are in meshing
engagement with planetary carrier teeth 54 and the working low gear position
(Fig. 6), in which
the sun gear teeth are in meshing engagement with planet gear teeth 40a-d of
planet gears 39a-d.
As will be further described below, other types of actuators can be used,
including a motor that
can be shifted between high gear and low gear to operate the jack without user
cranking.
[0030] Turning to Fig. 1, crank 30 can be termed a"Iow friction" crank in that
it minimizes
frictional losses when shifting between the working high gear position and the
working low gear
position by providing, via handles 32, 34, balanced exertion forces on shaft
28.
[0031] Fig.7 is a sectional view of the gearbox taken along line 7-7 of Fig.
5. As shown,
connector 44, for example a pin connector, connects planetary carrier 38 with
shaft 28. In the
working low gear position shown, sun gear 50 (shown in phantom) causes, via
planet gears 39a-
d, rotation of carrier 38, in turn rotating shaft 28.
[0032] Fig. 8 is a sectional view of a portion of the multi-speed jack taken
along line 8-8 of Fig.
5. As shown, gear 82 is connected to shaft 28 and is in meshing engagement
with crown gear 84,
with the crown gear in turn connected to jack shaft 86. In a known manner,
rotation of shaft 28
causes linear displacement of jack shaft 86, via crown gear 84, to raise and
lower jack 10.
[0033] In the working high gear, preferably between about 7 turns and 11
turns, and more
preferably about 9 turns, of sun gear 50 (Figs. 3-4) results in about one inch
of linear
displacement of jack shaft 86 (Figs. 3-4, 8), with this relationship generally
referred to as "turns
per inch" or TPI. In one preferred embodiment, the working high gear raises
loads that range
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from about 2,500 lbs to about 4,5001bs and lowers loads that range from about
4,200lbs to about
7,500 lbs. In the working high gear, one (1) revolution of sun gcar 50 results
in one (1)
revolution of planetary carrier 38 (Figs. 3-4).
[0034] The working low gear, preferably results in between about 24 and 30,
and more
preferably about 27.75 TPI. In one preferred embodiment, the working low gear
raises loads that
range from about 4,500lbs to about 10,0001bs and lowers loads from about
7,500lbs and above.
In the working low gear position, three (3) revolutions of sun gear 50 results
in one (1) revolution
ofplanetary carrier 38 (Figs. 5-6).
[0035] Accordingly, the ratio of the working low gear to the working high
gear, termed the
"working low gear-to-working high gear ratio" is preferably between about 2.4
to 1 and 5 to 1,
more preferably about 3 to 1, and even more preferably about 3.1 to 1. In one
preferred
embodiment, the gear ratio is 3.0833 to 1.
[0036] Typically the working low gear ratio (or mechanical advantage) is
chosen based on a
maximum lifting load. The working high gear ratio, in contrast, is chosen
based on speed. In the
present invention, both the working low gear and working high ratios are
selected for use
specifically with the jack drop leg feature. Because the drop leg provides the
through-the-air
function, the typical speed consideration becomes unimportant; therefore the
working high gear
ratio can be chosen based on raising or lowering significant but less than
maximum loads. The
user is therefore not confined to lift and lower all loads with only the
working low gear,
especially important when the size of the load is very small.
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[0037] The design of the gear ratios can take into account the fact that the
drop leg is available,
and as part of the design criterion, the working high gear and the gear ratios
can be selected to
carry a significant load. As a result, designing the working gears with the
drop leg in mind
eliminates high working gears that have to carry no load. Also, the gears can
be operator
selected to lift various loaded trailers with as much speed as possible. The
overall efficiency is
increased by reducing the time to raise and lower the jack in the loading
conditions for which it is
made. The two working gears plus drop leg design model is particularly desired
when the loads
change from fully loaded to unloaded, and where loading and unloading occurs
frequently, such
as in vehicle or animal trailers. The working high gear and the working low
gear each have a
turns per inch (TPI) parameter and each of the TPI parameters are selected at
least in part to
complement the drop leg. By "complement" it is mean that the TPI parameters
are selected
based on the anticipation of the availability of the drop leg.
[0038] Another embodiment, as shown in FIGS. 9 and 10, utilizes an actuator
comprising an
electric motor to input power to the jack rather than a hand crank. The motor
100 eliminates the
need for human effort to input power to the jack. Such an improvement retains
the "shift ability"
of the gearbox but does not require manual cranking. Other than the motorized
actuator 100, the
construction of the jack is substantially identical that the previous
embodiment.
[0039] As shown in FIG. 9, a motor assembly 102 comprises a gear motor 100, a
motor gearbox
110, and a sungear 112. The motor 100 provides power through the motor gearbox
110 to supply
torque to the sungear 112. As shown in FIG. 9, the sungear 112 engages the
planetary gear
carrier 50 to provide input power in a high gear. Therefore, the operation of
the jack perforins as
described above relative to power input at a high gear. As shown in FIG. 10,
the motor asseinbly
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100 can pulled outwardly so as to move the sungear 12 out of engagement with
the planetary
gear carrier 50 and into enagement with the planetary gears 39 so as to
provide input power in a
low gear. Therefore, the operation of the jack performs as described above
relative to power
input in a low gear. With regard to the selection of gear speed, it is
anticipated that the shifting
mechanism of the motor assembly could be done manually or automatically
without further
description herein.
[0040] The present invention has been described witli respect to several
einbodiments.
Equivalents, alternatives, and modifications, aside from those expressly
stated herein, are
possible and should be understood to be within the scope of the appending
claims.
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