Note: Descriptions are shown in the official language in which they were submitted.
CA 02365309 2004-10-13
TITLE OF THE INVENTION
Tapered roller screw driving apparatus
FIELD OF THE INVENTION
The present invention relates to driving apparatus, and more
particularly to the driving apparatus using an endless screw having tapered
rollers spacedly arranged along a helical line and rotatably engaging related
projection surfaces mounted on the driven device.
BACKGROUND OF THE INVENTION
In driving mechanisms, it is well known to use a gear and rack type
of assembly, especially when the driven part of the assembly is substantially
heavy such as a work platform of scaffolding or an elevator cage. In some
situations the load is so high, 1000 pounds and more, that a lot of drag
torque will
be caused by the friction between the gear and the different teeth of the
rack.
This drag torque might even be increased by dust depositions on the rack
teeth.
To enhance the efficiency of the driving mechanism by smoothing
the interface between the gear and the rack teeth is already known as shown in
U.S. Patents No. 4,541,297 granted on September 17, 1985 to Fujita and
No. 5,636,705 granted on June 10, 1997 to St-Germain.
St-Germain shows a driving mechanism where the endless screw
80 engages with a plurality of equally spaced studs 50 forming the rack
portion of
the assembly, each stud 50 having a roller bearing mounted at its extremity.
Fujita shows an opposite driving mechanism where the endless
screw is made with a cylindrical shaft proper having a plurality of rollers
spaced
along a helical line mounted thereon. The rollers engaging spaced projection
surfaces representing the rack portion of the assembly.
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Both of these mechanisms have a similar problem. Since the
rollers have a certain thickness, they obviously have a large portion of their
thickness that slides onto their respective engaging surface during the
movement
because of the varying radius from the axis of the endless gear, or shaft
proper,
of each engaging region between the roller and its engaging surface (or line).
The sliding tends to deteriorate the surface of the weaker engaging material,
thus
considerably limiting the life of the driving mechanism. Also, the bearings
being
generally expensive, one would like to limit the replacement frequency of
these, if
they have the weaker engaging material. On the other hand, the replacement of
either the endless screw or the rail projections of the driven structure is
also an
expensive situation.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a driving apparatus
for linearly moving a structure that will obviate the above-noted
disadvantages.
An advantage of this invention is that the driving apparatus has at
least two rollers simultaneously engaging projection surfaces.
Another advantage of this invention is that the driving apparatus
has the capability to drive its driven device into both directions of a linear
movement.
A further advantage of this invention is that the driving apparatus is
driven by a hydraulic system that includes two hydraulic motors for increased
load capabilities.
Yet an advantage of this invention is that the lifting driving
apparatus is driven by a hydraulic system which includes a manual backup valve
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allowing for a safe and smooth descending movement upon failure of the
hydraulic system.
Yet another advantage of this invention is that the structure includes
at least two lifting driving apparatus each being driven by an independent
hydraulic system.
Other objects and advantages of the present invention will become
apparent from a careful reading of the detailed description provided herein,
with
appropriate reference to the accompanying drawings.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, there is provided a
driving apparatus that comprises:
- a roller screw member including a main shaft, a plurality of roller shafts
projecting radially outwardly from the main shaft and arranged at equally
spaced
intervals along a helical line around the main shaft and, a plurality of
rollers
rotatably mounted on the roller shafts, the rollers including a bearing means
for
mounting the rollers on the roller shafts, the rollers being tapered to an
angle, the
rollers being oriented onto the roller shafts with the tapering inwardly to
the main
shaft; and
- a rail member adjacent and axially oriented with the main shaft of the
roller screw member, the rail member including a plurality of equally spaced
projections having inclined upper surfaces adapted for radial engagement with
a
bottom region of the tapered surfaces of the rollers, the inclination of the
projection upper surfaces being equal to that of the helical line of the
roller shafts
of the roller screw member;
- one of the roller screw and rail members being adapted for axial
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movement and the other one of the roller screw and rail members being fixed
against axial movement, the rotation of the main shaft providing a movable
member to move in the axial direction of the main shaft with the bottom
regions of
the tapered surfaces of the rollers rotatably engaging the projection upper
surfaces, the angle of the tapering being determined to have a projected
extension of the tapered roller bottom regions intersecting a rotation axis of
their
respective roller shaft on the rotation axis of the main shaft, thereby
providing a
sliding free engagement between the roller surfaces and the projection upper
surfaces during movement.
Preferably, the roller shafts projecting radially outwardly and
upwardly at the angle from the radial direction from the main shaft thereby
providing each roller with the bottom region of its tapered surface being
generally
perpendicularly oriented with the axis of the main shaft.
Alternatively, the projections of the rail member further having
inclined lower surfaces adapted for radial engagement with a top region of the
tapered surfaces of the respective rollers, the inclination of the projection
lower
surfaces being equal to that of the helical line of the roller shafts of the
roller
screw member, the opposite rotation of the main shaft providing the movable
member to move in the opposite axial direction of the main shaft with the top
regions of the tapered surfaces of the rollers rotatably engaging the
projection
lower surfaces, the angle of the tapering being determined to have a projected
extension of the tapered roller top regions intersecting the axis of their
respective
roller shaft on the axis of the main shaft, thereby providing a sliding free
engagement between the roller surfaces and the projection lower surfaces
during
opposite movement, the spacing between a projection upper surface and the
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facing lower surface of the adjacent projection being adapted to essentially
freely
receive the rollers thereby providing a smooth transition between the
movements
of the movable member along the axial direction and the opposite axial
direction
of the main shaft.
Preferably, the bearing means comprises roller bearings.
Preferably, the roller tapered surfaces are made of a material
selected from the group consisting of metal, rubber and thermoplastics.
Preferably, the roller screw member is adapted for axial movement
and the rail member is fixed against axial movement.
Alternatively, a second rail member adjacent the opposite side and
axially oriented with the main shaft of the roller screw member.
Preferably, at least two rollers are being simultaneously rotatably
engaging the projection upper surfaces at all time.
Preferably, the driving apparatus further comprises a structure
member fixedly attached to the roller screw member, the structure member
including a means for rotating the main shaft around its axis.
Alternatively, the means for rotating the main shaft being an
electrical motor, the structure member further including a power source means
connected to the electrical motor and a means for controlling the electrical
motor
whereby a user controllably operates the movement of the driving apparatus.
Preferably, the means for rotating the main shaft being a hydraulic
motor located at one end of the main shaft, the structure member further
including a hydraulic system linked to the hydraulic motor and a means for
controlling the hydraulic motor whereby a user controllably operates the
movement of the driving apparatus.
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Preferably, the hydraulic system comprises a means for
pressurizing a hydraulic liquid located into a reservoir and a plurality of
hose lines
and used to drive the hydraulic motor, a plurality of valve means for
controlling
the direction of the flow of hydraulic liquid within the lines, a plurality of
relieve
valve means for controlling the flow of hydraulic liquid, a flow limiting
means to
safely limit the maximum flow of the hydraulic liquid, the means for
controlling the
hydraulic motor being linked to the valve means and to the relieve valve
means,
the means for pressurizing being removably carried by the structure member.
Preferably, the driving apparatus is used to drive the roller screw
member against at least one constant pulling force, the hydraulic system
further
comprises a manual backup valve bypassing the relieve valve means and
operable by the user for safely and slowly allowing for the hydraulic liquid
to
circulate within the hydraulic motor thereby the movable member of the driving
apparatus being pulled back by the constant pulling force.
Preferably, the hydraulic motor being a first hydraulic motor, the
means for rotating further includes a second hydraulic motor located at the
other
end of the main shaft, the second hydraulic motor being linked in parallel
with the
first one within the hydraulic system to reduce the flow of the hydraulic
liquid
circulating into the motors thereby slowing down the axial movement and
increasing the loading capacity of the driving apparatus.
Preferably, the means for pressurizing being an internal combustion
engine driving a hydraulic pump and the constant pulling force being the
gravitational force.
Preferably, the movable member further having a security brake
member for mechanically preventing any relatively drastic axial movement of
the
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movable member along a non-movable member, the brake member comprising a
biased locking mechanism which engages the non-movable member at regular
intervals therealong and a lever mechanism allowing for the user to unbias the
locking mechanism whenever required.
Alternatively, the present invention provides, in combination, a
platform member, a post member, and a driving apparatus movingly mounting the
platform member along the post member, the driving apparatus being as above
described. The rail member is removably attached to the post member and, the
structure member, fixedly attached to the roller screw member and supporting
the
platform member, is at least partially surrounding the post member and
includes
a means for rotating the main shaft around its axis. The roller screw member
being adapted for axial movement and the rail member being fixed against axial
movement.
Alternatively, in the above combination, the projections of the rail
member further having inclined lower surfaces adapted for radial engagement
with a top region of the tapered surfaces of the respective rollers, the
inclination
of the projection lower surfaces being equal to that of the helical line of
the roller
shafts of the roller screw member, the opposite rotation of the main shaft
providing a movable member to move in the opposite axial direction of the main
shaft with the top region of the tapered surfaces of the rollers rotatably
engaging
the projection lower surfaces, the angle of the tapering being determined to
have
a projected extension of the tapered roller top regions intersecting a
rotation axis
of their respective roller shaft on the rotation axis of the main shaft,
thereby
providing a sliding free engagement between the roller surfaces and the
projection lower surfaces during opposite movement, the spacing between a
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projection upper surface and the facing lower surface of the adjacent
projection
being adapted to essentially freely receive the rollers thereby providing a
smooth
transition between the movements of the movable member along the axial
direction and the opposite axial direction of the main shaft.
Preferably, the above combination further includes a hydraulic
system as above described.
Preferably, the structure member being relatively long to
significantly enhance the structural rigidity of the post member especially
against
buckling, the structure member having a plurality of pair of free wheels
rotatably
mounted thereon, the free wheels bearing on the post member and guiding the
structure member therealong.
Preferably, the platform member is a work platform.
Alternatively, the platform member is an elevator cage.
Preferably, the structure member further having a security brake
member for mechanically preventing any relatively drastic axial movement of
the
movable member along a non-movable member, the brake member comprising a
biased locking mechanism which engages the post member at regular intervals
therealong and a lever mechanism allowing for the user to unbias the locking
mechanism whenever required.
Alternatively, in a modified combination, the post member and the
driving apparatus being a first post member and a first driving apparatus
respectively, the combination further including at least a second post member
spaced from the first post member, a second driving apparatus movingly
mounting the platform member along the second post member, each structure
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member supporting one end of the platform member located inbetween the two
post members.
Alternatively, the modified combination comprises at least two
platform members, at least three post members and at least three driving
apparatus, each of the platform members sharing a same post member
positioned between the two of them.
BRIEF DESCRfPTION OF THE DRAWINGS
In the annexed drawings, like reference characters indicate like
elements throughout.
Figure 1 is a front elevation view of the preferred embodiment of the
driving apparatus of the present invention and its driven device, the post
member
being broken at both extremities;
Figure 2 is an enlarged top view taken along line 2-2 of Fig. 1;
Figure 3 is a partially broken enlarged front view of the driving
apparatus;
Figure 4 is a partially broken enlarged side view taken along line
4-4 of Fig. 3;
Figure 4a is a view similar to that of Fig. 4 showing a second
embodiment of the driving apparatus being able to drive into the two opposed
linear directions;
Figure 5 is an isometric view of a tapered roller mounted on its roller
shaft; _
Figure 6 is a rotated sectional view taken along line 6-6 of Fig. 5,
showing the roller mounted on the main shaft;
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Figures 7 and 8 are side views of the security brake member taken
along line 7-7 of Fig. 2 showing the security brake member in its locking
operative
position and unlatched non-operative position respectively; and
Figure 9 is a schematic diagram representation of the hydraulic
system of the driving apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figs. 1 to 8 there is shown a scaffolding structure 30
used to raise a work platform 32 along a post 34. From Fig. 1, the work
platform
32 is supported by a structure member, preferably a sleeve 36, at least
partially
surrounding the post 34. Preferably, the sleeve 36 is moved along the post 34
using an embodiment of a tapered roller screw driving apparatus 38 according
to
the present invention and, both the sleeve 36 and the post 34 have a generally
square cross section, as seen in Fig. 2. A plurality of pairs of free wheels
40
rotatably mounted on the sleeve 36 bear on the post 34 and guide the sleeve 36
along the post 34 during the movement, as already illustrated in U:S. Patent
No
5,636,705 to St-Germain. Depending on the overall length of the post 34, the
latter may be secured to an adjacent building wall W via a plurality of anchor
members 42 spacedly located along the post 34. The sleeve 36 has a
longitudinal slit 44 opened at both ends for clearing the anchor members 42
during its vertical- movement along the post 34. The sleeve 36 is also
preferably
long to significantly enhance the structural rigidity of the post 34,
especially
against buckling and, allowing for support of a second work platform 32a if
required. The post 34 is adapted to be removably mounted at its' base onto a
support structure (not shown) -adapted to rigidly support the weight of the
whole
scaffolding structure 30.
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As shown in Figs. 3 and 4, the driving apparatus 38 comprises a
roller screw member 46 that is preferably mounted onto the sleeve 36. The
driving apparatus 38 includes a main shaft 48, a plurality of roller shafts 50
(better
shown in Fig. 5) projecting radially outwardly and preferably upwardly at an
angle
a from the radial direction from the main shaft 48. The roller shafts 50 are
preferably arranged at equally spaced intervals along a helical line 52 around
the
main shaft 48 and its axis A. A roller 54 is rotatably mounted, preferably
using a
roller bearing 56, at the projected extremity of each roller shafts 50. The
rollers
54 are tapered, preferably to the angle a, and are oriented onto the roller
shafts
50 with the tapering inwardly to the main shaft 48 in order to have the bottom
region 58 of their tapered surfaces 60 being generally perpendicularly
oriented
with the axis A of the main shaft 48, and their projected extensions 61
intersecting the axis 51 of the respective roller shaft 50 on that same axis A
of the
main shaft 48.
The driving apparatus 38 also includes a rail member 62 adjacent
and axially oriented with the main shaft 48. The rail member 62, preferably
removably mounted onto the post 34, includes a plurality of equally spaced
projections 64 having inclined upper surfaces 66 adapted for radial engagement
with the bottom region 58 of the tapered surfaces 60 of the rollers 54. The
inclination of the projection upper surfaces 66 is equal to that of the
helical 'line 52
of the roller shafts 54 on the main shaft 48. Preferably, both the roller
tapered
surfaces 60 and the projection upper surfaces 66 are made out of a relatively
hard metal such as high strength steel. Depending on the loading of the
driving
apparatus 38, the material may also be rubber or a thermoplastic.
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The rotation R of the main shaft 48 with the rollers 54 induces its
vertical displacement in the axial direction U of the main shaft 48 with the
tapered
roller bottom regions 58 rotatably engaging the projection upper surfaces 66.
The angle a of the tapering is determined to provide a sliding free engagement
between the roller surfaces 60 and the projection upper surfaces 66 during
movement. Accordingly, the projected extensions 61 of the bottom region 58 of
the roller surfaces 60 intersect the axis 51 of their respective roller shaft
50 at the
axis A of the main shaft 48, as shown in Figs. 4 and 6.
During the movement of the roller screw member 46 onto the rail
10. member 62, it is preferable to have at least eight (8) rollers 54
simultaneously
engaging the projections 64 at all time for smoother engagement.
In Fig. 3, there is shown a means for rotating the main shaft 48,
preferably a hydraulic motor 68 coaxially mounted on the top end 70 of the
main
shaft 48, fixedly attached to the sleeve 36. Also, the structure member
includes a
hydraulic system 72 linked to the hydraulic motor 68 and-a means for
controlling
74 the hydraulic motor 68. The means for controlling 74 is preferably a manual
lever 76 operated by a user 78 and allows for variable speed of the hydraulic
motor 68. To increase the loading capacity of the driving apparatus 38, a
second
hydraulic motor 68a is preferably coaxially mounted on the bottom end 70a of
the
main shaft 48. The second motor 68a is linked in parallel with the first motor
68
within the hydraulic system 72, and is activated by a two position switch 80
controlled by the user 78.
The hydraulic system 72, partially shown in Fig. 3, comprises a
means for pressurizing 82 the hydraulic liquid located into a reservoir 83,
preferably including a hydraulic dual stage pump 84 and an internal
combustion.
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engine 86 driving the hydraulic pump 84, a plurality of hose lines 88 to
circulate
the hydraulic liquid from the reservoir 83 to the hydraulic motors 68, 68a in
a
closed loop and connecting a plurality of valve means, preferably electrical
valves
90, to control the circulation of the hydraulic liquid within the lines 88, a
plurality of
relieve valve means 92 for controlling the flow of the hydraulic liquid
thereby
varying the speed of the hydraulic motor 68, and a flow limiting means 94 to
safely limit the maximum flow of hydraulic liquid. Since the hydraulic liquid
does
heat up very quickly under prolonged utilization, a radiator 96 is provided
within
the hydraulic system 72 to cool down the hydraulic liquid. The hydraulic
system
72 is schematically represented in Fig. 9.
In Fig. 5, there is shown a roller 54 mounted on its roller shaft 50
At the roller side extremity 98 of the roller shaft 50, there is a centered
and
preferably hexagonal cavity 100 used to screw down the roller shaft 50 into
the
main shaft 48 with the threads 102 located at the other extremity 104 of the
roller
shaft 50. Also, as seen in Fig. 6, there is a small angular channel 106
connecting
the roller bearing 56 to the hexagonal cavity 100. The small channel 106 is
used
during periodical maintenance of the bearing 56 for lubrication. The tapering
at
the angle a of the roller 54 is well illustrated in this figure, for a second
embodiment of the driving apparatus 38a described herebelow.
Since the driving apparatus 38 drives the sleeve 36 supporting the
work platform 32 upward against the constant pulling force of gravity, the
sleeve
36 also includes a security brake member 108 for mechanically preventing
drastic
downward axial movement of the sleeve 36 and the work platform 32 in case of
failure of the hydraulic system 72. The security brake member 108, as shown in
Fig. 7, preferably includes a locking mechanism 110 comprising a hook 112
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pivotally mounted on the sleeve 36 which abuttingly engages a series of
relatively
regularly spaced stops, preferably the top surfaces 114 of cross beams 116,
located along the post 34, with a biasing member 118, preferably a coil
spring, for
maintaining the hook 112 in its hooking position. During normal upward
movement U of the sleeve 36 along the post 34, the hook 112 is automatically
moved into the unhooking position while crossing the next cross beam 116 and
abutting its bottom surface 120, as shown in broken lines in Fig: 7. During
the
downward movement D of the sleeve, the user can pivot the hook 112 against
the biasing member 118 and keep it into its unhooking position via a lever
122, as
shown in Fig. 8.
The hydraulic system 72 also includes a manual backup valve 124
for the hydraulic liquid to bypass the different relieve valves means 92 and
circulate through the hydraulic motors 68, 68a, and allowing for a safe and
slow
downward movement D of the sleeve 36 and the platform 32 under the gravity
force in case of a problem with the hydraulic system 72. The user 78 via a
backup lever 126 preferably operates this manual backup valve 124.
In a second embodiment of this invention of the driving apparatus
38a of a scaffolding 30a, as shown in Fig. 4a and partially illustrated in
Fig. 6, the
roller shafts 50 are projected radially outwardly from the main shaft. 48 and
their
axes 51 are perpendicular to the axis A of the main shaft 48. Also, the
projections 64 have inclined lower surfaces 66a adapted for radial engagement
with the top regions 58a of the tapered surfaces 60 of the rollers 54. The
inclination of the projection lower surfaces 66a in the tangential direction
of the
main shaft 48 being also equal to that of the helical line 52 of the roller
shafts 54
on the main shaft 48. The opposite rotation Ra of the main shaft 48 with the
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rollers 54 induces its vertical displacement in the opposite axial direction D
of the
main shaft 48 with the tapered roller top regions 58a rotatably engaging the
projection lower surfaces 66a. The angle a of the tapering also provides a
sliding
free engagement between the roller surfaces 60 and the projection lower
surfaces 66a during opposite movement. This orientation of the axes 51 of the
roller shafts 50 with the projection upper 66 and lower 66a surfaces being
both
adapted at the angle a to engage the bottom 58 and top 58a regions of the
tapered surfaces 60 of the rollers 54 respectively. Accordingly, the projected
extensions 61, 61 a of the bottom 58 and top 58a regions respectively
intersect
the axis 51 of their respective roller shaft 50 on the axis A of the main
shaft 48.
The spacing between a projection upper surface 66 and the facing lower surface
66a of the adjacent projection is adapted to essentially freely receive the
rollers
54 and provides a smooth transition between the two direction movements of the
sleeve 36 and the work platform 32 along the axial direction U and the
opposite
axial direction D of the main shaft 48. This embodiment is particularly
adapted
for situations where both the axis A of the main shaft 48 and the rail member
62
are substantially horizontally oriented.
In a further embodiment of a scaffolding, the scaffolding comprises
a work platform 32 with at least two ends, each end of the work platform 32 is
supported by its related sleeve 36 combined with its related driving apparatus
38
and post 34. The work platform 32 being located inbetween the two posts 34. In
the same manner; other embodiments can be obtained such as scaffoldings
comprising at least two work platforms 32, at least three posts 34 and at
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three driving apparatus 38 with their respective sleeves 36, each of the work
platforms 32 sharing a same post 34 positioned between the two of them.
Also, the present invention is not limited to scaffoldings, it can also
be used for different types of elevators or in any situation where a platform
member needs to be driven along a linear direction.
Although embodiments of the invention have been illustrated in the
accompanying drawings and described in the foregoing detailed description, it
will
be understood-that the invention is not limited to the embodiments disclosed,
but
is capable of numerous rearrangements, modifications, and substitutions
without
departing from the scope of the invention.
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