Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02574252 2007-01-16
SAB 003
Twin Screw Scissor Lift Assembly
Field of the Invention
The present invention relates generally to the field of vertical lifts, and in
particular, to an improved lift mechanism for a scissor lift device.
Background of the Invention
Stairways employed in buildings and other structures present difficulties to
non-ambulatory individuals. For example, a non-ambulatory individual confined
to a
personal vehicle such as a wheelchair cannot easily negotiate common
stairwells. To
accommodate such individuals, separate elevator lifts, moving chair
arrangements, or
ramps are often provided. In stair structures extending a vertical distance
that is less than
a building story, such as those typically used near the entrance to a
building, a separate
elevator lift is not always practical, particularly in outdoor environments.
In such cases,
separate ramps or moving chair arrangements may be provided which facilitate
vertical
travel by a personal vehicle.
-1-
CA 02574252 2007-01-16
SAB 003
One drawback to the use of a separate ramp to provide personal vehicle access
to
elevated surfaces is that suitable ramps consume relatively large amounts of
space. As a
result, existing buildings must often be substantially altered to accommodate
the
installation of a ramp. In many circumstances, space constraints within, or
surrounding
the building, make installation of a ramp impossible.
Moving chair arrangements offer a solution in such low rise environments.
Moving chair arrangements comprise a chair that slides diagonally up and down
the
stairway. However, such arrangements require that the personal vehicle be
separately
transported up or down the stairway. Because personal vehicles can be quite
heavy,
separate transport of the personal vehicle can be difficult. Moreover, the
movable chair
itself, when not in use, still occupies stairway space and thus dictates the
appearance of
the staircase.
Separate vertical wheelchair lifts, which are termed in the industry as
"vertical
lifts" or more generally "lift assemblies", have also been employed for such
low rise
environments for use in situations in which there is inadequate room for an
access ramp.
Such devices, are commonly used both for interior or exterior applications,
and provide
the ability to reversibly raise or lower an essentially flat, horizontal
platform from a first
position to a second position. An example of such a vertical lift is provided
in US Patent
No. 5901812 issued to Meunier.
Various motive forces can be utilized for raising or lowering the platform
including hydraulic lifting systems, pneumatic lifting systems, scissor-jack
lifting
devices, or the like. A particularly common lifting motive force is an
electric motor
which uses one or two screw drives to operate a scissor lift assembly that
supports the
platform. A simple scissor lift assembly have a single screw is shown in US
Patent No.
7093691 (Vaughan et al.), and a more complex twin screw lift assembly is shown
in US
Patent No. 6109395 (Storm) as part of a convertible lift assembly.
In these types of assemblies, an electric motor is used to rotate a
horizontally
positioned "screw" which passes through a threaded nut which is in engagement
with a
-2-
CA 02574252 2007-01-16
SAB 003
lower movable bracket on the scissor lift. As the screw is rotated by the
motor, the nut is
forced to move horizontally along the screw, either away from, or towards, a
second
lower bracket of the scissor lift, which second bracket can be either fixed or
moveable.
Regardless, however, as the scissor lift brackets move away or towards each
other, upper
brackets which are connected through a pivot point to the lower screw
brackets, are also
forced to move closer or away from one another, and, more importantly, forced
to move
up or down since the lower brackets are maintained at a set height.
In operation, a platform is connected to the upper brackets, and the platform
is
raised or lowered as the upper brackets move up and down.
Several problems can occur with this type of arrangement. Most notably, the
electric motor is typically position at or near the screw position, and thus,
is typically
located underneath the platform assembly. As such, it is frequently
inconvenient to
access or service the motor. Also, the motor takes up space, and allowances
for the motor
must be made in installing the lift assembly, by either moving the lift away
from the
wall, or by providing a pit under the lift for the motor to rest in.
Further, when using multiple screws, it is important that operation of the two
or
more screws is synchronized so that they move at exactly the same rate and
time. This is
necessary so that the platform will remains level at all times as it moves up
and down.
Also, in a twin scissor lift assembly, the platform must also be easily
leveled on site, so
that an initial level position can be easily achieved.
While the prior art devices have demonstrated some utility in this area, there
still
continues to exist a need for a improved scissor lift assembly which provides
better
lifting performance than prior art scissor lift assemblies. Further, there
continues to be a
need for a twin screw scissor lift assembly wherein the platform of the lift
can be easily
leveled on-site, and the scissor lift assembly can be easily synchronized.
Still further, there continues to be a need for a scissor lift having improved
safety
features.
-3-
CA 02574252 2007-01-16
SAB 003
Summary of the Invention
Accordingly, it is a principal aspect of the present invention to provide a
twin
screw, scissor lift assembly that partially or fully meets the goals, needs
and/or objectives
set out hereinabove. These advantages, as well as other objects and goals
inherent
thereto, are at least partially or fully provided by the twin screw scissor
lift assembly of
the present invention, as set out hereinbelow.
In particular, the present invention fulfills the above needs, as well as
others, by
providing a twin screw scissor lift assembly which preferably provides a twin
screw
arrangement wherein both screws are powered by a single electric motor, and
both have
screw attachment mechanims that permit the platform of the lift to be easily
levelled, and
which operate in a synchronized fashion. Further, the electric motor operating
the twin
screw lift assembly is preferably easily serviced.
Accordingly, in one embodiment, the present invention provides a twin screw
scissor lift assembly comprising;
a support structure with a base for supporting said twin screw scissor lift
assembly components;
a raisable, essentially flat horizontal platform which can be moved between a
raised and a lowered position;
a pair of scissor jacks located on a first and second side of said lift
assembly,
each scissor jacket having a fixed lower bracket at one end of said base and a
moveable
lower bracket movable along said base, and each also having a fixed upper
bracket
indirectly attached to said raisable platform and a moveable upper bracket
moveable
along said raisable platform;
fixed, first and second rotatable, vertical screws located respectively on
said first
and second sides of said lift assembly;
connection brackets affixed to a said fixed upper brackets on each scissor
jack,
and thus also affixed to a first and second side of said raisable platform,
and being
threadably engaged with said first or second vertical screw so that rotation
of said
-4-
CA 02574252 2007-01-16
SAB 003
vertical screws causes said raisable platform to be raised or lowered on said
scissor
jacks;
a motive force, preferably located on one side of said lift assembly which
motive
force is operatively connected to said first vertical screw in order to
reversably rotate said
first vertical screw; and
connecting means, passing across the base of said support structure, which
operatively connects said first vertical screw to said second vertical screw,
whereby
rotation of said first vertical screw causes a corresponding rotation of said
second
vertical screw.
The motive force is proved by a single motor which is preferably located
within a
housing on one side of the vertical lift, and which is essentially directly
connected to the
first vertical screw. The motive force is therefore also indirectly connected
to the second,
and any other vertical screw, by a connecting means which is preferably a
locked linkage
assembly passing across the base of the support structure, from one side of
the vertical
lift to the other. As such, the two or more vertical screws are linked
together so that
rotation of one effects a corresponding rotation of the others.
Moreover, the essentially direct connection between the motor and the first
vertical screw is preferably also provided by a locked linkage assembly.
The locked linkage assembly is preferably provided by a toothed belt, a chain
and
sprocket or a fixed gear arrangement, or other such arrangement, wherein
rotational
movement of the motor output shaft results in an equal movement of all of the
vertical
screws. By avoiding the use of non-locked linkage assemblies, such as a plain
flat belt,
or a simple cross-sectional V-shaped belt, slippage of the screw drive
systems, relative to
one another, is minimized and/or avoided. Moreover, as a result, a
synchronized
movement of the vertical screws is ensured.
The number of rotating vertical screws is typically between 2 to 4 screws.
However, typically, only 2 screws are needed, and thus provide a twin screw
arrangement.
-5-
CA 02574252 2007-01-16
SAB 003
Also, while the screws are termed herein as being "fixed", this is to be
understood to mean that the screws do not move in location within the lift
assembly.
They merely rotate within a set position, and thus, they force an operatively
connected
threaded "nut" on the connection bracket, which causes the connection bracket
to travel
up or down depending on the direction of screw rotation.
The scissor jacks preferably comprise: two lower brackets, one of which is
fixed
in position, and the other of which is free to move along a base member
located on said
first and second sides of said lift assembly; and two upper brackets, one of
which is fixed
in position, and the other of which is free to move along the underside of an
upper frame
member connected to said first and second sides of said platform.
The raisable platform can be merely a single flat platform on which the user
is
positioned. However, the platform can also be formed as being part of a
movable shell
which covers the sides of the lift assembly, as will be described hereinbelow.
Brief Description of the Drawings
Embodiments of this invention will now be described by way of example only in
association with the accompanying drawings in which:
Figure 1 is a perspective view of the scissor lift assembly of the present
invention, which is shown with a twin screw arrangement
Figure 2 is a side view of a first side of the embodiment of Fig. 1 in a
raised
position;
Figure 3 is a. side view of the second side of the embodiment of Fig. 1 in a
collapsed position;
Figure 4 is a top view of the base of the embodiment of Figure 1;
Figure 5 is a side view of the first side, with optional batteries added;
Figure 6 is a perspective view of a further embodiment of the present
invention;
Figure 7 is a side view of the embodiment of Figure 6;
Figure 8 is a perspective view of the embodiment of Figure 6 and including
-6-
CA 02574252 2007-01-16
SAB 003
protective panels; and
Figure 9 is a cross-sectional view of the pin leveling system of the present
invention.
Detailed Description of the Preferred Embodiments
The novel features which are believed to be characteristic of the present
invention, as to its structure, organization, use and method of operation,
together with
further objectives and advantages thereof, will be better understood from the
following
drawings in which a presently preferred embodiment of the invention will now
be
illustrated by way of example only. In the drawings, like reference numerals
depict like
elements.
It is expressly understood, however, that the drawings are for the purpose of
illustration and description only and are not intended as a definition of the
limits of the
invention.
Also, while a plurality of vertical screws can be used in the practice of the
present
invention, in a preferred arrangement, two screws are used in the embodiment
shown
herein in a "twin screw" arrangement. For brevity the remaining discussion
will address
only a twin screw arrangement, but those skilled in the art will appreciate
that additional
vertical screws might also be used.
Referring to Figures 1 to 4, a twin screw scissor lift 10 is shown having a
support
structure consisting of a first side structure 12, a second side structure 14,
a first cross
member 16 and a second cross member 17. Each of sides 12 and 14, holds a
scissor jack
22 or 24. Resting on top of scissor jacks 22 and 24 are platform supports 11
which
supports are attached to a platform 18. Lower brackets 30 ofjacks 22 and 24
are
positioned on the lower frame members 32 and 34 of sides 12 and 14. Connecting
brackets 40 are provided on scissor jacks 22 and 24 to connect supports 11,
and thus
platform 18, to one of the upper brackets 20 of scissor jacks 22 and 24.
Scissor jacks 22 and 24 are essentially the same as the commonly available
-7-
CA 02574252 2007-01-16
SAB 003
scissor jacks known and used in the art. As such, in general they operate in a
known
fashion. However, in the present invention, the scissor jacks are preferably
located within
side structures 12 and 14 so as to be easily covered by a shell, as described
hereinbelow.
One lower bracket of each scissor jack is essentially fixed in place on the
base of
lift 10. A second lower bracket moves (by sliding or rolling) along the base
of lift 10.
One upper bracket is fixed to connection bracket 40, and/or alternatively,
directly to
platform 18. A second upper bracket is free to move (by sliding or rolling)
along the
underside of support 11 and/or platform 18. The design and selection of
appropriate
scissor jacks is known to those skilled in the art.
Connecting brackets 40 are also connected to threaded vertical screws 42 and
44
using a threaded "nut" which nut corresponds to the threads of screws 42 and
44. Since
screws 42 and 44 are fixed in place, rotation of screws 42 and 44 causes
connection
brackets 40 to move up or down depending on the direction of rotation of
vertical screws
42 and 44. Brackets 40 are connected to supports 11, and thus also affixed to
platform 18
(and/or an upper fixed bracket of scissor jacks 22 and 24), so that movement
of brackets
40 causes platform 18 to be raised or lowered.
Platform 18 is essentially flat in its interior portion, but is shown as
having raised
sides 23 when connecting to supports 11. This allows, platform 18 to be nearer
to the
ground when scissor jacks 22 and 24 are in a fully collapsed position. Also,
the front end
of platform 18 preferably has a hinge 15 with a moveable section 19, which can
also be
raised to the position shown in Figure 2, wherein it acts as a barrier to
movement of a
wheelchair off of platform 18. This can be done when platform 18 is off the
ground, such
as either when being raised, or when left in a raised position. Moveable
section 19 can
also be lowered to a position wherein a leading edge 13 is adjacent to the
ground, as
shown in outline in Figure 3, in order to facilitate entry of the user on to
platform 18.
Movement of section 19 can be accomplished in a manner known within this art,
and
will not be described in any further detail.
A single electric motor 50, which acts as the motive force for this assembly,
-8-
CA 02574252 2007-01-16
SAB 003
hangs from side 12, and is essentially directly connected by a toothed belt 53
to the upper
end of vertical screw 12. A toothed pulley 51 is attached to motor 50, and a
second
toothed pulley 52 (connected through belt 52) is attached to vertical screw
42.
At the opposite, lower end of vertical screw 42, a toothed pulley 62 is
positioned
which is connected to a corresponding toothed pulley 64 on the lower end of
vertical
screw 44. Pulleys 62 and 64 are also connected using a toothed belt 66 which
acts as a
locked linkage assembly, and which passes across the support structure by
passing
through cross member 18. Cross member 18 is essentially hollow and is sized so
as to
receive belt 66. Optionally, guide pulleys 70, or alternatively belt
tensioning devices,
might also be positioned within cross member 18 in order to keep belt 66 in
the proper
position.
It is to be noted that the combination of a toothed belt 66 and corresponding
toothed pulleys 62 and 64 is the preferred method for establishing a locked
linkage
between the components, and in particular, the linkage between pulleys 62 and
64. This
linkage provides the locked linkage necessary for the correct operation of the
present
invention. However, other methods of providing a locked linkage might be used
including, for example, a chain and sprocket combination, a direct gear
arrangement, or
the like.
A locked linkage between motor 50 and pulley 52 is not essential, but is
preferred
in order to minimize slippage of belt 53.
Each of sides 12 and 14 are also provided with optional support rods 41 which
are provided adjacent and essentially parallel to, vertical screws 42 and 44.
Preferably,
connecting brackets 40 extend from vertical screws 42 and 44 and have an
opening
through which support rods 41 can pass. With support rods 41 in place, any
tendency for
connecting brackets 40 to rotate with screws 42 or 44 is reduced and/or
prevented. As
such, while optional support rods 41 can be eliminated, they are preferably
used to
strengthen the structure of the connecting bracket assembly.
For improved clarity, in Figure 4, details of lift 10 are shown wherein
scissor
-9-
CA 02574252 2007-01-16
SAB 003
jacks 22 and 24, and platform 18 have been removed. The details of the
structure of lift
can thus be more clearly seen.
Also, it is noted that motor 50 can be any suitable electric motor which can
be
controlled by a control panel fitted within lift 10. Motor 50 can be an AC
motor
5 operating at any locally acceptable voltages and frequencies. Alternatively,
motor 50
might be a DC motor, again operating at any suitable voltage. In this
preferred
embodiment of the invention, lift assembly 10 can incorporate rechargeable DC
batteries
52 into side structure 12, for example, as shown in Figure 5. Use of a DC
motor 50 and
rechargeable DC batteries 52 permits lift 10 to continue to operate even in
the event of a
10 loss of electrical power to lift 10. This ensures that the user will be
able to complete the
transfer to a different floor level regardless of the loss of power, or to
allow emergency
use of the lift in the event of a power failure.
To incorporate motor 50 and optional batteries 52, it is noted that at least
side 12
is typically larger than normally used in a lift assembly. This permits these
components
to be housed within side 12 section, and thus permits easy access to these
components
for servicing or the like.
In Figure 6, a variation of an embodiment of the present invention is provided
wherein side structures 12 and 14 form a support for an inner shell cover 60
(Figure 8).
An outer shell cover 62 (Figure 8) can be attached, and extends over and
upper,
moveable side structures 12A and 14A which are connected to platform 18A
and/or
platform supports 11 A. As such, side structures 12A and 14A, as well as outer
shel162
are raised and lowered as platform 18A moves up and down.
Platform 18A can be directly connected to sides 12A and 14A. However,
platform 18A is preferably connected to sides 12A and 14A using platform
supports
11A. Side sections 12A and 14A therefore have modified supports 11A, similar
to
supports 11, as well as moveable side supports 66 and top supports 68.
Openings 70 are
provided in supports 1 lA in order to allow portions of side supports for side
sections 12
and 14 to pass through supports 11 A as platform 18A is raised and lowered. A
side view
-10-
CA 02574252 2007-01-16
SAB 003
of this arrangement can be seen in Figure 7.
A further advantage of the embodiment of Figure 6 is that the inner and outer
shells can be covered in a protective material, such as for example, sheet
metal, plastics,
wood panels or the like, and that these protective panels can be provided to
enhance
safety by preventing unintended access to the scissor lift components. This
can be seen in
Figure 8, wherein protective coverings have been placed as inner she1160, and
outer shell
62, respectively.
Inner shell 60 preferably covers said base, scissor jacks and at least a lower
section of the side sections. Outer shell 62 is preferably affixed to said
platform so as to
move with said platform, and further, preferably covers at least an upper
portion of said
side section. As such, outer shell 62 moves up and down over inner shell 60.
As a consequence of adding shells 60 and 62, and outer she1162, in particular,
while the user is riding up or down on platform 18A, it is virtually
impossible for the
user to reach any moving parts. Further, shells 60 and 62 are preferably made
of a
smooth material, and therefore, the possibility of injury on a sharp corner,
or the like, is
reduced. However, these covers can be easily removed for servicing.
Accordingly, in a further embodiment, an improved scissor lift assembly is
provided having the components hereinabove described, together with inner and
outer
protective shells around said assembly, wherein said inner shell covers said
base, scissor
jacks and at least a lower section of said side sections, and said outer shell
is affixed to
said platform so as to move with said platform, and covers at least an upper
portion of
said side section.
A further advantage of the scissor lift of the present invention is that the
platform
can be more easily leveled. In prior art applications, it is necessary to
level the base
structure for the lift in order to ensure that the platform was essentially
level. In a
preferred embodiment of the present invention, as seen in Figure 9, sides 23
of platform
18 are provided with connecting holes through which leveling pins 80 can be
inserted at
various locations. Pins 80 pass through side 23, and are inserted into any one
of a series
-11-
CA 02574252 2007-01-16
SAB 003
of leveling holes 81 on support 11, which act as leveling braces. In
operation, the base of
lift 10 of the present invention is positioned in a desired location. Once the
base is in
position, platform 18 is moved to a level position where one side is locked
into position,
and the other side is level to the first. At that time, pins 80 are inserted
through sides 23
and into a suitable and corresponding openings 81 on supports 11 (or 11 A) in
order to
lock platform 18 in a level orientation. Pins 80 can be provided at the four
corners of
platform 18, although any suitable variation on the number and location of the
pins can
be used.
Once platform 18 has been leveled, inner and outer shells 60 and 62 can be put
in
position.
As a result, the two scissor jacks 22 and 24 do not need to be perfectly
coordinated and at the same height in order to setup the lift of the present
invention.
Instead the scissor jacks can be positioned roughly in place, and the final
leveling of
platform 18 can be done using pins 80 and supports 11 or 11 A.
As such, an improved scissor lift assembly has been provided. Thus, in a still
further preferred embodiment, the present invention also preferably provides a
twin
screw scissor lift assembly as described hereinabove, wherein said platform
comprises an
essentially flat, horizontal section affixed to vertical side sections, and
wherein said
connection brackets are affixed to a leveling brace within each side section,
and wherein
said vertical side section has at least one connecting holes through which a
leveling pin
can be inserted, and said leveling brace has a series of holes that can be
selected for
receiving said pin, once said platform has been leveled.
Further, in general, it is also to be noted that lift 10 might also comprise a
series
of barrier plates or railings for the protection of the user. However, these
have been
omitted from the Figures of the present application, in order to improve the
brevity and
clarity of the figures. The skilled artisan would be well aware of their use
and utility in
the practice of the present invention. Additionally, for brevity, the user
operational
control panels have not been shown, but the skilled artisan would be well
aware of their
-12-
CA 02574252 2007-01-16
SAB 003
placement and use..
Moreover, the scissor lift of the present invention can be produced as a small
self-contained unit, self-contained unit with lower weight, and smaller size
than prior art
scissor lift assemblies. As such, lifts of the present invention will
typically weigh less
than 300 kg, and more preferably less than 250 kg. It is to be further noted,
that the
scissor lift assembly of the present invention is preferably fabricated to
provide
movement of the platform which will be roughly equivalent to 2 to 6 stairs,
and more
preferably 3 to 5 stairs. A typical embodiment will have a platform movement
of about te
height of 4 stairs. As such, the total vertical platform movement of the lift
of the present
invention is preferably less than 1.5 meters, and more preferably, less than
1.1 meters.
However, other heights may be utilized.
Thus, it is apparent that there has been provided, in accordance with the
present
invention, a scissor lift assembly which fully satisfies the goals, objects,
and advantages
set forth hereinbefore. Therefore, having described specific embodiments of
the present
invention, it will be understood that alternatives, modifications and
variations thereof
may be suggested to those skilled in the art, and that it is intended that the
present
specification embrace all such alternatives, modifications and variations as
fall within
the scope of the appended claims.
Additionally, for clarity and unless otherwise stated, the word "comprise" and
variations of the word such as "comprising" and "comprises", when used in the
description and claims of the present specification, is not intended to
exclude other
additives, components, integers or steps.
Moreover, the words "substantially" or "essentially", when used with an
adjective
or adverb is intended to enhance the scope of the particular characteristic;
e.g.,
"substantially planar", or "essentially planar" is intended to mean planar,
nearly planar
and/or exhibiting characteristics associated with a planar element.
Also, while this discussion has addressed prior art known to the inventor, it
is not
an admission that all art discussed is citable against the present
application.
-13-
