Note: Descriptions are shown in the official language in which they were submitted.
BP File No. 2681-028 2 0 8 4 S 61
Title: VEHICLE LIFT AND T~cRTNG M~r~ANIsM
FOR USE THEREWITH
This invention relates to lifts for vehicles,
and more particularly, is concerned with hydraulic lifts
for motor vehicles, including scissor mechanisms.
RArR~ouND OF THE INVENTION
At the present time, there are a large number of
different types of hydraulic or other lifts available.
Generally, these are designed within the constraints set
by the design requirements of the lift, such as lifting
capacity, lifting heights, and costs of materials and
individual components. As such, conventional designs
represent a compromise between these different
requirements.
The assignee of the present invention has
previously developed an hydraulic lift for motor vehicle,
which includes two separate scissor mechanisms, each for
one side of the lift (U.S. Patent 4,724,930). Each
scissor mechanism lifts a corresponding elongate wheel
deck, intended to support the wheels on one side of the
vehicle. Beneath each scissor mechanism, there is a base
unit, on which rollers of the scissor mechanism run. This
leaves a significant space between the two wheel decks,
which is largely unobstructed. Each scissor mechanism and
its associated wheel deck has a respective hydraulic
cylinder for raising and lowering it. To ensure that the
two wheel decks are maintained at the same height, there
is a cross brace between them, and also the hydraulic
circuit includes a valve arrangement, to ensure that the
flows to and from the two hydraulic cylinders are
essentially the same. Such a lift can be dimensioned to
lift a vehicle to a considerable height.
Such a hydraulic lift has a number of
advantages. However, it is relatively large, heavy and
immobile.
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In particular, the provision of the base units
renders the lift suitable only for a fixed installation.
The bases support and guide the scissor mechanisms. They
also ensure that the load is distributed to the underlying
floor, so that the floor need not be particularly flat or
smooth.
Similarly, there are available a variety of
lifts intended to lift a vehicle off its wheels, causing
the vehicle to be supported directly at its body or
chassis. To raise the deck, there are a number of
vertical posts, fixed to the ground around the deck, for
example, 2 or 4 posts. The assignee of the present
invention has developed such a 2 post lift (U.S. Patent
4,976,336). Then, some sort of a mechanism is provided
within or associated with the posts, for raising the deck.
Like the foregoing lift based on a scissor
mechanism, this suffers from the advantage that it is
essentially large, cumbersome and fixed installation.
There are also available so-called low rise
lifts. As compared to a full rise lift which can achieve
a lift of 6 feet, a low rise lift may provide a lift in
the range of the order of 23 - 28 inches. The intention
is to raise a vehicle sufficiently high to facilitate work
that really only requires exterior access, e.g. brake work
requiring access to the wheel hubs. Low rise lifts would
not be used for work requiring access to the underside of
the vehicle.
However, low rise lifts known to the assignee of
the present invention, suffer from a number of
disadvantages. Firstly, the lifting range of such low
rise lifts is usually inadequate. Thus, even at full
height, they will leave the wheel hubs and the like of a
vehicle at a height that is too low to be truly
comfortable for a mechanic to work on the brakes,
suspension, etc.
Secondly, to the assignee's knowledge, most such
low rise lifts rely on a parallelogram mechanism. As
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such, the wheel deck is pivotally connected to the ends of two arms,
forming two parallel sides of the parallelogram. The other, lower ends of
the arms, are pivotally secured to the ground.
It will be appreciated that, in initial lifting, the two arms are
essentially close to the horizontal. As such, the wheel decks are
cantilevered away, either in front of or behind, the ground pivot supports
for the arms. For this reason, it is essential that the arms be securely
attached to the ground.
SUMMARY OF THE PRESENT INVENTION
Accordingly, it is desirable to provide a lift having a rise or
lifting height which is greater than existing low rise lifts, but which need
not be as high as conventional full rise lifts. Such lifts should preferably
provide a lifting height of about 3 feet.
It is further desirable that such a lift should be simple,
robust, and be capable of ready installation or removable. It is even more
preferable that such a lift be capable of being readily moved at any time to a
location within a workshop, or even outside, for use on any suitable flat,
hard surface.
A further common problem with any lift arrangement is to
provide a locking or safety mechanism to ensure that, once a vehicle has
been raised, the lift can be locked, to prevent any accidental or
unintentional collapse of the lift while a user is underneath it.
Another aspect of the present invention is directed towards
a simple, robust and reliable locking mechanism.
In accordance with a first aspect of the present invention,
there is provided a lift for lifting a vehicle, the lift comprising:
a support platform for supporting a vehicle and comprising
a pair of main longitudinal members, which are parallel and spaced apart,
a plurality of first cross bars interconnecting the main longitudinal
members, and side elements secured to outer side surfaces of the main
longitudinal members, having a thickness less than that of the main
5~- longitudinal members and being generally flush with the bottom of the
main longitudinal members, the side elements including elongate slots
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generally parallel with the main longitudinal members;
a pair of scissor mechanisms secured symmetrically beneath
the support platform, each scissor mechanism being located under a
respective main longitudinal member and comprising first and second
scissor arms, which are pivotally connected generally at their mid points,
with the first scissor arm having a first end for supporting the lift on the
ground below one end of the support platform and including a roller at
the other end thereof engaging and supporting the other end of the
platform, and with one end of the second scissor arm being pivotally
attached to the support platform at said one end thereof, and including, at
the other end thereof, a ground engaging roller, a plurality of second cross
bars interconnecting the first and second scissor arms to ensure that the
scissor mechanisms operate in conjunction with one another;
support arms located above the side elements and pivotally
attached in the slots thereof, the support arms being generally flush with
the top of the main longitudinal members; and
an actuator connected between the first scissor arms and the
second scissor arms, for raising and lowering the lift.
Preferably the lifting means comprises a cart with a main
column having a handle at the upper end, and support wheels at the base
of the main column, and a lever arm projecting out from the main
column adjacent the wheels, for engaging and lifting the one end of the
lift.
The lift can be configured to have a low profile, for example,
of the order of 4 3/4 inches. For this purpose, a low profile actuator is
required, and a hydraulic actuator is suitable. In such a case, the cart
preferably includes a power unit for the hydraulic actuator. This can
include an electric motor, a hydraulic pump and reservoir unit, and
suitable hydraulic and electrical connection fittings.
In another aspect of the present invention, there is provided
a ratchet mechanism, for use in a vehicle lift, the ratchet mechanism
comprising:
a stop member defining a stop face and having a top surface;
!~ a locking bar defining an abutment face and mounted for
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sliding movement relative to the stop member;
guide means for maintaining the stop member and the
locking bar in alignment for relative sliding movement; a cam pivotally
attached to the locking bar adjacent the abutment face thereof, the cam
including a cam surface and being configured so that: the cam can pivot
and freely slide on the top surface of the stop member while the locking
bar is sliding across the stop member, in one direction; when the locking
bar travels off the top surface of the stop member, the cam can freely pivot
and remain on top of the top surface of the sliding member, to permit the
abutment face and the stop face to contact one another after relative
movement, in the other, opposite direction, to provide a locking action;
and when the locking bar is further displaced away from the locking
member in the one direction, the cam being capable of pivoting down
between the abutment and stop faces, so that the cam surface is inclined
relative to the stop face, to cause the locking bar to ride up over the stop
member when the locking bar is moved in the other, opposite direction, to
disengage the abutment and stop faces.
This ratchet mechanism is suitable for provision in any type
of vehicle lift, and can provide a secure locking mechanism to ensure that
a vehicle is securely held in an elevated position, even if the actuator or its
power supply fails in some way.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
For a better understanding of the present invention, and to
show more clearly how it may be carried into effect, reference will now be
made, by way of example, to the accompanying drawings, in which:
Figure 1 is a plan view of a vehicle lift in accordance with
the present invention;
Figure 2 is a side view of the vehicle lift of Figure 1,
showing the vehicle lift in a raised position, and with partial sections;
Figure 3 is a side view of the vehicle lift in a lowered
position;
Figure 4 is a plan view of the scissor mechanisms of the
vehicle lift, with the vehicle support
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platform removed;
Figures 5a - 5f are side views showing, on an
enlarged scale detail 5 of Figure 2, showing a locking
mechanism;
5Figure 6 is a top view of a hydraulic cylinder
and part of the locking mechanism;
Figure 7a - 7c are perspective views of the
support arms of the vehicle lift showing vehicle support
pads in different positions; and
10Figure 8 is a perspective view showing an end of
the vehicle lift and a power unit used in moving the lift.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to Figures 1 and 2, the top of
the vehicle lift is provided with a vehicle support
platform generally indicated by the reference 10. This
platform 10 has two elongate longitudinal members 12, each
of which comprises an inverted shallow U-shaped channel
section. There are a number of transverse bridging bars
or bracing elements, securing the two members 12 together,
shown in the partial sections in Figure 2. At one end,
there is a square section tube 14, welded across the ends
of the longitudinal members 12. At their mid points, the
longitudinal members 12 have a rectangular section tube 16
joining them. At the other end, there is another
rectangular section tube 18, provided with triangular
gusset pieces 20 to brace the platform 10 as a whole.
As described in greater detail below, to provide
mounting locations for support arms, four side elements 22
are provided. Each side element 22 is a solid piece of
steel welded to the side of the respective longitudinal
member 12, and includes an elongate slot 24. Gusset
pieces 23 reinforce the side elements 22.
To support the vehicle support platform 10, and
also to provide the mechanism for raising and lowering it,
a pair of scissor mechanisms 30 are provided, which are
substantially identical and symmetrical about a central
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vertical plane of the lift, as indicated in Figure 4.
Each scissor mechanism 30 comprises first and second
scissor arms 31, 32, which are pivotally connected at 34.
At their lower ends, the two first scissor arms
31 are joined by a square cross tube 36, as shown at the
lower left of Figure 2; as further shown in Figure 4, this
tube 36 extends out to either side, to enhance the
stability of the vehicle lift. The second scissor arms 32
are joined by an inverted U-section channel 38, towards
their left end or upper ends, as viewed in Figure 2, and
by a small inverted U-section channel 40 at their other,
lower ends. Each scissor arm 31, 32 is a rectangular
section tube.
As shown in Figure 2, the left hand ends of the
scissor arms 32 are connected by pivots 42 to the
longitudinal members 12. The other lower ends of the
scissor arms 32 are provided with ground support rollers
44. Correspondingly, the right hand or upper ends of the
first scissor arms 31, as viewed in Figure 2, are provided
with rollers 46, which engage the underside of the
longitudinal members 12.
To raise and lower the vehicle lift, an
hydraulic actuation cylinder 50 is pivotally connected at
52 by a short arm to the square cross tube 36, and at 54
to an extension arm 56 welded to the channel section 38.
The connection 52 is provided with triangular bracing
gussets 58, as shown in Figure 1.
The embodiment shown has the first scissor arms
31 outside the second scissor arms 32. To space the
rollers 44 further apart, to enhance stability, the arms
could be reversed, with the first arms 31 inside the
second arms 32. Then, the hydraulic cylinder would need
to be moved to the right hand side of Figure 2, to act
between the right hand ends of the second arms 32 and a
crossbar or channel, similar to U-channel 38, extending
between the first scissor arms 31.
It should be noted that the pivot connection 52
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is mounted as low as possible, while the extension arm 56 is dimensioned
to raise the pivot connection 54, while maintaining this below the top
surface of the vehicle lift. Similarly, the pivot at 34 is provided towards
the lower sides of the arms 31, 32. This ensures that a line extending
between the pivot connections 52, 54 is at a relatively large angle to a line
extending between the pivot connections 52, 34. This in turn ensures that
from a lowered position, the cylinder 50 has sufficient mechanical
advantage to commence raising the lift. As the lift is progressively raised,
the hydraulic cylinder 50 is acting at an increasingly more efficient angle.
Beside the extension arm 56, there is a second extension arm
60 for a locking mechanism. A locking bar 62 is pivotally connected to
this. A U-shaped bracket 64 is welded to the side of the cylinder 50, as
shown in detail in Figures 5 and 6. The bracket 64 is provided with
support members 66. On the bottom of the bracket 64, which is generally
flat, there is a rectangular stop member 68.
The free end of the locking bar 62 is provided with an
inclined abutment face 70. On top of the locking bar 62, a pair of
rectangular elements 72 are welded, and a cam 74 is pivotally mounted
between them. The cam 74 has the rounded profile as shown in Figure 5.
In use, when the lift is raised, the hydraulic cylinder extends
causing the piston rod to travel as indicated by arrow 76. Consequently,
the locking bar 62 slides through the U-shaped bracket 64, also in the
direction indicated by the arrow 76 in Figure 5a. The locking bar 62 has a
lower surface facing a top surface of the stop member 68, for relative
sliding movement. As this slides over the rectangular stop member 68,
the cam 74 freely pivots out of the way, as indicated in Figure 5a.
When the lift approaches its fully raised position, the
locking bar 62 drops off the end of the rectangular stop member 68, as
shown in Figure 5b. Again, the cam 74 can freely pivot, to permit this
action, as shown in Figure 5b.
As the bar 62 drops down, this provides an audible sound to
the user. The lower surface of the locking bar 62 then rests on an upper
surface of the bracket 64. The operation of the hydraulic cylinder 50 can
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then be reversed slightly, to bring the abutment face 70 into contact with
an end, stop face 69 of the stop member 68. This then locks the lift in the
raised position and prevents it collapsing, even in the event of a major
severance of the hydraulic supply line (Figure 5b).
To lower the lift, it is first raised further from its locked
position, as shown in Figure 5c. The locking bar 62 is then pulled further
away from the rectangular stop member 68; note that the bracket 64 is
dimensioned so that, even at the fullest extent of the cylinder 50, the bar 62
cannot drop out of it.
As indicated in Figures 5c and 5d, this enables the cam 74 to
drop down off the top of the rectangular stop member 68. The cam 74 is
pivotally mounted adjacent one side, so that its centre of gravity will be
below the pivot point in the configuration of Figure 5d.
As indicated in Figures 5d and 5e, the hydraulic cylinder 50
is caused to retract, and the lift lowered; the locking bar then travels
downwards, as indicated by the arrow 78. This causes the cam 74 to be
pivoted until it comes into abutment with the abutment face 70 (Figure
5e). It then presents an inclined cam surface to the stop face 69, inclined at
an acute angle to the top surface of the stop member 68, which causes the
cam 74 and hence the locking bar 62 to ride up on top of the rectangular
stop 68 again. This is shown in Figure 5f. For this purpose, the cam 74 can
have any suitable curved profile for its left hand or lower face, as viewed
in Figure 5. With the locking bar 62 on top of the stop 68, the lift can be
freely lowered to fully collapsed or lowered configuration.
In the collapsed configuration, the scissor arms 31, 32 are
both generally parallel and close to the ground, and they are received
within the inverted U-channel profile of the longitudinal members 12. As
shown in Figure 3, to accommodate the square bar 14, appropriate notches
would be cut in the inverted channel members 12.
Referring to Figure 7, this shows in greater detail the side
elements 22 and support arms mounted on them. Each side element 22 is
formed from solid one inch
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material, with elongate slots 24 having a width of 1.1/4
inch, and is flush with the bottom of its respective
longitudinal member 12.
As shown in Figure 7, support arms indicated at
80 are mounted by pivot pins 82 in these slots 24. In
known manner, the pivot pins 82 are shaped to support a
cantilevered load at the end of the support arms 80. Each
support arm 80 comprises an inner solid bar section 83,
and a channel section 84 welded thereto.
At the outer end of each arm 80, a pair of
support pads 85, 86 are mounted within the channel section
or slot as shown more clearly in Figure 7c, a cylindrical
mounting projection 87 is provided in the middle of the U
channel 84, and a pivot pin 88 extends through this and
through the support pads 85, 86 to secure them.
Turning now to Figure 8, a power unit for the
lift is indicated at 90. It has a main column 92, with a
handle 91 at the top. The power unit has small wheels 93
at the bottom of the column 92, to form a small cart. It
includes an electric motor 94, and a hydraulic pump and
hydraulic reservoir indicated generally at 96. An
electrical supply connection is indicated at 98, and this
would be provided with a plug for connection to a
conventional rib 110 volt A.C. outlet. An actuating lever
is indicated at 99, which can be moved in either of two
directions to raise and lower the lift. An hydraulic
connection line is indicated schematically at 100, for
connection to an hydraulic line 101 secured to the lift;
in known manner, the two lines 100, 101 include
complementary connection fittings, to form a suitable and
separable hydraulic connection 102.
To enable the lift to be moved, the cross bar 14
is provided with a projecting tab 104. Correspondingly,
a lever arm or base of the cart 90, indicated at 106, is
provided with a pin 108 adapted to engage an aperture of
the tab 104. As shown in Figures 2 and 3, the projecting
tab 104 inclines downwardly at a slight angle.
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In use, with the electrical supply line 98
disconnected and the hydraulic connection 102 separated,
the power unit 90 can be brought up to the lift and the
pin 108 engaged with the tab 104. Then, by pulling back
and down on the handle 91, in known manner, the front of
the lever 106 is raised. The tab 104 and hence that end
of the lift are levered upwards off the ground, and are
supported on the wheels 92 of the power unit 90. As the
lift is supported at the other end on the ground support
rollers 44, it can then be freely rolled about on any
suitable hard, flat support surface. Thus, the concrete
floor of most conventional repair shops would be suitable.
With the lift manoeuvred into an intended
operating position, the one or tab end 104 of the lift can
be dropped to the ground. The power unit 90 can then be
detached from the tab 104, and located some suitable
distance away from the side of the lift.
The hydraulic lines 100, 101 would then be
connected with the hydraulic connection 102, and the
electrical supply line 98 plugged into a suitable outlet.
A vehicle can then be driven over the lift, so
that its wheels lie on either side. The support arms 80
can then be swung outwards and slid along the slots 24 so
that the support pads 85, 86 are located at desired
positions below jacking or support points of the vehicle
` body or chassis. Depending on the vehicle and the desired
height that it has to be raised, different ones of the
support pads 85, 86 can be used.
Thus, as indicated in Figure 7a, the support
pads 85, 86 can be left in a lowered position, giving no
additional lifting range. For a first increase in the
lifting height, the support pad 85 can be flipped up, as
shown in Figure 7b. Alternatively, for a greater increase
in lifting height, and if there is sufficient space
beneath the support point on the vehicle body, etc., the
other support pad 86 could be flipped up as shown in
Figure 7c. The support pads 85, 86 are designed such
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that, when flipped up, they rotate slightly past a
vertical position and rest against the other pad which is
still lowered.
With the arms 80 and pads 85, 86 in the desired
position, the hydraulic supply unit 96 would be actuated
by the lever 99, to raise the lift. As indicated above,
it would be raised until the locking bar 62 passes the
stop 68, and then lowered slightly to the locked position
of Figure 5b. The necessary work can then be carried out
on the vehicle. For example, the wheels can be removed
and work carried out on the vehicle's brake or suspension
systems.
In this regard, the scissor arms are preferably
dimensioned to give a total lifting height of 32 inches.
The support pads 85, 86 are dimensioned to increase this
height to 34 and 37 inches respectively. This is
noticeably higher than conventional low rise lifts, and
should place vehicle brake and suspension systems at a
comfortable height for maintenance and repair work to be
effected.
With the work completed, the vehicle wheels
would be replaced. As detailed above, the lift would then
be raised an additional amount, to cause the locking
mechanism to pass through the sequence of Figures 5c - 5f.
With the lift completely lowered, the vehicle can be
driven away.
The lift is then ready for use with another
vehicle. Alternatively, if it is desired to move the lift
to another location, the power unit 90 can be detached,
both electrically and hydraulically, and then used to move
the lift, as detailed above.
By accommodating the scissor arms 31, 32 in the
longitudinal members 12, and by locating the support arms
80 beside the platform 10, the overall profile can be kept
low. The profile, in the collapsed position, can be kept
to a height of 4 3/4 inches, which to applicant's
knowledge, should not interfere with the chassis or
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suspension of any typical road vehicle.
While the lift is shown actuated by a hydraulic
cylinder, a variety of different actuation devices could
be used. For example, a pneumatic cylinder, connectible
to a compressed air supply, may be acceptable for some
cases, although generally, it would need to be of larger
diameter.
