Note: Descriptions are shown in the official language in which they were submitted.
~30Z~1!36
VEHICLE SCISSOR LIFT
FIELD OF THE INVENTION
This invention relates to automotive
service lifts of the type mounted on the floor in
service garages, and more particularly to service
lifts including scissor type linkages for raising a
vehicle.
~ACKGROUND PRIOR ART
Scissor lifts of the type mounted on
the floor of a service area project above the surface
even when fully collapsed. Typically, such lift
arrangements when fully collapsed have a height of at
least six inches above the floor and, in many cases,
more than that. When the service lifts are not in
use, they present an obstacle to people working in
the area and they obstruct movement of vehicles and
equipment in the service area. Accordingly, in many
cases, scissor lifts are recessed into the floor, and
installation of the lifts is e~pensive because of the
work required in forming a recess in the floor for
housing the service lift.
1302~86
. --2--
.
SUMMARY OF THE INVENTION
The present invention provides a
scissor lift for use in vehicle service ~acilities
which has a substantially reduced height or thickness
when the lift is collapsed and minimizes the need for
recessing the service lift into the floor.
In the scissor lift embodying the
invention, a hydraulic ram i5 connected to the pivot
of the pairs of scissors of the scissor lift by a
crank and roller assembly. The crank and roller
assembly is caused to pivot by initial elongation of
the hydraulic ram and functions to elevate the
scissors pivot point while at the same time
increasing the effective angle of the ram with
respect to horizontal to thereby increase the
mechanical advantage of the hydraulic ram. This
results in providing a means for initiating upward
movement of the scissor arrangement and also for
rapidly increasing the mechanical advantage of the
hydraulic ram during the initial stage of scissor
movement. The scissor lift embodying the invention
can have a height which is one-half the height of the
prior art scissor lifts and yet does not sacrifice
mechanical advantage.
Another feature of the scissor lift
embodying the invention is that it includes a lock
bar pivoted on the pivot pin interconnecting the
1302;~86
scissors legs and having a lower end which can engage
successive spaced stops on the base. The lock bar and spaced
stops function as a ratchet or rack and pawl arrangement as
the lift is raised, and if pressure in the hydraulic ram is
lost, the end of the lock bar engages a stop to prevent
dropping the load. To lower the scissor lift, the lower end
of the lock bar can be raised to lift the lower end of the
bar over the stops.
In summary, therefore, the present invention provides a
hydraulically operated scissor lift adapted to be supported
on a support surface. The lift includes a platform supported
for vertical movement with respect to the support surface.
The lift also has first and second legs each having opposite
ends. The first leg has one end pivotally connected to the
support surface and the other end slideably connected to the
platform while the second leg has one end pivotally connected
to the platform and the opposite end adapted to be slideably
supported by the support surface. The mid portions of the
legs are connected together by a pivot. A crank is provided,
which crank rotates independently of the legs. It is
pivotable between a first position in which it is generally
horizontal and a second position in which it is generally
vertical. A hydraulic ram has opposite ends, one end being
adapted to be supported by the support surface and the other
end being connected to the crank. The hydraulic ram is
extendable and is adapted to cause pivotal movement of the
LCM:jj
1302386
crank between its first and second positions during initial
extension of the ram. Initial movement of the hydraulic ram
pivots the crank to force a portion thereof against the
support surface so as to elevate the pivot vertically to
provide initial lift. Further movement of the hydraulic ram
lifts the crank out of engagement with the support surface as
the ram continues to raise the platform.
BRIEF DESC~IPI'IO2~ OF THE DR~WINGS
Fig. 1 is a plan view of a scissor lift embodying the
lo invention in a raised position.
Fig. 2 is a side elevation of the scissor lift shown in
Fig. 1.
Fig. 3 is a plan view of the lift shown in Fig. 1 in a
collapsed position.
Fig. 4 is a side elevation of the scissor lift shown in
Fig. 3, and showing the lift in a fully collapsed position in
phantom.
Fig. 5 is a detailed elevation view of the crank
assembly which imparts the initial upward movement to the
scissor lift shown in Figs. 1-4.
Fig. 6 is an enlarged partial view of the lifting ram
and crank assembly of the scissor lift shown in Figs. 1-4.
LCM:jj
130Z386
Fig. 7 is an enlarged view o~ a locking
bar assembly included in the scissor lift shown in
Figs. 1-4.
Fig. 8 is a cross section view taken
along line 8-8 in Fig. 3.
Fig. 9 is a cross-section view taken
along line 9-9 in Fig. 8.
DETAILED DESCRIPTION OF THE DRAWINGS
Illustrated in Fig. 1 is a vehicle
scissor lift embodying the invention and including a
base 10 supporting a set of inner scissor leys Z4 and
a pair of outer scissor legs 12. Each outer leg 12
includes one end pivotally supported on the base by a
pivot pin 14 in turn supported by a bracket or block
16. The other end of each leg 12 is provided with a
pivoted slider block 18 which slides in and is
restrained in a guide track 20 fixed to the elevating
platform 22. While the elevating platform 22 could
have other constructions, in the illustrated
arrangement it includes a frame comprised of a pair
of side bars 21 joined by end bars 23. The opposite
ends o the rame 22 each support a plurality of
pivoting arms 25, in turn, each supporting a support
pad 27 adapted to be positioned under the frame of a
vehicle for liting the vehicle.
1302386
-
Each inner leg 24 includes one end
pivotally joined to the platform 22 by a pivot pin
26, and an opposite end of each inner leg 24 is
pivotally connected by a pin 29 ~Fig. 6) to a slider
block 28 which is housed in a slider block guide
bracket 30 fixed to the base 10 and supported by the
guide bracket 30 for limited linear reciprocal
movement. The medial portions of the legs 12 and 24
are pivotally interconnected by a pivot pin 32. The
pivot pin 32 also supports and serves as a pivot or
fulcrum for a pivot bar or crank 34 positioned
between the two pairs of legs 12 and 24. The pivot
bar 34 constitutes a double ended crank having its
mid-portion pivoted on pin 32. Each end of the pivot
bar includes spaced apart ears 36, and the space
between the ears 36 is adapted to house an end of a
piston rod 38 of a hydraulic ram 40. A pivot pin 42
extends through all the ears 36 and through the ends
of pairs of piston rods 38. The opposite ends of the
hydraulic rams 40 are pivotally connected to the base
10 by brackets 39 fixed to the base 10 and pivot pins
41 extending through the brackets 39 and through ends
of the hydraulic cylinders 40.
The opposite "end~ of the pivot bar or
crank 34 includes two more pairs of spaced ears 44
(Fig. 3) which support pivot shafts 46 on which
rollers 48 are mounted. In the fully collapsed
position of the scissor lift, (as shown in phantom in
1302386
(I "
Fig. 4) the rollers 48 engage the upper su~face of
the floor of the base 10, and the crank 34 is
generally horizontally disposed but with pivot pin 42
slightly above the axis of the main pivot pin 32 and
above the pivot pin 41 supporting the lower end of
the ram 40. Thus, as best shown in Figs. 5 and 6,
when the scissor lift is in the fully lowered
position and when the ram is then extended, the ram
40 will apply a torque on the crank 34 about the main
pivot pin 32 in a counterclockwise direction, as seen
in Fig. 5, and force the crank 34 to pivot on pin
32. This causes the roller 48 to roll on the base
10. As the crank 32 rotates in the counterclockwise
direction, the pivot 32 is raised by the crank, and
the pivot pin 42 connecting the end of the crank to
piston end 38 also moves upwardly to now give the ram
40 an increased vertical angle and increased
leverage. The crank 34 pivots about pin 32
approximately 90 to the position shown in Fig. 6
wherein a stop surface 50 of the crank 34 engages the
edge of a stop plate 52 which interconnects and is
fixed between the inner legs 24. Once the crank 34
has pivoted to the generally vertical position, the
point of engagement of the ram 90 with the crank 34
is at a position of maximum advantage and continued
extension of the ram 40 will cause the scissor legs
12 and 24 to pivot about the anchor pivots 14 and 26
thereby causing the platform 22 to be elevated.
1302386
In the illustrated arrangement the
scissor lift also includes a lock bar 43 having one
end pivotally joined to the crank 34 by pivot pin
42. As the platform 22 rises, a lower end 54 (Fig.
7~ of the lock bar 43 will drag along the base and
will ride over spaced stops 56 fixed to the base 10.
In order to lower the scissor lift, the lower end 54
of stop bar 42 has to be raised over the stops 56.
When the scissor lift embodying the
invention is in the lowered or retracted position, it
has a very low profile. Because the scissor lift has
a low profile, it can be installed in a garage or
service area on the existing floor, and modification
of the floor to recess the scissor lift into the
floor is not required. Additionally, because the
scissor lift can be readily installed, it can be
moved from one service area to another at minimal
expense. The low profile of the scissor lift is
permitted by the provision of the crank arrangement
34 and provides means for initiating upward movement
of the scissor lift when the hydraulic ram is in a
nearly horizontal position, and the moment arm of the
force generated by the hydraulic ram would be
otherwise insufficient to cause lifting movement of
the lift arms o the scissor lift.
Various features of the invention are
set forth in the following claims.
