U.S. patent number 3,871,478 [Application Number 05/309,474] was granted by the patent office on 1975-03-18 for extendible stable working platform.
Invention is credited to Sherman W. Bushnell, Jr..
United States Patent |
3,871,478 |
Bushnell, Jr. |
March 18, 1975 |
EXTENDIBLE STABLE WORKING PLATFORM
Abstract
A portable elongated working platform supported by a plurality
of pneumatically extendible telescoping cylinders. The opposite
sides of the elongated platform are interconnected such that the
platform remains substantially level during a shift of weight from
one portion of the platform to the other. The interconnection is
such that the horizontal stability is a constant factor regardless
of the amount of extension of the cylinders. The lowermost stage of
the cylinders may be extended first, lifting the working platform
above the supporting surface and providing a leg structure enabling
the platform to straddle objects which would normally interfere
with the use. The control system is responsive to movement of the
extending cylinders, terminating flow and thus preventing an excess
build up of fluid in the event the cylinders should cease outward
movement.
Inventors: |
Bushnell, Jr.; Sherman W.
(Seattle, WA) |
Family
ID: |
26885740 |
Appl.
No.: |
05/309,474 |
Filed: |
November 24, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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190052 |
Oct 18, 1971 |
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Current U.S.
Class: |
182/69.4;
182/148 |
Current CPC
Class: |
B66F
11/04 (20130101); E04G 1/22 (20130101) |
Current International
Class: |
E04G
1/22 (20060101); E04G 1/18 (20060101); B66F
11/04 (20060101); E04g 001/22 () |
Field of
Search: |
;182/141,148,63,66,67,178 ;33/80 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Machado; Reinaldo P.
Attorney, Agent or Firm: Seed, Berry, Vernon &
Baynham
Parent Case Text
BACKGROUND OF THE INVENTION
This application is a continuation in part of U.S. Pat. application
Ser. No. 190,052 filed Oct. 18, 1971 now abandoned and entitled
"Extendible Stable Working Platform."
Claims
The embodiments of the invention in which a particular property or
privilege is claimed are defined as follows:
1. An elongated rectangular working platform secured to four
extendible telescoping cylinders, one at each corner, having an
inherently stable base, said base comprising;
framework rigidly interconnecting two of the lower cylinders,
a vertical rigid upright member parallel to the cylinders secured
to the framework,
extendible bracing means pivotally secured to the upright member
adapted to be extended to contact the floor at an angle to the
cylinders providing a rigid base, and
means rigidly interconnecting the lower section of the bracing
means with the framework, pivotally mounted to both the framework
and the bracing means whereby the interconnecting means may be
pivoted upwardly, collapsing the bracing means against the
framework, and
telescoping outrigger means mounted for horizontal extension in the
same direction as the axis of the framework to provide a broader,
more stable base.
2. A working platform as in claim 1 wherein the lowermost stage of
the cylinders is independently extendible serving as legs in the
event it is necessary to straddle an object.
3. A portable working platform capable of straddling material
beneath the working position comprising;
a platform,
a plurality of telescoping extendible cylinders carrying the
platform, only part of which are interconnected at the base portion
to thereby provide straddle space beneath the platform,
locking means for selectively interconnecting all of the stages of
the cylinders excepting the lowermost whereby the introduction of
fluid will extend only the lowermost stage of each cylinder,
latch means for securing the lowermost stage of each cylinder in
its extended position whereby the fluid may be evacuated leaving a
rigid platform spaced from the ground supporting surface, and
control means for further extending the cylinders following the
release of the locking means whereby the platform may be used
either in the normal or the straddle position and the entire unit
may be collapsed for portability.
4. A working platform as in claim 3 wherein the locking means
comprises a rigid selectively engageable means to prevent extension
of the locked stages.
5. A working platform as in claim 3 wherein the smallest of the
telescoping cylinders is lowermost.
6. A working platform as in claim 3 wherein the latch means is
operative from on top of the platform and may be selectively left
in the operational or non-operational position.
7. A working platform as in claim 3 wherein the cylinders are
interconnected such that a shift in weight will be equalized over
all of the cylinders retaining the platform in a horizontal
configuration at all times.
8. A hoist comprising;
two pairs of upright parallel spaced extendible cylinder units
adapted to be extended by compressed gas, a platform carried at
opposite ends by said cylinder units and adapted to be raised
responsive to extension thereof,
a pair of column units near said ends of the platform, means for
selectively supplying or exhausting compressed gas to or from said
cylinder units for responsively raising or lowering said platform,
and
a load-equalizing reeving system connected to said column units and
interconnecting said cylinder units whereby the latter are caused
to raise and lower in unison to keep the platform level
irrespective of the manner in which the platform is loaded.
9. A multi-stage hoist comprising;
base support means,
two pairs of upright parallel spaced multi-stage telescopic
cylinder units mounted on said base support means and adapted to be
extended by compressed gas, a platform carried at opposite of its
ends by said cylinder units and adapted to be raised responsive to
extension thereof,
a pair of multi-stage telescopic column units near said ends of the
platform, there being a column stage for each cylinder stage and
the vertical extension of each column stage geing greater than the
extension of the respective cylinder stage, means for selectively
supplying or exhausting compressed gas to or from said cylinder
units for responsively raising or lowering said platform, and a
respective load equalizing means for each cylinder stage connected
near the top of the respective column stage whereby the cylinder
units are caused to raise and lower in unison to keep the platform
level irrespective of the manner in which the platform is
loaded.
10. A multi-stage hoist according to claim 9 in which said
telescopic cylinder units have their largest cylinders at the top
whereby the upper stages of the cylinder units extend first and
retract last, a manifold connected to said largest cylinders and
arranged to raise and lower with the platform, a flexible supply
line for transmitting compressed gas to said manifold, and valve
means adjacent said platform for selectively charging and venting
said manifold whereby operation of the hoist can be controlled by
an operator located on the platform.
11. A multi-stage hoist according to claim 9 in which the bottom
stages of said column units and of said pairs of cylinder units are
not structurally interconnected along the dimension between said
pairs whereby the hoist can straddle objects therebetween.
12. A multi-stage hoist according to claim 11 in which the
respective stages of said cylinder units above the bottom stage are
interconnected in a manner whereby such interconnection does not
interfere with the vertical travel path of said platform.
13. A multi-stage hoist according to claim 9 in which each said
pair of telescopic cylinder units has its cylinders interconnected
at each stage, and in which said pairs are interconnected at each
stage above the bottom stage.
14. A multi-stage hoist according to claim 9 in which the bottom
stages of said pairs of cylinder units are not connected whereby
the hoist can straddle objects, and said telescopic cylinder units
have their largest cylinders at the top whereby the upper stages of
the cylinder units normally extend first, first locking means for
selectively locking said telescopic column units from extension
whereby the lowest stage of the cylinder units extend first; and
second locking means selectively locking said lowest stage in
extended position whereby the platform is given a higher straddle
height from which to operate when said first locking means is then
released.
15. A multi-stage hoist according to claim 9 in which the
respective stages of said cylinder units above the bottom stage are
structurally interconnected, and the respective stages of the
column units above the bottom stage are also structurally
interconnected.
16. A multi-stage hoist according to claim 9 in which the column
units are located between the cylinder units and the platform, and
in which the respective stages of the column units above the bottom
stage are structurally interconnected by horizontal cross-bracing
extending diagonally below the platform.
17. A hoist comprising:
a base support means,
first and second spaced columns on said base support means,
a platform having first and second ends facing respective of said
columns,
first and second sheaves during their journals fixed relative to
said first and second ends, respectively,
third and fourth sheaves having their journals fixed relative to
said second and first ends, respectively,
a first cable anchored near the top of the first column, passing
beneath the first sheave, and over the second sheave, and anchored
near the base of the second column,
a second cable anchored near the top of the second columns, passing
beneath the third sheave and over the fourth sheave, and anchored
near the base of the first column, and
a pair of upright spaced extendible cylinders on the base connected
to the ends of said platform and adapted to be extended by
supplying compressed gas thereto.
18. A multi-stage hoist comprising,
a base support means, spaced upright first and second multi-stage
telescopic cylinder units on the base support means and adapted to
be extended by compressed gas; a first group of columns on the base
support means, each column of such group being connected to the
base of a respective stage of the first cylinder unit and
projecting to a level well above such stage when the stage is
retracted;
a second group of columns on the base support means, each column of
such group being connected to the base of a respective stage of the
second cylinder unit and projecting to a level well above such
stage when the stage is retracted;
a platform between said groups and carried by the upper stages of
said cylinder units; and
a respective load-equalizing means for each stage of the cylinder
units and anchored to the respective columns of each stage whereby
the platform is maintained in a level condition.
19. Means to prevent excess building up of pressure within a
pneumatically expandable cylinder comprising;
means to detect relative movement of the parts of the cylinder;
a source of fluid under pressure,
valve means to selectively control the flow of fluid into the
cylinder,
override means responsive to non-movement of the parts of the
cylinder to prevent flow of air to the valve means.
20. Means as in claim 19 wherein means to detect relative movement
comprises a flexible means secured to one end of the cylinder and
passing over a rotatable member secured to the other end whereby
relative movement will cause rotation of the rotatable member.
21. Means as in claim 20 wherein rotatable means causes a release
of pressure when rotating but allows a pressure buildup during
non-rotation, said override means being normally open and closed by
a pressure buildup caused by lack of relative movement of the parts
of the cylinder.
22. Means as in claim 19 wherein the override means is a normally
open, pressure closed valve and where non-movement of the parts
causes a pressure buildup which closes the valve.
23. A pneumatic lift comprising,
a supply of air under pressure,
hollow telescopic cylinders closed upon their lower end to form a
respective piston for each cylinder,
hollow probe means integral with the larger of two of said pistons
extending toward the smaller of the two,
valve means controlling the flow of fluid through the hollow probe,
said valve means being biased toward a closed position,
a cavity in the smaller piston surrounding the probe means in the
larger piston, said cavity being of a predetermined size to control
the sequence of movement of the two pistons responsive to the
introduction of air under pressure.
24. A lift as in claim 23 wherein the valve is located in the
bottom of a cavity in the larger piston and a protrusion extends
downwardly from the smaller piston for engaging said valve to open
it.
25. A stable extendable working platform comprising;
a relatively planar working surface supported at the periphery by a
plurality of multi-stage telescoping pneumatic cylinders,
fixed length cable means secured to each stage and extending to an
upright member at the opposite side of the stage, said cable means
passing through pulley means secured to the next upper stage
whereby extension or contraction of a stage causes the cable means
to linearly translate from one side of the platform to the other
and the fixed length of the cable means transmits any downward
force upon one portion of the platform to the other side assuring a
substantially horizontal platform irrespective of the loading.
26. A working platform as in claim 25 wherein the working surface
is rectangular in configuration and the cables extend along the
diagonal thereby transmitting downward forces to the opposite
corner.
27. A working platform as in claim 25 wherein the uprights are
interlocking and telescoping channel members which each have one
end of the cable secured at the upper end thereof.
28. A working platform as in claim 25 wherein the corresponding
stage of each telescoping cylinder is interconnected by a rigid
framework.
29. A platform as in claim 25 wherein the lowest stage includes a
plurality of outriggers to increase the stability when the
cylinders are extended.
30. A platform as in claim 29 wherein the outriggers have rollers
thereon and are pivotable from a position whereat they are no wider
than the platform to a position whereat they extend substantially
outward from the frame and are in contact with the supporting
surface.
31. A pneumatically operated telescoping platform supporting
cylinder comprising;
a plurality of closed ended nesting cylindrical elements, the one
with the largest diameter being uppermost,
an upwardly extending hollow probe integral with the next to the
smallest element, said probe extending the full thickness of the
closed ends of those elements located between the probe and the
element with the largest diameter when such elements are in a
collapsed condition and said probe having a normally closed valve
at its upper end, said valve being held open so long as the
elements excepting the one with the smallest diameter are
collapsed, the probe presenting an exposed surface smaller than the
surface of the closed end of the element with the smallest diameter
whereby upon introduction of air under pressure the element with
the probe extends first.
32. A multi-stage hoist comprising:
a platform,
a pair of upright multi-stage cylinder means interconnected at each
stage and adapted to be extended by compressed gas, said cylinder
means being located at opposite sides of the platform and having
their uppermost stages connected to the platform,
a pair of multi-stage extendible column means at said opposite
sides of the platform and interconnected at each stage, said column
means each having a stage corresponding to each stage of the
cylinder means, the interconnections between like stages of said
cylinder means being at substantially the same level as the
interconnections between the respective stages of said column
means,
means for selectively supplying or exhausting compressed gas to or
from said cylinder means for respectively raising or lowering said
platform, and
load-equalizing reeving means connected to both said column means
and operatively associated with both said cylinder means whereby
the latter are caused to raise and lower in unison to keep the
platform level.
33. A multi-stage hoist according to claim 32 in which the
interconnections at each stage between the pair of cylinder means
and between the pair of column means collectively comprise a
respective rigid generally rectangular frame, said frames being
arranged to vertically nest beneath the platform when the platform
is in lowered position.
34. A multi-stage hoist according to claim 33 in which said frames
have diagonal cross-braces which also serve as guideways for cables
in said reeving means.
35. A multi-stage hoist according to claim 33 in which said reeving
means comprises at each stage four respective cables of fixed
length each connected at one of its ends at the top of a respective
one of the four columns at the stage and each connected at its
other end to the respective said frame at the diagonally opposite
side thereof, and respective guide sheaves for said cables
journaled on the frame of the next higher stage.
36. A multi-stage hoist according to claim 32 in which each said
pair of column means comprises a pair of extendible interfitted
column units interconnected at the bottom of each stage, said
column units being located at the corners of the platform inwardly
of the hoist means.
37. A multi-stage hoist according to claim 36 in which each of said
column units is housed in a respective tube projecting upward from
the platform when the platform is in lowered position.
38. Means to prevent excess pressure from building up within a gas
expandable cylinder comprising:
a source of fluid under pressure, valve means to selectively
control the flow of said fluid into the cylinder,
a normally-open valve arranged to be closed by predetermined
pressure build-up,
a whisker valve arranged to prevent said build-up by venting when
the whisker valve is periodically opened,
flexible means fixed relative to one end of the cylinder and
passing over a rotatable means fixed relative to the other end of
the cylinder, and
projecting resilient arm means on said rotatable means arranged to
periodically wipe and open said whisker valve during rotation of
the rotatable means responsive to relative endwise movement of the
parts of the cylinder.
39. Means according to claim 38 in which retarding means is located
adjacent said whisker valve such that engagement of the arm means
with the retarding means will cause the arm means to flex and be
retarded until the rotatable means has advanced sufficiently to
cause the flexed arm means to then contact and pass the whisker
valve by spring action of the flexed arm means.
40. In combination,
an elongated rectangular working platform secured to two pairs of
extendible cylinder units, one pair at each end,
a base framework rigidly interconnecting the lower ends of one of
said pairs and having a rigid upright member parallel to said
units,
an extendible tripod leg pivotally secured at its upper end to said
upright member and adapted to be swung outwardly from such member
in a swing plane at an acute angle to the plane of said one pair of
cylinder units, and be extended to contact the ground,
inwardly collapsible link means pivotally interconnecting the lower
portion of the tripod leg with said framework and adapted to limit
said acute angle when said bracing means is in ground contact,
and
a pair of telescoping outrigger means mounted on the base framework
for selected opposite horizontal extension from the framework at
right angles to said swing plane.
41. In a lift,
a telescopic cylinder assembly including cylinders with pistons at
one end, one of said pistons having a probe with a passage
continuing through the piston, and another of said pistons having a
cavity with a supply passage thereto and being arranged to receive
said probe,
sealing means for sealing the cavity around the probe when occupied
by the probe,
normally-closed valve means controlling the flow of gas through the
probe,
valve opening means for responsively opening the valve means when
the probe occupies the cavity,
and means for selectively introducing pressurized gas to said
cavity through said supply passage.
42. A lift as in claim 41 in which there is a piston located
between the probe and the cavity and having an opening therethrough
for passage of the probe.
43. A lift as in claim 42 in which said piston with the probe is
smaller than the piston with the cavity.
44. A lift as in claim 41 in which the probe has a recess in which
the valve means is housed, and in which said valve opening means
comprises a protrusion in said cavity for engaging the valve
means.
45. A lift as in claim 41 in which said piston with the probe is
larger than the piston with the cavity.
46. A lift as in claim 41 in which the piston with the cavity has a
second probe at its opposite end and with said supply passage
extending therethrough,
the next piston having a second cavity with a respective supply
passage thereto and arranged to receive said second probe,
second sealing means for sealing the second cavity around the
second probe when occupied by the second probe,
normally-closed second valve means controlling the flow of gas
through the second probe,
second valve opening means for responsively opening the second
valve means when the second probe occupies the second cavity,
and means for selectively introducing pressurized gas to said
second cavity through its supply passage.
Description
The need for a working platform which enables a repairman or
construction worker to be raised to the ceiling of auditorium-type
spaces or alternatively to be raised to a higher elevation for more
convenient working conditions is well known. Besides the auditorium
factor many other facilities such as banks, office buildings and
the like have areas wherein it would be impractical to have a
ladder moved around to change light bulbs or do minor repair
work.
In order to obviate the inconvenience and time factor inherent in a
ladder, there have been provided a plurality of designs of
extendible, collapsible platform apparati. These platforms are of
necessity portable, such that they may be rapidly moved to the area
where they are needed. For reasons of safety, the worker climbs
onto the platform when the supports are collapsed and then the
supports are extended to a sufficient extent providing a
comfortable working height.
The extendible working platforms heretofore known have been
elevated by electricity, a liquid such as oil, or a compressed gas.
The problem with electrical control is in the fact that the
platform is not completely portable. In order for the platform to
be operational there must be a source of electrical current, often
not the case during new construction. Further, the inconvenience of
having to carry the electrical transmission cord necessary for
remote usage is undesirable since it introduces the dangers
inherent with long distance extension of electrical power on a
temporary and not completely safe basis.
The use of liquid, such as oil, presents the problem in that the
liquid occupies the same volume in the stored condition as it does
when it is in use and it is supporting the platform. This fact
introduces a large volume, heavy weight factor to the appparatus at
all times, greatly reducing portability.
The use of a compressed gas has proven to be the most portable and
thus the most desirable in many applications in that firstly, it
occupies less bulk in the compressed state than it does when it is
in its working condition and further, it introduces very little
extra weight. When the platform is lowered, the air within the
cylinders may be vented to the atmosphere with no danger of
pollution, thus eliminating the need for storage following use. One
of the problems, however, with using a compressed gas is that when
weight is shifted upon the working platform the supporting
cylinders closest to the weight is compressible and thus responsive
to external forces. The partial collapse of some cylinders of a
platform supported by several gaseous supported cylinders causes
the platform to be at an angle to the horizon. This slope, although
quite possibly safe, gives the worker a feeling of relative
instability and increases the danger of objects falling from the
platform endangering persons working below the platform.
With any of the working platforms hereinabove described it is
desirable to be able to move the platform from place to place thus
allowing one platform to be used in a plurality of locations,
greatly decreasing the total cost factor over having a plurality of
such devices. To facilitate the movement of the platform from place
to place it is desirable that said platform be collapsed to its
utmost in both the vertical and the horizontal direction. Normally
the collapsing is done by using telescoping cylinders thus allowing
the entire platform to be lowered to close proximity of the wheels
allowing movement through doorways and the like.
The total collapsibility of the working platform as hereinabove
described introduces another factor, however, in that when the
platform is used in areas which are already occupied objects such
as desks, bookcases and the like are often immediately below the
area needing maintenance or service. Having the platform at the
extreme bottom portion of the assembly necessitates the movement of
any objects in the way prior to doing the necessary service.
In addition to the height of the supporting structure, safety
requirements necessitate the inclusion of guard rails about the
platform. To assure passage through doors or the like the platform
must either be designed to nest between the uprights or the guard
rails must be adapted to collapse. Either of the above alternatives
introduces severe design restrictions as to the size and shape of
the platform. Further, the requirement of having a relatively small
base for easy passage through doors presents a stability problem
when the platform is extended, simply because of the fact that the
height in relation to the width is so great that the entire
platform is not stable.
A problem unique to the usage of compressed gas for expanding
supporting cylinders is the fact that if the cylinder is prevented
from expanding because of a mechanical malfunction or the like and
the operator continues to introduce fluid under pressure a
dangerous over pressurization may result. For reasons of safety the
extreme over pressurization must be prevented since a sudden
release of the pressure could easily result in injury.
With the above noted prior art structures and problems in mind it
is the primary object of the present invention to provide a working
platform which is selectively moved from a collapsed, compact
configuration to an extended extremely high working position. The
platform is made inherently stable by the use of stabilizing means
at the base and further, although the construction takes advantage
of the many advantages of compressed gas to support the collapsible
cylinders, the platform supporting cylinders are interconnected
such that a shift of weight will not cause a noticeable deviation
from the horizontal position of the platform.
It is another object of the present invention to provide a
collapsible working platform wherein the lower stage may
selectively be extended first while retaining the remainder of the
stages in collapsed condition thus providing a leg structure
allowing the platform to straddle objects located beneath the area
to be worked upon. Once the lowermost section is extended it may be
locked in position until it is desired to again completely collapse
the platform for storage or movement to another location.
Still another object of the present invention is to provide an
extendible working platform having a plurality of stabilizing means
at the base which are movable from a collapsed portable position to
an horizontally extended stabilizing position providing an
inherently stable base for the platform when extended and yet
allowing ready mobility through doors and the like when in a
collapsed condition.
It is still a further object of the present invention to provide at
least one pair of cables of fixed length for each stage of the
telescoping elevatable platform. The cables are mounted upon
elements fixed to each stage, one end above and the other below the
associated stage, passing through pulleys such that the weight
carried upon the platform is equalized throughout the entire
supporting structure of said platform assuring a consistently
horizontal platform.
Yet another object of the present invention is to provide means for
interlocking some of the stages of a telescoping cylinder
supporting the platform whereby a portion of said cylinders may be
retained in their collapsed condition while the remainder is
extended.
Yet another object of the present invention is to provide an
outrigger and stabilizing mechanism for use with the platform
whereby the mechanism of the platform is stable when in the
extended position.
Still another object of the present invention is to provide
telescoping cylinders for supporting a working platform and
utilizing said cylinders with the smallest cylinder serving as the
base element whereby the uppermost cylinder of each set, which has
the largest cross section, serves not only to provide the enclosing
shell for the smaller cylinders when in the collapsed condition but
also serves as the corner post for the guard rail surrounding the
working platform, permitting almost total collapsibility.
Still a further object of the present invention is to provide a
control mechanism for a pneumatically extensible set of telescoping
cylinder wherein the supply of fluid to the cylinders is terminated
a predetermined time following the cessation of outward movement of
the set.
Yet a further object of the present invention is to provide an
interconnecting means between pairs of extendible telescoping
cylinders whereby the cylinders will expand or remain stable with a
joining platform continuously in a horizontal plane even though the
platform is not evenly loaded.
A further object of the present invention is to provide a
configuration for at least one stage of a set of telescoping
pneumatically extensible cylinders whereby the lift off pressure
for that stage may be accurately predetermined.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of a working platform with the
cylinders in their collapsed condition and the outriggers shown in
phantom in their extended condition.
FIG. 2 is an elevational view along lines 2--2 of FIG. 1 showing
details of construction of one embodiment of the stabilizing means
and relative location with respect to the stages of the
cylinders.
FIG. 3 is an enlarged sectional view taken along lines 3--3 of FIG.
1 detailing the vertical element which serves as an anchor point
for the stabilizing means and is secured to each stage of the
cylinder.
FIG. 4 is a schematic view of the working platform in an extended
condition, depicting the interconnection of the stabilizing
elements and the supporting cylinders.
FIG. 5 is an elevational view of one end of the platform showing a
latching mechanism used for retaining the lowermost stage in an
extended condition and further showing the tripod type
stabilizer.
FIG. 6 is an enlarged view of the deactivating mechanism for the
latch means of FIG. 5.
FIG. 7 is an enlarged view of the pulley, deadhead stabilizer
combination which in the preferred embodiment is mounted to each
corner of each stage of the telescoping cylinders.
FIG. 8 is a perspective view of the platform in the straddle or
lowermost stage extended and with the remainder of the stages
retained in their collapsed status.
FIG. 9 is a perspective view of the subject platform in the fully
extended position.
FIG. 10 is an isometric view of a second embodiment of working
platform with portions shown in phantom to emphasize the
stabilizing means and the interconnection between the cylinders and
the outrigger supports.
FIG. 11 is a sectional view through the telescoping cylinders
depicting the internal structure which allows selective expansion
of the respective cylinders.
FIG. 12 is an enlarged partial sectional view taken along lines
12--12 of FIG. 10.
FIG. 13 is a vertical section taken along lines 13--13 of FIG.
12.
FIG. 14 is a schematic view of a probe piston over pressurization
system which may well be incorporated in the hereinabove described
platform.
FIG. 15 is a schematic of a pneumatic circuit which prevents
dangerous over pressurization of the telescoping cylinders.
DETAILED DESCRIPTION OF THE DRAWINGS
As can be seen in FIG. 1 a preferred embodiment of the subject
working platform includes four telescoping cylindrical support
members 2 having secured to the uppermost and largest diameter
stage 6 a working platform 4. The largest cylinder 6 serves as the
corner post and supports a guard rail 8. There is further provided
an upstanding edge 10 around the entire periphery of the platform 4
preventing the accidental falling of small objects which may roll
or be bumped toward the edge of the platform.
Although the present structure is shown with four stages it is to
be understood that the number of stages and the size of the
cylinders will be determined by the amount of weight which the
platform will support, the height at which the platform will be
used or other design factors. The platform 4 also serves as a
rigidifying framework for the uppermost stage 6 and each of the
supporting stages 7 have a rectangular framework 14 around their
entire periphery secured to the stage by clamps 15. The bottom of
each of the telescoping cylinders supporting the working platform
is supported by a wheel 16 mounted upon a plate 18. The lowermost
stage of the collapsing cylinder is secured to a socket 20 mounted
to said plate but could also be secured to a stud or post.
Mounted upon the plate 18 in a position which generally parallels
the ends of the working platform and abuts the outside of the
socket 20 are a pair of parallel, hollow rectangular cross pieces
22. A pair of outriggers 24 are telescopically fitted within cross
pieces 22 of each end. The outriggers in each piece being
extensible in opposite directions to provide a very wide base. The
outboard end of the outriggers 24 includes a threaded
surface-contacting support means 26. It will be apparent that when
the outrigger 24 is extended from each side of each end of the
platform and the floor contacting member 26 is rotated to a point
where its bottom plate 27 is in contact with the floor the
effective base of the entire platform is approximately three times
the telescoped movable width.
Further, to be seen in FIG. 1, and to be described in greater
detail hereinafter are the stage interlocking and latch mechanism
28 and the tripod type stabilizing element 30. Likewise seen in
this Figure is the control element 32, mounted for convenience upon
a portion of the guard rail 8 such that it may be moved from one
end of the platform to the other as necessary, and the collapsing
rigid uprights 34, to be described in much greater detail
hereinafter. The collapsing uprights provide one of the anchoring
points, assuring the stability of the platform when the cylinders
are in their extended condition.
Referring now to FIG. 2 it can be seen that the lowermost cylinder
38 is the smallest of the group and has mounted thereto at each end
of the platform a rigid vertical upright 90, which is a part of the
stabilizing system to be described hereinafter. The lowermost
cylinder 38 which, as explained hereinafter, serves as the legs
when the platform is in the straddle condition, is fixedly mounted
to the plate 18 between the horizontal stabilizing members 22. As
noted above, the stabilizing members have the outriggers 24
telescoped therein. As can be seen in this view, each of the
telescoping stages is interconnected by a framework 14, as noted
above, including horizontally placed channel members 52 running
along the long dimension of the platform joined by interconnecting
channel members 50 at the ends thereof. It is to be understood that
if the platform is relatively square, members 50 and 52 will be
along adjacent sides. For strength and rigidity an interconnecting
plate 54 is welded to the interior portions of frame members 50 and
52 at an angle to both of them forming a triangular structure. A
generally vertical member 56 is rigidly secured to the exterior
portion of the frame member 52 and serves as both a mounting plate
for a double pulley 58 as well as an anchor point 60 for the
stabilizing cables as explained hereinafter, reference being had to
FIG. 7.
Referring to FIG. 4 it can be seen that each of the stages of the
telescoping platform, in addition to the framework 14 comprising
members 50, 52 and 54, includes a vertical upright designated
generally as 34 in FIG. 1 but herein specifically noted as 90 for
the lowermost upright. Secured to the upper portion of the
lowermost upright 90 is an anchor bolt 64 which secures one end of
cable 66 which passes downwardly over a double pulley 58
transverses the entire length of the frame member 52 passes over a
second double pulley 58 and then proceeds vertically downwardly to
a second anchor point 68. The cable 66 is of fixed length and the
movement of the frame section 52 upwardly or downwardly under the
control of the operator causes the cable member 66 to move through
both of the pulleys 58 thus keeping the cable in constant tension
and stabilizing the particular stage. A turnbuckle 59 is provided
to assure a constant tension on the cable. Through the use of
counteracting cables, as described above, downward pressure on one
end of the platform results in an equal downward pressure on the
other end and thus assures a continuous horizontal disposition of
the platform.
As will be seen in FIg. 5 a similar stabilizing apparatus is
included for each stage and it is to be noted at this point that
for the purposes of end to end stability of the platform one such
cable extending in opposite directions from end to end would be
sufficient. The second cable is denoted as 70 and it passes over
the same double acting pulleys and is anchored at points 72 and 74.
To reiterate, one such pair is all that is absolutely necessary for
stability in the other dimension, it has been found to be desirable
to use a pair of such stabilizing cable mechanisms along each
longitudinal edge of the platform thus providing stability in all
directions.
Referring now to FIG. 3, the elements necessary to provide the
vertical upright or upper anchoring point for the stabilizing cable
can be seen. As seen in this view, which as noted above is along
line 3--3 of FIG. 1, the vertical member for the lowermost or
smallest cylinder is the outboard support and is denoted as 90.
Successively upward stages and thus larger cylinders include
upright members 92, 94, 96 respectively, securely attached to their
respective stages. It is to be noted that each of the upright
supports has a cross sectional shape of a J and are interlocking
thus providing a self-guiding structure as well as allowing the
supports to occupy less overall space. It is to be noted that each
of the upright supports 90 and 92-96 includes a pair of cables
generally enclosed therein said cables being guided to either of
the upper or lower fixed securements to conform with the secific
description regarding the lowermost stage. Located generally at the
bottom of each of the vertical support members is the double pulley
hereinafter described. Thus it can be seen that the entire support
mechanism including the vertical stabilizer as well as the
stabilizing cables are all contained within a relatively compact
package.
When it is desired to use the platform in its straddle position as
shown in FIGS. 5 and 8 the interlocking apparatus, denoted
generally as 28 in FIG. 1, is placed in operational position. As
can be seen in FIGS. 1, 5, 8 and 9 the essential elements of
mechanism 28, one means for accomplishing the straddle position,
comprise a vertical post 100 rigidly mounted to the lowermost
framework which surrounds the platform 4 and a complementing angle
bracket 102 secured to the adjoining portion of the platform border
10. A pin 104 is adapted to interlock with the bracket 102 and the
vertical rod 100 thus interconnecting all of the stages of the
telescoping elements with the exception of the bottommost or one
with the smallest diameter. Gas under pressure is introduced to the
system following the interlock of mechanism 28 forcing the
lowermost cylinder to extend, raising the assembly to the position
as shown in FIG. 5. When the lowermost cylinder is extended to its
fullest a spring biased latch mechanism 110 hooks over a horizontal
bar 112 which, as to be described hereinafter, also serves as a
support for the third tripod leg 30. Once the latch mechanism 110
is locked over 112 the interlocking apparatus is released by
removal of pin 104 and if desired the platform can then be extended
to any desired height without affecting the rigidity of straddle
legs 38.
The latch 110 is pivotally mounted to a support 114 attached to the
frame and is normally spring biased to the position shown in FIG.
5. To retain the latch 110 in its disengaging position ring 120 at
the top of vertical hollow bar 100 is pulled upwardly and turned
(See FIG. 6) so that ears 122 extending diametrically outboard from
pin 123 cannot pass through the hole 124 in the top of the bar 100.
Attached to the lower portion of the pin 123 of loop 120 is a cable
126 which extends downwardly through the interior of vertical
hollow bar 100 and thence outwardly to the back end of latch 110.
It will be obvious that the pulling upwardly of pin 120 causes the
latch to pivot about its axis moving the latch 110 to a position
whereat it will not engage bar 112. The movement of latch 110 to a
disengaging position extends spring 128. When the latch is in the
disengaged position, as hereinabove described, the entire tower may
be collapsed for movement. For purposes of convenience of the
operator, a second cable 130 may be attached to the loop 120 and
extend upwardly to the top of the rail whereat there would be
provided a second ring 130 allowing operation of the latch by an
operator on the platform 4 from a standing position.
The rigidifying tripod leg 30 extends from and is pivotally secured
to horizontal member 112. The leg 30 has located therein a
telescoping extension 134. The connection between the framework at
the base of the platform and the stabilizing leg 30 comprises a
hinged connecting bar 136 interconnected with leg 134 such that the
amount of extension of leg 134 will control the angle at which a
leg 30 has with respect to the vertical. The leg 134 can be locked
in any one of a number of positions by means of a thumb screw or
pin 138. Hinged connecting bar 136 allows the leg 30 to be pivoted
to a position adjacent the ends of the platform when not in use.
Further, leg 30 is of a length that it has sufficient clearance
from the floor when extension 134 is retracted allowing ready
movement of the platform.
Referring now to FIG. 7 the actual structural details of the fixed
securement and double pulley combination for the stabilizer can be
seen. Mounted to a horizontal frame member 50 is a vertical plate
150 having at one portion a bolt 152 extending therethrough to
serve as an anchoring point for one end of the cable stabilizing
means. Likewise secured to plate 150 are a pair of coaxial pulleys
154, 156 which serve as the guide means for a pair of opposed
cables as described hereinabove.
As seen in FIG. 8, the working platform is shown in its straddle
position, i.e., with the lowermost cylinder extended and with the
outriggers and stabilizing tripod leg in operational position. It
is to be understood that when the platform is in this position, it
could be placed over a desk or other object beneath the desired
working location. Once the lowermost stage of the platform is
locked in position, as described hereinabove, the remaining stages
may be extended to the heighth desired. As seen in FIG. 9 the tower
is shown in a completely extended position and it will be readily
seen that although the heighth is quite great with respect to the
actual dimension of the platform base the addition of the tripod
stabilizes the leg and outriggers provide a perfectly stable
working condition.
Reference is now made to FIGS. 10, 12 and 13 wherein a second
embodiment of the invention is shown. As seen in FIG. 10, the
collapsible cylinders which support and control the heighth of the
working platform are shown in phantom and broken away, leaving only
the top section of the Figure so that the stabilizing structure may
be seen. Telescoping cylinders, generally denoted as 200, are
located at the outermost corners and operate in substantially the
same fashion as the telescoping cylinders hereinabove described.
Diagonally, inwardly of the telescoping cylinder 200 is a hollow
cylindrical case 202 which serves as a container for the necessary
rigid supports, as described in detail hereinafter, when the
platform is in its collapsed condition. It is to be noted at this
time that although the structure is shown somewhat schematically,
it is well within the contemplation of this species as well as that
described hereinabove that there be safety features such as guard
rails and the like.
The basic structure of the embodiment now described as somewhat
different from, but the concept of the stabilized platform is
identical to, that hereinabove described. As will be recalled, the
platform as described hereinabove had upright end supports 90-96
which provided a base for the stabilizing cables. Further, as will
be recalled, the platform described hereinabove included a pair of
opposing cables which were of fixed length and threaded through
pulleys and their mirror image stairstep fashion at each side of
the platform. Shifting of a load from one end of the platform to
the other, because of the non-expandability of the cables,
effectively balanced the load over the opposite cylinders assuring
a stable platform. As the shape of the working area of the platform
approaches the shape of a square rather than a rectangle the
possibility of a weight movement causing a slanted work surface
becomes more probable. An excess of weight along one edge may cause
the platform to tip in a direction transverse to the direction of
placement of the cables.
In order to alleviate this possibility of instability in even one
direction, the stabilizing cables as shown in FIG. 10, although
operating on the same principle, pass a configuration beneath the
platform as well as at the upper portion of each stage of the
expandible supporting elements. As can be seen, the platform is of
a generally rectangular configuration having a base with linking
members 204 and further having wheels for ease of mobility of the
platform. The wheels in this embodiment are mounted upon pivotal
generally horizontal arms 206 which move from a position whereat
they generally underlie the platform as shown in phantom to an
outwardly extending position as shown in solid whereat they extend
outwardly of the uprights and serve as outriggers. It is to be
understood that the wheels may be locked in a variety of positions
such that once they are in a position preferred for stability in
the particular operation they will not be inadvertently moved
resulting in unexpected instability.
Extending upwardly from the wheel supports 206 and linking members
204 are a plurality of nesting individual uprights 208 each of
which is linked to the base of each individual cylindrical section
of each stage. The uprights 208 provide a rigid relatively fixed
member supporting the pulleys 210 and thus assuring the stair step
configuration. The stabilizing cable 212 is secured to the base
member, extends upwardly through pulley 210 passes under the
platform along a line diagonal to the rectangular shape of the
platform and passes through a second pulley and then upwardly to
the top of the upright 208. This configuration is repeated for each
stage and for each corner such that the stabilizing cables cross in
a X configuration beneath the platform as well as the top of each
stage. It is to be understood that for greater rigidity as well as
safety the cables as they pass in the X configuration at each stage
may well be encased in a shield member such that they are not
exposed. The shielding member thus provides a stiffening force in
addition to the safety factor.
Reference is now had to FIG. 12 which is a section along lines
12--12 of FIG. 10 and shows the collapsing cylinder shown denoted
as 200 mounted directly above the arm 206 which supports the
wheels. The rectangular framework 214 of the structure can be seen
and it is to be understood that this framework 214 can be of any
rectangular shape, will normally support the working platform.
Further rigidifying corner braces 216 assure rectangularity and
rigidity of the structure.
The generally J shape of the rigid upright supports 208 in their
nesting condition can be seen and are shown within the confines of
shielding tube member 202. It is to be noted that the J shape of
elements 208 permits the elements to move relative to each other in
a vertical direction and yet retain a substantial amount of lateral
contact rigidifying the members 208 even when the elements are
extended. The top of each J shaped member 208 is provided with a
stop 215 which not only prevents over-extension of the elements 208
but also serves as the anchor point for the cable 212 as described
hereinabove.
Further to be seen in this picture, as noted above, is the
encompassing shield member 218 which extends from corner to corner
beneath the platform confining the cables 212 as well as providing
additional rigidity to the entire structure.
Reference is now had to FIG. 13 wherein the relative location of
the rigid support members 208 encompassing tube 202 and the cable
enclosing rigidifying members 218 can most readily be seen.
As noted above, it is often necessary and certainly desirable that
the working platform be able to go into a straddle condition so
that it may be used around desks or the like without necessity of
movement of the objects in the way. FIG. 11 depicts an alternative
approach to the straddle position as differentiated from the
mechanical approach described hereinabove.
As seen in FIG. 11 the telescoping cylinder assemblies are shown
somewhat schematically, however, the internal mechanism is clearly
shown. The upper portion 220 of piston 222 of the next to lowest
cylinder has the configuration of a probe which extends upwardly
through the pistons 224, 226 respectively of the second and third
stages of the collapsed cylinder assembly. It is to be understood
that although it is shown with only five stages, the mechanism
could easily be applied to as many stages as is desired. The probe
220 has an interior bore 228 which has secured to its upper portion
a spring biased normally closed piston valve 230. The uppermost
piston 232 has a pair of conduits 234, 236 for supplying air and
has a cavity 238 to receive the upper portion of the probe 220.
Piston 232 has a downwardly extending protrusion 240 which rests
upon the top of valve 230 when the cylinder assembly is in its
collapsed condition holding valve 230 in its open condition. An
O-ring 242 seals the area around the exterior of probe 220
preventing leakage about this probe.
Air introduced through conduit 236 passes downwardly into the
cavity 238 through the normally closed but held open valve 230 and
down conduit 228. The air forced onto piston 244 of the bottom
cylinder assembly beneath piston 222 causes piston 222 to elevate
i.e., lifting the next to lowest stage first. This movement is
contrary to what would normally occur since the cylinder assemblies
as described herein and above is inverted, i.e. the larger cylinder
is at the top and the smaller cylinder is at the bottom. By
introducing air downwardly through the larger pistons 224, 226, it
then becomes obvious that piston 222 is the largest as far as the
area which is acted upon by the compressed gas and it is raised
first. Following the introduction of sufficient air into the next
to lowest stage there will occur a slight lifting of the uppermost
stage closing valve 230 and thus sequentially allowing the
expansion of the other stages of the cylinder assembly. It is to be
understood that the relative size of the uppermost surface of the
cavity 238 will determine the amount of over-pressurization of the
loweremost stage in this assembly sequence. However, this over
pressurization can be avoided by introducing gas through conduit
234 as soon as the next to lowest stage is fully extended.
If it is desired to elevate the uppermost stage first this can be
done by simultaneously introducing gas through both conduits 234
and 236 thus exposing pressure to the entire area of piston 232,
which is the greatest.
As noted above, in the pneumatic lift utilizing one or more
telescoping cylinder assemblies, the extended column may be made
stiffer and hence more rigid or stable by increasing the pressure
in the column in excess of the pressure needed to lift the
predetermined load. For the best result, this should be done one
stage at a time over pressurizing each lower stage before allowing
the stage above it to extend and maintaining the pressure in each
stage until the lift lowers again to that point.
The structure of FIG. 11 may easily be modified to form an
anti-bounce exhaust system. To form the anti-bounce exhaust, the
set of cylinders will be inverted, the supply and exhaust lines
will be connected to the largest cylinder of the set and vent 250,
shown in phantom, will be added. During operation, the supporting
gas is exhausted from the larger and thus lower of a pair of
contiguous cylinders, the probe will cause the opening of the next
succeeding valve. This structure permits the gas to escape
gradually and thus not causing a sudden upward movement when the
gas from the smaller cylinder rapidly enters the larger
cylinder.
The probe piston over pressurization system as shown in FIG. 14
accomplishes this desired result by providing a means for
accurately predetermining the pressure to be reached in each stage
and a means for preventing the next step or stage from extending
until this pressure is maintained. This system also provides a
means for maintaining the pressure in each stage independent of any
others until that particular stage is to be lowered.
In FIG. 14 there is shown a multi-stage telescoping cylinder
assembly in its retracted or lowered position. The upper portion of
piston 300 forms a probe 302 and is sealed by an O-ring 304.
Spring-loaded valve 306 is held in an open position by protuberance
307 on piston 308. This interacting assemmbly is repeated between
piston 308 and adjacent piston 310. It is to be understood that
this system may be used for as many additional stages as
desired.
Air introduced through the top of the cylinder assembly denoted 312
passes through the pistons 310, 308 and 300 and open valves 306 and
314 causing the largest stage to lift off since piston 300 has the
greatest area. After the second stage is fully extended there will
be no further movement until the pressure has increased enough
against the cavity area of piston 308 to cause the third stage to
extend. This transitional period is known as the over-pressurized
period. The O-ring seal 304 prevents the pressure from acting on
the total area of piston 308 thereby assuring that the area of the
cavity portion only will determine the lift-off pressure needed.
With piston 308, lift-off valve 306 will close locking the pressure
in the first stage.
By controlling the cavity area or the diameter of the probe it is
possible to keep the top state from extending until a predetermined
pressure is reached in the remainder of the set of cylinders
without the need of a flow control valve.
Referring now to FIG. 15, there is depicted a schematic of a time
delay overload control. Air under pressure passes through conduit
350, enters normally open valve 352 and fills the volume chamber
354 before the time delay controlled by needle valve 356 can
actuate the pilot actuator closing the valve 352 and cutting off
supply pressure to foot control valve 358.
To operate the lift, the up valve on control 358 is depressed
applying pressure to the system from volume chamber 354 which is
sufficient to start motion. Spring loaded reel 362 which is
connected to the base of the lift by a cable 360 starts turning
causing the spring leaf extensions 364 to wipe whisker valve 366,
bleeding the circuit and allowing pilot operated valve 352 to open
and continue the supply pressure to the system.
If the upward motion ceases while the foot control 358 is
depressed, reel 362 will cease rotation permitting a pressure
increase through the needle valve to actuate the pilot actuator and
closing valve 352 within a preset time delay. Supply to the foot
control 358 is now cut off preventing a dangerous
over-pressurization. The overload is reset by lowering the lift
causing spring extensions 364 on reel 362 again to contact the
whisker valve 366 sufficiently to exhaust the pilot circuit and
open the valve 352 or alternatively by a manual reset valve
368.
The key feature of this mechanical reel assembly is the post or
spring snap pivot 370 which is located in relation to the sensor
probe 367 on the whisker valve 366 so that the spring leaf
extensions 364 are momentarily stopped as the reel rotates and then
they snap past this pivot momentarily activating the whisker valve
sensor sufficient to keep the pilot and circuit exhausted. This
snap pivot point is absolutely necessary to assure that the reel
would not accidentally stop at a position where the spring leaf
extensions would be holding the whisker valve sensor permanently
open and thereby preventing the time delay control from
operating.
Thus it will be noted that the present invention provides a working
platform which has a versatility of being able to straddle objects
immediately below the area to be worked and further is stable in
that a shifting of weight from one end of the platform to the other
will not significantly effect the attitude of the platform. The
combination of horizontal stability in conjunction with the floor
contacting outriggers and tripod mechanisms provides a platform
supported by pneumatic cylinders with a stability heretofore
unknown. It is to be understood that the air used to extend the
telescoping cylinders may be from a portable container or may be
directly from a compressor. It is to be understood that minor
changes could be made, such as placing the controls upon the floor
of the platform and have them adapted to be foot operated.
* * * * *