U.S. patent number 3,893,540 [Application Number 05/422,971] was granted by the patent office on 1975-07-08 for lifting mechanism.
Invention is credited to Robert A. Beucher.
United States Patent |
3,893,540 |
Beucher |
July 8, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Lifting mechanism
Abstract
Apparatus for raising and lowering workmen and tools into
proximity with elevated structures during construction and repair
thereof comprises a platform, a frame and a hydraulically-actuated
linkage assembly connecting the platform to the frame. The linkage
assembly comprises an elongated boom assembly pivotally connected
to one end of the platform, a compression member assembly pivotally
connected to one end of the frame and to the boom assembly, and a
tension member assembly pivotally connecting the other end of the
boom assembly to the frame. A main hydraulic actuator is connected
between the compression member assembly and the frame and operates
upon extension to pivot the compression member assembly in one
direction to cause the tension member assembly to pivot the boom
assembly in the other direction for raising the platform. Auxiliary
hydraulic actuator means connects the boom assembly to the
platform, and an automatic levelling system is provided to operate
the auxiliary actuator means for maintaining the platform level
during raising and lowering thereof.
Inventors: |
Beucher; Robert A. (Media,
PA) |
Family
ID: |
23677159 |
Appl.
No.: |
05/422,971 |
Filed: |
December 7, 1973 |
Current U.S.
Class: |
182/2.9; 182/141;
182/63.1 |
Current CPC
Class: |
B66F
11/044 (20130101) |
Current International
Class: |
B66F
11/04 (20060101); B66f 011/04 (); B04g
001/22 () |
Field of
Search: |
;182/2,141,148,63
;254/1R,1C,DIG.9 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Machado; Reinaldo P.
Attorney, Agent or Firm: Howson & Howson
Claims
I claim:
1. Load lifting apparatus, comprising:
a frame,
a compression member pivotally connected to said frame at one
location,
an elongated boom pivotally connected to said compression
member,
an elongated load support platform pivotally connected to one end
of said boom and extending therefrom so as to overlie said boom and
said frame for supporting a load moveable on the platform above the
frame,
a rigid tension member pivotally connected to the other end of said
boom and pivotally connected to said frame at another location
spaced from said one location,
first actuator means connecting said compression member to said
frame for pivoting the compression member and causing said tension
member to pivot said boom relative to the compression member for
raising and lowering said load support, and
second actuator means associated with said support and boom for
pivoting said support relative to said boom to permit leveling of
said support during raising and lowering thereof, whereby said load
support platform may be raised and lowered upon extension and
retraction of said first actuator means.
2. Apparatus according to claim 1 wherein the pivot connection of
said tension member to said frame is spaced from the pivot
connection of said tension member to said boom a first
predetermined dimension, the compression member to frame pivot
connection is spaced from the compression member to boom pivot
connection a second predetermined dimension greater than said first
dimension; and the pivot connection of said tension member to said
boom is spaced from the pivot connection of said compression member
to said frame a third predetermined dimension greater than said
second-mentioned dimension.
3. Apparatus according to claim 2 wherein said second dimension is
related to said first dimension in a ratio of substantially 1.3/1,
and said third dimension is related to said first dimension in a
ratio of about 1.7/1, said ratios being determined when the
compression member is disposed horizontally and said tension member
is disposed at about a 5.degree. downward angle with respect to
horizontal and said boom is disposed at about a 6.degree. upward
angle with respect to horizontal.
4. Apparatus according to claim 1 wherein said members are disposed
in substantially parallel relation and said one end of said boom
overlies the pivot connection of said compression member to said
frame.
5. Apparatus according to claim 4 wherein said first actuator is
pivotally connected to said frame at a third location spaced from
said first-mentioned frame location and said tension member to
frame pivot connection is located intermediate said first and third
frame locations.
6. Apparatus according to claim 5 wherein said first actuator is
pivotally connected to said compression member outward of said
compression member to frame pivot connection, and said first
actuator is inclined with respect to said frame to dispose the line
of action of the first actuator transverse to the compression and
tension members and in the same direction as the boom.
7. Apparatus according to claim 6 including a vehicle having a pair
of spaced parallel chassis members, said frame including a pair of
main frame members fastened to said chassis members and at least
one supplemental frame member inclined with respect to said main
members and disposed inboard of said chassis members, said tension
member being secured to said supplemental frame member at a level
below the level of said compression member to frame pivot
connection, to afford folding of the apparatus into a compact
transport configuration.
8. Apparatus according to claim 1 including automatic leveling
means associated with said second actuator means for maintaining
said support level during raising and lowering thereof, said
automatic leveling means including an operator mounted to said
support, gravity sensing means associated with said operator, and
means connecting said operator means to said second actuator means,
said operator being operable to extend and retract said second
actuator means to maintain said support level as said boom pivots
in opposite directions relative to said compression member.
9. Apparatus according to claim 8 wherein said operator means
includes a housing and a rotor mounted for rotation relative to
said housing about a horizontal axis parallel to the pivot axis of
the support, and said gravity sensing means includes a mass
connected to said rotor and depending below its pivot axis for
causing said rotor to pivot relative to said housing during pivotal
movement of said boom.
10. Apparatus according to claim 9 wherein said second actuator
means includes at least one hydraulic cylinder, and said operator
includes rotary valving means associated with said rotor in said
housing, said connecting means providing fluid communication to
opposite ends of said cylinder for supplying pressure fluid thereto
and exhausting pressure fluid therefrom for extending and
retracting said cylinder in response to pivotal movement of said
housing relative to said rotor and said valving means.
11. Apparatus according to claim 10 wherein said connecting means
includes slave valve means associated with said rotary valving
means and connected to said second actuator means and a source of
pressure fluid to extend and retract said second actuator means in
response to operation of said rotary valving means.
12. Apparatus according to claim 1 wherein said support is
elongated and overlies said boom, and said second actuator means
includes a pair of hydraulic cylinders, means pivotally mounting
said cylinders outboard of said boom, and means pivotally
connecting said cylinders to said support.
13. Apparatus according to claim 1 wherein said second actuator
means includes an hydraulic cylinder, a shaft pivotally connected
to said boom adjacent said support pivot connection, a crank arm
connected to said shaft, at least one arm secured to said shaft,
and at least one link connecting said arm to said support for
pivoting the support relative to the boom upon extension and
retraction of said hydraulic cylinder.
14. Apparatus according to claim 1 wherein said second actuator
means includes an hydraulic cylinder, a crank having a shaft
pivotally connected to said boom adjacent said support pivot
connection, at least one arm secured to said shaft and connected to
said cylinder, and at least one link connecting said arm to said
support for pivoting the support relative to the boom upon
extension and retraction of said hydraulic cylinder.
Description
The present invention relates to man-lifting apparatus, and more
particularly, the present invention relates to apparatus for
raising and lowering a platform designed to support workmen while
working on elevated structures.
In the construction and maintenance of elevated structures, it is
often necessary for workmen to be supported in close proximity with
the structures. A so-called "Cherry-Picker" type of lifting
apparatus has found wide-spread use as in recent years since it is
capable of omni-directional control by the workman supported
therein. Although Cherry Picker apparatus is adapted to be utilized
in a variety of environments, it is generally not designed to
accommodate more than one workman at a time or to support a
relatively large complement of tools and equipment. Thus, it is not
particularly useful in servicing overhead electric cables, such as
extend above railroad tracks, because such servicing requires a
number of workmen to be able to walk back and forth along the cable
while working. At present, some railroads have elevated platforms
permanently mounted on railroad cars for supporting workmen at the
proper elevation with respect to an overhead cable. Although this
approach is satisfactory, it has the obvious disadvantage of
typing-up a railroad car which could be used for other purposes.
Moreover, when work is to be conducted at a particular track
location, it is necessary for the car to be coupled to an engine
and transported to the location. Hence, even when only a relative
minor amount of work is to be performed, a considerable amount of
equipment is required merely to provide a platform for workmen.
Trucks having retractable track-engaging wheels which enable the
truck to travel along railroad tracks are presently used to
transport railroad crews to various track locations. Such trucks
have the advantage of being able to get on and off the tracks at
railroad grade crossings, and although capable of transporting
workmen and tools to a work site, heretofore they have not been
equipped with means to elevate a platform to enable workmen to work
on overhead cables. Accordingly, it should be apparent that such a
vehicle equipped with lifting apparatus which is capable of being
transported in a compact configuration and which is capable of
being extended into an erect usage configuration to dispose a
platform into proximity with overhead structures is highly
desirable.
With the foregoing in mind, it is a primary object of the present
invention to provide an improved man-lifting device.
It is another object of the present invention to provide a novel
mechanism for raising and lowering a work platform.
As a further object, the present invention provides a man-lifting
device which is capable of being transported on a vehicle in a
compact folded configuration and of being extended into an erect
usage configuration at a work site.
It is a further object of the present invention to provide a simple
linkage assembly for mounting a work platform to a mobile frame in
such a manner as to permit the platform to be elevated steadily to
a substantial level with respect to the frame and with a minimum of
horizontal movement.
Yet another object of the present invention is to provide a safe
but simple man-lifting structure.
These are other objects, features and advantages of the present
invention should become apparent from the following description
when taken in conjunction with the accompanying drawings in
which:
FIG. 1 is a side elevational view of lifting apparatus embodying
the present invention, the view illustrating in full lines the
position of the apparatus in its extended usage configuration and
illustrating in broken lines the position of the apparatus in its
folded transportation configuration.
FIG. 2 is an enlarged side elevational view of the apparatus of
FIG. 1, the view illustrating the position of the apparatus in an
intermediate location;
FIG. 3 is a rear elevational view looking leftward along lines 3--3
in FIG. 2;
FIG. 4 is a fragmentary side elevational view of a modified
embodiment of the present invention;
FIG. 5 is an inverted plan view taken along lines 5--5 of FIG. 4;
and
FIG. 6 is a schematic diagram illustrating an hydraulic system for
automatically maintaining the platform level during raising and
lowering thereof.
Referring now to the drawings, there is illustrated in FIG. 1
lifting apparatus 10 embodying the present invention. As best seen
therein, the apparatus 10 is mounted on a truck 11 of the type
which mounts retractable railroad wheels 12 and 13 to enable the
truck 11 to travel either on a road or on railroad tracks when the
wheels 12 and 13 are extended. The truck 11 has a chassis formed by
a pair of rearwardly-extending chassis members 14a and 14b, and the
lifting apparatus 10 is mounted on the chassis members 14a and
14b.
The lifting apparatus 10 is capable of being transported in a
compact configuration, illustrated in broken lines in FIG. 1, and
the apparatus 10 is capable of being expanded into an erect usage
configuration, illustrated in full lines therein. To this end, the
apparatus 10 comprises a frame 15 having a pair of
horizontally-disposed parallel frame members 15a and 15b (FIG. 3)
which are secured onto the top sides of the chassis members 14a and
14b, and which are tied together front and rear by braces 16 and
17, respectively. A platform 20 having a rectangular plan
configuration and sized to support a crew of workmen overlies the
frame 15. Preferably, the platform 20 measures about 8 feet in
width by about 12 feet in length and is constructed so as to be
rigid both lengthwise and widthwise.
In order to raise and lower the platform 20 with respect to the
frame 15, a linkage and actuator system is provided. As best seen
in FIG. 2, the linkage system comprises an elongated boom assembly
22 pivotally connected at R.sub.1 to the front of the platform 20,
a compression member assembly 23 pivotally connected at P.sub.2 to
the boom assembly 22 and pivotally connected at P.sub.3 to the
frame 15, and a tension member assembly 24 pivotally connected at
P.sub.4 to the other or rear end of the boom assembly 22 and
pivotally connected at P.sub.5 to the frame 15. A first or main
hydraulic actuator 25 connected the compression member assembly 23
to the rear of the frame 15, and upon extension and retraction, the
actuator 25 pivots the compression member assembly 23
counterclockwise and clockwise, respectively. As will be discussed
more fully hereinafter, second or auxiliary hydraulic actuator
means comprising a pair of actuators 27a and 27b interconnects the
platform 20 and the boom assembly 22 for levelling the platform 20
during raising and lowering thereof.
With this structure, extension of the main actuator 25 pivots the
compression member assembly 23 counterclockwise, and by viture of
the interconnection of the tension member assembly 24 between the
frame 15 and the rear end of the boom assembly 22, the rear end of
the boom assembly 22 pivots downwardly about the pivot point
P.sub.2 at the outer end of the compression member assembly. This
causes the front end of the boom assembly 22 to move upwardly for
raising the platform 20. Of course, retraction of the actuator 25
causes the reverse to occur for lowering the platform 20.
For the purpose of ensuring substantially vertical movement of the
platform 20 with a minimum of horizontal front to rear displacement
during raising and lowering, it is important for certain
dimensional relations to be observed in the design of the linkage
system. For example, as may be seen in FIG. 2, the dimension
between the pivot points P.sub.4 and P.sub.5 of the tension member
assembly 24 is less than the corresponding dimension between the
pivot points P.sub.2 and P.sub.3 of the compression member assembly
23. Moreover, the dimension between the pivot points P.sub.3 and
P.sub.4 is greater than both of the aforementioned dimensions. In
the present invention, it has been found desirable for the
second-mentioned dimension (P.sub.2 -P.sub.3) to be related to the
first-mentioned dimension (P.sub.4 -P.sub.5) in a ratio of about
1.3/1 and for the third-mentioned dimension (P.sub.3 -P.sub.4) to
be related to the first-mentioned dimension in a ratio of about
1.7/1. The dimension between the pivot point P.sub.3 and the pivot
point P.sub.5 is related to the (P.sub.4 -P.sub.5) dimension in a
ratio of about 1/2 The dimension between pivot points P.sub.2
P.sub.4 is related to the dimension between the pivot points
P.sub.1 and P.sub.4 in a ratio of about 1/6. A preferred value for
the P.sub.4 -P.sub.5 dimension is about 84 inches; a preferred
value for the P.sub.2 -P.sub.3 dimension is about 108 inches; a
preferred value for the P.sub.1 -P.sub.4 dimension is about 152
inches; a preferred value for the P.sub.3 -P.sub.5 dimension is
about 46 inches; and a preferred value for the P.sub.3 -P.sub.4
dimension is about 120 inches. The above ratios are determined when
the compression member assembly is disposed horizontally and the
tension member assembly is disposed at about a 5.degree. downward
angle with respect to horizontal and the boom is disposed at about
a 6.degree. upward angle with respect to horizontal as for example
when the apparatus is in its folded transport configuration.
As may be seen in FIGS. 1 and 2, the compression and tension member
assemblies 23 and 24, respectively, extend away from the frame 15
in substantially parallel relation, and the compression member
assembly 23 is pivoted from its lower limit position adjacent the
frame 15 and into its upper limit position at a substantially right
angle to the frame 15. For this purpose, the main actuator 25 has a
casing 25a which is pivotally connected at P.sub.6 to the rear of
the frame 15, and the actuator 25 has an operating rod 25b which is
pivotally connected at P.sub.7 to the compression member assembly
23. In the illustrated embodiment, the main actuator pivot point
P.sub.6 is located below the level of the compression member pivot
point P.sub.3, and the operating rod pivot point P.sub.7 is located
outwardly adjacent the compression member to frame pivot point
P.sub.3. The pivot point P.sub.5 of the tension member assembly 24
is located intermediate the compression member to frame pivot point
P.sub.3 and the main actuator to frame pivot point P.sub.6 . The
line of action of the actuator 25 is thereby inclined and directed
above the compression member pivot point P.sub.3 a sufficient
distance as to provide an adequate moment arm to initiate pivoting
of the compression member assembly 23 even when in its downwardmost
or transportation position with the rod 25b fully retracted. Of
course, when the rod 25b is fully extended, the platform 20 is in
its uppermost limit position. In the present invention, the length
of the stroke of the actuator rod 25b is selected to be about 36
inches, or approximately 1/4 of the P.sub.4 -P.sub.5 dimension.
For the purpose of providing a rigid but relatively lightweight
apparatus, the various components of the linkage system are
arranged in pairs and are fabricated of hollow structural members.
For instance, as best seen in FIG. 3, the boom assembly 22
comprises a pair of boom members 22a and 22b which are disposed in
spaced parallel relation and tied together at spaced locations by
transverse braces 31, 32 and 33. The compression member assembly 23
similarly comprises a pair of compression members 23a and 23b. Each
member, such as the left hand member 23a, mounts onto its
associated frame member 15a between a pair of plates 34a and 34b
welded on opposite sides of the frame member 15a. In the
illustrated embodiment, the boom members 22a and 22b are located
inboard of the compression members 23a and 23b, and the pivot
connection P.sub.2 is provided by a shaft 35 which extends through
the pairs of members within bushings. The tension member assembly
24 also comprises a pair of members 24a and 24b, and these members
are located inboard of the boom members 22a and 22b. The tension
members 24a and 24b are secured to the boom members 22a and 22b in
the same manner in which the compression members 23a and 23b are
secured.
The lower end of each tension member, such as the left hand member
24a, is pivotally connected by a pin 29 between a pair of plates
36a and 36b which project upwardly from a supplemental frame member
15c. The right hand tension member 24b is similarly connected to a
right hand supplemental frame member 15d. The supplemental frame
members 15c and 15d are located inboard of the main frame members
15a and 15b and are fastened to the front brace 16. The
supplemental frame members are secured to the rear brace 17 by a
depending block 39 to which the casing 25a of the main hydraulic
actuator 25 is fastened. Thus, the pivot connection P.sub.5 of the
lower end of each tension member 24a and 24b is located at a level
intermediate the level of the pivot connections P.sub.3 and P.sub.6
of the compression members and actuator, respectively. By virtue of
this structure, the apparatus 10 may be folded into a relatively
compact transportation configuration.
The platform 20 is leveled automatically as the linkage system
moves. To this end, the auxiliary hydraulic actuators 27a and 27b
are mounted outboard of the boom members 22a and 22b on arms 41a
and 41b extending laterally of the boom members. Each actuator,
such as the left actuator 27a (FIG. 3) has an operating rod 27c
which is pivotally fastened to the platform 20 by a pin 43
extending through a pair of depending plates 44a and 44b. Moreover,
the head ends of the casings are pivotally mounted in yokes 45a and
45b, to permit the casings 27a and 27b to pivot relative to their
mounting arms and thence relative to the boom 22 during extension
and retration. Thus, extension and retraction of the auxiliary
actuators 27a and 27b causes the platform 20 to pivot relative to
the boom assembly 22 about the pivot point P.sub.1.
In order automatically to extend and retract the actuators 27a and
27b, an hydraulic control system is provided. As best seen in FIG.
6 (Sheet 3) the system includes a four-way, hydraulically-actuated,
closed-center slave valve 50 connected to opposite ends of each
actuator, such as the actuator 27a. The slave valve 50 is
internally constructed so that pressurized control fluid applid at
controller 50a causes extension of the rod 27a, and pressurized
control fluid at the right controller 50b causes retraction of the
rod 27c. The slave valve 50 is biased into a closed position to
maintain the actuator rod stationary in the absence of control
pressure fluid at either controller. Preferably, both actuators 27a
and 27b and the main actuator 25 are provided with safety lock
valves to prevent collapse of the linkage and hence the platform 20
in the event of a sudden loss in pressure as by breakage of a
hydraulic line, etc.
The level of the platform 20 is sensed by a rotary pilot valve or
operator 55 which is mounted on the platform 20 adjacent the
platform-boom pivot connection P.sub.1. The valve 55 is
conventional, having a housing 56, a rotor 57, and a mass 58
depending from a shaft 59 connected to the rotor 57. The rotor 57
has passages 57a, 57b and 57c which control the distribution of
pressure fluid to the slave valve 50, depending on the orientation
of the rotor 57 with respect to the housing 56. The rotor shaft 59
is disposed with its pivot axis parallel to the pivot axis P.sub.1
of the platform 20. The housing 56 is immersed in hydraulic fluid
60 contained in the body of the valve 55, the fluid 60 serving to
dampen movement of the mass 58.
Hydraulic fluid is supplied to pressure ports 65 and 66 of the
valve housing 56 by a supply line 67 connected through a pump 68 to
a sump 69. Control pressure fluid is supplied to controller 50a by
a line 71 and is supplied to controller 50b by a line 72. The line
71 is connected to control port 74, and the line 72 is connected to
the control port 75. A return line 70 is provided to vent control
fluid from the valve 55 and to the sump 69.
With this system, clockwise pivotal movement of the housing 56
relative to the rotor 57, as during clockwise pivotal movement of
the boom 22 during raising of the platform, causes the rotor
passage 57a to provide fluid communication from pressure port 66 to
pressure port 74 and through line 71 to controller 50a of the slave
valve 50 for extending the rod 27c of the actuator 27a to pivot the
platform 20. At the same time, control fluid from controller 50b is
vented to the sump 69 by virtue of the registry of the rotor
passage 57b with pressure ports 76 and 75 and hence lines 70 and
72. Of course, during lowering of the platform 20, the rotor
passage 57c provides fluid communication between ports 65 and 75 so
that control fluid is flowed through line 72 to controller 50b from
pressure, and control fluid is vented through the line 70 to the
sump 69 by virtue of the registry provided by the passage 57b with
ports 76 and 74 and hence lines 70 and 71. Thus, with this control
system, the platform 20 is maintained substantially level during
raising and lowering thereof, and the level control is
automatic.
If desired, the structure of the present invention may be modified
to enable a single auxiliary actuator to level the platform. As
best seen in FIGS. 4 and 5, an hydraulic actuator 127 is mounted in
a yoke 140 which is secured to a brace 131 extending between boom
members 122a and 122b. The actuator 127 has an operating rod 127c
which is pivotally connected to a crank 170. The crank 170 extends
upwardly from a shaft 171 which extends between and is rotatably
mounted to boom members 122a and 122b. A pair of arms 172a and 172b
extend away from the crank-shaft 171, and each arm such as the arm
172a is pivotally connected to a link 173a which in turn is
pivotally connected to the underside of the platform 120. Thus,
extension of the actuator rod 127c pivots the crank 170 and arms
172a and 172b clockwise (FIG. 4) to displace the links 173a and
173b lengthwise for pivoting the platform 120 counterclockwise
relative to the end of the boom members 122a and 122b. Actuator of
the single actuator 127 may be controlled automatically by the
system illustrated in FIG. 6 to maintain the platform 120 level
during raising and lowering thereof. With this structure, a single
relatively short stroke-actuator may be utilized in lieu of the two
relatively long stroke (and expensive) actuators described in the
first mentioned embodiment.
In view of the foregoing, it should be apparent that novel
man-lifting apparatus has now been provided. The apparatus is
strong and safe while being relatively simple in construction.
While preferred embodiments of the present invention have been
described in detail, various modifications, alterations and changes
may be made without departing from the spirit and scope of the
present invention as defined in the appended claims.
* * * * *