Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF INVENTION
(i) Field of the Invention
This invention relates to scaffolding systems, and more particularly to a pole
jack
for travelling up and down a pole for supporting a scaffold.
(ii) Description of the Related Art
In numerous industries, it is necessary to erect scaffolding both for internal
use
as well as for external use in order to permit workers to stand at an
elevation above
ground surface. Typically, by way of example, a scaffolding system is utilized
in the
installation of aluminum siding on the exterior of housing. Such scaffolding
is
conventionally erected by utilizing pump jack poles which are spaced apart and
secured
in spaced relationship to a house by means of braces. Pump jacks are used to
ride up and
down the poles. The pump jacks typically include support arms on which are
extended
scaffold staging. The workers can stand on the scaffold staging and operate
the pump
jacks to move the staging up and down along the pump jack poles.
U.S. Patent No. 4,597,471 discloses a heavy duty pump jack which includes a
frame with upper and lower shackle members supported by the frame. A pump arm
is
pivotally provided on the frame and operates the shackles in alternating
relationship. The
pump arm serves to position the upper shackle in a twist gripping securing
relationship
on the pole while it then serves to raise the frame stepwise upwardly along
the pole. The
weight of the jack then shifts so that the lower shackle twist grips the pole
and the upper
shackle steps up to a next position on the pole. In this manner, the non-
gripping shackle
steps up the pole while the opposing shackle grips the pole. To ride the pump
jack down
the pole, the lower shackle is released from its gripping relationship and the
upper
shackle is rolled down the pole by means of a handle.
U.S. Patent No. 4,382,488 describes a pump jack pole formed of elongated
hollow
metal with a rubberized surface on one side of the pole. Such poles were found
to be
strong, long lasting and easier to manipulate than the standard wooden poles.
U.S. Patent
No. 4,463,828 and aforementioned U.S. Patent No. 4,597,471 describe improved
pump
jacks which include features to improve the safety of the pump jack as well as
its
strength. Such features include the ability to release one of the shackles by
means of a
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foot release pedal, thereby avoiding the necessity of bending over and
releasing the lower
shackle by hand. It is also known to employ an over-the-center spring loaded
handle to
control the rolling down of the pump jack.
The aforementioned features provided in pump jacks have served to improve the
operation and safety of such pump jacks in the industry. Nevertheless,
additional safety
measures are always warranted with respect to this type of scaffold system.
For example,
the known spiral rod utilized to control rolling down of the pump jack along
the pump
jack pole has a tendency to wear, thereby causing accidental sliding of the
pump jack
down the pole. Additionally, as the spiral rod wears, it may have a tendency
to snap
outwardly, thereby further causing additional accidents.
While heretofore pump jacks and pump jack poles were typically utilized to
support scaffolding in the installation of aluminum siding, such equipment can
actually
by utilized in other scaffolding sectors. For example, in industrial or marine
use,
scaffolding is often required both for internal use and external use. In
warehouses, where
access to various tiers of stored objects is required, the use of the pump
jack and pump
jack poles would be convenient. Platform and pallet staging could be raised
and lowered
in order to reach the desired objects. Similarly, in marine applications, the
loading and
unloading of ships could use the present pump jack and pump jack pole
arrangement to
advantage.
While utilizing the pump jack and pump jack pole for industrial use, however,
additional strength would be needed for the pump jack in order to support the
extra
weight of the platforms. Such extra strength is required not only in the
construction of
the pump jack itself, but in the operative portions thereof, including the
shackles, the
platform, etc.
Accordingly, while the aforementioned prior art patents have provided
improvements in the utilization of pump jacks and pump jack poles, all such
systems are
dependent on frictional engagement for climbing and for support.
Accordingly, it is a principal object of the present invention to provide an
alternative to the use of pump jacks and pump jack poles dependant on friction
for
supporting scaffolding equipment.
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Another object of the present invention is the provision of an improved
primary
pole jack having a positive interlock system to prevent accidental
disengagement or
slipping of the jack on the pole.
Still another object of the present invention is the provision of an improved
jack
which includes a simple directional selector arrangement for lowering the pole
jack down
the jack pole.
And a further object of the present invention is to provide a pole jack having
an
independent secondary locking system to engage the pole in the event of
failure of the
primary mechanism.
SummarX of the Invention
Briefly, in accordance with the present invention, there is provided a pole
jack
arranged for travelling up and down a pole. The pole jack includes a frame
member, with
upper and lower engagement mechanisms supported on the frame member. A pump
lever is pivotally coupled to the frame member for causing a pair of upper and
lower
engagement mechanisms to alternately engage the pole. The non-engaging
mechanism
is stepped upwardly along the pole while the other mechanism engages the pole.
A
support arm projects from the pole for holding a weight such as a scaffold
platform. A
spring loaded selector is provided for alternately disengaging the one
mechanism from
the pole while ensuring that the other engages the pole. A button on the top
of the jack
is depressed to release a secondary engagement during descent.
In an embodiment of the invention, the upper and lower mechanisms are each
comprised of a horizontal pin mounted within two lugs and arranged with a
spring to
move the pin into engagement with an extended lip or flange on the pole which
contains
a series of equipspaced climbing holes. A linkage bracket is also provided so
that the
lower mechanism is coupled to the pump arm.
The two engagement pins are able to move horizontally but are prevented from
rotating by means of horizontal spring pins that engage a horizontal slot
adjacent to each
pin. The engagement end of the pin is inclined to provide a ramp effect so
that the pin
automatically disengages the climbing holes when moved in the up direction.
The rear
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of each pin is angled to provide a vertical ramp profile that engages a
vertical interlock
member when the pin moves into the disengaged position. The rear ramp profiles
on the
upper and lower pin are opposite to one another so that engagement with the
interlock
element by one pin causes the interlock element to move into a blocking
position with
the other pin. This feature prevents both pins from disengaging the pole at
the same time.
A separate spring-biased dog brake device is fitted within the operating
mechanism. This dog device automatically engages the climbing holes and must
be held
in the released position by depressing a release button during descent.
In its broad aspect, the pole jack of the invention for climbing and
descending a
pole having a plurality of vertically equispaced holes formed therein
comprises a frame
member, upper and lower engagement mechanisms mounted for horizontal
reciprocal
travel in said frame member for selectively engaging the holes in the pole, a
pump lever
pivotally mounted on the frame member and operatively connected to the lower
engagement mechanism for causing the upper and lower engagement mechanisms to
alternately engage the holes in the pole for climbing the pole or descending
the pole, and
a vertically aligned interlock member pivotally mounted within the frame
member for
engaging at least one or other of the engagement mechanisms whereby the
engagement
mechanism engaging a post hole is blocked from releasing the pole while the
other
engagement mechanism is stepped up or down the pole by pivoting of the pump
lever.
Each said engagement mechanism comprises an engagement pin mounted for
horizontal
reciprocal travel within the frame member, spring means for biasing the
engagement pin
in a forward extended frame hole engaging position, the upper and the lower
engagement
pins having oppositely bevelled rear ends, and means for biasing the pivotally
mounted,
vertically aligned interlock member into a neutral position, said interlock
member having
a mating bevelled ramp surface opposite each engagement pin bevelled rear end,
whereby
retracting an engagement pin causes the engagement pin bevelled rear end to
engage the
interlock mating bevelled ramp surface to pivot the interlock member to block
the other
interlock pin while in its forward extended post hole engaging position.
The interlock member comprises a vertical bar attached to a cylindrical rod
mounted for rotation within the frame member, a pin extending radially from
the rod, and
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a spring secured to the frame member receiving the pin coaxially therein
whereby the
spring biases the rod and the bar attached thereto to a neutral position.
More particularly, the upper engagement mechanism comprises an engagement
pin having a downwardly bevelled front end mounted for horizontal reciprocal
travel on
the frame member, said engagement pin having a guide pin extending
diametrically
therethrough with exposed radial ends for anchoring a compression spring
concentric
with the engagement pin for biasing the engagement pin in a forward extended
frame
hole engaging position and for guided reciprocal travel of an end of the guide
pin in a
horizontal slot for preventing rotation of the engagement pin, a slide plate
mounted for
vertical reciprocal travel within the frame member, means for interconnecting
the pump
lever to the slide plate, the lower engagement mechanism comprises an
engagement pin
having a downwardly bevelled front end mounted for horizontal reciprocal
travel on the
slide plate, said engagement pin having a guide pin extending diametrically
therethrough
with exposed radial ends for anchoring a compression spring concentric with
the
engagement pin for biasing the engagement pin in a forward extended frame hole
engaging position and for guided reciprocal travel of an end of the guide pin
in a
horizontal slot formed in the guide plate for preventing rotation of the
engagement pin,
said upper and lower engagement pins having oppositely outwardly bevelled rear
ends,
and means for biasing the pivotally mounted, vertically aligned interlock
member into
a neutral position, said interlock member having a mating bevelled ramp
surface opposite
each engagement pin bevelled rear end, whereby retracting an engagement pin
causes the
engagement pin bevelled rear end to engage the interlock mating bevelled ramp
surface
to pivot the interlock member and to block the other interlock pin in its
forward extended
post hole engaging position.
The means for connecting the pump lever to the slide plate comprises as
downwardly extending lever pivotally connected to the pump lever, an actuating
pin
extending from the downwardly extending lever to the slide plate, and means
for
resiliently connecting the actuating pin to the side plate and lifting the
slide plate upon
upward pivotal movement of the pump lever. The means for resiliently
connecting the
actuating pin to the slide plate comprises a vertical slot formed in the slide
plate, said
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actuating pin having an extension projecting through the vertical slot for
vertical
reciprocal travel therein, and a tension spring interconnecting the actuating
pin to the
slide plate whereby upward movement of the actuating pin lifts the slide plate
while
compensating for excess lifting resistance.
The pole jack further comprises a ramp guide mounted for vertical reciprocal
travel within the frame member, and means for raising and lowering the said
ramp guide
and locking the ramp guide in a selected position, said ramp guide having a
pair of
spaced apart ramps selectively actuable upon raising or lowering the ramp
guide to
engage the upper and lower guide pins upon lowering of the pole jack to
alternately
disengage the upper and lower engagement pins. A tension spring for connecting
the
ramp guide to the frame member continuously biases the ramp guide downwardly.
The pole has an elongated flange extending the pole has an elongated flange
extending the length of the pole, said flange having a plurality of equispaced
holes
formed along it length for receiving the upper and lower engagement pins, the
frame
member has a slot for receiving the pole flange for slidable travel therein,
and the frame
member has upper and lower brackets attached thereto, each bracket having a
roller at a
distal end thereof for engaging the pole for lateral support of the frame
member on the
pole. A pair of pole jacks, each in combination with a pole on which the pole
jack is
mounted and each spaced apart in proximity to a wall surface, have brace means
attached
to an upper end of each pole for securing the pole to the wall surface and a
scaffold
extending between the pole jacks mounted on pole jack support arms extending
laterally
from the frame member at the base thereof for raising and lowering of the
scaffold on
the poles.
Brief Description of the Drawings
The objects of the invention and the manner in which they can be attained
will become apparent from the following detailed description, taken in
conjunction with
the accompanying drawings, in which:
Figure 1 is a perspective view of pole jacks of the invention
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supporting a platform;
Figure 2 is a side elevational view of the pole jack shown in Figure
1;
Figure 3 is an enlarged perspective view of the pole jack shown in
Figure 2;
Figure 4 is a side elevation of the pole jack in two positions on the
pole;
Figure 5 is a perspective fragmentary view of a portion of the pole;
Figure 6 is a horizontal section of the pole jack through line 6-6 of
Figure 3;
Figure 7 is a perspective view, partly cut away, of the pole jack
mechanism;
Figure 8 is a side elevation of the pole jack mechanism illustrated
in Figure 7 in a first operative "up" position;
Figure 9 is a side elevation of the pole jack mechanism shown in
Figure 7 in a second operative "up" position;
Figure 10 is a side elevation of the pole jack mechanism shown in
Figure 7 in a first operative "down" position;
Figure 11 is a side elevation of the pole jack mechanism shown in
Figure 7 in a second operative "down" position;
Figure 12 is a horizontal section taken along line 12-12 of Figure 8;
Figure 13 is a horizontal section taken along line 13-13 of Figure 9;
Figure 14 is a horizontal section taken along line 14-14 of Figure 9
when both engagement pins are extended;
Figure 15 is a vertical section along line 15-15 of Figure 16,
additionally showing a post flange by ghost lines;
Figure 16 is a perspective view of the top of jack 10; and
Figure 17 is a side elevation, partly in section, of the top of jack 10.
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Description of the Preferred Embodiment
Referring now to Figures 1 - 5, there is shown a pair of pump jacks, shown
generally at 10, each housed in a vertical U-shaped frame 12. Each pump jack
10 is
slidably mounted on a jack pole 14 which is seated on a supporting surface,
not shown,
and attached at its upper distal end to a lateral support such as a roof
surface 16 or a wall
surface 17 of a building by a brace 18 to ensure lateral stability and safe
attachment of
each pole. A supporting bracket arm 20, shown projecting laterally from the
base of each
vertical frame 12, can support a plank 22, shown in ghost lines, to form a
scaffold
platform. Upper and lower brackets 24, 26 extending outwardly from the
opposite of
each pump jack frame 12 at each end thereof, can support a work bench bracket
28,
shown in ghost lines, secured to brackets 24, 26 by connectors in holes 30.
The upper
horizontal portion 32 of bracket 28 can support a work bench or a guardrail,
not shown.
Vertical pivotal movement or jacking of pump lever arm 36 and linkages 37
pivotally connected thereto selectively raises or lowers the pump jack up or
down post
14, jack frame 12 straddling and sliding vertically along post flange 38 by
engagement
with flange holes 39, while supported laterally by rollers 40 rotatably
mounted in
brackets 26, 30 and 42, as shown most clearly in Figure 3.
Turning now also to Figures 6 - 9, the jack mechanism housed in frame 12
comprises pump lever arm 36 with fork extensions 36a straddling and pivotally
mounted
onto the opposite sides of vertical frame 12 by bolts 50. Downwardly depending
linkages
37 are pivotally mounted at one end on lever arm extensions 36a by bolts 52.
The
opposite lower ends of linkages 37 converge and are secured such as by welding
to
horizontal actuating pin 54 which is mounted for vertical reciprocal travel in
central slot
56 of frame 12. Actuating pin 54 extends through vertical slot 58 in slide
plate 60 which
is mounted for vertically reciprocal guided travel in frame 12 by guide rods
62 welded
to opposite sides of frame 12. The extension of pin 54 is operatively
connected to slide
plate 60 by a tension spring 64, whereby lowering or downward pivoting of
lever arm 36
with lower sliding engagement pin 66 biased to the left as viewed in Figure 8
by
compression spring 68 for engagement with pole flange 38 through a flange hole
39,
raises frame 12 until upper sliding engagement pin 70 is urged into the next
upper hole
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39 in flange 38 by compression spring 72, as viewed in Figure 9. Lower
engagement pin
66 is mounted for horizontal slidable travel in aligned apertures in a pair of
spaced-apart
plates 73, 75 secured such as by welding to plate 60 (Figure 13). Upper
engagement pin
70 is mounted for horizontal slidable travel in aligned apertures in a pair of
spaced-apart
plates 77, 79 secured such as by welding to plate 81 of frame 12 (Figure 12).
The operator then raises, i.e. pivots upwardly, lever arm 36 causing lower
sliding
pin 66 to disengage from the pole flange 38 and move upwardly with upward
vertical
travel of sliding plate 60 to its next hole-engaging position. Repeating the
pivotal lever
action results in continued upward vertical travel of the pole jack.
With reference to Figures 7 - 9, particularly Figure 7, vertical interlock bar
74
attached to cylindrical rod 76 is shown rotatably mounted in aligned apertures
in upper
and lower plates 78, 80 welded to frame 12. Bar 74 is biased into the neutral
position
typified in Figure 7 by radial pin 82 extending from rod 76 inserted into
spring 84; the
interaction of pin 82 with spring 84 tending to bias the bar into the neutral
position while
allowing the bar to pivot by rotation of rod 76 as depicted by arrow 86.
Turning to Figures 12 and 13, Figure 12 illustrates upper pin 70 retracted and
pin
66 extended into a flange engaging position. The rear end of pin 70 is
bevelled as
depicted by numeral 90 to engage mating ramp 92 of interlock bar 74 to pivot
bar 74
counter-clockwise as viewed in Figure 12, thereby locking lower pin 66 in its
forward
flange-engaging position. The retraction of lower pin 66 as viewed in Figure
13 pivots
bar 74 clockwise, thereby blocking upper pin 70 in its forward, flange-
engaging position.
The blocking of pins 66 and 70 in their respective forward-extended flange
engaging positions ensures that at least one pin will be engaged with flange
38 at all
times. The interaction of pin 28 with spring 84 urges bar 74 to pivot to its
neutral
position as shown in Figures 7 and 14 when both engagement pins 66, 70 are in
their
extended engagement position with flange 38.
There will be occasions during initial engagement between the pole jack 10 and
the pole 44 when the upper engagement pin 70 is not aligned with a hole 39 in
the pole
flange 38 and, as a result, engagement pin 70 is held back and in contact with
interlock
bar 60 so that continued upward operation of lever 36 could force lower pin 66
out into
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contact with the interlock bar 74, potentially causing damage to the
mechanism. To
protect against this, linkage 37 is connected to sliding pin plate 60 by means
of a slot 58
and spring 64 which are arranged to provide positive upward transmission of
lever force
when the lever is lifted up but allow the force to dissipate through spring 64
in the event
that excess resistance is encountered.
As the jack moves up the pole, the pivotally-mounted deadman emergency
locking dog 90 functions as a ratchet, engaging and disengaging holes 39 in
pole flange
38 in succession (Figure 15). Compression spring 92 mounted coaxially on
release pin
94 maintains positive contact between dog 90 and pole flange 38 during upward
travel
so that in the event of a failure of the climbing mechanism dog 90 will engage
a hole 39
in the flange and arrest the load.
In order to return down the pole, vertical ramp guide 100 is moved downwardly
from the upper position shown in Figures 8 and 9, and by ghost lines in Figure
17, to the
lower position shown in Figures 10, 11, 16 and 17. Ramp guide 100 is
selectively held
in its upper, up-travel position by spring-loaded selector knob 102 which is
urged to the
right as viewed in Figure 17 to engage detent 106 by compression spring 104
concentric
with rod 105. Extension of knob 102 to the left, again as viewed in Figure 17,
clears
detent 106 to allow knob 102 to be moved downwardly and to slide ramp guide
100
connected to knob 102 by rod 105 downwardly. Tension spring 110 secured to
ramp
guide 100 and to frame 12 biases ramp guide 100 downwardly to maintain ramp
guide
100 locked in its downward position.
Follower guide pins 110, 112 mounted diametrically through lower and upper
locking pins 66, 70 respectively have exposed radial ends which slide in
horizontal
recesses 114, 116 during reciprocal travel of pins 66, 70 to maintain the
bevels 113, 115
of pins 66, 70 facing upwardly while engaging and anchoring compression
springs 68,
72. During upward travel of the jack 10, follower pins 110, 112 are not
deflected by
ramp guide 100 as shown in Figures 8 and 9. During downward travel of jack 10,
however, ramp guide 100 engages follower pins 110, 112, as shown in Figures 10
and
11, to alternately disengage engagement pins 66, 70 from pole flange 38. The
vertical
spacing of ramps 116, 118 allows the vertical load on the jack to be supported
by
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extended lower engagement pin 66 while upper ramp 118 causes upper engagement
pin
70 to retract from the pole flange (Figure 10). As the operator releases the
downward
pressure on jack lever 36, the jack moves down the pole. When upper engagement
pin
70 moves closer to lower engagement pin 66, the lower ramp 116 contacts
horizontal
engagement pin 66 through follower pin 111 to urge engagement pin to the
right, as
viewed in Figure 10. However, since the pin 66 supports the load on the jack,
frictional
engagement between pin 66 and post flange 38 prevents retraction of engagement
pin 66,
forcing ramp guide upwardly against the bias of tension spring 110 so that
contact
between upper ramp 118 and follower pin 112 is removed, as shown in Figure 11,
allowing upper engagement pin 70 to re-engage a hole 39 in pole flange 38 as
the pin 70
moves into alignment with the next lower hole position. The operator at this
time
reverses the pivotal travel of lever 36 so that the jack load shifts to upper
engagement pin
70. The lower ramp 116 causes the lower engagement pin 66 to disengage the
pole
flange, permitting pin 66 to move down the pole to the next lower hole 39. The
continued lowering of lever 36 lowers plate 60 whereby lower engagement pin 66
moves
below lower ramp 116 and is biased to the left as viewed in Figure 11 to re-
engage the
pole flange 38. Repeat of this procedure continues downward travel of the
jack.
During downward travel the operator must depress release pin 94, to cause
locking dog 90 to be held clear of the pole flange 38. In the event of a
mechanical failure
resulting in sudden downward movement of the jack, it is expected that the
operator will
lose contact with release pin 94, thus allowing locking dog 90 to engage the
pole flange
3 8 and arrest the load.
It will be understood that modifications can be made in the embodiment of the
invention illustrated and described herein without departing from the scope
and purview
of the invention as defined by the appended claims.
