Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to doors and more
particularly to overhead doors which are employed in
industrial applications including mining applications.
It is known to construct an industrial door
structure which includes a curtain for closing the doorway
and a curtain winding mechanism for raising and lowering
the curtain. Such a door structure is disclosed in South
AErican patent no. 80/0440 wherein the inventor is Glenn R.
Palmer. This known door is advantageous in that damage is
minimal if the door is struck by a vehicle which must pass
through the door on a regular basis. The curtain is made
of a rubber composition and it is thicker along its side
edges so that it is normally retained at the side edges in
guide channels. In many mining applications, there is
often a pressure difEerential on opposing sides of the door
and the edges of the curtain are designed to sealingly
engage the guide channels in order to maintain the pressure
differential.
In applications where doors, including flexible
curtain doors, have to be maintained closed to maintain a
predetermined pressure within an environment, experience
has shown that differential pressure building up on
opposing sides of the door can make it extremely difficult
if not impossible, to open the door.
The preferred pressure-differential compensating
door disclosed herein can be readily opened when different
pressures exist on opposing sides of the door. The
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pressure-differential compensating door i5 also a
damage-minimizing door which can be readily repaired and
maintained subsequent to impact by vehicular traffic.
It should be understood that the expression "door
surrounding structure" referred to herein and in the
appended claims means a frame or that portion of a wall to
which the door is mounted.
According to the present invention, a roll-up
door comprises a flexible curtain for closing a doorway
having a first end, a second lower end, and side ed~e,~ and
a curtain winding mechanism having the first end of the
curtain attached thereto for raising and lowering the
curtain. This door includes a pair of space-apart guide
channel means with side edge sections of the curtain being
movable in the guide channel means and engagable therewith.
Friction reducing members are affixed to both of the side
edge sections and extend therealong to reduce the amount of
friction between the side edge sections and their
respective guide channels.
In one preferred embodiment, the curtain is made
of rubber or synthetic rubber and the friction reducing
members comprise plastic strips. The plastic strips are
made of ultrahigh molecular weight plastic and are affixed
to both the front and the back of each side edge section.
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Further features and advantages will be apparent
Erom the following detailed description given by way of
example, when read in conjunction with the accompanying
drawings.
In the drawings,
Figure 1 is a fxont elevational view of a
preferred embodiment of the present invention.
Figure 2 is a side elevational view showing the
door of figure 1 secured in sealing engagement to the door
surroundin~ structure.
Figure 3 is a sectional elevation of a door taken
along the line III-III of Fi~ure 1.
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Figure 4 is a side elevation of the upper portion
only of the door structure wherein the door has been moved
away from the door surrounding structure.
Figure 5 is a sectional view taken at line V-V of
:Eigure 1.
E`igure 6 is a sectional view taken at line VI-VI
o figure 1 showi.ng one side edge of the curtain and its
respective guide channel and :illustrating how the side edge
section can be pulled from the channel under impact.
Figure 7 is a front detail of the side edge
section of the curtain.
Figure 8 is a detail view illustrationg the bar
on the bottom of the curtain.
Referring to figures 1 to 4 there is shown a
pressure-di~ferential compensating door 10 which is also a
damage minimi~ing door suitable for use in mining
application. The door 10 includes a flexible curtain 12
having a first upper end 14 attached to a curtain winding
mechanism which includes a spring barrel 16. The spring
barrel 16 is a well known feature of overhead doors and
further description of this barrel and the mounting
therefor is deemed to be unnecessary. A shaft 17 projects
from each end of the barrel and is mounted in a vertical
support plate 19.
' An idler barrel 18 is located below the spring
barrel and is attached to the support plates or end
brackets 19 by inserting a shaft 21 on either end of the
idler barrel into holes provided near ~he base of each
support plate 19. The curtain winding mechanism includes a
door lift power unit 22 which is attached to the upper
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section of the door 10 to provide a lift force required to
lift the curtain under normal operating condi-tions. The
curtain will lower to the closed position under its own
weight. The preferred power unit 22 is electrical and is
~n integrated completely enclosed prime mover consisting of
a worm gear ~ox, control section and electric motor (not
shown). The control section can contain a solenoid
operated brake, rotary limit switches and a mechanical
interlock to prevent electrical operation when a manual
chain hoist is engaged. Additional controls for a safety
edge, radio control, time delay, etc. may be incorporated
into the control section if desired. Such electrical power
units for the operation of overhead doors are well known
and the power unit per se does not form a novel aspect of
the present invention.
The upper portion of the door structure further
includes channel members 23 and 25 that extend between and
connect the side support plates 19. The channel member 25
is longer than the upper member 23 to permit hydraulic
jacks to be connected thereto as explained hereinafter~
The back edge of each support plate 19 is rigidly connected
to a respective vertical channel member 27 which can be
seen in cross section figures 5 and 6. Each of the two
channel members 27 extends from the floor to the very top
of the door structure. Extendin~ between and connecting
the channel members 27 are horizontal channel members 29
and 31. The bottom end of each channel member 27 is
pivotally secured by an anchor hinge 38 to the wall or door
surrounding structure 36. The preferred door surrounding
structure is one made of steel and it can for example be
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made from wide flanged beams. A steel surrounding
structure permits easy attachment of such parts of the door
structure as the anchor hinges 38 and the hydraulic
cylinders 44 described hereinafter.
Turning now to the construction of the flexible
curtain 12, there is provided at its lower end 24 a rigid
bar 26 attached by means of bolts 33. The lower end 24 is
clamped between a structural angle 35 and a flat elongate
plate 37 which together make up the bar 26. The purpose of
the bar 26 is to resist the bending action of the curtain
and to maintain the curtain parallel with the threshold of
the door. There can also be clamped between the angle 35
and the plate 37 a section of a flexible sealing strip 28.
This strip 28 which can be made of rubber provides the
means to seal the curtain with the threshold when the
curtain is lowered to its closed position. If desired the
strip 28 can contain electrical wiring 39, forming part of
a known electrically actuated safety system which provides
for emergency stoppage of the downward action of the door
should an obstruction be present in the opening. Such an
emergency safety system is well known in the overhead door
art and further description of this system in the present
application is deemed unnecessary. The preferred means of
attachment for the lower end 24 of the curtain is to cut
V-shaped notches in ~he bottom edge to accomodate the bolts
33. In this way the curtain is less likely to be damaged
under impact because the bar 26 can be pulled from the
bottom edge of the curtain without tearing or damaging the
latter.
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The construction of the vertical side edges of
the curtain can be seen from figures 5 to 7. The side
edges 30 are thicker than the remaining portion of the
cuJ^tain 12 and are movable in the aforemention guide
channels 20. In the preferred embodiment shown the side
edges are more than twice as thick as the remaining portion
of the curtain and are formed by adhering a second layer of
rubber to each side edge, The inner side of the additional
layer of rubber is bevelled at 41 and along the sloping
surface is arranged friction reducing means in the fo~m of
short plastic strips 43. Further friction reducing means
are provided on the opposite side of the curtain and these
means are made of long plastic strips 45. The plastic
strips 43 and 45 are provided to reduce the amount of
friction between the side edge sections 30 and their
respective guide channels 20. The preferred plastic strips
are constructed with ultrahigh molecular weight plastic
which has a low coefficient of friction. It is preferable
for the two strips 45 located on the hack surface of the
curtain to be continuous strips in order that a seal will
be provided between the side edge sections of the curtain
and their guide channels. The strips 45 can be continuous
without creating problems when the curtain is wound up
because these strips are located on the radially outer side
of the rolled up curtain. It is preferable that the strips
43 be short and spaced apart along the bevelled shoulder 41
as shown in figure 7 in order that these strips will not be
bent unduly or separated from the rubber curtain as the
-` result of numerous operations of the door.
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g
Only recently has it become possible to
satisfactorily bond plastic strips of the type illustrated
irl figures 5 -to 7 to rubber. The process that is used is a
molecular process. In the actual construction of
appllcant's door, the plastic strips 43 and 45 are
purchased with a -thin layer of rubber already bonded to one
surface by this molecular process. Strips of this nature
are sold under the trade mark RB85 by Robco Incorporated.
When these particular strips are being used, it then
becomes necessary only to bond rubber to rubber, a well
known operation.
The construction of the guide channels 20 can be
seen readily from figures 5 and 6. In particular there is
a large, elongate structural angle 47 and a smaller
structural angle 49. Both the outer angles 47 extend from
the floor of the door opening to the location 51 indicated
in figure 2. The inner angle 49 extends from the floor of
the door opening to a hinge member 50. ~ne leg of the
angle 49 is bent inwards towards the corresponding leg of
the angle 47 to form a sloping shoulder 51 which is engaged
by the plastic strips 43 of the curtain under normal
conditions. Preferably the angles 47 and 4g are
constructed from ordinary mild steel of approximately 1/4
inch thickness. Such steel is flexible enou~h not to
damage the rubber curtain if it is pulled from the guide
channel as shown in figure 6. It will be appreciated -that
under vehicular impact, the side edge sections of the
curtain can be pulled from the guide channels because the
bent legs of the angle 49 will flex sufficiently to enable
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the side edge sections to come out. The angles 47 and 49
are bolted to one another by means of bolts 53 and nuts 55.
The leg 57 of the angle ~7 can be rigidly attached (such as
by welding) to the adjacent channel memher 27.
Connected to each of the aorementioned hinges 50
is a relatively short angle member 48 forming an upper
portion of the guide channel. The plate 48 can be pivoted
about its hinge connection as illustrated in dashed lines
in figure 3 to facilitate insertion of its respective side
edge section into the guide channel. As illustrated, each
member ~8 can be held inplace by two bolts. If desired
each plate 48 can be spring biased by a coil spring located
at the hinge 50 towards the position shown in solid lines
in figure 3.
It should be understood that the bar 26 shown in
figure 1 does not extend into the guide channels 20. This
arrangement is necessary in order for the damage to the
door structure to be minimal if the door is struck by a
vehicle.
In mining applications for the present door
structure, the door operates to seal one section of a mine
off from another section of a mine. In certain instances a
considerable pressure differential buildup may occur on
opposing sides of the door (in the order of 8-10 tons)
resulting in the curtain bending as shown in figure 5 and
making it difficult to raise and lower the door even with
the use of the plastic strips ~3 and 45. To overcome this
problem door pressure releasing means which connect the
door and se~ling engagement with the door surrounding
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structure are employed. These releasing means are operable
to move the door 10 away from the door surrounding
structure 36 prior to the cur~ain being raised and to
release any pressure diEferential existing on opposing
sides of the door. The preferred door pressure releasing
tneans includes the aforementioned hydraulic cylinders 44.
One of these cylinders is located on each side of the door
near the top. A hydraulic piston member 56 is slidable in
each cylinder and is connected to lugs 59 that extend
upwardly from the channel member 25. Each hydraulic
cylinder is pivotally connected by means of lugs 61 to the
door surrounding structure 36. The hydraulic cylinders are
connected to a hydraulic power unit 65 in a well known
manner. The hydraulic power unit is of standard
construction and a detailed description of this unit is
deemed unnecessary. In one preferred embodiment of the
present door structure each hydraulic cylinder has a stroke
of approximately nine inches.
It will now be understood that in order to
overcome a pressure differential buildupl the hydraulic
cylinders 44 can be actuated to push the door structure to
the position shown in figure 4. The door structure pivots
about the hinge anchors located at 38. As a result
pressure equalizes on opposing sides of the door making it
relatively easy to move the side edges 30 of ~he curtain in
the guide channels. After the curtain is raised, the
hydraulic cylinders 44 are returned to the position shown
in figure 2 bringing the door back into engagement wi-th the
door surrounding structure.
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It will be obvious to those skilled in the art
that there are alternatives to the hydraulic cylinder shown
or providing door pressure releasing means. ~or example,
these cylinders could be replaced by pneumatic cylinders.
Pneumatic cylinders may however be less reliable than
hydraulic cylinders. Alternatively a rack and pinion
mechanism could be employed to move the door s-tructure away
from the door surrounding structure. The pinion could then
be operated by an electric motor.
In order to provide an air tight seal between the
vertical channel members 27 and the door surrounding
structure 36, flexible flaps 67 can be provided. Each flap
is attached to the outer flange oE the channel member 27 by
means of bolts or other suitable connectors 69.
The gap between the end 71 of the angle member 49
and the leg 57 is sized so that the curtain 12 can be
pulled under impact from the guide channel without damage
to the curtain. In one preferred embodiment wherein the
curtain 12 is 1/4 inch thick (except for -the side edge
section 30) the gap formed by each guide channel measures
approximately 1/2 inch. It will be appreciated that the
side edge section 30 in ~his preferred embodiment has a
thickness which excseds l/2 inch so that under normal
conditions the side edge section will not be pulled from
its guide channel.
In applications requiring an overhead door of the
present type but not requiring a door that is capahle of
being open even when a pressure diEferen-tial exists, the
aforementioned plastic strips 43 and 45 are still very
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useul because of their ability to reduce friction. Thus
these strips can be used on doors in above ground locations
where a door pressure releasing mechanism such as the
hydrauLic cylinders 44 are not required.
S It will be clear to those ~;killed in the art that
various modifications and changes can be incorporated in
the door structure of the present invention. All such
modificactions and changes that fall within -the scope of
the appended claims are intended to be covered by the
present application.
.
