Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
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This invention relates to snow removal apparatus,
and particularly to apparatus for removing snow from
an inclined plane surface such as is commonly found
on residential homes. In northern climates the problem
of snow accumulation on rooftops during the wlnter is
significant for several reasons. First, the continual
accumulation of snow causes a weight loading problem
which, over the period of a winter, may damage structural
roof members, and has on occasion caused a roof to collapse.
Second, snow accumulation on rooftops is subjected to
alternate heating and cooling during winter days and
nights, causing moisture to run down the roof surface
and accumulate in the form of ice formations along the
eaves of the structure. Heat absorbed by the roof ;~`
surface from inside, and from the sun on the outside
of the structure, causes the snow accumulation to
begin melting, but no heat is present over projecting
eaves, and the water from melted snow refreezes when
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it runs down to the projecting unheated eave surface.
Accumulation of ice formed along the eaves soon causes
water to be dammed and thereby prevented from running
off the roof, and this water eventually seeps up
underneath shingles to leak into the inside of the
structure.
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Problems such as described above have been solved
in the past indirectly by placing heating elements along the
eaves of a structure so as to supplement the melting process
and allow water to drain completely from the roof. However,
these heating elements are often unsightly and require
service, in addition to requiring a continual çost in supply-
ing electrical energy for heating. Other solutions to the
problem have resulted in the design of light weight plows
and "rakes" on the end of long poles so that the homeowner
10 may either push or pull snow accumulation from the rooftop.
These devices either require that the operator climb atop
the roof and push snow accumulation away from the crown of
the roof and off the edge, or require that the operator
stand below the roof and pull snow accumulation toward him.
Usual-ly a great deal of effort is required to move snow
r accumulation in this manner, and the removal operation is
time consuming and often dangerous.
Summary of the Invention
The present invention comprises an apparatus for
20 removing snow from a surface, comprising a rectangular sheet
of plastic material having a length dimension substantially
longer than its width dimension; an edge support rod attached ~;
to said rectangular sheet along a width dimension; support
means attached to said edge support rod for supporting said
rod in spaced and slidable relationship to said surface;
transport means attached to said edge support rod for moving
said apparatus through snow on said surface. `
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Brief Description of the Drawing
A preferred embodiment of the present invention
is described herein and is illustrated on the attached
drawing in which:
FIG. 1 is an isometric view of a preferred embod-
iment of the invention;
FIG. 2 shows the preferred embodiment on a
roof surface;
FIG. 3 shows the preferred embodiment in side ~
10 view; and :--
FIG. 4 shows an isometric view of an alternative ~ :
embodiment of the invention. ~-
Descriptlon of the Preferred Embodiment
FIG. 1 shows an isometric view of a preferred
.~ embodiment of the invention. An elongated pole or ~;
shaft 12 is attached to a U-frame 14 by means of a
suitable connecting bracket 15. Shaft 12 may be
constructed from an aluminum or fiberglass tube or
from any other material adapted to have strength over
an elongated length, and U-frame 14 is preferably
constructed from a resilient tubular material~
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although U-frame 14 and bracket 15 may be formed of suitable
plastic in a single-piece mold operation. The vertical
legs of U-frame 14 may be flattened to reduce the resistance
of moving the apparatus through a snow accumulation, by
thereby creating more of a knife-edge surface for cutting
through the snow. Shaft 12 may be ten to twenty feet or
more in length depending upon the nature and size of the ~ - ;
roof the invention is used with and the shaft may be assembled
with interlocking or attaching tubular sections.
The legs of U-frame 14 are adapted for inserting ~-~
therethrough a rod or axle 16 which has wheels 18 and 19
attached at its ends. U-frame 14 is typically 18-30 inches
in width, although it may be wider, to provide a snow removal
path of reasonable size. Wheels 18 and 19 are freely
rotatable and adapted for easy rolling along a roof surface,
being typically at least several inches in diameter.
Alternatèly, wheels 18 and 19 could be replaced by a simple
pair of runners or other glide surface, so long as the
rod or axle 16 is supported for relatively easy sliding ;~
over the roof surface.
A flexible sheet 20 is attached around rod 16 i~-
over substantially its entire length between the members
of U-frame 14. Sheet 20 is preferably formed of a plastic
material such as polyethylene, of thickness .002" - .010",
and having a length of at least several feet. In a preferred
~ embodiment sheet 20 may be made 10-15 feet~long, or longer,
;~ to enable the sheet to overhang the lower roof edge as the
, apparatus is moved upward along the roof surface. The
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surface of sheet 20 is preferably of a low coefficient of
`~ friction, for example less than 0.2, which presents a slippery
surface to cause snow to readily slide over the surface of
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sheet 20. Plastic sheet material is commercially available
having a reinforcin~ filament embedded therein, and this
type of plastic sheet material may be used to provide ad:
ditional strength against tearing of the sheet. In any event
axle 16 is preferably removable from U-frame 14 to permit
the attachment of a new sheet 20 when excessive wear occurs.
Sheet 20 may be attached around rod 16 by sewing, glueing,
or thermally bonding according to practices known in the
art, but it is advantageous to form such an attachment while
leaving an opening for rod 16 which is larger than rod 16
to permit freedom oE movement of sheet 20 about rod 16.
FIG. 2 shows an isometric view of a roof structure
10 of a type commonly found on residential buildings. Two
operational embodiments of the invention are also illustrated.
In the first operational embodiment, the elongated pole or
shaft 12 extends downwardly to a point below the roof where
the operator can grasp it and propel the apparatus upward
along the roof su~face.
In the alternative operational embodiment shown
in FIG. 1, all structural members are identically constructed
2a to that described hereinbefore, the only difference being
that sheet 20 is positioned away from the U-frame in an
opposite direction. The alternative embodiment therefore
enables the apparatus to be propelled by a person standing
on the crown of the roof and pulling the apparatus towards
him, whereas the first embodiment requires that the
operator preferably stand on the ground below the roof
and push the apparatus away from him up the roof surface.
In either event, if an accumulation of snow exists on the
roof surface rod 16 and sheet 20 will undercut the snow
accumulation, causing it to settle on sheet 20. Since
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sheet 20 is selected from materials having a very low
coefficient of friction, a gra~itational sliding force will
cause the snow resting on sheet 20 to slide downwardly off
the edge of the roof.
FIG. 3 illustrates the invention in side view
on a roof surface 10. The top of U-frame 14 has a vertical
height H above roof surface 10 sufficient to pass over
any reasonable snow accumulation depth. A height H of
12 inches has been found satisfactory for most purposes.
U-frame 14 is propelled upwardly along roof surface 10, -
with the wheels rolling along the roof surface, by applying
upward force to shaft 12. This causes the rod attached
to the wheels to undercut the snow accumulation 22 and to
slide sheet 20 under snow accumulation 22. As U-frame `~
14 is pushed upwardly a snow accumulation fracture 24
occurs, wherein a portion of the accumulated snow breaks `
away from the snow remaining on the roof surface. ~ ~
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The invention undercuts a snow accumulation at ;
a depth d which corresponds to the height of the rod `~
above the roof surface. This height is typically about
I/2 - 2 inches and results in a very thin layer of snow
accumulation being left on the roof. It has been found
that this thin snow layer is of no harmful consequence i'
and is usually dissipated by sublimation, melting or
blowing after only a short period of time. -
Fractured snow accumulation 24 is subjected to a ;
vertical downward weight force W which has a component
F acting downwardly in parallel with the roof surface. -"
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Because the coefficient of friction of sheet 20 is very
; low, the gravitational sliding force F is sufficient
to cause the fractured snow accumulation 24 to move
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along sheet 2U and over the edge of roof surface lO, dropping
to the ground. The magnitude of sliding ~orce F is dependent
upon the weight of fractured snow accumulation 24 and the
pitch of roof sur~ace lO. In practice it has been found
readily possible to remove a snow accumulation from roof
surfaces that have a pitch of 20 degrees, and it is believed -
that accumulations may be removed from roof surfaces of
even lower pitch angle. For example, if the roof surface
lO were nearly flat, U-frame 14 could be propelled into a ~
portion of the snow accumulation and then lifted from the - -
roof to cause the accumulation trapped on sheet 20 to lift
to an elevation sufficient to cause sliding. The lifting
of U-frame 14 from the roof in this example may be enhanced
by utilizing shaft 12 as a lever, pivoting about a contact
point on the roof edge. However, if the invention is to be
used in this manner care must be taken to insure that
shaft 12 is of sufficient streng~h to withstand the lifting
forces which will be imposed upon it due to such leverage
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action. It is also possible to lift U-frame 14 upwardly
through a snow accumulation and then withdraw shaft 12
backwardly toward the roof edge, thereby trapping a portion
of the snow accumulation on sheet 20 and forcing it back-
wardly over the edge of the roof. This operational approach
has the advantage of not subjecting shaft 12 to the bending
stresses which would otherwise occur in the leverage
operation described above.
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FIG. 4 shows an alternative embodiment of the
invention wherein the invention may be propelled along
a roof surface by means of a rope or cord. In this
embodiment, an elongated plastic sheet 30 of a preferable
length of about 20 feet has attached at either of its
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- ends rods 32 and 34, each with.a pair of wheels. A long
cord loop 35 i5 attached to rod 32, and a second cord loop ;.
37 is attached to rod 34. Loops 35 and 37 are preferably . : ~
formed in lengths sufficient to be thrown or propelled .
over the entire roof surface so that they may be grasped
from the opposite side of the roof. In this embodiment :
a person or machine-dr.iven power source pulls cord 35 up-
wardly along the roof surface, causing rod 32 and sheet 30
to undercut the snow accumulation. Sheet 30 may be propelled
over the crown of the roof and down the other side of the .. :
roof in this manner, and may be returned by pulling cord ~ .
loop 37. Loops 35 and 37 therefore enable the sheet 30 ~ :
to be moved over the entire roof surface and remove all .
snow from the surface. Of course, obstructions such as
chimneys and ventilators will prevent the sheet from
removing snow at these locations, but the amount of snow .`
accumulated which remains on the roof surface because of j .. :.
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such projections is normally very small. .
Although various modifications may be made to
either the preferred or alternative embodiments described
herein it is believed that the emb~diments described herein `. .
will provide a satisfactory appar~tus under most conditions.
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