Note: Descriptions are shown in the official language in which they were submitted.
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DRIVE MECHANISM FOR USE WITH AN OVERHEAD SHAFT OF A
SECTIONAL DOOR
Field of the invention
The present invention relates to a drive mechanism. More particularly, the
present invention relates to drive mechanism for use with an overhead shaft of
a
sectional door, such as garage doors and the like, for raising and lowering
the
door, the drive mechanism having an integrated ratchet mechanism and acting
also as a safety braking device for preventing an uncontrollable raising
and/or
lowering of the sectional door.
Background of the invention
It is known in the art that commercial and residential sectional garage
doors usually require counterbalancing mechanisms to counterbalance the weight
of the door in order to decrease the force required to open the door and also
facilitate its closing from a raised to a lowered position. Large sectional
garage
doors used in commercial and residential applications may be manually or power
operated. In either case, but particularly for manually operated doors,
counterbalancing mechanisms have been used for many years to counterbalance
the weight of the door and control its opening and closing movements so that
one
person can control the operation of the door more easily. Counterbalancing
mechanisms are also advantageous for power operated overhead doors since
they reduce the power requirements needed for the motor and they lower the
structural strength required for the door opening and closing mechanism. In
other
words, lighter weight, lower cost, door controlling mechanisms, such as chain
hoists for example, may be used if a counterbalancing mechanism is connected
to
the door to assist it in its opening and closing movements. Furthermore, the
provision of a counterbalancing mechanism minimizes the chance of a rapid and
uncontrolled closing of the door in the event of a failure of the door opening
and
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closing mechanism, which can result in serious damages or even personal
injuries.
It is also known in the art that a widely used type of counterbalancing
mechanism generally comprises a pair of spaced apart cable drums connected to
cables, each cable being in turn connected to a lower opposite side edge of
the
garage door. The cable drums are usually mounted onto an overhead shaft which
is supported above the door opening and is connected to one or more torsion
springs which are each fixed to the shaft at one end, and secured to a fixed
structure such as the wall for example at the other end, so that the cable
drums
are biased to rotate in a direction which winds the cables onto the drums and
counteracts the weight of the door connected to the cables. The torsion
springs
are adjusted to properly balance the weight of the door so that minimal
opening
and closing efforts are required, either manually or when motor controlled..
An
example of a conventional cable-operated sectional door and its corresponding
counterbalancing mechanism is shown in Figure 1, the sectional door being
shown
provided with a chain hoist for raising and lowering the door.
It is also known in the art that certain garage doors are not always properly
counterbalanced or simply are operated without the use of a counterbalancing
mechanism. Since these doors are not properly counterbalanced or are simply
not
counterbalanced at all, they are either always pulling on the cables with a
downward force due to the weight of the door, or have a tendency to move
upwards because the counterbalancing force of their torsional springs is too
strong. This type of situation is particularly dangerous when the door is
raised or
lowered by means of a conventional drive mechanism, such a manually-operated
chain hoist for example, because an operator needs to continuously hold the
chain
of the hoist, otherwise the door may fall to the ground or move up in an
uncontrolled manner with an increasing speed. Such a situation is dangerous
and
often arises suddenly, particularly in the case of commercial doors which are
known to be heavier than residential doors, because as soon as the hand chain
of
the hoist slips away from an operator's hand, its speed tends to increase to a
level
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that is practically impossible and/or very unsafe to stop manually, thereby
often
resulting in the door raising up or dropping in a very undesirable manner,
i.e. with
an increasing speed, which often in turn results into serious damages and/or
personal injuries. Indeed, not only is the door itself dangerous when falling
or
moving up in an uncontrolled manner because it may severely impact an item or
a
person, but also hand injuries are very likely to occur when an operator of
the
chain hoist attempts to regain control of the chain which often rotates much
faster
than the overhead shaft of the door.
There exist several prior art documents describing different drive
mechanisms for use with sectional doors. Known to the Applicant are the
following
United Sates patents which describe different drive mechanisms and the safety
devices used therewith: 1,621,951; 2,095,695; 2,878,865; 3,188,698; 3,637,004;
4,112,996; 4,669,775; 4,704,914; 4,721,146; 4,997,022; 5,022,452; 5,291,686;
5,482,103; 5,494,093; 5,971,055; 6,029,735; 6,042,158; 6,059,008; 6,070,641;
and 6,123,134.
It is also known in the art that occasionally, for one reason or the other,
one of the cable of the counterbalancing mechanism brakes or one of the
elements holding such cables undergoes failure, leading to the garage door
falling
all the way down, potentially causing damages or personal injuries. There
exist
some systems that prevent the free falling of a garage door by breaking it in
its
track in the advent of a failure of the counterbalancing mechanism. There are
also
systems that stop the door (i.e. let it go up, but do not let it go down) in
such
circumstances. Finally, there are also systems that slow down the falling of
the
door in case of an emergency condition, such as a fire for example. However,
there seems to be no drive mechanism which not only is used for raising and
lowering a sectional door, such as garage doors and the like, but which also
acts
as a safety device for preventing an uncontrollable raising and/or lowering of
the
sectional door as a result of the aforementioned adverse situations.
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Hence, in light of the above-discussed, there is a need for an improved
drive mechanism which, by virtue of its design and components, would not only
be
able to raise and lower a sectional door, such as garage doors and the like,
but
would also act as a safety device for preventing an uncontrollable raising
and/or
lowering of the sectional door, whether the latter be balanced, unbalanced or
improperly balanced.
Summary of the invention
The object of the present invention is to provide a drive mechanism which
satisfies some of the above-mentioned needs and which is thus an improvement
over the devices known in the prior art.
In accordance with the present invention, the above object is achieved
with a drive mechanism for use with an overhead shaft of a sectional door for
raising and lowering said door via a rotation of the overhead shaft, the drive
mechanism comprising:
support means through which the overhead shaft is pivotally inserted;
a first gear securely mounted about the overhead shaft of the sectional
door;
a drive shaft pivotally mounted to the support means;
a second gear securely mounted about the drive shaft, the second gear
being operatively interconnected to the first gear so that a rotation of the
second
gear is transmitted to the first gear and vice versa, the second gear being
rotatable
along a first direction corresponding to a raising of the sectional door and
along an
opposite secona direction corresponding to a lowering of the sectional door;
a driving link mounted about the drive shaft and being rotatably movable
therealong between a first position where the driving link is away from the
second
gear and a second position where the driving link is operatively secured
against
the second gear and where further rotation of the driving link biases the
second
gear to rotate along the first direction; and
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actuating means for rotating the driving link about the drive shaft, operating
5 the said driving link between the first and second positions, and driving
the second
gear along the first and second directions when the driving link is in the
second
and first positions respectively.
Preferably, the driving link is a pocket wheel. The driving link may come in
the form of other suitable embodiments, as apparent to a person skilled in the
art.
The objects, advantages and other features of the present invention will
become more apparent upon reading of the following non-restrictive description
of
preferred embodiments thereof, given for the purpose of exemplification only
with
reference to the accompanying drawings.
Brief description of the drawings
Figure 1 is a schematic front view of a conventional cable-operated
counterbalanced sectional garage door, the sectional door being shown provided
with a drive mechanism according to the prior art.
Figure 2 a perspective exploded view of a drive mechanism according to
the preferred embodiment of the invention, the drive mechanism being shown co-
operating with an overhead shaft of a sectional door.
Figure 3 is schematic cross-sectional view taken along line III-III of the
drive mechanism shown in Figure 2.
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Figure 4 is a schematic side view of the drive shaft shown in Figure 2.
Figure 5 is side view of the drive mechanism of Figure 2 when in an
assembled configuration.
Figure 6 is a cross-sectional view of a drive mechanism according to
another preferred embodiment of the invention.
Detailed description of preferred embodiments of the invention
In the following description, the same numerical references refer to similar
elements. The embodiments shown in Figures 2-6 are preferred.
Although the present invention was primarily designed for use with a
cable-operated counterbalanced sectional garage door, it may be used with
other
types of doors, such as slidable truck doors, or with any other items which
can be
opened or closed by means of a chain hoist, as apparent to a person skilled in
the
art. For this reason, the expressions such "cable-operated",
"counterbalanced",
"sectional", "garage" and/or "door" and any other references and/or other
expressions equivalent thereto should not be taken as to limit the scope of
the
present invention and include all other kinds of doors or items with which the
present invention could be used and may be useful.
Moreover, in the context of the present invention, the expressions
"sectional door", "cable-operated door" and/or "garage door", as well as any
other
equivalent expressions and/or compound words thereof, may be used
interchangeably, as apparent to a person skilled in the art. The same applies
for
any other mutually equivalent expressions known in the art, such a "drive
mechanism" and "chain hoist" for example, as well as "counterbalanced" and
balanced", as also apparent to a person skilled in the art. -
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In addition, although the preferred embodiment of the present invention as
illustrated in the accompanying drawings comprises various components such as
a pair of ratchet gears, pawl arms, friction pads, washers, a chain, a
threaded
drive shaft, etc., and although the preferred embodiment of the present
invention
as shown consists of certain geometrical configurations, not all of these
components and geometries are essential to the invention and thus should not
be
taken in their restrictive sense, i.e. should not be taken as to limit the
scope of the
present invention. It is to be understood, as also apparent to a person
skilled in the
art, that other suitable components and cooperations thereinbetween, as well
as
other suitable geometrical configurations may be used for the drive mechanism
according to the present invention, as will be explained hereinafter, without
departing from the scope of the invention.
Referring to Figure 1, there is shown a schematic front view of a
conventional cable-operated counterbalanced sectional garage door 1, the
sectional door I being shown provided with a chain hoist 3. Indeed, most
sectional
doors 1, whether manually or power-operated, are connected to an overhead
counterbalancing mechanism 5 that provides a counterbalancing force in order
to
decrease the force required to open the door 1 and also facilitate its
closing. The
garage door 1 is usually connected to the counterbalancing mechanism 5 by
means of two cables 7, one at the right and one at the left. The cables 7 are
usually made of steel and the lower free end of each cable 7 is usually
attached at
the bottom of the door 1. As is known in the art, each cable 7 cooperates with
a
corresponding cable drum 9 which is mounted to the overhead support shaft 11
in
order to facilitate raising and lowering of the cable-operated sectional door
1.
Torque is transferred between the torsional springs 13 and the overhead shaft
11
by means of plugs 15 which operatively connect the shaft 11 to the springs 13
in
order to counterbalance the weight of the garage door 1. Since the cables 7
are
respectively coiled up onto a corresponding drum 9 that is mounted on the door
shaft 11, a rotation of the door shaft 11 along one direction moves the door 1
upwards while a rotation of the door shaft 11 along another direction moves
the
door 1 downwards.
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As is known in the art, chain hoists 3 are usually operatively connected to
the overhead shaft 11 of sectional doors 1 for driving the same in order to
ease the
opening and the closing of such doors 1. They ease the manipulation by giving
access to high height doors 1 or height offset doors 1, for example, and by
reducing the initial pulling force needed in the hand chain caused by door's
inertia.
Because most doors 1 are counterbalanced, the only point in time at which one
usually needs to substantially pull on the hand chain 17 of the hoist 3 with
some
force is at the beginning of the door raising movement, after which, one only
has to
assist the raising movement of the door 1 with a minimal pulling force. Also,
because most doors 1 are not perfectly counterbalanced, one can let go off the
chain 17 of the hoist 3 and the door 1 will continue to move upwards or
downwards, accordingly, in a fairly slow manner due to the presence of the
counterbalancing mechanism 5 of the door 1. This is why chain keepers 19 are
widely used, because they enable to selectively prevent any movement of the
chain 17, and thus block the raising and/or lowering of the door 1.
Similarly, in the case of a conventional non-counterbalanced sectional
garage door 1, the door 1 is attached, on its leaf, with two cables 7, one on
each
side. These cables 7 are coiled up on a drum 9 that is mounted on the door
shaft
11. Thus, the rotation of the door shaft 11 also moves the door 1 upwards and
downwards accordingly. A non-counterbalanced or "unbalanced" door 1 does not
have torsion springs 13 mounted onto the door shaft 11, so that the door
weight is
not balanced.
Chain hoists 3 are also used to ease the opening and the closing of such
unbalanced doors 1. They ease the manipulation by giving access to high height
doors I or height offset doors 1, for example, and by reducing the pulling
force
needed in the hand chain 17 to move the door 1. However, because the door 1 is
not balanced, one always need to substantially pull on the chain 17 of the
hoist 3
in order to raise and/or lower the door 1. To stop the door 1 at a given
position,
one needs to 'xlock the chain 17 in a chain keeper 19. For unbalanced doors
1,
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the chain keeper 19 now becomes an essential accessory of the door I because
it
will prevent the free falling or the rapid rising of the door 1. Finally,
because the
door 1 is not balanced, if one lets go off the chain 17, the door I will fall
with an
increasing speed and thus will be unstoppable, increasing the possibilities of
injuries and/or damages to property and the door mechanism.
Broadly described, the drive mechanism 101 according to the
present invention, as illustrated in the accompanying drawings, is a drive
mechanism 101 for use with an overhead shaft 103 of a sectional door 105 for
raising and lowering said door 105 via a rotation of the overhead shaft 103.
As
better shown in Figures 2 and 6, the drive mechanism 101 comprises support
means 107, a first gear 109, a drive shaft 111, a second gear 113, a pocket
wheel
115 and actuating means 117.
The overhead shaft 103 of the sectional door 105 is preferably
pivotally inserted into the support means 107 of the drive mechanism 101
through
corresponding bores 119 thereof. The first gear 109 is securely mounted about
the
overhead shaft 103 by appropriate fastening means, such a key way for example
or any other suitable means, as apparent to a person killed in the art.
The drive shaft 111 is pivotally mounted to the support means 107
and preferably rotates about corresponding sleeves 121 thereof, as also better
shown in Figure 2. The second gear 113 is securely mounted about the drive
shaft
111 and is operatively interconnected to the first gear 109 so that a rotation
of the
second gear 113 is transmitted to the first gear 109 and vice versa, as can be
easily understood when referring to Figure 2. The second gear 113 is rotatable
along a first direction 123 corresponding preferably to a raising of the
sectional
door 105 and along an opposite second direction 125 corresponding preferably
to
a lowering of the sectional door 105. Alternatively, it is worth mentioning
that, still
according to the present invention, the first and second directions 123, 125
along
which the drive shaft 111 rotates may correspond to the lowering and raising
movements of the door 105 respectively, depending on how the cables of the
door
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105 are wound about the drums and/or depending on how the sectional door 105
rotates about the overhead shaft 103, as apparent to a person skilled in the
art.
The pocket wheel 115 is mounted about the drive shaft 111 and is rotatably
5 movable therealong between a first position where the pocket wheel 115 is
away
from the second gear 113 and a second position where the pocket wheel 115 is
operatively secured against the second gear 113 and where further rotation of
the
pocket wheel 115 biases the second gear 113 to rotate along the first
direction
123, as can be easily understood when referring to Figure 2.
The actuating means 117 are used for rotating the pocket wheel 115 about
the drive shaft 111, operating the said pocket wheel 115 between the first and
second positions, and driving the second gear 113 along the first and second
directions 123, 125 when the pocket wheel 115 is in the second and first
positions
respectively.
According to a preferred embodiment of the invention, the drive mechanism
101 comprises a first ratchet assembly 127 for blocking rotation of the second
gear
along 113 the second direction 125 when the pocket wheel 115 is in the second
position. This first ratchet assembly 127 preferably comprises a ratchet gear
129
and a pawl arm 131 positioned and sized to cooperate .with said ratchet gear
129 ,
the ratchet gear 129 being mounted about the drive shaft 111 between the
pocket
wheel 115 and the second gear 113 and being rotatably movable therealong.
Preferably, as can be understood when referring to Figures 2 and 3, the
ratchet
gear 129 is rotatable about the driving shaft 111 when the pocket wheel 115 is
in
the first position and is securely clamped between the pocket wheel 115 and
the
second gear 113 when the pocket wheel 115 is in the second position so as to
be
blocked by the pawl arm 131 when the second gear 113 is rotated along the
second direction 125 by the first gear 109.
Preferably, the drive shaft 111 comprises a threaded portion 133 and first
and second opposite segments 135, as better shown in Figure 4. Preferably
also,
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the first and second segments 135 of the drive shaft 111 are peripherally
smooth
and are mounted into corresponding support sleeves 121 of the support means
107 while the pocket wheel 115 and the ratchet gear 129 are threadedly mounted
about and movable along the threaded portion 133 of the drive shaft 111, as
better
shown in Figure 2. The end extremities of the drive shaft 111 are preferably
threaded for receiving suitable fasteners and so as to securely mount the
drive
shaft 111 onto the support means 107, as apparent to a person skilled in the
art.
As better shown in Figures 2 and 3, the drive mechanism 105 preferably
comprises a friction pad 137 mounted about the drive shaft 111 between the
pocket wheel 115 and the ratchet gear 129, as well as a washer 139 mounted
about the drive shaft 111 between the ratchet gear 129 and the second gear
113.
Preferably, the washer 139 is intended to provide a good contact surface
between
the second gear 113 and the ratchet gear 129 (and also between the bearing and
the ratchet gear 129) while the friction pad 137 is preferably intended to
optimize
the contact surface between neighboring parts and also help to have a good
friction between the pocket wheel 115 and the ratchet gear 129, as apparent to
a
person skilled in the art.
Preferably also, as better illustrated in Figure 2, the pawl arm 131 is
mounted onto a rod 141, the rod 141 being pivotally mounted to the support
means 107 and being provided with a spring 143 having one end connected to the
support means 107 and another end connected to the rod 141 for biasing the
pawl
arm 131 against the ratchet gear 129.
Preferably also, the actuating means 117 comprise a chain 145 mounted
about the pocket wheel 115 for rotating the same about the drive shaft 111
between the first and second positions and for driving the second gear 113
along
the first and second directions 123, 125 when the pocket wheel 115 is in the
second and first positions respectively, as can be easily understood when
referring
to Figure 2. Instead of a manually pulled chain 145, the actuating means 117
may
consist of other suitable means for rotating the pocket wheel 115 about the
drive
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shaft 111, such a motorized driving device operatively connected to the pocket
wheel 115 for example, or another slidable gear system connected to the pocket
wheel 115, as apparent to a person skilled in the art.
The support means 107 preferably comprise a casing 147 formed of two
portions 147a, 147b which are removably connectable to one another by suitable
means, such as fasteners, hooks, etc., so as to allow an easy opening and
closing
of the casing 147 in order to facilitate the inspection, maintenance and/or
repair of
the components of the drive mechanism 101 inside the casing 147.
According to the present invention, the use of the drive mechanism 101,
also commonly referred to commonly as "anti-back drive" 101, enables to remove
the potential dangers inherent to unbalanced garage doors 105 without having
to
resort to the addition of a counterbalancing system. Indeed, the ratchet
assembly
127 of the drive mechanism 101 acts as an "integrated braking device" which is
devised to prevent any downward movement of the door 105, thus limiting
damages and/or injuries. In fact, the drive mechanism 101 according to the
first
preferred embodiment explained hereinabove does not allow a downward
movement of the door 105 without actuating the pocket wheel 115 back into the
first portion.
Indeed, as can be understood when referring to Figure 2, by pulling the
hand chain 145, the pocket wheel 115 rotates about the drive shaft 111 on
which
the second gear 113 is securely mounted. The second gear 113 carries the first
gear 109 which is securely mounted about the door shaft 103. Preferably, the
parameters of the first and second gears 109, 113 (dimensions, teeth, etc.)
are
selected so that the rotational speed of the door shaft 103 is smaller than
the
rotational speed of the drive shaft 111.
As aforementioned, the drive shaft 111 has a threaded portion 133 on
one side and the second gear 113 is rigidly mounted at the other side of the
same
shaft 111. The bore of the pocket wheel 115 is preferably threaded so as to be
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screwed onto the threaded portion 133 of the drive shaft 111. The pocket wheel
115 moves onto the ratchet gear 129 when screwed onto the drive shaft 111 by
means of the chain 145. The ratchet gear 129 is rotatably movable along the
axis
of the drive shaft 111 so that when the pocket wheel 115 is screwed onto the
ratchet gear 129, the latter is rotated until it abuts onto the second gear
113 which
is rigidly mounted about the drive shaft 111. When all of these three (3)
components (pocket wheel 115, ratchet gear 129 and second gear 113) are
operatively clamped together, the drive shaft 111 begins to rotate around its
axis
and the second gear 113 thus carries the first gear 109 in rotation in order
to move
the door 105 in the first direction 123, corresponding to an upward movement
of
the door 105.
When a user of the drive mechanism 101 lets go off the hand chain 145,
since the door 105 is not balanced, the door shaft 103 carries the first gear
109
which in turn carries the second gear 113 which is rigidly mounted onto the
drive
shaft 111 and secured against the ratchet gear 129 and the pocket wheel 113. A
downward movement of the door 105 will thus screw the pocket wheel 115 onto
the ratchet gear 129 and onto the second gear 113. Therefore, as can be easily
understood, the pawl arm 131 will engage with the ratchet gear 129 and will
prevent the same from rotating, because the ratchet gear 129 is clamped
between
the second gear 113 and the pocket wheel 115 (when the latter is in the second
position). Hence, because the ratchet gear 129 is blocked, the second gear 113
is
also blocked which means that drive mechanism 101 prevents the first gear 109
from rotating along the second direction 125, and thus prevents the door 105
from
going down because the overhead shaft 103 is blocked by the first gear 109.
The only way one may release the door 105 is to create a slack between
the ratchet gear 129, the second gear 113 and the pocket wheel 115, i.e.
trigger
the pocket wheel 115 back into the first position, away from the second gear
113.
In order to do so, the user needs to move the hand chain 145 with a constant
tension preferably. As soon as the tension is released in the hand chain 145,
the
pocket wheel 115 screws back onto the ratchet gear 129 that moves onto the
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second gear 113 and ultimately prevents any downward movement of the door 105
by preventing rotation of the second gear 113 in the manner explained
hereinabove. It is to be understood that a minimum door weight is required for
the
drive mechanism 101 to be functional in the manner explained herein, as
apparent
to a person skilled in the art.
According to another preferred embodiment of the present invention, the
drive mechanism 101 may also comprise a second ratchet assembly 149 for
blocking rotation of the second gear 113 along the first direction 123 when
the
pocket wheel 115 is in the first position. This two-ratchet-assembly drive
mechanism 101 allows the installation of the chain hoist 101 on any side of
the
garage door 105 as well as the possibility to flip it toward its own plane, if
need
may be.
Indeed, according to this particular embodiment, as better shown in Figure
2, the drive mechanism 101 preferably comprises a second ratchet gear 151 and
a
second pawl arm 153 positioned and sized to cooperate with said second ratchet
gear 151. As shown, the second ratchet gear 151 is mounted about the drive
shaft
111 between the pocket wheel 115 and an abutment of the drive shaft 111
opposite to the second gear 113 and is rotatably movable therealong. As can be
easily understood, the second ratchet gear 151 is rotatable about the drive
shaft
111 when the pocket wheel 115 is in the second position and is securely
clamped
between the pocket wheel 115 and the abutment of the drive shaft 111 when the
pocket wheel 115 is the first position so as to be blocked by the second pawl
arm
153 when the second gear 113 is rotated along the first direction 123 by the
first
gear 109.
Preferably, the pocket wheel 115 and the first and second ratchet gears
129, 151 are threadedly mounted about the threaded portion 133 of the drive
shaft
111 and are movable therealong within their respective ranges.
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According to this embodiment, the drive mechanism 101 comprises first and
second friction pads 137, 155, the first friction pad 137 being mounted about
the
drive shaft 111 between the pocket wheel 115 and the first ratchet gear 129,
and
the second friction pad 155 being mounted about the drive shaft 111 between
the
5 pocket wheel 115 and the second ratchet gear 151. Preferably also, the drive
mechanism 101 comprises first and second washers 139, 157, the first washer
139 being mounted about the drive shaft 111 between the first ratchet gear 129
and the second gear 113, and the second washer 157 being mounted about the
drive shaft 111 between the second ratchet gear 151 and the abutment.
Preferably also, according to this embodiment, the first and second pawl
arms 131, 153 are mounted onto a same rod 141, the rod 141 being pivotally
mounted to the support means 107 and being provided with a spring 143 having
one end connected to the support means 107 and another end connected to the
rod 141 for biasing the first and second pawl arms 131, 153 against the first
and
second ratchet gears 129, 151 respectively, as better shown in Figure 2.
With the addition of a second ratchet assembly 149, the drive mechanism
101 becomes particularly useful with doors 105 having counterbalancing
mechanisms which are not perfectly adjusted. On such doors 105, at any moment
in time during opening or closing, the counterbalancing system may carry the
door
105 upwards or downwards, randomly. However, with the provision of two ratchet
assemblies 127, 149 in the manner explained hereinabove, the drive mechanism
101 does not allow the door 105 to drive overhead shaft 103 in any of the
directions. Indeed, movement of the door 105 becomes blocked along both
directions 123, 125, i.e. second gear 113 is prevented from rotating along the
first
and second directions 123, 125, and the only way to raise or lower the door
105,
i.e. to drive the overhead shaft 103, is to employ the pocket wheel 115
between
the first and second positions respectively, in the manner explained herein.
The drive mechanism 101 and its integrated braking principle according to
the present invention as explained herein may be used in different fields, as
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apparent to a person skilled in the art, and may take on further embodiments.
For
example, although gears 109, 113, 129, 151 have been used in the context of
the
present description, it could also be possible to use other transmission
systems,
as also apparent to a person skilled in the art, such as sprockets with roller
chains,
for instance. The working principle would still remain the same, in that,
according
to the present invention, the drive mechanism 101 is devised to prevent
movement
to the door 105 coming from the output shaft (most of the time, the overhead
door
shaft 103), while enabling the door 105 to be raised or lowered by means of
the
input shaft (most of the time, it is the pocket wheel drive shaft 111).
As may now be appreciated, the present invention is a substantial
improvement over the chain hoists known in the art, in that, as explained
hereinabove, it prevents a conventional garage door 105 from free falling or
moving upwards in an uncontrolled manner, and thus there is no need for chain
keepers 19. Indeed, the drive mechanism 101 according to the present invention
is
built with an integrated brake device, preventing unwanted and dangerous
motions
of the door 105. According to the present invention, the drive mechanism 101
is
advantageous in that, as explained hereinabove, it can be used with a door 105
which may be unbalanced in either the downward or upward direction, even
though most unbalanced situations arise in the downward direction. Load can be
moved up and down with the drive mechanism 101 but cannot go down by its own
weight, therefore eliminating the risk of serious injuries caused by the door
closing
too rapidly for example. Furthermore, the present invention may be used in the
garage door industry, with balanced or unbalanced garage doors 105, whether
they be new or old. As it is evident from reading the above description, the
present
invention is a more reliable and safer drive mechanism 101 than those
available in
the prior art. Furthermore, the present invention may be used with other kinds
of
doors 105, such as slidable truck doors 105 for example, or with any other
items
which are operated by chain hoist 101, as apparent to a person skilled in the
art.
CA 02453838 2004-01-06
WO 03/004815 PCT/CA02/01047
17
Of course, numerous modifications could be made to the above described
embodiments without departing from the scope of the invention as defined in
the
appended claims.
