Note: Descriptions are shown in the official language in which they were submitted.
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ECCENTRICALLY MOUNTED PLUG FOR OPERATIVELY CONNECTING
TORSION SPRINGS TO OVERHEAD SHAFTS OF COUNTERBALANCING
SYSTEMS USED FOR GARAGE DOORS AND THE LIKE
Field of the invention
The present invention relates to a plug, also known as a "collar" or an
"anchor", such as the ones used for operatively connecting torsion springs to
overhead shafts of counterbalancing mechanisms used for garage doors and the
like, in order to allow a torque transfer between the torsion spring and the
overhead shaft so as to counterbalance such cable-operated doors.
Background of the invention
It is known in the art that large, vertical, cable-operated doors, such as
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 easily control the
operation of the door. 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 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
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the door opening and closing mechanism, which can result in serious injury or
damage.
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
flexible cables, each cable being in turn connected to a lower opposite side
edge
of the garage door. The cable drums are usually mounted on a 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.
It is also known in the art that conventional, low cost adjustment devices
used for the above-mentioned type of counterbalance mechanism, and widely
utilized in the garage door industry, are generally cylindrical "collars"
commonly
referred to also as "plugs" (or "cones") which are connected to the so-called
fixed
ends of the torsion springs and are thus mounted on the aforementioned shaft
for
adjusting the deflection of the springs to preset the counterbalance force.
The
aforementioned collars usually include one or more setscrews which lock the
collars to the shaft to prevent rotation thereabout except during normal
adjustment
of the spring deflection. The collars also usually include sockets for
receiving
winding bars whereby the springs are manually preset, or "preloaded", by
rotating
the collars with respect to the shaft using the winding bars and then locking
the
collars to the shaft with the setscrews. Each collar also may include a slot
onto
which a corresponding free end of the torsion spring is hooked on. These slots
are
usually T-shaped, and are thus commonly known as "T-slots".
An important problem associated with the aforementioned type of
counterbalancing mechanism, or with any other type of counterbalancing
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mechanism which uses winding collars (also known as "anchors") having T-slots
and tensioning springs, arises when the radial space between the inside of the
collar and the outside of the shaft is limited. Given the fact that most
overhead
shafts employed in the industry are usually of standard diameter, the above-
mentioned problem generally arises either when the shaft is covered with an
additional fitting placed thereabout, or when the torsion spring mounted about
the
shaft (which may or may not be covered with an additional fitting) has a
reduced
inside diameter. In the first case, when the radial space between the shaft
and the
torsion spring is limited as a result of a shaft being covered with an
additional
fitting so as to protect the shaft and/or transfer the load, collars having
larger
inside diameters are required to be able to mount them onto the fitting-
covered
shaft. Not only are large inside diameter collars more expensive, but they
need to
be used with torsion springs having larger inside diameters in order to render
the
counterbalancing mechanism operable. Torsion springs having large inside
diameters (i.e. greater than 2") are also more expensive and are limited in
choice,
that is, they are not readily available because most of the torsion springs
being
used in the industry have generally an inside diameter of equal to or less
than 2".
Now, in the second case, that is, when the radial space between the shaft and
the
torsion spring is limited as a result of using torsion springs having reduced
inside
diameters, the free ends of such springs hooked onto the plugs do not allow
the
latter to be mounted about the overhead shafts. There is simply not enough
clearance between the shaft and the collar for a spring's free end (also known
as a
"spring tail") to be lodged thereinbetween, and as a result, the collars
simply do
not fit onto the overhead shaft. Furthermore, if the radial distance between
the
overhead shaft and the collar is limited, the spring tail may not be property
hooked
onto the collar which might in turn render the counterbalancing inoperable
and/or
unsafe and may also lead to the spring tail damaging the outer surface of the
overhead shaft which is also undesirable for reasons well known in the art.
The
above-described problems are inherent to the collars known in the art which
are
inadequate for those cases where the space between the inside of the plug and
the shaft (which may or may not be covered with an additional fitting) is
small.
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Another major problem is that none of the types of collars known in the art
provide a simple, quick, reliable, and cost effective way for operatively
connecting
a torsion spring having a reduced inside diameter to an overhead shaft of a
counterbalancing mechanism used for garage doors and the like.
Hence, there is a need for a more compact, more reliable, easier to use,
easier to maintain, safer, quicker, and more cost effective device for
operatively
connecting torsion springs to overhead shafts of counterbalancing systems used
for cable-operated doors, such as garage doors for example, particularly for
when
the space between the inside of the plug and the shaft (which may or may not
be
covered with any additional fitting) is limitedly small.
Summary of the invention
The object of the present invention is to provide a "plug", also known as a
"collar", an "anchor", or a "cone", which satisfies some of the above-
mentioned
needs and is thus an improvement over the devices known in the prior art.
More particularly, the object of the present invention is to provide a new
approach for operatively connecting torsion springs to overhead shafts of
counterbalancing systems used for garage doors and the like.
In accordance with the present invention, the above object is achieved
with a plug for use in a counterbalancing mechanism of a cable-operated door,
said plug being used for operatively connecting an overhead shaft to a torsion
spring co-axially mounted thereon, said plug comprising:
a cylindrical collar having opposite first and second portions, said
collar being provided with a hooking slot for hooking a free end of the
torsion
spring thereon and said torsion spring having a segment coaxially mounted
about
the first portion of the collar; and
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a cylindrical flange rigidly affixed to the second portion of the collar,
said flange being used for transferring a torque between the torsion spring
and the
overhead shaft when the flange is securely fixed about the overhead shaft;
wherein the collar is eccentrically mounted about the overhead shaft.
5
The objects, advantages and other features of the present invention will
become more apparent upon reading of the following non-restrictive description
of
a preferred embodiment thereof, given for the purpose of exemplification only
with
reference to the accompanying drawings.
Brief description of the drawings
Figure 1 is a perspective view of a sectional garage door connected to a
counterbalancing mechanism provided with stationary and winding plugs
according to the prior art.
Figure 2 is a perspective view of one of the stationary plugs shown in
figure 1.
Figure 3 is a side plan view of the stationary plug shown in figure 2.
Figure 4 is a partial sectional side view of the stationary plug shown in
figure 2, said stationary plug being shown concentrically mounted about an
overhead shaft and cooperating with a free end of a torsion spring.
Figure 5 is a side view of a stationary plug and a winding plug according to
preferred embodiments of the invention, said stationary and winding plugs
being
eccentrically mounted about the overhead shaft and each plug cooperating with
a
free end of the torsion spring.
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Figure 6 is a partial sectional side view of the stationary plug shown in
figure 5, said stationary plug being eccentrically mounted about the overhead
shaft.
Figure 7 is a sectional top view of the stationary plug shown in figure 6,
said stationary plug being eccentrically mounted about the overhead shaft and
being shown cooperating with a free end of the torsion spring.
Detailed description of a preferred embodiment of the invention
In the following description, the same numerical references refer to similar
elements. The embodiments shown in figures 5-7 are preferred. In the context
of
the present description, the expressions "plug", "collar", "anchor", and any
other
equivalent expression known in the art (such as "cone" for example) used to
designate those structures employed to operatively connect torsion springs
onto
overhead shafts of counterbalancing mechanisms used for garage doors and the
like will be used interchangeably. Furthermore, although the present invention
was
primarily designed for a counterbalancing mechanism of a garage door, it may
be
used for counterbalancing mechanisms of other kinds of doors, such as slidable
truck doors, or with any other items suspended by a cable, as apparent to a
person skilled in the art. For this reason, the expression "garage door"
should not
be taken as to limit the scope of the present invention and includes all other
kinds
of doors or items with which the present invention may be useful. Hence, also
in
the context of the present invention, the expressions "garage door" and "cable-
operated door" will be used interchangeably as well.
The plug 1 according to the preferred embodiment of the invention as it is
illustrated with accompanying drawings is a plug 1 for use in counterbalancing
mechanisms 3 of garage doors 5 and the like. The plug 1, also known as a
"collar", an "anchor", and/or a "cone", as aforementioned, is used to
operatively
connect an overhead shaft 7 to a torsion spring 9 coaxially/concentrically
mounted
onto the overhead shaft 7.
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Referring to figure 1, most cable-operated garage doors 5, whether
manually or power operated, are connected to an overhead counterbalancing
mechanism 3 that provides a counterbalancing force in order to decrease the
force
required to open the door 5 and also facilitate its closing. The garage door 5
is
usually connected to the counterbalancing mechanism 3 by means of two cables
11, one at the right and one at the left (not shown). The cables 11 are
usually
made of steel and the lower free end of each cable is usually attached at the
bottom of the door 5. As illustrated in figure 1, each cable 11 cooperates
with a
corresponding cable drum 13 which is mounted to the overhead shaft 7 in order
to
facilitate raising and lowing of the cable-operated door 5. Torque is
transferred
between the torsion spring 9 and the overhead shaft 7 by means of plugs 1
which
operatively connect the shaft 7 to the spring 9 in order to counterbalance the
weight of the garage door 5. Usually, each torsion spring 9 is fixed to the
overhead
shaft 7 at one end, by means of a plug 1 known as a "winding plug" 1 b, and
operatively secured to the wall at the other end, by means of another plug 1
known
as a "stationary plug" 1 a. The above-mentioned types of counterbalancing
mechanisms 3 can be found in other types of cable-operated doors 5, such as
slidable truck doors for example.
Referring now to figures 2 to 4, an example of a typical anchor slot plug 1,
also known as a cone, as already known in the prior art, is shown. The form of
the
slot 15 allows the introduction of the free end 17 of the spring 9, also known
as a
"spring tail", without the use of any tool. Once the tail is introduced into
the entry
section of the collar slot 15, the collar 19 is rotated in the spring axis.
The collar 19
is then pushed towards the spring 9 to be placed in the second section of the
slot
15, after what it is rotated around the axis to be blocked there by the T-
shaped slot
section 16. This type of plug 1 is suitable for torsion springs 9 having
inside
diameters of 2" and more but cause several problems, that is, they do not fit
and
thus cannot be used with torsion springs 9 having inside diameters of 1.75"
and
smaller. This last category of springs 9 represents an important market part
of the
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springs 9 being used in the industry of garage door counterbalancing
mechanisms
3.
According to the present invention and as better shown in figures 5 and 7,
the plug 1, whether it is a stationary plug 1 a or a winding plug 1 b,
comprises a
cylindrical collar 19 and a cylindrical flange 21. The cylindrical collar 19
has
opposite first and second portions 23, 25, and is provided with a hooking slot
15
for hooking a free end 17 of the torsion spring 9 onto the plug 1, as better
shown in
figure 5. As also shown in figure 5, a segment 27 of the torsion spring 9 is
preferably coaxially mounted about the first portion 23 of each collar 19. The
cylindrical flange 21 is rigidly affixed to the second portion 25 of the
collar 19.
Preferably, the collar 19 and the flange 21 are made integral to each other,
that is,
they are made of one single piece. The cylindrical flange 21 can be securely
fixed
to the overhead shaft 7 by means of fasteners, such as setscrews for example,
so
as to allow a proper torque transfer between the torsion spring 9 and the
overhead
shaft 7. The plug 1 according to the present invention is characterized in
that the
collar 19 is eccentrically mounted about the overhead shaft 7 so as to allow
the
free end 17 of the torsion spring 9 to be lodged between the collar 19 and the
overhead shaft 7, as better shown in figure 7, thereby allowing the plug 1 to
be
used when the space between the inside of the plug 1 and the shaft 7 is
limited,
either as a result of the shaft 7 being covered with an additional fitting
(not shown)
placed thereabout, or as a result of the plug 1 being used with torsion
springs 9
having reduced inside diameters (preferably, torsion springs 9 having an
inside
diameter of 1.75" or smaller which represent a major part of the market), or
as a
result of both. By eccentrically mounting the collar 19 about the overhead
shaft 7,
more clearance is allowed between the inside of the collar 19 and the shaft 7
so as
to properly hook the spring's free end 17 onto the collar 19 and lodge it
between
the inside of the plug 1 (or the inside of the collar 19 for that matter) and
the shaft
7, as better shown in figure 7.
According to a preferred embodiment of the invention and as better shown
in figure 5, each torsion spring 9 is preferably coaxially mounted onto the
overhead
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shaft 7 and is preferably connected with a stationary plug 1 a at one end 17,
and a
winding plug 1 b at the other end 17. The stationary plug 1 a is preferably
connected to a fixed structure, such as for example, a bracket rigidly mounted
to a
wall. The winding plug 1 b is removably fixed to the overhead shaft 7 and is
used to
operatively connect the torsion spring 9 to the overhead shaft 7 so as to
allow a
torque transfer between the latter two. Preferably, the flange 21 of the
winding
plug 1 b is provided with sockets 29 for receiving winding bars in order to
manually
preset a given torque onto the torsion spring 9, prior to securing the winding
plug
1 b onto the overhead shaft 7, by rotating the winding plug 1 b with respect
to the
overhead shaft 7. Once an appropriate amount of torque ("preload") has been
applied to the torsion spring 9 in order to allow an appropriate
counterbalancing
force as apparent to a person skilled in the art, the winding plug 1 b is
secured to
the shaft by means of setscrews provided for that purpose in order to prevent
any
substantial rotational relative movement between the winding plug 1 b and the
shaft 7, in order to assure a good torque transfer between the torsion spring
9 and
the overhead shaft 7. Preferably, the winding plug 1 b may allow an
appropriate
relative sliding of the corresponding spring end 17 attached thereon so as to
compensate for the contraction or extension of the spring 9 in function of the
compression torque. The plugs 1, whether stationary or winding, can be easily
removed from the overhead shaft 7, for easier maintenance and/or repair of the
counterbalancing mechanism 3, and more specifically for spring replacement, by
unfastening the setscrews and/or unhooking the free ends 17 of the torsion
springs 9, or by any other appropriately safe manner, as apparent to a person
skilled in the art.
As better shown in figures 6 and 7, the present invention is characterized
in that the collar 19 of the plug 1 is eccentrically mounted about the
overhead shaft
7. In doing so, the slot part is moved off the collar axis to allow reducing
of collar
diameter, in order to be able to use the plug 1 according to the present
invention
with torsion springs 9 of reduced inside diameters, preferably equal to or
less than
2". Furthermore, by eccentrically mounting the plug 1 about the overhead shaft
7,
the plug 1 can also be used and thus mounted onto a shaft 7 covered with an
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additional fitting (not shown), which could be used for protecting the shaft's
surface
and/or for transferring the load, so as to allow the spring's free end 17 to
be
hooked onto the collar's slot 15 and lodged between the inside of the collar
19 and
the fitting. As better shown in figure 7, the aforementioned geometry, that
is, the
5 eccentric mounting, allows the spring end 17, also known as "spring tail",
to be
safely hooked onto the hooking slot 15 and be inserted into the collar 17
without
scraping nor damaging the shaft 7. The eccentricity of the collar 19 with
respect to
the overhead shaft 7 is calculated based on several parameters such as
capability
of spring steel rod, tool to make spring tail, tolerance on spring diameters,
etc.
10 such as apparent to a person skilled in the art.
The present invention is an improvement and presents several
advantages over other plugs known in the prior art, such as the one
illustrated in
figure 2-4. For instance, by eccentrically mounting the collar 19 about the
overhead shaft 7, the plug 1 according to the present invention can be used
for
when the space between the inside of the plug 1 and the shaft 7 is limited,
either
as a result of the shaft 7 being covered with an additional fitting (not
shown)
placed thereabout, or as a result of the plug 1 being used with torsion
springs 9
having reduced inside diameters (preferably, torsion springs 9 having an
inside
diameter equal to or less than 2", which represent a major part of the
market), or
as a result of both. By eccentrically mounting the collar 19 about the
overhead
shaft 7, more clearance is allowed between the inside of the collar 19 and the
shaft 7 so as to hook the spring's free end 17 onto the collar's slot 15 and
lodge it
between the inside of the plug 1 (or the inside of the collar 19 for that
matter) and
the shaft 7. The present invention can also be used with torsion springs 9
having
different sizes of inside diameter, whether greater or smaller than the
aforementioned. The present invention allows the free ends 17 of the torsion
springs 9 (also known as "spring tails") to be hooked onto the slots 15 of the
plugs
1, easily, quickly, safely, and reliably, without any special tooling, so that
the spring
tails 17 can be safely inserted into the collars 19 without scrapping the
overhead
shaft 7. Conversely, the present invention allows the same spring tails 17 to
be
hooked off the slots 15 of the plugs 1, with the same above-described
advantages,
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for each maintenance and/or repair to the counterbalancing mechanism 3. The
present invention may be used in the garage door industry, with
counterbalancing
mechanisms of new garage doors 5 or existing garage doors 5. As it is evident
from reading the above description, the present invention is a more compact,
more
reliable, easier to use, easier to maintain, safer, quicker and more cost
effective
plug 1 than those available in the prior art. Furthermore, the present
invention may
be used with other kinds of doors 5, such as slidable truck doors, or with any
other
items suspended by a cable 11, as apparent to a person skilled in the art.
Of course, numerous modifications could be made to the above described
embodiments without departing the scope of the invention as defined in the
appended claims.
