Note: Descriptions are shown in the official language in which they were submitted.
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BALANCING SPRING SYSTEM FOR SLIDING WINDOW SASH
FIELD OF THE INVENTION
The present invention relates to sliding window
sash systems and, more particularly, to a balancing spring
system for facilitating the manual opening and closing of
window sashes.
BACKGROUND OF THE INVENTION
Double hung and single hung windows known in the
art comprise vertically translating window sashes. The
window sashes slide in channels located alongside the window
jambs of a window frame. Either sash can overlap the other
sash to provide varying openings of the window. A window
sash generally comprises, at its top end, a locking
mechanism to engage the window sash in a stationary position
along the window jambs.
Balancing spring systems have been provided to
facilitate the opening and closing of window sashes. For
instance, window sashes having large dimensions, thick glass
or many layers of glass would be a handful to manually lift.
Furthermore, such heavy window sashes would also be subject
to the risk of forcefully sliding down the window jambs,
possibly causing the shattering of the glass and endangering
the people of the surrounding environment. Therefore,
balancing spring systems known in the art provide spring
mechanisms along window jambs to upwardly bias the window
sash, such that only a small amount of force needs to be
applied to the window sash for the lifting and opening
thereof. Also, the window sash is kept in vertical balance
within the channels of the window jambs by the spring
mechanism. Similarly, only a small amount of force needs to
be applied to the window sash for the closing thereof.
Curled ribbon springs have been used in balancing
spring systems as they have the distinct advantage of
providing a constant force, whereby the counterbalancing of
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the window sash is possible by opposing the constant force
of such springs to the constant weight of the window sash.
A curled ribbon spring consists in a spring ribbon curled
around a reel, whereby the ribbon has been formed such that,
when a free end portion thereof is extended and uncurled
from the reel, that extended free end portion recurls itself
around the reel. The recurling force of the curled ribbon
spring is a function of the width thereof, amongst other
factors.
U.S. Patent No. 5,232,208, issued on Aug. 3, 1993
to Braid et al., discloses a frame tensioning arrangement,
wherein a ribbon spring is curled to a reel. The curled
ribbon spring is idle and free to rotate within a channel of
a window jamb. A tongue at a free end of the curled ribbon
spring is connected to a window sash shoe. The window sash
shoe supports a window sash and comprises a pivoting
mechanism enabling the latter to pivot outwardly of the
window jambs. The window sash shoe is also slidably mounted
in the channel of the window jamb, such that the window sash
may move vertically. The curled ribbon spring applies an
upward force on the window sash via the shoe, for
facilitating the opening and the closing of the window sash.
If the amount of upward force required to
counterbalance the window sash is greater than what can be
provided by the curled ribbon spring in place, a few
possibilities are at hand to increase the force thereof. As
mentioned above, the width of the curled ribbon spring can
be increased, but only to a certain extent as the available
space within the channel is a limitation.
Because of the restricted space in the channels of
the window jambs, curled ribbon springs have been added in
series in window jamb channels rather than having an
increase in width to enhance the biasing force thereof. The
prior art system of the above referred-to patent discloses
slots and indentations on the tongue of the free end of the
first curled ribbon spring, whereby a second curled ribbon
spring can be attached thereto, for the afore-mentioned
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purpose. Furthermore, the first and second curled ribbon
springs are identical, whereby other curled ribbon springs
can be added in series.
However, it is found that adding either slots or
indentations weakens the ribbon spring. Furthermore, the
area comprising the slots or indentations is subject to a
greater stress as it serves as connections means and thus
sustains the biasing forces of the added curled ribbon
springs. This may result in the premature failure of the
curled ribbon spring. In this case, the repair is a lengthy
and inconvenient operation as it requires the removal of the
window sash. Furthermore, as the ribbon springs are in
series, the replacement of a broken ribbon spring may
require the removal of the ribbon springs connected thereto,
thereby extending the repair time.
It is also found that when using stacks of curled
ribbon springs that are interconnected as shown in the above
described prior art, the lowest curled ribbon spring does
not require to be as long as the highest one. This involves
keeping an inventory of different lengths of curled ribbon
springs for one size of window sash.
SUMMARY OF THE INVENTION
It is a feature of the present invention to
provide a balancing spring system for facilitating the
manual opening and closing of window sashes and
substantially overcoming the above mentioned disadvantages
of the prior art.
According to a broad aspect of the present
invention there is provided a balancing spring system for
facilitating the opening and the closing of a window sash
assembly slidably mounted in channels of opposed window
jambs, said balancing spring system comprising: a connector
strip having an elongated rectangular shape defining a front
surface and a rear surface, at least two slots formed in
said connector strip, each of said slots extending from said
front surface to said rear surface; said connector strip
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having a connecting head section at a bottom end thereof,
adapted for connection to a window sash; at least a first
and a second curled ribbon spring adapted to be mounted idle
and free to rotate in one of said channels of said window
jambs, said first and second curled ribbon spring each
having a connecting free end section, for releasably
connecting each of said first and second curled ribbon
spring to a respective one of said slots of said connector
strip, whereby said first and second curled ribbon springs
apply an upward force to said window sash assembly.
According to a still further broad aspect of the
present invention there is provided a connector strip
adapted for connecting a window sash assembly slidably
mounted in channels of opposed window jambs to a biasing
mechanism applying an upward force to said window sash
assembly, said connector strip having: an elongated
rectangular shape defining a front surface and a rear
surface; at least two slots in said connector strip, each of
said slots extending from said front surface to said rear
surface and adapted for releasable connection of said
connector strip to said biasing mechanism; said connector
strip having a connecting head section at a bottom thereof
adapted for connecting said connector strip to said window
sash assembly.
According to a still further broad aspect of the
present invention there is provided a balancing spring
system for facilitating the opening and the closing of a
window sash assembly slidably mounted in channels of opposed
window jambs, said balancing spring system comprising: a
connector strip having an elongated rectangular shape
defining a front surface and a rear surface, at least two
slots formed in said connector strip, each of said slots
extending from said front surface to said rear surface, the
slots being aligned with respect to one another in a
longitudinal vertical di_mension of the connector strip and
spaced by a given distance; said connector strip having a
connecting head section at a bottom end thereof, adapted for
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connection to a window sash; at least a first and a second
curled ribbon spring adapted to be mounted idle and free to
rotate in a vertical dimension of one of said channels of
said window jambs, the curled ribbon springs being generally
spaced by said given distance, the curled ribbon springs
each having a connecting free end section, for connecting
said curled ribbon spring to said slots of said connector
strip such that the curled ribbon springs have a same
length, whereby said first and second curled ribbon springs
apply an upward force to said window sash assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention
will now be described in detail having reference to the
accompanying drawings in which:
Fig. 1 is a schematic front elevational view,
partly fragmented, of a balancing spring system mounted to a
window sash assembly in accordance with the present
invention;
Fig. 2 is a perspective view of the balancing
spring system;
Fig. 3 is a front elevational view of a connector
strip in accordance with the present invention
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Fig. 4 is a side elevational view of the connector
strip; and
Fig. 5 is a perspective view of a spring cassette
in accordance with the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
According to the drawings and more particularly to
Figs. 1 and 2, a balancing spring system in accordance with
the present invention is generally shown at 10, Fig. 1
showing the location thereof in a window frame. The
balancing spring system is shown secured in a channel 1 to a
window jamb 2, and connected to a window sash shoe 3. The
shoe 3 is slidably mounted in the channel 1. A window
sash 4 comprises a frame member 5 and a glass 6. The
frame 5 is connected to the shoe 3 by a pivot 7, whereby the
window sash 4 translates vertically in response to the
sliding motion of the shoe 3 in the channel 1, as
demonstrated by arrow A. Still referring to Fig. 1, only
one balancing spring system 10 is shown, but the opposed
window jamb 2' also has a channel 1' holding an identical
balancing spring system (not shown). However, in some
applications, a single balancing system may be provided in
one of the channels.
As best shown in Fig. 2, the balancing spring
system 10 comprises a connector strip 11 and a plurality of
spring cassettes 12 (e.g. four cassettes) removably secured
to the connector spring 11. Referring now to Figs. 3-4, it
can be seen that the connector strip 11 is an elongated
rectangular strip having a front surface 13 and a rear
surface 14. An inverted T-shaped connector portion 15 is
located at a bottom end thereof, and comprises a throat
section 16 and a horizontal end section 17. The throat
section 16 is of narrowed width with respect to the width of
the connector strip 11.
The connector strip 11 further comprises pairs of
indentations 18a, 18b, 18c and 18d in the front surface 13
thereof, disposed on each side of a slot 20a, 20b, 20c and
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20d, respectively. The indentations 18a, 18b, 18c and 18d
are generally equally spaced apart therein, with the
indentation 18a being adjacent the bottom end of the
connector strip 11 and the indentation 18d adjacent a top
end thereof. Corresponding protrusions 19a, 19b, 19c and
19d are formed on the rear surface 14 as a result from the
indentations 18a, 18b, 18c, and 18d, respectively. The
slots 20 are generally rectangular-shaped and vertically
oriented on a central longitudinal axis of the connector
strip 11.
The connector strip 11 is adapted to be secured to
a window sash shoe, such as the shoe 3 of Fig. 1, by its
inverted T-shaped connector portion 15 being held captive
therein, as known in the art. The connector strip 11 will
thereafter be connected to spring cassettes 12, as will be
explained hereinafter.
Referring to Fig. 5, there is shown one of the
cassettes 12. The cassette 12 comprises a casing 25,
defined by a front wall 26, a rear wall 27, side walls 28
and 29, a top wall 30 and a bottom wall 31. A reel 32 of
curled ribbon spring 33 is enclosed in the casing 25. The
reel 32 of curled ribbon spring 33 is idle and free to
rotate within the casing 25. An opening 34 is defined in
the side wall 28. The opening 34 is sized such that a free
end 35 of the ribbon spring 33 can be displaced
therethrough. An inverted T-shape connector portion 36 is
located at the tip of the free end 35. The T-shape
connector portion 36 has a vertical throat section 40 and a
horizontal end section 41. The vertical throat section 40
is of narrowed width with respect to the width of the curled
ribbon spring 33.
A hole 37 is generally centered in the front
wall 26 of the cassette and extends through to the rear
wall 27 thereof. The hole 37 is bounded by a cylindrical
wall 38. A countersink 39 is located between the
cylindrical wall 38 and the front wall 26. The portion of
the cylindrical wall 38 within the casing 25 serves as a
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pivot for the reel 32 of curled ribbon spring 33.
Furthermore, the hole 37 and the countersink 39 are sized to
receive a fastening element therein, such as a screw.
Consequently, the spring cassette 12 can be fixedly mounted
to a window jamb, within a channel, as shown in Fig. 1.
Still referring to Fig. 5, the spring cassette 12
also comprises legs 42 downwardly projecting from the bottom
wall 31, and complementary grooves 43 in the top wall 30
thereof. As shown in Fig. 2, similar cassettes 12 can be
connected together one on another to form a stack. For
instance, the legs 42 of a cassette B are mounted in
complementary engagement with the grooves 43 of cassette A.
Although the curled ribbon spring 33 has been described as
being enclosed in a casing, it is readily understood that
the curled ribbon spring 33 may be mounted with a different
type of support to the channel of a window jamb.
According to the window sash weight, the available
space in the window jamb channels and the upward force
supplied by a cassette, the number of cassettes required for
the counterbalancing of the window sash is determined. For
instance, a stack of four cassettes 12 is shown in Fig. 2.
Once the stack of cassettes 12 is assembled, it is secured
in the channel alongside the window jamb, as schematically
shown in Fig. 1. As described above, fasteners such as
screws are used for this purpose. It is noted that the
stack of cassettes 12 is disposed above the top of the
window sash 4, such that the upward force thereof may be
supplied throughout the vertical displacement of the window
sash 4. Also, a connector strip 11 is fixedly mounted to
the shoe 3, as described previously.
When the connector strip 11 is mounted to the
shoe 3, and the stack of cassette 12 is secured within the
channel 1, the curled ribbon springs 33 of each cassette 12
of the stack is connected to the connector strip 11. As
best shown in Fig. 2, this is achieved by the inverted
T-shape connector portion 36 of the free end 35 of the
curled ribbon spring 33 being captively engaged in the slot
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20/indentation 18 configuration of the connector strip 11.
It is noted that the narrowed width of the vertical
member 40 of the T-shape connector portion 36 is generally
similar to the width of the slot 20 of the connector
strip 11, whereby the horizontal member 41 is abutted at
both its ends on either side of the slot 20. As shown in
Fig. 2, cassettes A, B, C and D are connected to the slots
20a, 20b, 20c and 20d, respectively. It is also noted that
the indentations 18a-18d allow for the horizontal members 41
of the curled ribbon spring 33 connected thereto to be
generally co-planar with the front surface 13 of the
connector strip 11, whereby optimizing the space
utilization. It is noted that other connection means may be
used to secure the free ends 35 of the curled ribbon springs
33 to the connector strip 11, such as corresponding hooks
and slots, fasteners or the like.
When the balancing spring system 10 is connected
to the window sash 4 on each side thereof, a portion of the
curled ribbon spring 33 is extended out of its cassette 12,
whereby it exerts an upward force on the window sash 4 as it
is biased to recurl. Thus, the window sash 4 is subject to
the constant upward force of the balancing spring system 10
connected thereto, whereby it remains idle in any vertical
position along the window jamb 2 as it is also subject to
the downward force of its weight. In consequence thereof,
only a slight amount of force needs to be applied to
displace the window sash 4 vertically upon the window
jamb 2.
As the connector strip 11 need not be resilient
materials, it may be comprised of a strong or reinforced
rigid materials, whereby it can sustain stress for longer
periods and thus be more durable. Accordingly, the
attachment between the cassettes and the sash is much
stronger with the use of the connector strip than the prior
art systems and the curled ribbon springs 33 are not
weakened at their connecting point as is the case with some
of the prior art, as discussed herein. Furthermore, the
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curled ribbon springs 33 of the stack of cassettes 12 are
independently connected to the connector strip 11, whereby
they can individually be replaced in the event of a ribbon
spring failure. The distance between the slots 20 of the
connector strip 11 is generally equivalent to the distance
between the curled ribbon springs 33. This ensures that the
curled ribbon springs 33 can all be of the same length,
whereby the need to keep an inventory of various lengths of
curled ribbon spring for one size of window sash is
eliminated.
It is within the ambit of the present invention to
cover any obvious modifications of the embodiments described
herein, provided such modifications fall within the scope of
the appended claims.
