Note: Descriptions are shown in the official language in which they were submitted.
W093/03250 2 ~ ~ ~ 3 ~ ~ PCT/US92/0612S
--1--
MONOCONTROL V~'N~'l'lAN BLIND
Bac~Loulld to the Invention and Prior Art
Our invention relates to venetian blinds, and, more
part:icularly to monocontrol venetian blinds that use the
same=operating control both for controlling the tilting of
the ~.lats, and for raising and lowering the blind.
The headrail me~h~n;~cm of a venetian blind must provide
for t:wo operations; first, lifting and lowering the blind,
and second, controllably tilting the slats to open or close
the blind or set the slats at any desired angle. The ideal
monocontrol headrail me~h~n;s~ would require low operating
effort, even when lifting heavy and long blinds. It would
provi.de for accumulating the lift cords or tapes within a
relat:ively small headrail. It would have a tilt mechanism
capable of providing good closure. And finally, it would
contain a minimum of parts and be easy to assemble and
require a minimum of adjustment.
The prior art does contain a number of designs for
monoaontrol Venetian blinds. Some of them do not tilt
sufficiently to provide good closure. Many of them use a
large number of complex parts and are difficult to adjust.
The prior art reveals two general methods for accumu-
lating lift cords or tapes within a Venetian blind headrail.
One method is to wind the lift cords or tapes onto spools.
This method suffers the two disadvantages. One disadvantage
is that the cords or tapes do not wind evenly onto their
respective spools, and very slight differences in diameter
produce easily noticeable unevenness in the blind as it is
raised. The other disadvantage is that the mechanical
advantage of the lift meçh~n;c~ decreases as the diameter of
the accumulated cord or tape increases on the spools. this
progressive decrease in mech~n;cal advantage occurs as the
lift cords support more of the blind's weight, causing a
large increase in the effort required to further lift the
W093/03250 2 U ~ 2 3 ~ ~ PCT/US92/06125
blind. The m~c-hAnical advantage decreases just when it
should increase.
The other, and preferred method is to accumulate the
cords onto a shaft that moves laterally, or traverses, so
that the lift cords wind in a single layer onto the shaft.
This insures even winding of each of the lift~cords, and it
maintains a constant me~hAn;cal advantage so that the lift-
ing effort increases only in proportion to thè weight sup-
ported by the lift cords. Several methods ~ave been used to
produce the traversing of the rod. A rack~and gear arrange-
ment has been used. U.S. Patent No. l,343,527 reveals a
lead screw and nut to accomplish the traversing. Another
method, one that is free of any gears or leadscrews, is
revealed in U.S. Patent No. 4,625,012 in which the lift
cords, acting on cam features of their supporting cradles,
produce the lateral forces to traverse the rod. Although,
this method is presently used in a variety of blinds that
lift from the bottom, it was not believed that the method
could work with Venetian blinds because it was expected that
the weight of the blinds hanging on the tilters would add so
much frictional drag that the rod would not traverse proper-
ly.
The headrail m~chAn;~m must also provide for tilting
the slats of a Venetian blind. In a monocontrol blind that
employs a traversing rod on which to accumulate the lift
cords, the tilt mech~ni~ must rotate in either direction
along with the traversing rod until the position for full
closure is reached. Thereafter, the tilt ~Pc-hAn;sm must
slip, maintA;ni~g its position, while the blind is raised or
lowered. In a traversing rod monocontrol Venetian blind,
the drive shaft for the tilt ~echAnism is the traversing
rod. The ladder cords are attached to the tilter mechanism.
Generally, in a monocontrol blind, there will be one tilter
m~chAn;~m for each ladder cord in the blind. The best
tilting results if the ladder cords are attached to the
tilter at a separation equal to the width of the slats.
W093/03250 ~-y~ PCT/US92/06125
Furthermore, a line between these attachment points should
pass through the centerline of the traversing rod. This
will keep the tilter at the same angle as the slats. If
this geometric relationship is not maintained, then it will
be necessAry for the tilt mPchAn;sm to be capable of lifting
the hlind if full closure is to be achieved.
In a Venetian blind having separate lift and tilt
mech~ln;cms, there is no difficulty in providing a tilt
~e~h~n;sm capable of lifting the weight of the entire blind.
However, in a traversing rod monocontrol blind, the travers-
ing rod must drive both the tilt and the lift mechanisms.
When the fully tilted position is reached, the tilt mecha-
nism must partially disengage and slip, providing, thereaf-
ter, sufficient tbrque to maintain full tilt as the rod
continues to rotate for lifting or lowering the blind.
Whatever force is needed to maintain full tilt is added to
the effort required to lift the blind. This force will be
minimum if, (a) the tilter geometry is as described above,
and (b) if the tilter mechAn;sm is capable of adjusting its
grip on the traversing rod to provide only that amount of
torque needed to maintain full tilt. Furthermore, the
smaller the separation of the two sides of the ladder cords
at full tilt, the better the closure will be. This last
requirement will be best satisfied if the tilters are mount-
ed directly on the traversing rod. Any intermediate partbetween the tilters and the rod will increase the separation
of the ladder cords at full tilt. U.S. Patent No. 4,697,630
reveals a tilter mechAn;~ which has good gripping torque
between extremes of tilt while partially releasing its grip
when full tilt is reached. This tilter is made in the form
of a Nultiturn helical band clutch which grips the travers-
ing rod during tilting. When the position for full tilt has
been reached, the leading end of the tilter contacts a stop
which prevents further movement of the tilter and partially
releases the grip of the tilter on the rod, thereby limiting
the frictional drag of the tilters on the rod to just that
W093/03250 ~9 2 3 0 0 PCT/US92/06125
amount of torque required to maintain the fully tilted
condition of the blind. The rod can continue to rotate,
winding or unwinding the lift cords to raise or lower the
blind according to the direction in which the rod is being
rotated.
U.S. Patent Numbers 2,737,235, 2,758,644, and
3,352,349, describe prior art monocontrol ~enetian blinds
that employ a variety of traversing rod iift mechanisms. In
order to achieve traversing in each of the prior art blinds
it is necessary to overcome all of the frictional force due
to the weight of the blind acting on the traversing rod.
The grip of the tilt ~ch~ni cr on the traversing rod must be
sufficient to ensure complete closure. And, of course, both
the tilt force and the drag on the rod must be overcome to
cause the rod to traverse. These frictional forces are
large enough to make these blinds very difficult to operate.
It is, therefore, not surprising that Venetian blinds using
this type of mechAn;c~ have never been popular.
Summary of the Invention
The desirable characteristics of the helical band
tilter of U.S. Patent No. 4,696,630 can be combined with the
traversing rod system according to U.S. Patent No. 4,623,012
to produce a Venetian blind that has monocontrol operation
and accumulates the lift cords within the headrail. This
combination has been tried and found to be unsatisfactory
because the tilters impose so much frictional drag on the
traversing rod that it does not traverse reliably. Our
invention consists in providing a novel bearing arrangement
that removes much of this frictional drag. In the preferred
embodiment, the band clutch of U.S. Patent No. 4,697,630 is
modified so that the tilter is supported directly by the
cradle rather than by the traversing rod. This greatly
reduces the frictional forces on the traversing rod which
improves the reliability of operation. The blind has good
3S closure, and yet it is easy to raise and lower. It has a
small number of parts and is easy to assemble and adjust.
W093/032~0 2 ~ ~ 2 3 0 0 PCT/US92/06125
The inventive combination has the advantages of both the
tilting mec-h~n;sm and the lifting mechAn;sr without the
prob:Lem of sliding the rod against large frictional forces
found in prior art blinds.
The use of the helical wrap band clutch tilter is
cruc.ial because it alone, among the various know methods for
driving the tilters in a monocontrol blind, is capable of
providing large friction when needed during tilting, while
controlling the frictional forces between the tilters and
the t:raversing rod to the ~;ni~ amount needed to maintain
full tilt. Other methods that employ a predetermined fric-
tional connection between the rod and the tilter must, due
to thLe variability of frictional forces, provide an excess
of frictional force to ensure good closure of the blind.
This extra force adds undesirably to the effor~ of operating
the blind. U.S. Patent No. 3,352,349 reveals a monocontrol
Venetian blind using a traversing rod and a tilter which
frictionally grips the traversing rod. Lift cord carrier 15
is "arranged in a slightly clamping manner" on operating
shaft 2. But experience has shown that the tilter must grip
the operating shaft tightly during tilting to provide good
closure of the blind, and the friction from this tight grip
will require the exertion of large forces by the traversing
mec~Al~;sm to cause the shaft to slide.
rn a fully extended Venetian blind, the ladder cords
suppo:rt the entire weight. As the blind is raised, weight
is transferred to the lift cords. When the blind is fully
raised, virtually the entire weight of the slat pack and the
bottom rail are supported by the lift cords. The ladder
cords are attached to the tilters, so whatever supports the
tilters must also support the weight of the extended portion
of the blind. The normal forces between the tilters and
their supports, and the resulting friction caused thereby,
can make traversing difficult when the blind nears full
extension. At that time the tilters are supporting most of
the weight, producing maximum friction, and the tension in
W093/03250 2 0 9 2 3 ~ ~ PCT/US92/06125~
the lift cords, which is needed to produce the traversing
motion, is at its m;~ value.
It is surprising that it is possible to produce suffic-
ient tilt drive without burdening the traversing mechanism
with so much friction that traversing fails. The reason
that it is possible can be understood as f~llows. The force
needed to produce relative motion between ~two fictionally
coupled objects is greater if only that ~f~orce is active than
it is if another force is also causing m~tion, even if that
motion is in a different direction. For instance, referring
to FIG. 1, the force, Fl, needed to slide an object of
weight W across a horizontal surface equals uW, where u is
the coefficient of friction between the object and the
surface. But if the object is moving under the action of
two perpendicular forces, Fl and F2, then it is the vector
sum of Fl and F2 that equals uW, and as seen in FIG. 2, in
which A is the angle between F2 and the actual direction of
motion. In this situation, both Fl and F2 are smaller than
uW and, if the angle A is small, Fl will be far smaller than
uW.
In our case, F2 corresponds to the force causing the
rod to rotate, which forces it to slip within the tilter,
and Fl corresponds to the force required to cause the rod to
traverse. In a typical embodiment of our invention, we have
use a rod of 0.375" diameter, and lift cords of about 0.040"
diameter. Since the rod rotates one complete revolution
while traversing only a distance equal to the thickness of
the cord, the surface motion in the rotational direction is
about 30 times the motion in the traversing direction,
30 making the angle A quite small, somewhat less than 2 de-
grees. In this case, the force, F2, which causes the rota-
tional motion does most of the work against friction, and Fl
is only about 3% of what it would have to be to cause the v
traversing motion in the absence of F2. In a blind having
35 an intermediate piece between the tilter and the drum, the
full amount of work must be done at both interfaces, between
W093/032~0 21 Q 9 2 ~ O ~ PCT/US92/06125
the t:ilter and the drum, and between the drum and the rod.
As the entire amount of work must be provided by the opera-
tor ~f the blind, this considerably increases the effort
required to operate the blind.
It has been found neceCc?ry~ in very long blinds that
use the tilter of U.S. Patent No. 4,697,630, to add weight
to the bottom rail to insure that the traversing rod returns
fully to its starting position. In the preferred embodiment
of our invention great improvement is achieved by modifying
the tilter and cradle so that the tilter is supported di-
rectly by a bearing surface on the cradle rather than by the
traversing rod. The improved performance comes from the
reduction in formal forces between the rod and the tilters.
This greatly reduces the force needed to traverse the rod.
In the earlier system, the force required to cause travers-
ing increased just as the force available to cause travers-
ing was decreasing. In this, preferred embodiment while the
force available to cause traversing still decreases as the
blind is lowered, the frictional force impeding the travers-
ing motion of the rod r~;n~ constant and small.
~ccordingly, it is an object of our invention to pro-
vide a monocontrol lift and tilt mechanism for a Venetian
blind that requires minimal effort to operate and which
maintains constant mechanical advantage during lifting.
It is another object of our invention to provide a
monocontrol lift and tilt m~ch~n;-c~ for a Venetian blind
with low operating effort in lifting heavy and long blinds.
It is a further object of our invention to provide a
monocontrol lift and tilt mech~nism for Venetian blinds
which can lift long blinds in a relatively small headrail.
i~nother object of our invention is to provide a monoc-
ontro:L lift and tilt ~ech~nisr for Venetian blinds which can
exert enough torque to ensure good closure.
~ further object of our invention is to provide a
monocontrol lift and til~ r?ch~n;cr for Venetian blinds
W093/03250 2 ~ 9 2 3 0 0 PCT/US92/06125 ~
which permits the close alignment of the ladder cords at the
positions of full tilt.
Still another object of our invention is to provide a
monocontrol lift and tilt mechAn;cm for Venetian blinds in
which the entire torque required for tilting does not have
to be reacted during raising of the blind~
Yet a further object of our invention is to provide a
monocontrol lift and tilt meçhAn;sm for~Venetian blinds
having a minimum of component parts and which can be easily
assembled and adjusted for proper operation.
~rief Description of the Drawinqs
Further object, features and advantages of our inven-
tion will become apparent upon consideration of the follow-
ing detailed description in conjunction with the drawings,
in which:
FIG. l is a vector diagram of the force Fl, equal to uW
in this situation, needed to cause traversing in the absence
of other motion;
FIG. 2 is a vector diagram of the forces Fl and F2 and
their resultant uW, where Fl, now much smaller than uW, is
the force needed to cause traversing in the presence of
other motion at the same interface;
FIG. 3 is an isometric view of a Venetian blind headr-
ail that has been cut away to reveal the parts within;
FIG. 4 is an enlarged view of a portion of the mecha-
nism of FIG. 3 to better show the detail of the lifting and
tilting parts and the inventive feature of the preferred
embodiment of our invention;
FIG. 5 is an enlarged side elevation and partial cross-
sectional view according to the prior art of a lift tilt
mechanism at one of the lift points, showing a tilter, the
traversing rod and a cradle;
FIG. 6 is a similar of the same components, in this
case, showing the tilter supported by the cradle according
to the principles of our invention;
W093/03250 2 0 9 2 3 0 ~ PCT/US92/06125
FIG. 7 is a view of the same components as in FIG. 5
but shown during lifting of the blind and, thus, with the
tilter rotated 90 degrees; and
FIG. 8 is an enlarged side elevation and partial cross-
sectional view of another embodiment of our invention thatemploys a spool with either cord or tape for lifting the
blind.
Detailed Descrition of the ~rawings
The general organization of the lift system within the
headrail can be seen in FIG. 3. Headrail 1 can be of any
convenient cross-sectional shape having sufficient interior
space to accommodate the hardware. Holding mechanism 3,
which could be any of a wide variety of devices, is prefera-
bly mounted at an end of headrail 1, although other place-
ments are possible. Some appropriate operating means isneeded for operating holding mechanism 3. In this case cord
loop 5 is shown, although any of a number of other combina-
tions of holding mechAni~m and operating means might be used
instead. Splines 7 are attached to the output of holding
mechAn; 3. Splines 7 together with disk 9 which is at-
tached to traversing rod 11 form an axially slidable torque
carrying connection between holding mechAn;~r 3 and tra-
versing rod 11. The particular spline and disk arrangement
shown here for making the connecting to the holding mecha-
nism is intended only as an example, and other means foraccom;plishing the connection may be used without deviating
from the intent and purpose of our invention.
The remaining parts within the headrail are associated
with the attachment, control, and operation of lift cord 13
and ladder cord 15. One such set would, ordinarily, be
provided for each set of lift and ladder cords. The identi-
fication of parts, forces, and descriptions of operation are
- made for one set of these lift and tilt components, and are
intended to apply to the other sets as well. In some
blinds, a partial set of components may be used in one or
more locations. For instance, blinds often have three
W093/03250 2 ~ ~ 2 ~ O ~ PCT/US92/0612 ~
1 0
ladder cords but only two lift cords. This is done when two
lift cords are sufficient to lift the blind, but a central
ladder cord is still needed for proper support of the slats.
In such cases, the operation of the blind r~; n~ the same
as it relates to the components in the incomplete set.
Cradle 17 and tilter 19 are arranged generally in
accordance with the principles of U.S. Patent No. 4,697,630.
Each of the side of ladder cord 15 is attached to one of the
two arms 21 of tilter 19 as best seen in FIG. 4. Lift cord
13 is arranged generally in accordance with the principles
of U.S. Patent No. 4,623,012, entering the headrail through
a hold in the bottom of the rail, passing over roller 23,
seen in FIG. 5, and terminating in its attachment to rod 11
by means of clip 25 or by any other suitable means.
FIG. 5 shows the prior art combination of a traversing
rod lift system according to the principles of U.S. Patent
No. 4,623,012 with a helical band tilter according to the
principles of U.S. Patent No. 4,697,630. Traversing rod 27
is supported directly by cradle 29 whose bearing surface 31
is shaped to accept rod 27. Tilter 33 is disposed about and
entirely supported by rod 27.
FIG. 6 shows the tilt and lift components of our inven-
tion with the slats in a horizontal position. In this view,
arms 21, shown in FIG. 4, but omitted from FIG. 5 for clari-
ty, would lie in the horizontal plane passing through thecenter of rod 35. Tilter 37 is wrapped about rod 35 as in
the earlier embodiment, but in this case the tilter has be-
aring 39 which is supported at bearing surface 41 on cradle
43. Flange 45 at the end of tilter 37 forms a retaining
barrier to prevent axial movement of tilter 37 in relation
to cradle 43 along rod 35. The outer surface of flange 45
is angled to form-c~m;ng surface 47 according to the prin-
ciples of U.S. Patent No. 4,623,012. The angle is shown in
FIG. 6 as angle A. The desirable size of angle A depends
upon the ratio of the diameter of lift cord 47 to the diame-
ter of the rod. Sufficient movement must be produced by the
W093/03250 2 ~ 9 2 3 0 ~ PCT/US92/06125
--11--
camming action to provide space for the incoming cord so
that it will not override the previous turns. When the
blind is fully lowered and most of the weight is hanging
from the blind's several ladder cords, then very little of
the blind's weight is supported at the surface between rod
35 and tilter 37. Instead, most of the weight is supported
at bearing surface 41 between cradle 35 and tilter 37. This
reduc:tion of frictional force between the tilter and the
trave.rsing rod allows the rod to be moved-much more easily.
With this improved bearing support for tilter 37, much less
tension in lift cord 49 is needed to insure the complete
return of traversing rod 35 to its starting position as the
blind is fully lowered.
FIG. 7 shows the same components as shown in FIG. 6 but
during lifting of the blind. Lift cord 49, as it is wound
onto rod 35, contacts camming surface 47, forcing rod 35 to
traverse to the left, away from the c~mm; ng surface. Tilter
37 is fully rotated to the limit permitted by stop 51 which
loosens the grip of tilter 36 on rod 35, retaining only
sufficient grip to maintain its orientation. In this posi-
tion, arms 53 are roughly vertical, and the ladder cords, of
which only the near one, ladder cord 55 is visible, are in
the fully tilted position.
The r~ch~nicm of U.S. Patent No. 4,632,012 has no
tilter. The camming surface is formed as a part of the
cradle. In our invention, the cord comes into contact with
the tilter flange. Therefore it is necessary to incorporate
the camming surface onto this flange. One of the features
of our inventive blind is that it can be raised by rotating
the rod in either direction. This requires that the camming
surface be on the right side when the blind is being lifted
by ccunterclockwise rotation of the rod, and on the left for
- the cpposite rotation. When the blind is being raised, the
tilter rotates 90 degrees in the direction of the rod's
rotation. This orients camming surface 47 properly for that
winding direction of the lift cord. The c7mming action
W093/03250 2 0 9 2 3 0 0 PCT/US92/06125~
takes place in about a one hundred and twenty degree arc
between the point where the cord first contacts the shaft
and the top of the shaft. When tilter 37 is horizontal, as
seen in FIG. 6, camming surface 47 occupies the lower por-
tion of flange 45. As the tilter r~tates 90 degrees one wayor the other, the camming surface rotates into the required
orientation.
In another embodiment of our invention, tilters are
also supported directly by the cradles rather than by the
operating rod which, in this case does not traverse, but
simply rotates. In this type of monocontrol blind, lifting
is accomplished by winding the tape or cord onto spools.
Although there is no traversing rod in this type of blind,
the reduction of operating friction remains a serious issue
to which great amounts of effort have been directed, even to
the extent that production tooling has been replaced several
times to achieve small improvements in the operating "feel"
of blinds made with this hardware. FIG. 8 show the lifting
and tilting components for this embodiment that correspond
to the components of the preferred embodiment shown in FIGS.
5 and 6. Rod 57 has tilter 59 disposed thereabout. Tilter
59 has be~ring groove 61 which rotates on and is supported
by bearing surface 63 of cradle 65. Cradle 65 is similar to
cradle 37 of the preferred embodiment except that in place
of a roller to guide a lift cord, it has a slot 67 to guide
cord or tape 69 onto spool 71. Since there is no traversing
of the rod in this case, spool 71 is firmly attached to rod
57 so as to rotate with it. As before, tilter 59 must
rotate with rod 57 until reaching its stop. Thereafter, it
must remain in position, maintaining full tilt, while rod 57
continues to rotate within it to raise or lower the blind.
The control of friction is important in this case to insure
that there be sufficient grip of the tilter on rod 57 to
produce full tilt. But any additional frictional drag
between these parts will simply add to the effort of operat-
ing the blind. A significant savings in operating effort is
W093/032S0 2 ~ O ~ PCT/US92/06125
~ ' ' :
-13-
obtained by shifting the support load from rod 57 to bearing
surface 63 of cradle 65. Because in this embodiment the rod
does not traverse, there is no requirement for a c~mm;ng
surface, and flange 73 of tilter 59 can have an exterior
surf.ace normal to the axis of rod 57.
It will thus be seen that the objects set forth above
among those made apparent from the prec~;ng description,
are efficiently attained and, since certain changes may be
made in the construction of the inventive spring clutch
without departing from the spirit and scope of the inven-
tion, it is intended that all matter contained in the above
description or shown in the accompanying drawings shall be
interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims
are :intended to cover all of the generic and specific fea-
tures of the invention herein described and all statements
of the scope of the invention which, as a matter of lan-
guage, might be said to fall therebetween.
