Spring system for roller blinds
A roller blind including a roller of having a roller length and a roller outer diameter, a fabric attached to said roller for winding and unwinding from said roller. The fabric has a fabric length, a fabric weight, a fabric height, and fabric thickness. The blind includes a bottom bar having a bottom bar weight, and at least one spring operatively connected to the roller to drivingly rotate the roller in at least one direction of rotation. The spring is selected according to a Protocol such that it's length ensures that it drives the roller with a constant operating force.
1. A roller blind comprising
a roller;
a fabric attached to the roller for winding about and unwinding from the roller;
a stationary shaft extending inside the roller;
at least one helically wound torsion spring arranged about the stationary shaft and operatively connected to the roller to drivingly rotate the roller in at least one direction of rotation; and
an electric motor coupled to an end of the stationary shaft for drivingly rotating the roller in combination with the at least one spring, the motor having an output shaft on an end of the motor remote from the stationary shaft.
2. The roller blind of claim 1 , wherein the at least one spring is selected according to a Protocol such that a length of the at least one spring ensures that the blind operates with a constant operating force.
3. The roller blind of claim 2 , wherein the length of the at least one spring is determined based on pre-selected wire and spring diameters.
4. The roller blind of claim 2 , wherein the at least one spring comprises at least two springs each having identical lengths and wherein the springs are selected according to the Protocol and which springs in combination drive the roller with the constant operating force.
5. The roller blind of claim 2 , wherein the at least one spring comprises at least two springs each having different lengths, the at least two springs are selected according to the Protocol, and the at least two springs in combination drive the roller with constant operating force.
6. The roller blind of claims 1 , 2 , or 3 , wherein the at least one spring comprises at least two springs having identical wire diameters and/or spring diameters.
7. The roller blind of claims 1 , 2 , or 3 , wherein the at least one spring comprises at least two springs having different wire diameters and/or spring diameters.
8. The roller blind of claim 2 , further comprising a bottom bar attached to a lower edge of the fabric, and wherein:
the roller has a roller length and a roller outer diameter;
the fabric has a fabric length, a fabric weight, a fabric height, and a fabric thickness;
the bottom bar has a bottom bar weight; and
the Protocol according to which the at least one spring is selected includes at least formula 1 as follows:
M
=
⌈
(
4
×
h
st
×
t
st
π
+
d
we
2
-
d
we
2
×
t
st
+
4
×
h
st
×
t
st
π
+
d
we
2
×
b
st
×
G
ul
×
(
4
×
h
st
×
t
st
π
+
d
we
2
-
d
we
)
[
d
we
×
b
st
×
(
G
ul
+
h
st
×
G
st
)
-
4
×
h
st
×
t
st
π
+
d
we
2
×
b
st
×
G
ul
]
×
2
×
t
st
)
×
[
d
we
×
b
st
×
(
G
ul
+
h
st
×
G
st
)
-
4
×
h
st
×
t
st
π
+
d
we
2
×
b
st
×
G
ul
]
×
t
st
4
×
h
st
×
t
st
π
+
d
we
2
-
d
we
Md
0
Fe
×
n
0
Fe
⌉
in which formula 1:
M=number of springs in the roller blind
d we =outer diameter of the roller
h st =height of the fabric sheet
b st =width of the fabric sheet
t st =thickness of the fabric sheet
G st =Weight of the fabric sheet
G ul =Weight of the bottom rail
Md0 Fe =assumed torque increase of the spring w.r.t. its length LK0 Fe
n0 Fe =maximum number of rotations for LK0 Fe .
9. The roller blind of claim 2 , further comprising a bottom bar attached to a lower edge of the fabric, and wherein:
the roller has a roller length and a roller outer diameter;
the fabric has a fabric length, a fabric weight, a fabric height, and a fabric thickness;
the bottom bar has a bottom bar weight; and
the Protocol according to which the at least one spring is selected includes at least formula 2 as follows:
LK
1
Fe
=
LK
0
Fe
×
Md
0
Fe
×
M
×
(
4
×
h
st
×
t
st
π
+
d
we
2
-
d
we
)
[
d
we
×
b
st
×
(
G
ul
+
h
st
×
G
st
)
-
4
×
h
st
×
t
st
π
+
d
we
2
×
b
st
×
G
ul
]
×
t
st
in which Formula 2:
M=number of springs in the roller blind
d we =outer diameter of the roller
h st =height of the fabric sheet
b st =width of the fabric sheet
t st =thickness of the fabric sheet
G st =Weight of the fabric sheet
G ul =Weight of the bottom rail
Md0 Fe =assumed torque increase of the spring w.r.t. its length LK0 Fe
LK0 Fe =assumed spring length w.r.t. to Md0 Fe
LK1 Fe =calculated spring length adapted to the roller blind
n0 Fe =maximum number of rotations for LK0 Fe
n1 Fesp =number of rotations as pre-tension of the blind in the lifted position.
10. The roller blind of claim 1 , further including a spring assist module holding the at least one spring, the module including a stationary carrier and at least one rotatable member keyed to the roller such that rotation of the roller rotates the rotatable member,
the at least one spring having a first end operatively coupled to the stationary carrier and a second end operatively coupled to the at least one rotatable member, whereby in use upon rotation of the at least one rotatable member in one direction of rotation, kinetic energy is stored by the at least one spring from the at least one rotatable member, and upon rotation of the at least one rotatable member in an opposite direction of rotation, the kinetic energy stored by the at least one spring is released to the at least one rotatable member, and wherein the spring assist module is pre-assembled as a self-contained unit.
11. The roller blind of claim 10 , wherein the stationary carrier includes the stationary shaft.
12. The roller blind of claim 11 , wherein the stationary has a continuous unround profile.
13. The roller blind of claim 11 , wherein the at least one spring concentrically surrounds the stationary shaft.
14. The roller blind of claim 10 , wherein the at least one rotatable member includes a radially extending flange having a circumferentially shaped contour for engaging a mating formation on the roller of the roller blind.
15. The roller blind of claim 10 , wherein the stationary carrier has a connector on each axial end for keeping the stationary carrier stationary with respect to the roller blind with which the spring assist module is adapted to cooperate.
16. The roller blind of claim 15 , wherein the connectors on either axial end of the stationary carrier maintain the integrity of the spring assist module as a self-contained unit.
17. The roller blind of claim 1 , further comprising an electrical lead wire for powering the electric motor, wherein the stationary shaft has a hollow interior, and wherein the electrical lead wire extends through the hollow interior of the stationary shaft.
18. The roller blind of claim 1 , wherein the motor is axially spaced from the at least one spring.
19. The roller blind of claim 1 , wherein the motor is positioned within the at least one spring.
20. The roller blind of claim 1 , further comprising a rotatable member keyed to the roller, and wherein the output shaft of the motor engages the rotatable member.
21. The roller blind of claim 20 , wherein the at least one spring extends axially over the motor and engages the rotatable member.
22. The roller blind of claim 21 , wherein the at least one spring engages a perimeter surface of the rotatable member.
23. The roller blind of claim 10 , wherein the motor is housed within the spring assist module.
24. The roller blind of claim 10 , wherein the motor is positioned adjacent the spring assist module.