Balanced spring-loaded roller blind, and a torsion spring, a method, and a system therefor

1. A method of making a roller blind for selectively covering a window having a known height thereof, the method comprising:

providing a cylindrical rotatable roller;

mounting a sheet to the roller for being rolled thereon and unrolled therefrom during rotation of the roller between a first position at which the sheet is fully rolled about the roller and a second position wherein a hanging portion of the sheet hangs from the roller in order to fully cover the window height, the sheet comprising a rolled portion thereof that is rolled about the roller between the first and second positions thereby defining a roll with the roller, the roll defining a lateral circular profile defining a roll radius that varies in diameter between the first and second positions, wherein the hanging portion of the sheet comprises a varying weight thereof between the first and second positions;

mounting a torsion assembly to the roller, the torsion assembly comprising a rotatable torsion spring fitted within the roller for being rotated thereby during rolling and unrolling movement of the sheet between the first and second positions to provide a spring force in a direction opposite the rotational direction of the roller from the first to the second positions, wherein the blind provides a blind force on the spring that is a function of the varying weight of the sheet hanging portion multiplied by the varying radius of the roll between the first and second positions;

determining the weight of a strip of the sheet that is unrolled from the roll at a one radian rotation of the roller, wherein the weight of the strip comprises a numerical value; and

providing for the spring to have a spring constant thereof that has a numerical value equal to the numerical value of the weight of the strip at the one radian rotation between the first and second positions thereby providing for the blind force to be equal to the spring force between the first and second positions thereby balancing the roller blind.

2. A method according to claim 1 , wherein the step of determining the weight of a strip of the sheet that is unrolled from the roll at a one radian rotation of the roller comprises multiplying a surface area of the strip by the weight per square inch of the sheet.

3. A method according claim 2 , wherein the surface area of the strip is provided by the width of the sheet multiplied by a radius average of the varying radius.

4. A method according to claim 3 , wherein the average radius is determined by an equation comprising:

Ravg

=

R

⁢

t

+

R

⁢

max

2

wherein, Rt is the radius of the roller,

wherein Rmax is the maximum radius of the roll at the first position.

5. A method according to claim 4 , wherein the Rmax is determined by an equation comprising:

R max=√{square root over (RLSA/π)}

wherein RLSA is the surface area of the lateral circular profile.

6. A method according to claim 1 , wherein the varying radius of the roll between the first and second positions is provided in the form of a radius average.

7. A method according to claim 1 , wherein providing for the spring to have a spring constant thereof that has a numerical value equal to the numerical value of the weight of the strip at the one radian rotation between the first and second positions comprises modifying the spring.

8. A method according to claim 7 , wherein the spring before modification thereof comprises a given initial spring constant thereof and a given initial length thereof, wherein modification of the spring comprises shortening the initial length of the spring by a proportion that is equal to the provided spring constant divided by the initial spring constant, wherein the initial length is divided by the proportion to provide the modified length, wherein the modified length provides the spring constant that has the numerical value equal to the numerical value of the weight of the strip at the one radian rotation between the first and second positions.

9. A roller blind obtained by the method of claim 1 .

10. A roller blind comprising for a window having a known height, the roller blind comprising:

a cylindrical rotatable roller;

a sheet mounted to the roller for being rolled thereon and unrolled therefrom during rotation of the roller between a first position at which the sheet is fully rolled about the roller and a second position wherein a hanging portion of the sheet hangs from the roller in order to fully cover the window height, the sheet comprising a rolled portion thereof that is rolled about the roller between the first and second positions thereby defining a roll with the roller, the roll defining a lateral circular profile defining a roll radius that varies in diameter between the first and second positions, wherein the hanging portion of the sheet comprises a varying weight thereof between the first and second positions; and

a torsion assembly mounted to the roller, the torsion assembly comprising a rotatable torsion spring fitted within the roller for being rotated thereby during rolling and unrolling movement of the sheet between the first and second positions to provide a spring force in a direction opposite the rotational direction of the roller from the first to the second positions, wherein the blind provides a blind force on the spring that is a function of the varying weight of the sheet hanging portion multiplied by the varying radius of the roll between the first and second positions,

wherein a strip of the sheet that is unrolled from the roll at a one radian rotation of the roller has a given weight thereof comprising a numerical value, the spring having a spring constant thereof that has a numerical value equal to the numerical value of the weight of the strip at the one radian rotation between the first and second positions thereby providing for the blind force to be equal to the spring force between the first and second positions thereby balancing the roller blind.

11. A method for modifying a torsion spring to be used in a roller blind so as to balance the roller blind, the roller blind comprising: cylindrical rotatable roller, a sheet mounted to the roller for being rolled thereon and unrolled therefrom during rotation of the roller between a first position at which the sheet is fully rolled about the roller and a second position wherein a hanging portion of the sheet hangs from the roller in order to fully cover the window height, the sheet comprising a rolled portion thereof that is rolled about the roller between the first and second positions thereby defining a roll with the roller, the roll defining a lateral circular profile defining a roll radius that varies in diameter between the first and second positions, wherein the hanging portion of the sheet comprises a varying weight thereof between the first and second positions; and a torsion assembly mounted to the roller, the torsion assembly providing for receiving the torsion spring to be fitted within the roller for being rotated thereby during rolling and unrolling movement of the sheet between the first and second positions to provide a spring force in a direction opposite the rotational direction of the roller from the first to the second positions, wherein the blind provides a blind force on the torsion spring that is a function of the varying weight of the sheet hanging portion multiplied by the varying radius of the roll between the first and second positions, the method comprising:

determining the weight of a strip of the sheet that is unrolled from the roll at a one radian rotation of the roller, wherein the weight of the strip comprises a numerical value;

modifying the torsion spring so as to provide for the spring to have a spring constant thereof that has a numerical value equal to the numerical value of the weight of the strip at the one radian rotation between the first and second positions comprises modifying the spring, wherein the spring before modification thereof comprises a given initial spring constant thereof and a given initial length thereof, wherein modification of the spring comprises shortening the initial length of the spring by a proportion that is equal to the provided spring constant divided by the initial spring constant, wherein the initial length is divided by the proportion to provide the modified length, wherein the modified length provides the spring constant that has the numerical value equal to the numerical value of the weight of the strip at the one radian rotation between the first and second positions.

12. A torsion spring obtained by the method of claim 11 .

13. A kit for providing users to manufacture a roller blind for selectively covering a window having a known height thereof, the kit comprising a set of rules to follow in accordance with the method of claim 1 .

14. A kit for providing users to modify a torsion spring, the kit comprising a set of steps to follow in accordance with the method of claim 1 .

15. A computer implemented system for determining a spring constant required for a torsion spring of a roller blind for a window having a height in order to balance the roller blind, the roller blind comprising a roller and a sheet mounted thereto, the system comprising:

a controller having an associated memory of a processor executable code;

a client interface device in communication with the controller for providing client inputs thereto and for transmitting controller outputs therefrom;

wherein execution of the processor executable code causes the controller to execute real time computer implementable steps comprising:

receiving inputs via the client interface device related to parameters of a roller blind comprising:

(a) a radius of the roller;

(b) a thickness of the sheet;

(c) a width of the sheet;

(d) a length of the sheet to cover the height of the window;

(e) a weight of the sheet per square inches;

determining a numerical value of the weight of the sheet along a length of the sheet that is unrolled by the roller at one radian (WFabx_θ) by executing the following computer implementable steps:

determining an average radius (Ravg) of the roller with the sheet rolled thereon during movement of the sheet along the length of (d), wherein the average radius (Ravg) is provided by an equation comprising:

R

⁢

avg

=

R

⁢

t

+

R

⁢

max

2

wherein Rt is a radius of the roller without the sheet and Rmax is determined by an equation comprising:

R max=√{square root over (RLSA/π)}

wherein RLSA is provided by the following equation:

RLSA=TLSA+SRLSA

wherein TSLA is provided by the following equation:

TLSA=π( Rt ) 2

wherein SRLSA is provided by the following equation:

SRLSA=(MSPL)(STH)

wherein MSPL is the length at (d) and STH is the sheet thickness;

executing an equation comprising:

Wfabx _θ=( Sw )( R avg)( Wfab /in 2 )

wherein Sw is (c) and Wfab/in 2 is (e),

wherein Wfabx_θ is a numerical value of the weight of the sheet along a length of the sheet that is unrolled by the roller at one radian

wherein Wfab is the weight of the sheet

wherein a numerical value of the spring constant is equal to a numerical value of Wfabx_θ

communicating the numerical value of the spring constant via the client interface device.

16. A computer implemented system according to claim 15 , wherein execution of the processor executable code causes the controller to execute computer implementable steps comprising:

receiving inputs via the client interface device related to a given client comprising a given spring constant of the given client spring and a given spring length of the given client spring;

determining a modification of the given length (modified length) that provides the given client spring to have a modified spring constant that is equal to the communicated spring constant by calculating a proportion that is equal to the communicated spring constant divided by the given spring constant and calculating the modified length of the spring by dividing the given length by the proportion;

communicating the modified length via the client interface device.