CA3030892C - System and roll-up door for maintaining a downward tension on a roll-up door curtain - Google Patents

Abstract

A roll-up door and a system for maintaining a downward tension on a roll-up door curtain are disclosed. The roll-up door includes a flexible curtain, a horizontal roller on which the flexible curtain can be rolled when raised, and a bottom bar extending on a bottom of the flexible curtain. Located on each lateral side of the roll-up door are a tensioning weight, an upper pulley mounted above the horizontal roller, a lower pulley mounted near a bottom of the roll-up door, and a cable having a first end attached to the tensioning weight, a first section of the cable proximate to the first end passing around the upper pulley, the cable having a second end to a respective side of the bottom bar, a second section of the cable proximate to the second end passing around the lower pulley.

Description

SYSTEM AND ROLL-UP DOOR FOR MAINTAINING A
DOWNWARD TENSION ON A ROLL-UP DOOR CURTAIN
TECHNICAL FIELD
[0001] The present disclosure relates to the field of door systems.
More specifically, the present disclosure relates to a system for maintaining a downward tension on a roll-up door curtain and to a roll-up door integrating the system.
BACKGROUND

[0002] Roll-up doors offer wide flexibility in terms of sizes and the capability of undergoing large numbers of fast opening and closing cycles in a single day. They are used, predominantly in commercial and industrial applications. These doors usually comprise a large curtain made of a flexible material, for example rubber, supported by guides on each side of a door frame. Figure 1 (prior art) is an example of a releasable roll-up door system, as disclosed in US Patent Application Publication Number 2016/0177624 Al, to Palencia et al., published on June 23, 2016. A roll-up door system 100 comprises a curtain 102, a pair of lateral, vertical door guides 104 configured to hold sides of the curtain 102 when lowered, and a curtain riser, generally at 111. The curtain riser 111 includes a standard motorized drive 108 operably connected to a roller 110 on which the curtain 102 can be rolled when raised.
The roller 110 may for example comprise a hollow tube, a rod, or the like, and generally has a circular cross-section to facilitate rolling of the curtain 102. The curtain 102 may terminate on a lower horizontal bar 112. A controller 128 controls turning on and off the motorized drive 108 in distinct directions for raising and lowering the curtain 102.

[0003] Because roll-up doors may be very large, they may withstand excessive wind loads leading to ripping or tearing of the curtain, or to breakage 13901682.1 of the guides or door frame. An example of a rollable door and rollable door guiding system having a deformable guide is disclosed in US Patent Number 9,416,589 B2, to McTavish et al., issued on August 16, 2016. Figure 2 (prior art) is a cross-sectional view of the door guide and edge of the curtain of Figure 1. The vertical door guide 104 comprises a longitudinal rear base wall 50 extending along a height of the vertical door guide 104 when viewed in the orientation as shown on Figure 1. Holes such as 52, optionally threaded, are provided to allow installation of the vertical door guide 104 on a doorway frame using bolts (not shown). A pair of longitudinal, spaced apart and parallel or substantially parallel wall sections 54 and 56 extends from the longitudinal base wall 50 to define a cavity 58 between the wall sections 54 and 56. In a particular embodiment, the wall section 54 has a thinner cross-section 55 when compared to a cross-section 57 of the wall section 56. Consequently, while both wall sections 54 and 56 are deformable, the wall section 54 tends to flex with greater amplitude than the wall section 56 when a force is applied to the vertical door guide 104. On the front side of the vertical door guide 104, the wall portion 56 is bent a first time at 90 degrees to form a longitudinal front wall portion 62. The wall portion 56 is bent a second time at 90 degrees to define a wall portion parallel to the wall portions 54 and 56 and defining an inner longitudinal planar face 66, parallel to both the wall portions 54 and 56, and an inner longitudinal edge 68 at an extremity of the inner longitudinal planar face 66. On the front side thereof, the wall portion 54 is bent inwardly at an obtuse angle (see 70) to form an angular longitudinal wall 72 with a free longitudinal edge 74.

[0004] The vertical door guide 104 is sized to accommodate dimensions of a vertical side strip 5 attached on a side edge of the curtain 102.
The side strip 5 comprises a proximate longitudinal portion 12, which is U-shaped in cross section for attachment to an edge of the curtain 102, and a 13901682.1 distal longitudinal end-section for sliding into the vertical door guide 104.
Opposite from the proximate longitudinal portion 12 of the vertical side strip

5 are, on one side, a first longitudinal rib 22 and, on another side, a shifted wall section 24. The shifted wall section 24 forms a free edge of the vertical side strip 5. The shifted wall section 24 also defines a second longitudinal rib 28 with a sloping wall 30 on the corresponding side of the vertical side strip 5.
[0005] The first longitudinal rib 22 is generally trapezoidal in cross section and is positioned on the side of the vertical side strip 5 opposite the second longitudinal rib 28. Also, the first longitudinal rib 22 is laterally shifted inwardly with respect to the second longitudinal rib 28.

[0006] The vertical side strip 5 defines a first planar surface 6 between the proximate U-shaped longitudinal portion 12 and a shifted wall section 24. The inner longitudinal planar face 66 of the vertical door guide is a mating surface for the first planar surface 6. The first planar surface 6 can rest or slide on the inner longitudinal planar face 66. The inner longitudinal edge 68 of the vertical door guide 104 is a mating surface for a sloping wall of the second longitudinal rib 28. The sloping wall 30 can rest or slide on the inner longitudinal edge 68 to maintain the vertical side strip 5 into the cavity 58 of the vertical door guide 104.

[0007] In the same manner, the vertical side strip 5 defines a second planar surface 7 opposite the first planar surface 6 between the proximate U-shaped longitudinal portion 12 and the generally trapezoidal first longitudinal rib 22. The second planar surface 7 slides onto the longitudinal edge 74 while a sloping wall 8 of the generally trapezoidal first longitudinal rib 22 slides on the inner surface of the angular longitudinal wall 72 to maintain the vertical side strip 5 into the cavity 58 of the vertical door guide 104.

[0008] When assembled, the vertical side strip 5 attached to the curtain 102 is movable or slidable longitudinally in the vertical door guide as the curtain 102 is raised or lowered during use thereof. Together, the 4503461.1 vertical side strip 5 and the vertical door guide 104 form a guiding system for a roll-up door having the curtain 102. For this, the longitudinal edge 74 defines with the inner longitudinal planar face 66 a longitudinal slot to receive the vertical side strip 5 between the proximate U-shaped longitudinal portion 12 and a first longitudinal rib 22. Embodiments of the guiding system may comprise two opposed vertical door guides 104 on either sides of the curtain 102. In such cases, two symmetrically mounted vertical side strips 5 attached to opposed vertical edges of the curtain 102 move or slide within corresponding vertical door guides 104.

[0009] In normal operation, the vertical door guide 104 has a cross-section shaped substantially as shown on Figure 2. As the curtain 102 of the roll-up door system 100 is raised or lowered, the vertical side strip 5 slides within the vertical door guide 104. More specifically, the first planar surface 6 slides on the inner longitudinal planar face 66 with the sloping wall 30 of the shifted wall section 24 sliding on the inner longitudinal edge 68 to retain the vertical side strip 5 into the cavity 58 of the vertical door guide 104. Also, the second planar surface 7 opposite the first planar surface 6 slides onto the longitudinal edge 74 while the sloping wall 8 of the generally trapezoidal first longitudinal rib 22 mates with an inner surface 9 of the angular longitudinal wall 72, sliding or resting thereon to maintain the vertical side strip 5 into the cavity 58 of the vertical door guide 104.

[0010] However, when a wind load or impact causing a load exceeding a predetermined threshold is applied upon the curtain 102, this load being transmitted to the vertical side strip 5, such wind load or impact will cause deformation of the vertical door guide 104, in which the wall portions and 56 separate from each other at the front of the vertical door guide 104 to thereby spread apart the longitudinal edge 74 and the inner longitudinal planar face 66, thereby widening the longitudinal slot defined between them. Because the cross-section 55 of the wall portion 54 is thinner than the cross-section 4503461.1 of the wall portion 56, the wall portion 54 tends to undergo a greater deformation than the wall portion 56 when a force is applied to the vertical door guide 104. Widening of the longitudinal slot in turn allows the generally trapezoidal first longitudinal rib 22, at first, and then the shifted wall section 24, to pass through the longitudinal slot and release the vertical side strip 5 from the vertical door guide 104 with little, if any, damage to the curtain 102 or the vertical door guide 104. Notably, the obtuse angle 70 allows the sloping wall to slide on the angular longitudinal wall 72 with relative ease.

[0011] While the roll-up door system 100 is very efficient in allowing release of the door curtain 102 in case of impact from a vehicle or in case of excessive wind, improvements are still desired in some applications. In particular but without limitation, when the roll-up door system 100 is used in underground mines, forced ventilation oftentimes causes very heavy pressure being applied on the curtain 102. For example, an 8-foot high by 12-foot wide curtain 102 may be exposed to nearly 3000 pounds of pressure. When closing the door, as the pressure builds up on unrolled parts of the curtain 102, its edges may tend to wave and fail to freely move within the vertical door guides 104. As the motorized drive 108 continues rotating the roller 110, the curtain 102 may remain stuck about the roller 102. Even without waving of the edges of the curtain 102, because of the ventilation, there have been events when the heavy pressure that built on the curtain 102 as it rolled down caused it to blow out of its guides 104.

[0012] This problem can cause heavy damages in roll-up door systems that are not configured to release their curtains in case of high wind or impact. Blow out of the curtain in such roll-up door systems are very serious events in which door guides, curtains or even door frames may be damaged.

[0013] Therefore, there is a need for a roll-up door system capable of preventing damages to roll-up door systems under excessive wind load situations.
4503461.1 SUMMARY

[0014] According to the present disclosure, there is provided a roll-up door comprising a flexible curtain, a horizontal roller on which the flexible curtain can be rolled when raised, and a bottom bar extending on a bottom of the flexible curtain. The roll-up door also comprises, on each of its lateral sides, a tensioning weight, an upper pulley mounted above the horizontal roller, a lower pulley mounted near a bottom of the roll-up door, and a cable.

The cable has a first end attached to the tensioning weight and a second end opposite from the first end, the second end being attached to a respective side of the bottom bar. A first section of the cable proximate to the first end passes around the upper pulley and a second section of the cable proximate to the second end passes around the lower pulley.

[0015] According to the present disclosure, there is also provided a system for maintaining a downward tension on a roll-up door curtain, the roll-up door curtain having a bottom bar extending on its lower end. Each lateral side of the system comprises a tensioning weight, an upper pulley mountable above a top of the roll-up door curtain, a lower pulley mountable near a position of the bottom bar when the roll-up door curtain is fully lowered, and a cable. The cable has a first end attached to the tensioning weight and a second end opposite from the first end, the second end being attached to a respective side of the bottom bar. A first section of the cable proximate to the first end passes around the upper pulley and a second section of the cable proximate to the second end passes around the lower pulley.

[0016] The foregoing and other features will become more apparent upon reading of the following non-restrictive description of illustrative embodiments thereof, given by way of example only with reference to the accompanying drawings.
4503461.1 BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Embodiments of the disclosure will be described by way of example only with reference to the accompanying drawings, in which:

[0018] Figure 1 (prior art) is an example of a releasable roll-up door system;

[0019] Figure 2 (prior art) is a cross-sectional view of the door guide and edge of the curtain of Figure 1;

[0020] Figure 3 is a schematic rear elevation view of a roll-up door according to an embodiment;

[0021] Figure 4 is a schematic top plan view of the roll-up door of Figure 3;

[0022] Figure 5 is a rear perspective view of the roll-up door of Figure 3;

[0023] Figure 6 shows details of an upper pulley and cable of the roll-up door of Figure 3;

[0024] Figure 7 shows details of a lower pulley and cable of the roll-up door of Figure 3;

[0025] Figure 8 shows details of an attachment point of the cable to the bottom bar of the roll-up door of Figure 3; and

[0026] Figure 9 is a side elevation view showing details of a tensioning weight of the roll-up door of Figure 3.
DETAILED DESCRIPTION

[0027] Like numerals represent like features on the various drawings.

[0028] Various aspects of the present disclosure generally address one or more of the problems related to lowering of roll-up doors under 4503461.1 excessive wind load situations.

[0029] According to the present disclosure, a downward tension is applied at the bottom of a flexible curtain of a roll-up door. To this end, tensioning weights are provided on each side of the flexible curtain and are connected via cables and pulleys to a bottom bar fixedly attached at the bottom of the flexible curtain. The tensioning weights are raised and lowered with the flexible curtain while maintaining the downward tension. Problems related to wind load on the flexible curtain are alleviated in that the downward tension prevents, at least to a large extent, problems related to waving of edges of the flexible curtain within their lateral guides. The downward tension also tends to maintain the edges of the flexible curtain in their lateral guides, preventing blow out of the flexible curtain.

[0030] It may be observed that the tensioning weights do not function in the same manner as so-called counterweights that are sometimes used to facilitate rising a door curtain by applying an upward force to counteract the weight of the door curtain itself. The tensioning weights of the present system actually add to the effort required to raise the door curtain.

[0031] Referring now to the drawings, Figure 3 is a schematic rear elevation view of a roll-up door according to an embodiment. Figure 4 is a schematic top plan view of the roll-up door of Figure 3. Referring at once to Figures 3 and 4, a roll-up door 200 comprises a flexible curtain 202, which may also be called a roll-up door curtain. The flexible curtain 202 has two sides and 206, a top 208 and a bottom 210. At a top of the roll-up door 200 is a horizontal roller 212 on which the flexible curtain 202 can be rolled when raised. The flexible curtain 202 is illustrated in a partially lowered position on Figure 2. A bottom bar 214 extends on the bottom 210 of the flexible curtain 202. The roll-up door 200 has two (2) lateral sides. A vertical door guide 216 adapted to slidably receive a respective side edge (similar to vertical side strip of Figure 2) of the flexible curtain 202 may be present on each lateral side of 4503461.1 the roll-up door 200. The vertical door guides 216 may optionally be configured to release the respective side edge of the flexible curtain 202 upon application on the flexible curtain 202 of a force exceeding a predetermined threshold.

[0032] A tensioning weight 218, an upper pulley 220, a lower pulley 222 and a cable 224 are also located on each lateral side of the roll-up door 200. The upper pulleys 220 are mounted above the horizontal roller 212. The lower pulleys 222 are mounted near a bottom of the roll-up door 200, near a position of the bottom bar 214 when the flexible curtain 202 is fully lowered.

[0033] On each lateral side of the roll-up door 200, the cable 224 has a first end 226 attached to the tensioning weight 218. A first section 228 of the cable 222 proximate to the first end 226 passes around the upper pulley 220.
The cable 224 has a second end 230 opposite from the first end 226. The second end 230 is attached to respective attachment points 232 of the bottom bar 214. A second section 236 of the cable 224 proximate to the second end 230 passes around the lower pulley 222.

[0034] As best seen on Figure 4, in an embodiment, the tensioning weights 218, the vertical door guides 216, the upper pulleys 220, the lower pulleys 220 and the flexible curtain 202 are generally aligned within a common vertical plane, schematically represented by a dashed line 238. Bottom ends 240 of the tensioning weights 218 as shown on Figure 3 are positioned substantially at a level of the bottom bar 214 in relation to the ground 242;
the tensioning weights 218 could be positioned somewhat higher in some embodiments. An overall length of the cables 224 is selected so that the bottom ends 240 of the tensioning weights 218 do not reach the ground 242 before the flexible curtain 202 is fully lowered, the bottom bar 214 resting on the ground 242. A longer length of the cables 224 may be used if apertures (not shown) are dug in the ground 242 to freely receive the bottom ends 240 of the tensioning weights 218. A shorter length of the cables 224 may keep the bottom ends 240 of the tensioning weights 218 floating above the ground 242 4503461.1 when the flexible curtain 202 is fully lowered, but the cables 224 should be sufficiently long to prevent a top 234 of the tensioning weights 218 from colliding with the upper pulleys 220 when the flexible curtain 202 is fully raised.

[0035] In the shown embodiment, the upper pulleys 220 have rotational axes 244 normal to the common vertical plane 228 and are each substantially positioned above outer edges 246 of respective vertical door guides 216 opposite from the curtain 202. The lower pulleys 222 have rotational axes 248 normal to the common vertical plane 238 and are each positioned within respective vertical door guides 216.

[0036] Further details of the roll-up door 200 are depicted in Figures 5 to 9, of which Figure 5 is a rear perspective view of the roll-up door of Figure 3, Figure 6 shows details of an upper pulley and cable of the roll-up door of Figure 3, Figure 7 shows details of a lower pulley and cable of the roll-up door of Figure 3, Figure 8 shows details of an attachment point of the cable to the bottom bar of the roll-up door of Figure 3, and Figure 9 is a side elevation view showing details of a tensioning weight of the roll-up door of Figure 3.
Referring at once to Figures 3 to 9, a vertical hollow enclosure 250 is located on each lateral side of the roll-up door 200. For safety reasons, the tensioning weights 218 are placed within respective vertical hollow enclosures 250. The tensioning weights 218 are each sized and configured to freely move up and down within a respective vertical hollow enclosure 250. In the shown embodiments, each of the vertical hollow enclosure 250 is cylindrical and thus has a circular cross-section. The tensioning weights 218 are also cylindrical in shape. Other matching shapes of the vertical hollow enclosures 250 and of the tensioning weights 218 may also be contemplated.

[0037] In an embodiment, the vertical door guides 216 are each formed of a pair of separable vertical members 252 and 254. The vertical members 252 and 254 are connected via a plurality of hinges 256 distributed along their height. Opening the vertical door guides 216 by separating the 4503461.1 vertical members 252 and 254 allows easy access to the lower pulleys 222, to the cable 224 and facilitates attachment of its end 230 to the attachment points 232 of the bottom bar 214. The vertical members 254 are fixedly attached to a frame on which the roll-up door 200 is mounted. In operation, the vertical members 252 are moved toward the vertical members 254 in order to form slots receiving the sides 204 and 206 of the flexible curtain 202. The vertical members 252 and 254 may be joined by use of bolts (not shown) distributed along their height.

[0038] As shown on Figure 9, the bottom end 240 of the tensioning weight 218 is substantially at a same height as the bottom bar 214, with respect to the ground 242.

[0039] A motorized drive 258 is operably connected to the horizontal roller 212, for example via a chain 260 driving a sprocket 264 mounted to an external shaft 264 of the horizontal roller 212. The motorized drive 258 is operable to raise and lower the flexible curtain 202. The downward tension on the flexible curtain 202 caused by the tensioning weights 218 adds to the effort of the motorized drive 258 when raising the flexible curtain 202. This added effort can be compensated by proper dimensioning of a ratio between a sprocket (not shown) of the motorized drive 258 and the sprocket 264 or by proper selection of a gear ratio or of an electric motor in the motorized drive 258. When lowering the flexible curtain 202, as wind pressure may build on the flexible curtain 202, the downward tension provided at its bottom 210 by the tensioning weights 218 tends to prevent waving of the sides 204 and 206 of the flexible curtain 202, thereby preventing that the flexible curtain 202 remains stuck within the vertical door guides 216. This downward tension also limits the risk of the flexible curtain 202 being released from the vertical door guides because of the wind pressure. In an embodiment, a weight of each tensioning weight 218 is substantially equal to a quarter of a weight of the flexible curtain 202. Other ratios between the respective weights of the flexible curtain 202 and of the tensioning weights 218 are also contemplated. These ratios may be selected in view of expected wind loads on the flexible curtain 202.

[0040] Those of ordinary skill in the art will realize that the description of the door and of the system for maintaining a downward tension on a roll-up door curtain are illustrative only and are not intended to be in any way limiting.
Other embodiments will readily suggest themselves to such persons with ordinary skill in the art having the benefit of the present disclosure.
Furthermore, the disclosed door and system may be customized to offer valuable solutions to existing needs and problems of limiting damages to buildings under excessive load situations.

[0041] In the interest of clarity, not all of the routine features of the implementations of the door and system are shown and described. It will, of course, be appreciated that in the development of any such actual implementation of the door and system, numerous implementation-specific decisions may need to be made in order to achieve the developer's specific goals, such as compliance with application-, system-, and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the field of door systems having the benefit of the present disclosure.

[0042] Although the present disclosure has been described hereinabove by way of non-restrictive, illustrative embodiments thereof, these embodiments may be modified at will within the scope of the appended claims without departing from the spirit and nature of the present disclosure.
4503461.1

Claims (17)

WHAT IS CLAIMED IS:

1. A roll-up door, comprising:
a flexible curtain having a pair of lateral side edges;
a pair of deformable vertical door guides located on lateral sides of the roll-up door, each deformable vertical door guide being adapted to slidably receive a respective side edge of the flexible curtain, the vertical door guides being configured to release the respective side edges of the flexible curtain upon application on the flexible curtain of a force exceeding a predetermined threshold;
a horizontal roller on which the flexible curtain can be rolled when raised;
a bottom bar extending on a bottom of the flexible curtain; and on each lateral side of the roll-up door:
a tensioning weight, an upper pulley mounted above the horizontal roller, a lower pulley mounted near a bottom of the roll-up door, and a cable having a first end fixedly attached to the tensioning weight, a first section of the cable proximate to the first end passing around the upper pulley, the cable having a second end opposite from the first end, the second end being fixedly attached to a respective side of the bottom bar, a second section of the cable proximate to the second end passing around the lower pulley.

2. The roll-up door of claim 1, wherein:
the tensioning weights, the vertical door guides, the upper pulleys, the lower pulleys and the flexible curtain are generally aligned within a common vertical plane;
the upper pulleys have rotational axes normal to the common vertical plane and are each substantially positioned above edges of respective vertical door guides opposite from the flexible curtain; and the lower pulleys have rotational axes normal to the common vertical plane and are each positioned within respective vertical door guides.

3. The roll-up door of claim 2, wherein the vertical door guides are each formed of a pair of separable vertical members.

4. The roll-up door of claim 1, further comprising, on each lateral side of the roll-up door, a vertical hollow enclosure, wherein the tensioning weights are each sized and configured to freely move up and down within a respective vertical hollow enclosure.

5. The roll-up door of claim 4, wherein each of the vertical hollow enclosure has a circular cross-section and wherein the tensioning weights are cylindrical in shape.

6. The roll-up door of claim 1, wherein a weight of each tensioning weight is substantially equal to a quarter of a weight of the flexible curtain.

7. The roll-up door of claim 1, further comprising a motorized drive operably connected to the horizontal roller for rising and lowering the flexible curtain.

8. The roll-up door of claim 1, wherein the tensioning weights move up and down when the bottom bar moves up and down so that bottom ends of the tensioning weights remain substantially at a same height as the bottom bar with respect to the ground.

9. The roll-up door of claim 1, wherein, on each lateral side of the roll-up door, a rolling axis of the upper pulley is parallel to a rolling axis of the lower pulley.

10. A system for maintaining a downward tension on a roll-up door curtain, the roll-up door curtain having a pair of lateral side edges and a bottom bar extending on its lower end, each lateral side of the system comprising:
a vertical door guide adapted to slidably receive a respective side edge of the roll-up door curtain, each vertical door guide being configured to release the respective side edge of the roll-up door curtain upon application on the roll-up door curtain of a force exceeding a predetermined threshold;
a tensioning weight;
an upper pulley mountable above a top of the roll-up door curtain;
a lower pulley mountable near a position of the bottom bar when the roll-up door curtain is fully lowered; and a cable having a first end fixedly attached to the tensioning weight, a first section of the cable proximate to the first end passing around the upper pulley, the cable having a second end opposite from the first end, the second end being fixedly attached to a respective side of the bottom bar, a second section of the cable proximate to the second end passing around the lower pulley.

11. The system of claim 10, wherein:
the tensioning weights, the vertical door guides, the upper pulleys, the lower pulleys and the roll-up door curtain are generally aligned within a common vertical plane;
the upper pulleys have rotational axes normal to the common vertical plane and are each substantially positioned above edges of respective vertical door guides opposite from the roll-up door curtain;
and the lower pulleys have rotational axes normal to the common vertical plane and are each positioned within respective vertical door guides.

12. The system of claim 11, wherein the vertical door guides are each formed of a pair of separable vertical members.

13. The system of claim 10, further comprising, on each lateral side of the roll-up door curtain, a vertical hollow enclosure, wherein the tensioning weights are each sized and configured to freely move up and down within a respective vertical hollow enclosure.

14. The system of claim 13, wherein each of the vertical hollow enclosure has a circular cross-section and wherein the tensioning weights are cylindrical in shape.

15. The system of claim 10, wherein a weight of each tensioning weight is substantially equal to a quarter of a weight of the roll-up door curtain.

16. The system of claim 10, wherein the tensioning weight moves up and down when the bottom bar moves up and down so that bottom ends of the tensioning weights remain substantially at a same height as the bottom bar with respect to the ground.

17. The system of claim 10, wherein, on each lateral side of the system, a rolling axis of the upper pulley is parallel to a rolling axis of the lower pulley.