AU2017101180A4 - Retrofittable mechanism for adjustment of roller door spring torsion - Google Patents

Abstract

Disclosed herein is a retrofittable mechanism 10 comprising a roller door shaft support bracket 12 for fixed connection to a wall mounting bracket 300. The bracket 12 defines an opening 12a for receiving one end of roller door shaft 202 and, when the shaft 202 is engaged in the opening 12a, for restraining the shaft 202 against translation transverse to the shaft's axis but permitting rotation of the shaft about its axis. Collar 16 of mechanism 10 is fixedly connectable to shaft 202 and coupling 18 is defined between bracket 12 and collar 16. Coupling 18 is configured to selectively permit and prevent relative rotation between bracket 12 and collar 16 when mechanism 10 is installed in roller door assembly 100. tu CD, rr r4_ __ _ toN

Description

2017101180 29 Aug 2017 ι "Retrofittable mechanism for adjustment of roller door spring torsion" Cross-Reference [0001] The entire disclosure of Australian Patent Application No. 2016903460, filed 30 August 2016, is incorporated herein by way of reference.

Technical Field [0002] The present disclosure relates to a retrofittable roller door spring torsion adjustment mechanism. The retrofittable mechanism has been developed primarily for retrofitting to existing roller doors to simplify and reduce the risk associated with adjusting the torsion of the roller door’s torsion spring(s). However, it will be appreciated that the retrofittable mechanism is not limited to this particular application and that it may also, for example, be installed on new roller doors.

Background [0003] Typically, roller doors comprise curtain assembly that includes a shaft, two or more wheels spaced along the shaft and rotatable with respect to the shaft, and a corrugated sheet or “curtain” wound around the wheels, with the corrugations oriented parallel to the shaft.

Mounting brackets for the curtain assembly are fixed to the wall on either side of the opening that the roller door is to service. The mounting brackets each support an opposite end of the shaft of the curtain assembly and are located at a height suitable to position the curtain assembly above the wall opening.

[0004] In normal operation, the shaft of the curtain assembly is tightly clamped to the mounting brackets by U-bolts, which prevents the shaft from rotating about its axis relative to the mounting brackets. To balance the weight of the curtain, it is common to sleeve at least one spiral torsion spring over a portion of the shaft inside the curtain, with one end of the torsion spring being fastened relative to the shaft and the other end being fastened relative to the curtain. When installing the door, the torsion spring is adjusted such that it assists with controlling lowering of the curtain and with aiding raising the curtain. 2 2017101180 29 Aug 2017 [0005] During closing/lowering of the door, the wheels of the curtain assembly rotate on the shaft and the curtain unrolls and hangs down between vertical guides mounted on each side of the wall opening. As the door is closed/lowered, the torsion stored in the torsion spring increases, which helps to balance the weight of the curtain. During opening/raising of the door, the wheels of the curtain assembly rotate in the opposite direction on the shaft and the curtain rolls up around the wheels, aided by the torsion stored in the spring.

[0006] Adjustment of the torsion spring, both when installing the door and to account for any loss of torque over time, is a relatively time-consuming, complicated and hazardous process, especially for inexperienced technicians or end users. As such, it presents quite a burden in storage facilities that may have hundreds of doors, as well as presenting a safety risk regardless of where or how many doors are involved.

[0007] Adjustment of the torsion spring is achieved by releasing the U-bolts, rotating the shaft as required to produce the desired torque, and then re-tightening the U-bolts. Because of the existing torque in the spring, this procedure is dangerous to an untrained person and normally requires two people with socket wrenches and pipe wrenches to have a reasonable chance of performing the job safely.

[0008] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

Summary [0009] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0010] Disclosed herein is a retrofittable mechanism for adjustment of roller door spring torsion, the mechanism comprising: 3 2017101180 29 Aug 2017 a roller door shaft support bracket for fixed connection to a roller door wall mounting bracket, the shaft support bracket defining an opening for receiving one end of a roller door curtain assembly shaft and, when the shaft is engaged in the opening, for restraining the shaft against translation transverse to the shaft’s axis but permitting rotation of the shaft about its axis; a collar for fixed connection to the shaft; and a coupling defined between the shaft support bracket and the collar, the coupling being configured to selectively permit and prevent relative rotation between the shaft support bracket and the collar when: the shaft support bracket is fixedly connected to the mounting bracket, said one end of the shaft is engaged in the opening of the shaft support bracket, and the collar is fixedly connected to the shaft.

[0011] The opening in the shaft support bracket may be positioned such that, when the retrofittable mechanism is installed, an underside of the shaft is spaced less than 100mm above the mounting bracket. In some embodiments, the underside of the shaft is spaced less than 70mm, or less than 50mm, or less than 40mm, or less than 30mm, or less than 20mm, or less than 15mm, or less than 10mm above the mounting bracket.

[0012] The coupling may comprise a ratchet. The ratchet may comprise teeth fixedly connected relative to the collar and a projection for engaging the teeth movably connected to the shaft support bracket, or vice versa. The projection may comprise a pawl. The projection may be biased into engagement with the teeth, for example by gravity or by a spring. The teeth may be defined on a ratchet wheel. The ratchet wheel may be welded or otherwise suitably fixedly connected to or integrally formed with the collar.

[0013] In one or more alternative embodiments, the coupling may comprise a fixed cog associated with one of the collar and the shaft support bracket and a rotatable cog or worm drive engageable with the other of the collar and the shaft support bracket.

[0014] The collar may have an engagement formation therein or thereon for engagement by a lever tool, such as a spanner, to facilitate manual rotation of the collar together with the shaft, in use. One or more openings may be provided in the collar for receiving one or more fasteners to fixedly connect the collar to the shaft. In addition to or instead of the one or more openings, a clamp may be provided to fixedly connect the collar to the shaft. The retrofittable mechanism may be configured to inhibit relative rotation between the collar and shaft support bracket by 4 2017101180 29 Aug 2017 unauthorised persons, for example by providing non-standard or uniquely configured engagement between the collar and lever tool.

[0015] The shaft support bracket may comprise a base portion configured for fixed connection to the mounting bracket (for example by having one or more openings therein for receiving one or more fasteners) and an upper portion extending substantially perpendicularly to the base portion, the opening for receiving the shaft being provided in the upper portion. In embodiments in which the coupling comprises a ratchet having a pawl, the pawl may be pivotally mounted to the upper portion and may extend substantially horizontally so as to be biased, at least in part, by gravity into engagement with the ratchet teeth.

[0016] In use, abutment of the collar with the shaft support bracket, directly or via the coupling, may limit axial movement of the shaft in at least one direction.

[0017] A second roller door shaft support bracket may be provided for use with the retrofittable mechanism. Like the shaft support bracket of the retrofittable mechanism, the second shaft support bracket may be configured for fixed connection to a roller door wall mounting bracket, define an opening for receiving one end of a roller door curtain assembly shaft and, when the shaft is engaged in the opening, restrain the shaft against translation transverse to the shaft’s axis but permit rotation of the shaft about its axis. However, the second shaft support bracket need not have a pawl mounted thereto or otherwise be configured for coupling to an associated collar. Similarly, a second collar may be provided for use with the retrofittable mechanism. The second collar may be configured for fixed connection to the shaft, particularly to an end of the shaft associated with the second shaft support bracket. In use, abutment of the second collar with the second shaft support bracket may limit axial movement of the shaft in at least one direction.

[0018] Also disclosed herein is a roller door assembly, comprising: a roller door curtain assembly comprising: a shaft, two or more wheels spaced along the shaft and rotatable with respect to the shaft, a corrugated curtain having one end connected to the wheels, the curtain being windable around the wheels and unwindable from the wheels, wherein the corrugations of the curtain are oriented parallel to the shaft, and wherein the curtain has a width less than the length of the shaft, such that opposite ends of the shaft project beyond the curtain, and 5 2017101180 29 Aug 2017 at least one torsion spring extending over a portion of the shaft that is inside the curtain when the curtain is wound up on the wheels, wherein one end of the torsion spring is fastened relative to the shaft and the other end of the torsion spring is fastened relative to the curtain; a pair of roller door wall mounting brackets for connection to a wall of a structure comprising an opening that is to be closed by the curtain, the wall mounting brackets each being adapted for supporting a respective end of the shaft; a retrofittable mechanism as defined in paragraph [0010] above, optionally including any one or more of the features defined in paragraphs [0011] to [0016], wherein: the shaft support bracket of the retrofittable mechanism is fixedly connected to one of the wall mounting brackets, the respective end of the shaft is engaged in the opening of the shaft support bracket, and the collar of the retrofittable mechanism is fixedly connected to the respective end of the shaft.

[0019] In some embodiments, a pair of retrofittable mechanisms as defined in paragraph [0010] above, optionally including any one or more of the features defined in paragraphs [0011] to [0016], may be provided, each for installation on a respective end of the shaft. In embodiments in which a said retrofittable mechanism is provided at only one end of the shaft, a second roller door shaft support bracket may be provided for fixed connection to the roller door wall mounting bracket associated with the other end of the shaft. The second shaft support bracket may define an opening for receiving the other end of the shaft and, when the shaft is engaged in the opening, restrain the shaft against translation transverse to the shaft’s axis but permit rotation of the shaft about its axis. The second shaft support bracket need not have a pawl mounted thereto or otherwise be configured for coupling to an associated collar. A second collar may be provided for fixed connection to the other end of the shaft. In use, abutment of the second collar with the second shaft support bracket may limit axial movement of the shaft in at least one direction.

[0020] The wall mounting brackets may comprise two arms that together form an L-shape, wherein one of the arms is adapted for connection to the wall and the other arm is adapted for fixed connection to the shaft support bracket.

[0021 ] Also disclosed herein is a method of retrofitting a roller door assembly with a mechanism for adjustment of roller door spring torsion, wherein: 6 2017101180 29 Aug 2017 the method is for a roller door assembly of the type comprising: a roller door curtain assembly comprising: a shaft, two or more wheels spaced along the shaft and rotatable with respect to the shaft, a corrugated curtain having one end connected to the wheels, the curtain being windable around the wheels and unwindable from the wheels, wherein the corrugations of the curtain are oriented parallel to the shaft, and wherein the curtain has a width less than the length of the shaft, such that opposite ends of the shaft project beyond the curtain, and at least one torsion spring extending over a portion of the shaft that is inside the curtain when the curtain is wound up on the wheels, wherein one end of the torsion spring is fastened relative to the shaft and the other end of the torsion spring is fastened relative to the curtain; a pair of roller door wall mounting brackets for connection to a wall of a structure comprising an opening that is to be closed by the curtain, the wall mounting brackets each being adapted for supporting a respective end of the shaft; and one or more clamp for fixedly connecting the shaft to the mounting brackets and for preventing rotation of the shaft relative to mounting brackets whilst the clamp is tightened; and wherein the method comprises: removing the one or more clamp; and replacing at least one of the one or more clamp with a retrofittable mechanism as defined in paragraph [0010] above, optionally including any one or more of the features defined in paragraphs [0011] to [0016].

[0022] In some embodiments, a pair of retrofittable mechanisms as defined in paragraph [0010] above, optionally including any one or more of the features defined in paragraphs [0011] to [0016], may be provided, each being installed on a respective end of the shaft. In embodiments in which a said retrofittable mechanism is provided at only one end of the shaft, a second roller door shaft support bracket may be fixedly connected to the roller door wall mounting bracket associated with the other end of the shaft. The second shaft support bracket may define an opening for receiving the other end of the shaft and, when the shaft is engaged in the opening, restrain the shaft against translation transverse to the shaft’s axis but permit rotation of the shaft about its axis. The second shaft support bracket need not have a pawl mounted thereto or 7 2017101180 29 Aug 2017 otherwise be configured for coupling to an associated collar. A second collar may be fixedly connected to the other end of the shaft. In use, abutment of the second collar with the second shaft support bracket may limit axial movement of the shaft in at least one direction.

Brief Description of Drawings [0023] An embodiment of the principles disclosed herein will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows rear and opposite end elevational views of a typical roller door assembly;

Figure 2 shows rear and opposite end elevational views of the roller door assembly of Figure 1 after it has been retrofitted with an embodiment of the presently disclosed retrofittable mechanism for adjustment of roller door spring torsion;

Figure 3 is a first elevational view of a shaft support bracket assembly of the retrofittable mechanism shown in Figure 2, wherein Figure 3 is taken at the same angle as the view shown in Figure 2 b);

Figure 4 is a second elevational view of the assembly of Figure 3, wherein Figure 4 is taken at right angles to the views shown in Figures 2 b) and 3;

Figure 5 is a first elevational view of a collar and ratchet wheel assembly of the retrofittable mechanism shown in Figure 2, wherein Figure 5 is taken at the same angle as the view shown in Figure 2 b);

Figure 6 is a second elevational view of the assembly of Figure 5, wherein Figure 6 is taken at right angles to the views shown in Figures 2 b) and 5;

Figure 7 is a first elevational view of a second shaft support bracket for use, together with the retrofittable mechanism of Figures 3 to 6, in the roller door assembly of Figure 2, wherein Figure 7 is taken at the same angle as the view shown in Figure 2 b);

Figure 8 is a second elevational view of the bracket of Figure 7, wherein Figure 8 is taken at right angles to the views shown in Figures 2 b) and 7; 8 2017101180 29 Aug 2017

Figure 9 is a first elevational view of a second collar for use, together with the retrofittable mechanism of Figures 3 to 6 and the bracket of Figures 7 and 8, in the roller door assembly of Figure 2, wherein Figure 9 is taken at the same angle as the view shown in Figure 2 b);

Figure 10 is a second elevational view of the collar of Figure 9, wherein Figure 10 is taken at right angles to the views shown in Figures 2 b) and 9; and

Figure 11 shows a lever tool for manual rotation of the collar and ratchet wheel assembly of the retrofittable mechanism of Figures 2 to 6.

Description of Embodiments [0024] Figure 1 shows a typical conventional roller door assembly 100. Roller door assembly 100 comprises a roller door curtain assembly 200 comprising a shaft 202, two or more wheels 204 spaced along the shaft 202 and rotatable with respect to the shaft, and a corrugated curtain 206 having one end connected to the wheels 204 by mechanical fasteners, such as screw fasteners. The corrugations of the curtain 206 are oriented parallel to the shaft 202 so as to permit the curtain 206 to wind around the wheels 204 when it is raised and to unwind from the wheels 204 when it is lowered. The curtain 206 has a width less than the length of the shaft 202, such that opposite ends of the shaft 202 project beyond the curtain 206. At least one torsion spring 208 extends over a portion of the shaft 202 that is inside the wound up portion of the curtain 206. One end of the torsion spring 208 is fastened relative to the shaft 202 and the other end of the torsion spring is fastened relative to the curtain 206. The roller door assembly 100 also comprises a pair of L-shaped roller door wall mounting brackets 300, each of which comprises a first arm 302 for connection to a wall W of a structure comprising an opening O that is to be closed by the curtain 206 and a second arm 304 for supporting a respective end of the shaft 202. The roller door assembly 100 further comprises a pair of clamps 400 for fixedly connecting the shaft 202 to arm 304 of the mounting brackets 300 and for preventing rotation of the shaft relative to mounting brackets whilst the clamps are tightened.

[0025] Figure 2 shows the roller door assembly 100 of Figure 1 after it has been retrofitted with an embodiment of a retrofittable mechanism 10 for adjustment of torsion in spring 208. The method of retrofitting roller door assembly 100 with a retrofittable mechanism 10 involves removing the clamp 400 at one end of the shaft 202 and replacing it with a retrofittable 9 2017101180 29 Aug 2017 mechanism 10. The clamp 400 at the other end of the shaft 202 is kept tightly in place whilst retrofittable mechanism 10 is installed to prevent the shaft from rotating under the influence of the torsion spring 208. In some embodiments (not shown), after retrofittable mechanism 10 has been installed on one end of the shaft 202, a second retrofittable mechanism 10 is installed on the other end of the shaft 202. However, in the embodiment shown in Figure 2, a second shaft support bracket 500 and second collar 600 are instead installed on the other end of the shaft 202. Before and during installation of the retrofittable mechanism(s), the curtain 206 is ideally raised or lowered to a height that minimises the amount of torsion stored in the spring 208.

[0026] Retrofittable mechanism 10 will now be described in more detail with reference to Figures 2 to 6. As shown, the mechanism 10 comprises a roller door shaft support bracket 12 for fixed connection to mounting bracket 300. The shaft support bracket 12 defines an opening 12a for receiving one end of shaft 202 and, when the shaft 202 is engaged in the opening 12a, for restraining the shaft 202 against translation transverse to the shaft’s axis but permitting rotation of the shaft about its axis. The opening 12a is positioned such that, when the retrofittable mechanism 10 is installed, as shown in Figure 2, an underside of the shaft 202 is spaced about 5 to 10mm above mounting bracket arm 304. Mechanism 10 further comprises a collar 16 for fixed connection to the shaft 202 and a coupling 18 defined between the shaft support bracket 12 and the collar 16. The coupling 18 is configured to selectively permit and prevent relative rotation between the shaft support bracket 12 and the collar 16 when the mechanism 10 has been installed in the roller door assembly 100 as shown in Figure 2. In the illustrated embodiment, the coupling 18 takes the form of a ratchet.

[0027] Referring to Figures 3 and 4, the shaft support bracket 12 comprises a base portion 12b having openings therein for receiving one or more fasteners to fixedly connect shaft support bracket 12 to mounting bracket arm 304. An upper portion 12c of the shaft support bracket extends substantially perpendicularly to the base portion 12b, with the opening 12a for receiving the shaft 202 being formed in the upper portion. A projection, in the form of a pawl 18a, of coupling/ratchet 18 is pivotally mounted to the upper portion 12c and extends substantially horizontally, in use, so as to be biased, at least in part, by gravity into engagement with the teeth of ratchet wheel 18b.

[0028] Referring to Figures 5 and 6, the collar 16 has an engagement formation, in the form of recesses 16a, for engagement by a lever tool to facilitate manual rotation of the collar 16 together with the shaft 202, in use. An example of such a lever tool is the pin or hook spanner 700 shown ίο 2017101180 29 Aug 2017 in Figure 11, which has pins/projections 702 configured for engaging the collar recesses 16a.

One or more openings 16b are provided in the collar 16 for receiving one or more fasteners 16c, such as screws or bolts, to fixedly connect the collar to the shaft 202, as shown in Figure 2. The retrofittable mechanism 10 may be configured to inhibit relative rotation between the collar 16 and shaft support bracket 12 by unauthorised persons, for example by the pins/projections 702 and recesses 16a having a non-standard or uniquely configured engagement to provide a nonstandard or uniquely configured engagement between the collar 16 and lever tool 700. The toothed ratchet wheel 18b of coupling/ratchet 18 is fixedly connected, such as by welding, relative to one end of the collar 16.

[0029] As shown in Figure 2, abutment of the collar 16 with the shaft support bracket 12, directly or via the coupling 18, limits axial movement of the shaft 202 in one direction.

[0030] Referring to Figures 7 and 8, the second shaft support bracket 500, like the shaft support bracket 12, is configured for fixed connection to a roller door wall mounting bracket 300, defines an opening 502 for receiving one end of shaft 202 and, when the shaft 202 is engaged in the opening 502, restrains the shaft 202 against translation transverse to the shaft’s axis but permits rotation of the shaft 202 about its axis. However, the second shaft support bracket 500 does not have a pawl mounted thereto and is not otherwise configured for coupling to a collar 16.

[0031] Referring to Figures 9 and 10, the second collar 600 is configured for fixed connection to the shaft one end of the shaft 202 and is intended for installation on the same end of the shaft as the second shaft support bracket 500, as shown in Figure 2. In use, abutment of the second collar 600 with the second shaft support bracket 500 limits axial movement of the shaft in an opposite direction to the limitation provided by abutment of the shaft support bracket 12 and collar 16.

[0032] Once the retrofittable mechanism 10 is installed, as shown in Figure 2, adjustment of torsion in spring 208 becomes a relatively simple exercise. To increase torsion in the spring 208, the spanner 700 is engaged with the collar 16 and used to rotate the collar 16, and thereby the ratchet wheel 18b and shaft 202, against the resilient bias of the torsion spring 208. When the desired increase in torque has been achieved, the spanner 700 is removed and engagement of pawl 18a with the teeth of ratchet wheel 18b prevents reverse rotation of the collar 16, ratchet wheel 18b and shaft 202. To reduce torsion in the spring 208, the spanner 700 is engaged with the collar 16 and used to rotate the collar 16, ratchet wheel 18b and shaft 202 slightly, against the 11 2017101180 29 Aug 2017 resilient bias of the torsion spring 208, to allow the pawl 18a to be disengaged from the teeth of ratchet wheel 18b. With the pawl 18a disengaged, the spanner 700 is used to control rotation of the collar 16, ratchet wheel 18b and shaft 202 in the same direction as the bias applied by the torsion spring 208. When the desired reduction in torque has been achieved, the pawl 18a is reengaged with the teeth of ratchet wheel 18b to prevent further rotation of the collar 16, ratchet wheel 18b and shaft 202 under the influence of the torsion spring 208, after which spanner 700 can be removed. Ideally, curtain 206 is raised or lowered to a height that minimises the amount of torsion stored in the spring 208 during adjustment of the spring torque.

[0033] Persons of skill in the art will recognise that the illustrated retrofittable mechanism 10 provides significant advantages. In particular, the provision of retrofittable mechanism 10 facilitates safer adjustment of torque in torsion spring 208, with the torque adjustment being performable by a single person, and without the need for the person(s) carrying out the torque adjustment to have specialist training.

[0034] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. Examples of possible variations and/or modifications include but are not limited to: • the underside of the shaft 202 being spaced more than 5 to 10mm above mounting bracket arm 304, such as anything up to about 100mm above mounting bracket arm 304; • the ratchet teeth being provided on or fixedly connected relative to the shaft support bracket 12 and the projection (e.g., pawl 18b) being provided on or connected to the collar 16; • the ratchet wheel 18a being integrally formed with, mechanically fastened to or otherwise fixedly connected relative to the collar 16; • the coupling 18 taking a form other than a ratchet, such as the coupling 18 comprising a fixed cog associated with one of the collar 16 and the shaft support bracket 12 and a rotatable cog or worm drive engageable with the other of the collar and the shaft support bracket; and/or • in addition to or instead of the one or more openings 16b, a clamp being provided to fixedly connect the collar 16 to the shaft 202.

Claims (5)

1. CLAIMS:

   1. A retrofittable mechanism for adjustment of roller door spring torsion, the mechanism comprising: a roller door shaft support bracket for fixed connection to a roller door wall mounting bracket, the shaft support bracket defining an opening for receiving one end of a roller door curtain assembly shaft and, when the shaft is engaged in the opening, for restraining the shaft against translation transverse to the shaft’s axis but permitting rotation of the shaft about its axis; a collar for fixed connection to the shaft; and a coupling defined between the shaft support bracket and the collar, the coupling being configured to selectively permit and prevent relative rotation between the shaft support bracket and the collar when: the shaft support bracket is fixedly connected to the mounting bracket, said one end of the shaft is engaged in the opening of the shaft support bracket, and the collar is fixedly connected to the shaft.
2. 2. A mechanism as defined in claim 1, wherein the coupling comprises a ratchet.
3. 3. A mechanism as defined in claim 1 or claim 2, wherein the opening in the shaft support bracket is positioned such that, when the retrofittable mechanism is installed, an underside of the shaft is spaced less than 100mm, or less than 70mm, or less than 50mm, or less than 40mm, or less than 30mm, or less than 20mm, or less than 15mm, or less than I Omm, or about 5mm to about 10mm, above the mounting bracket.
4. 4. A roller door assembly, comprising: a roller door curtain assembly comprising: a shaft, two or more wheels spaced along the shaft and rotatable with respect to the shaft, a corrugated curtain having one end connected to the wheels, the curtain being wind able around the wheels and unwindable from the wheels, wherein the corrugations of the curtain are oriented parallel to the shaft, and wherein the curtain has a width less than the length of the shaft, such that opposite ends of the shaft project beyond the curtain, and at least one torsion spring extending over a portion of the shaft that is inside the curtain when the curtain is wound up on the wheels, wherein one end of the torsion spring is fastened relative to the shaft and the other end of the torsion spring is fastened relative to the curtain; a pair of roller door wall mounting brackets for connection to a wall of a structure comprising an opening that is to be closed by the curtain, the wall mounting brackets each being adapted for supporting a respective end of the shaft; a retrofittable mechanism as defined in any one of claims 1 to 3, wherein: the shaft support bracket of the retrofittable mechanism is fixedly connected to one of the wall mounting brackets, the respective end of the shaft is engaged in the opening of the shaft support bracket, and the collar of the retrofittable mechanism is fixedly connected to the respective end of the shaft.
5. 5. A method of retrofitting a roller door assembly with a mechanism for adjustment of roller door spring torsion, wherein: the method is for a roller door assembly of the type comprising: a roller door curtain assembly comprising: a shaft, two or more wheels spaced along the shaft and rotatable with respect to the shaft, a corrugated curtain having one end connected to the wheels, the curtain being windable around the wheels and unwindable from the wheels, wherein the corrugations of the curtain are oriented parallel to the shaft, and wherein the curtain has a width less than the length of the shaft, such that opposite ends of the shaft project beyond the curtain, and at least one torsion spring extending over a portion of the shaft that is inside the curtain when the curtain is wound up on the wheels, wherein one end of the torsion spring is fastened relative to the shaft and the other end of the torsion spring is fastened relative to the curtain; a pair of roller door wall mounting brackets for connection to a wall of a structure comprising an opening that is to be closed by the curtain, the wall mounting brackets each being adapted for supporting a respective end of the shaft; and one or more clamp for fixedly connecting the shaft to the mounting brackets and for preventing rotation of the shaft relative to mounting brackets whilst the clamp is tightened; and wherein the method comprises: removing the one or more clamp; and replacing at least one of the one or more clamp with a retrofittable mechanism as defined in any one of claims 1 to 3.