GB2218142A - A tensioning mechanism for roller shutters - Google Patents

Abstract

A tensioning mechanism for use with a cylindrical roller member of a roller shutter of a cabinet comprises three different types of parts, namely fixed, sliding or rotating. The fixed parts include a hexagonal shaft (20) with flanged bushes (24) at each end with a flange (25) inwardly facing the other bush but spaced apart by the whole of the central zone of the roller member. The flanged bushes (24) are keyed on the hexagonal shaft (20). The sliding parts include respective keyed bushes (32) and at the right hand end only a pawl member (34). The bushes (30, 32) are keyed on the hexagonal shaft (20) and can only slide longitudinal therealong at respective ends thereof. The keyed bush (32) has diametrically opposite T-shaped grooves (33). The rotating parts include a tubular element (40), an integrally formed bush member (not shown) and a ratchet member (44) provided with angled teeth (45) which is independently rotatable with respect to the tubular element (40) and slidable with respect to the flanged bush (24). A helical spring has one end attached to the hexagonal shaft (20) by passing through a hole in the shaft and the other end in a hole in the outer peripheral surface of the ratchet member (44). <IMAGE>

Description

"A tensioning mechanism" The present invention relates to a tensioning mechanism for use with a cylindrical member within which it is housed, such that the cylindrical member can be rotated once installed between a pair of retaining means.

More particularly, the present invention relates to a tensioning mechanism for roller shutters used in cabinets. There are many types of cabinets provided with roller shutters, the shutters effectively constituting a door the full width and height of the cabinet. The roller shutters are in the form of slats hinged along their longitudinal edges to one another to provide both the necessary rigidity when forming a door to close the cabinet and also the necessary flexibility so that they can be wound up on a roller when the cabinet is "open".

The roller mechanism is generally sold separately and fitted into the cabinet either initially or to replace a borken or defective roller mechanism.

As is well known with roller blinds for windows, the roller mechanism is provided with spring means which has to be pre-tensioned before use, so that the roller mechanism will wind-up the blind when released from the extended position.

When sold separately roller shutters have to be pre-tensioned to the correct value before they are packed and transported. They then have to be installed in the cabinet without releasing the pre-tensioning given to the helical spring mechanism within the tubular element of the roller. Previously, such roller shutters have been provided with either dog clutches or gravity acting pawls and ratchets, which enable the pre-tensioning to be maintained before installation, and released once the roller shutter has been correctly installed in the cabinet. In the case of gravity acting pawls or ratchets, an impulse force may dislodge the pawl.

However, the width between the side walls of manufactured cabinets may vary very considerably, and the tolerance permitted in longitudinal movement where dog clutches are concerned is quite critical, so that if the walls of the cabinet are too close together, it may be impossible to install the roller shutter, and if they are too far apart, the clutch mechanism may become disengaged during installation with the result that the pre-tensioning is lost and cannot be restored.

It is therefore an object of the present invention to provide a tensioning mechanism which overcomes this disadvantage.

According to the present invention there is provided a tensioning mechanism for use with a cylindrical member within which it is housed, such that said cylindrical member can be rotated once installed between a pair of spaced apart retaining means; including: (a) means for locking said tension mechanism against rotation relative to the cylindrical member so that a rotational tension can be pre-stored within the mechanism; (b) means for permitting said cylindrical member to be installed within said pair of retaining means permitting a substantial tolerance in the distance between said retaining means without loss of the pretension stored; and (c) means for releasing said locking means once installation has been effected, whereby said cylindrical member is free to be rotated relative to the tensioning mechanism.

Preferably the locking and unlocking of said mechanism is effected by means of a ratchet and pawl arrangement. The ratchet may be provided with substantially triangular shaped teeth having one perpendicular and one inclined face. The pawl may be constituted by an annulus having longitudinal bar-shaped ribs.

Preferably said various means for locking and unlocking is constituted by an annular keyed bush provided with a pair of diametrically opposite T-shaped grooves, the bush sliding within the pawl member which is provided with a pair of diametrically arranged studs on its inner surface to engage within the grooves of the bush.

The grooves preferably have a first section parallel to the longitudinal axis of the bush, the first section being provided for assembly purposes, and a second section at right angles thereto and extending a short distance around the circumference of the bush on either side of the first section, the second section providing the locking of the teeth on the ratchet with the ribs on the pawl.

The present invention will now be described in greater detail by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a cross-sectional elevation view of a roller shutter having the tensioning mechanism of the present invention installed therein; Fig. 2 is an exploded perspective view of the essential parts of the tensioning mechanism; Figs. 3A to 3C are cross-sectional elevation views of the roller shutter and tensioning mechanism shown in Fig. 1, showing the variation in the overall length of the shutter roller and the position of the various parts during installation of a pre-tensioned roller shutter into a cabinet; and Figs. 4A and 4B are elevation views of the holders fixed to the walls of a cabinet in which the roller shutter is to be installed.

Referring to the drawings, the tensioning mechanism is housed within a tubu#lar element 40 on which a roller shutter 10 is provided. The side walls 12 and 14 on a cabinet (not shown) are provided with respective holders 16 and 18 for receiving the ends of the tensioning mechanism. The holder 16 is provided with a large sized keyed slot 17 whilst the holder 18 is provided with two layers, an outermost layer having an hexagonal shaped keyed slot 19a and an inner layer having a round hole 19b for the purpose of re-tensioning in situ.

The tensioning mechanism comprises three different types of parts which are categorized according to their freedom of movement, i.e. fixed, sliding or rotating.

The fixed parts include a hexagonal shaft 20 and a pair of flanged bushes 22 and 24 having flanges 25 inwardly facing one another but spaced apart by the whole of the central zone of the roller. The flanged bushes are keyed on the hexagonal shaft 20 and securely fixed thereto so that they are in fixed relation to one another.

The sliding parts include keyed bushes 30 and 32 and at the right hand end only a pawl member 34. The bushes 30 and 32 are keyed on the hexagonal shaft 20 and can only slide longitudinal therealong at respective ends thereof.

The rotating parts include a tubular element 40 forming part of the shutter 10, an integrally formed bush member 42 at the left hand end of the sleeve member and a ratchet member 44 at the right hand end which is independently rotatable with respect to the tubular element 40 and slidable with respect to the flanged bush 24.

A helical spring 50 has one end 51 attached to the hexagonal shaft 20 by passing through a hole (not shown) in the shaft and the other end 52 anchored in a hole in the outer peripheral surface of the ratchet member 44.

The hexangonal shaft 20 is provided with a pair of starlock washers 26 and 28 which are fixed to the shaft for the purpose of retaining the sliding and rotating parts of the tensioning mechanism. A secondary spring 27 is provided to assist in the installation of the roller shutter in a cabinet.

Referring more specifically to Fig. 2, the keyed bush 32 is provided with diametrically opposite T-shaped grooves 33 on its outer cylindrical surface. Each groove 33 comprises a first straight section a-b which is parallel to the longitudinal axis of the bush 32, and a second straight section c-d at right angles to the first section around the circumference of the outer surface of the bush 32, the two sections together forming the T-shaped groove 33.

The pawl member 34 is provided with a plurality of bar-shaped ribs 35 which are equi-shaped around its outer cylindrical surface. A pair of studs 36 are arranged diametrically opposite one another on the inner cylindrical surface of the pawl member 34. The studs are such a size that they engage in the groove 33 of the bush 32. Thus the relative longitudinal movement of the bush 32 within the pawl member 34 is determined by the first section a-b of the groove 32. Short rotational movements of the bush 32 relative to the pawl member 34 are determined by the second section c-d, and the purpose of which will be described later on in greater detail.

The ratchet member 44 is provided with angled teeth 45. The teeth 45 are equi-shaped in a peripheral zone around an annular face 46 thereof. Each tooth 45 has an inclined face 47 and a face 48 which is perpendicular to the annular face 46 of the ratchet member 44. The perpendicular faces 48 are adapted to engage against the ends of the bar-shaped ribs 35, and when in contact therewith prevent rotation of the ratchet member 44 in a clockwise direction relative to the pawl member 34.

However, anti-clockwise rotation of the ratchet member 44 relative to the pawl member 34 is possible since the ends of the bar-shaped ribs 35 will slide over the inclined faces 47 of the teeth 45.

The tubular element 40 is provided with a longitudinal peripheral groove 41 which engages with a rib member (not shown), in the roller shutter 10, so that the tubular element 40 is keyed for rotation with the roller shutter 10 of the cabinet.

Referring more specifically to Figs. 3A to 3C the various positions of the parts of the tensioning mechanism are shown during assembly of the roller shutter into a cabinet.

Firstly, as shown in Fig. 3A, the parts of the roller shutter are in the position where it is packed for transportation. In this position, the studs 36 have been moved along the groove 33 of the bush 32 so that they are located in the groove at d. In this position, relative longitudinal movement of the bush 32 relative to the pawl member 34 is prevented, and also the perpendicular faces 48 of the teeth 45 are held into engagement against the ends of the bar-shaped ribs 35 by the tension stored in the spring 50, which has been pre-set to the desired value during manufacture.

Next, in order to assemble the roller shutter to a cabinet, the right hand end of the shaft 20 is inserted into the hexagonal shaped keyed slot 19a in the holder 18 which is fixed to the wall of the cabinet. Once the shaft 20 has been keyed into the slot 19a, the whole mechanism can be pushed to the right in order to provide sufficient clearance to key the left hand end of the mechanism.

As will be noted from Fig. 3A, where the roller shutter is in the packed position, the flange 25 of the bush 24 is in abutment with the left hand end of the ratchet member 44, whilst there is a considerable distance between the flange 25 of the bush 22 and the right hand end of the member 42. In assembling the shutter roller, the tubular element 10 is effectively urged to the right against the action of the secondary spring 27. During this movement the bush 34 passes over the starlock washer 28, the spring 27 being compressed as will be seen from Fig. 3B. Movement to the right is asserted when the flange 25 of the bush 22 abuts against the right hand end surface of the integrally formed bush 42. As will be noted from Fig. 3B, there is a short gap between the left hand end of the keyed bush 30 and the peripheral flange of the holder 16.

Finally, the tubular element is moved to the left to permit the keyed bush 30 to locate within the large sized keyed slot 17 of the holder 16. During this operation the secondary spring 27 urges the sliding parts to the left and it should be noted that the flanges 25 of the flanged bushes 22 and 24 are approximately equidistant from the ends of the integrally formed bush member 42 and the ratchet member 44 respectively.

The mechanism comprising the pawl member 34 with its bar-shaped ribs 35, and the keyed bush 32 with its grooves 33 will now be explained in greater detail.

When tensioning, the pawl member 34 is pushed so that its studs 36 are aligned with the section c-d of the groove 33. As the shaft 20 is wound round relative to 40, the studs 36 engage at c. The pawl can 'jump' the ratchet due to the triangular parts 47 of the teeth 45, and acting against the spring 27. When tensioning is complete and the shaft 20 is released, the pawl member 34 rotates back under the action of the spring 50 until its teeth 35 engage with the perpendicular face 48 of the ratchet teeth 45. The mechanism is now locked.

When installed and required for use, the roller shutter 10 is pulled, rotating the tubular element 40 to which it is attached. The triangular teeth 45 of the ratchet then cause the pawl member 34 to rotate until the studs 36 coincide with the section a-b of the groove at which point the pawl member 34 can move longitudinally allowing disengagement.

For increasing the tension in situ the shaft 20 is shifted such that the hexagonal section clears the keyed slot 19a, the mechanism resting on the cylindrical and undersized part 29 of the hexagonal shaft 20.

A spanner can then be used on the rotationally unrestrained shaft 20 to increase the tension of the mechanism, after first engaging the ratchet by aligning the studs 36 in the pawl member 34 in the second section of the groove at c.

The advantages of the above described mechanism are as follows: (a) the tension in the spring 50 can be pre-set and stored during packaging and transportation.

(b) due to the T-shaped groove there is no danger that the spring 50 can become untensioned during installation.

(c) due to the provision of the sliding parts including the provision of the first section of the groove 33, there is no problem in fitting the mechanism to cabinets where the distances between the side walls varies in manufacture.

It will be appreciated that although the invention has been described in relation to a roller shutter for cabinets, it may have other applications where it is desired to use a tensioning mechanism with a cylindrical member, such that the cylindrical member can be rotated once installed between a pair of spaced apart retaining means and the novel locking mechanism has been released. For example the invention could find application in pretensioned cable and drum mechanisms which have to be installed on location.

Claims (7)

CLAIMS:

1. A tensioning mechanism for use with a cylindrical member within which it is housed, such that said cylindrical member can be rotated once installed between a pair of spaced apart retaining means; including: (a) means for locking said tension mechanism against rotation relative to the cylindrical member so that a rotational tension can be pre-stored within the mechanism; (b) means for permitting said cylindrical member to be installed within said pair of retaining means permitting a substantial tolerance in the distance between said retaining means without loss of the pre-tension stored; and (c) means for releasing said locking means once installation has been effected, whereby said cylindrical member is free to be rotated relative to the tensioning mechanism.

2. A tensioning mechanism according to claim 1, wherein the locking and unlocking of the tensioning mechanism is effected by means of a ratchet and pawl arrangement.

3. A tensioning mechanism according to claim 2, wherein the ratchet is provided with substantially triangular teeth having one perpendicular and one inclined face.

4. A tensioning mechanism according to claim 2 or 3, wherein the pawl is constituted by an annul us having longitudinal bar-shaped ribs.

5. A tensioning mechanism according to claim 2, wherein said means for locking and unlocking is constituted by an annular shaped bush provided with a pair of diametrically opposed T-shaped grooves, the bush sliding within the pawl member which is provided with a pair of diametrically arranged studs on its inner surface to engage within the grooves of the bush.

6. A tensioning mechanism according to claim 5, wherein the grooves have a first section parallel to the longitudinal axis of the bush, the first section being provided for assembly purposes, and a second section at right angles thereto and extending a short distance around the circumference of the bush on either side of the first section, the second section providing the locking of the teeth on the ratchet with the ribs on the pawl.

7. A tensioning mechanism for use with a cylindrical member within which it is housed, constructed substantially as herein described with reference to and as illustrated in the accompanying drawings.