GB2246383A

GB2246383A - A friction brake

Info

Publication number: GB2246383A
Application number: GB9015447A
Authority: GB
Inventors: Roger Kenneth Gunn
Original assignee: VENTOLITE NSB Ltd
Current assignee: VENTOLITE NSB Ltd
Priority date: 1990-07-13
Filing date: 1990-07-13
Publication date: 1992-01-29
Also published as: GB9015447D0

Abstract

A friction brake for use in conjunction with a cylindrical shaft for supporting a roll of material, such as a roller blind, comprises a capsule housing a rotatable pulley including an opening through which portions of a compressible cord (18), slung around the pulley, pass, wherein the maximum dimension of the opening is less than twice the diameter of the cord in its uncompressed state. In use, the pulley is connected to a roll shaft of a roller blind and is operated by pulling the cord. On releasing the cord the friction brake acts to prevent free rotation of the blind under its own weight. <IMAGE>

Description

FRICTION BRAKE This invention relates to a friction brake and particularly to a friction brake for use in conjunction with a cylindrical shaft for supporting a roll of material, such as a roller blind.

It is known to support one end of the shaft on a holder housing a rotatable cord pulley, which is coupled to a roller blind shaft. A cord is slung around the pulley and the free portions of the cord pass through an opening in the holder. Pulling one of the free portions of the cord causes the roller blind shaft to rotate and either wind or unwind the blind.

A friction brake may be provided to prevent the rolled up blind from unwinding under its own weight.

One known type of friction brake comprises a loose clamp which encloses a short length of the two free portions of the cord in a space defined generally between the cord pulley and the opening in the holder. On releasing the cord, rotation of the shaft causes the clamp to move laterally, and trap the cord between itself and the pulley. A brake of this kind is described in European Patent No. 0086000.

It is also known to use a brake which does not It is also known to use a brake which does not require a loose clamp to effect the necessary braking force to the roll shaft. Instead, the device includes two separate cord passages terminating in separate apertures through which the free portions of the cord respectively pass. The passages meet in a chamber adjacent the pulley.

On releasing the cord, rotation of the roll shaft causes one of the free portions to engage frictionally the other free portion and force it against a wall of the chamber; the resulting frictional forces act to prevent further rotation of the pulley.

The above friction brakes, although they prevent unwinding, permit a considerable degree of rotation of the pulley under the weight of the blind before coming into play. This is clearly undesirable since it allows partial unwinding of the blind.

Hence, there is a need for a more efficient friction brake, that is, a brake which permits a minimum degree of rotation of the pulley before taking effect.

The present invention provides a more efficient friction brake which obviates the need for the clamp or separate cord passages described above.

According to the invention there is provided a friction brake comprising a capsule housing a rotatable pulley including an opening through which portions of a compressible cord, slung around the pulley, pass, wherein the maximum dimension of the opening is less than twice the diameter of the cord in its uncompressed state.

In use, the pulley is preferably connected to a roll shaft.

The portions of the cord frictionally engage one another in the opening. Any rotation of the pulley acts to displace the cord portions to one side of the opening, thereby jamming the pulley to prevent further rotation.

Thus. the above frictional engagement improves the efficiency of the friction brake in preventing rotation of the roll shaft.

The pulley and roll shaft can be rotated, either clockwise or anti-clockwise, by pulling the individual cord portions which pass through the opening.

Preferably, the capsule is formed of two interengaging parts.

Preferably, one of the parts is a closure member having a projection which extends into a recess in the other part, to define the opening.

The pulley advantageously includes connection means to enable it to be connection to a roll shaft, which is preferably a roller blind shaft.

The capsule parts may be fastened into engagement with one another by any suitable means, for example, by using screws or, alternatively, the parts can be formed to snap-fit together.

Preferably, the pulley includes projections which engage the cord slung around it to increase the friction between cord and pulley and prevent slippage.

It is preferable that the friction brake additionally includes mounting means which enable it to be mounted on a wall, or a window frame, for example.

Preferably, the mounting means is a mounting bracket including a cruciform hole into which a cruciform peg, mounted on the capsule of the friction brake, fits. Other shapes of hole and peg are, of course, possible. For example, the hole and peg may be of square or octagonal cross-section. This enables fitting of the friction brake into the bracket in any of four positions, allowing either wall or ceiling mounting. It will be apparent to one skilled in the art that the friction brake can be used in conjunction with any pulley which employs a compressible cord or the like.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is a side view of a friction brake; Fig. 2 is a section through a support member; Fig. 3 is a plan view of the support member of Fig.

2; Fig. 4 is an underside plan view of the support member of Figs. 2 and 3; Fig. 5 is a plan view of a closure member; Fig. 6 is a side view of the closure member of Fig.

5; Fig. 7 is a side view of a pulley.

Fig. 8 is an underside plan view of the pulley of Fig. 7; Fig. 9 is a side view of a mounting bracket; and Fig. 10 is a perspective view of an assembled friction brake mounted to the bracket of Fig. 9.

housing a rotatable pulley 2. The capsule is formed by engagement of two members, an annular closure megbei 3 and a circular support member 4.

As shown in Figs. 2 and 3 the circular support member 4 comprises a disc having an axially extending circumferential rim 5 and a central circular post 6.

The support member 4 also includes a circular inner waii 7, which is concentric with the rim 5 and extends axially, by a shorter distance than the rim 5 and post 6 to form a support surface 8. The space defined generally between the post 6 and the inner wall 7 comprises an annular recess 10.

As shown in Figs. 1 and 3 the circumferential rim 5 1 us a slot 9. A portion of the inner wall 7 extends utwardly. as shown in Fig. 3, to connect the Si#t 9 with the annular recess 10.

As shown in Figs. 1.2 and 4 the closure member 4 also includes a cruciform peg 11, diametrically opposite the post 6.

As shown in Figs. 5 and 6, the closure member 3 comprises a flat annular ring having a projection 12 and a closure surface 13. The width of the closure surface 13 is sliahtl-y greater than the distance between he circumferential rim 5 and inner wall 7 of the support member 4, and the thickness of the ring is approximately equal to the axial distance between the support surface 8 of the inner wall 7 and the end of the rim 5 of the support member 4.

As shown in Figs. 7 and 8, the friction brake further comprises a pulley 2 having a plurality of teeth 14, and includes an inner axially extending connector 15, -jameti-ically opposite a circular central recess 16.

The conneczor 15 iay be circular as shown or of any othel- shape tnat provides grip within the roller blind. The diameter of the circular central recess is is slightly greater than that of the post 6 of the spot member 4, and the diameter of the pulley 2, as shown in Fig. 8, is slightly less than that of the annular recess 10 of the support member 4.

The width of the pulley, that is, the distance x-x' in Fig. 7, is approximately equal the axial distance y-y'. from the support surface 8 to the disc of the support member 4, in Fig. 2.

To assemble the friction brake, a compressible cord 17 is slung around the pulley 2, and the circular central recess 16 of the pulley 2 is located on the post 6 of the support member 4, so that the pulley 2 seated in the annular recess 10. The free ends of the cord pass through the slot 9.

the cord pass through the slot 9.

As shown in Fig. 1, the closure surface 13 of the closure member 3 is supported on the support surface 8 of the support member 4. The projection 12 engages the slot 9 to define a rectangular opening 19 having a maximum dimension less than twice that of the cord 17 in its uncompressed state.

As shown in Figs. 9 and 10 the assembled brake is mounted onto a bracket 21, including a cruciform hole 22 into which the cruciform peg 11 of the support member 4 fits. This enables fitting of the friction brake into the bracket 21 in any of four positions, allowing either wall or ceiling mounting.

As shown in Figs. 3 and 5 the support and closure members include screw holes 20, enabling the assembled device to be firmly fastened together using suitable screws.

In use, the connector 15 of the pulley 2 is coupled to a roll shaft of a roller blind. By pulling on a individual free portion 18 of the cord 17, the pulley 2 and roller blind shaft can be rotated to raise or lower the blind. On releasing the cord, free rotation of the blind under its own weight is restricted by the frictional engagement, between the portions 18 of the cord and the walls of the opening 19, and between the portions 18 themselves. Upon rotation of the roller blind shaft, the portions 18 of the cord 17 are displaced to one side of the opening 19, thereby jamming the pulley 2 to prevent any further rotation.

Claims

1. A friction brake comprising a capsule housing a rotatable pulley including an opening through which portions of a compressible cord, slung around the pulley, pass, wherein the maximum dimension of the opening is less than twice the diameter of the cord in its uncompressed state.

2. A friction brake as claimed in cai 1, wherein the capsule is formed of two interengagable parts, one of which is a closure member having a projection which extends into a recs in the other art, t define the opening.

3. . friction brake as claimed in n claim 1 er ^, wherein the pulley includes connection means te enable ~-~~ e it tc be connected te a reil shaft, which ;- preferably a roller blind shaft

4. A friction brake as claimed in any proceding claim, wherein the pulley includes protections for engagement with the cord to increase the friction therebetween.

5. A friction brake as claimed in any preceding claim, wherein the friction brake includes mounting means comprising a mounting bracket having a cruciform hole for engagement with a cruciform peg.

6. A friction brake as claimed in claim 5, wherein the cruciform peg is mounted on the capsule.

7. A friction brake substantially as described herein with reference to the accompanying drawings.