GB2376051A

GB2376051A - Speed restricting mechanism with latched brake elements integral to rotor

Info

Publication number: GB2376051A
Application number: GB0111159A
Authority: GB
Inventors: Terence Ronald Green
Original assignee: QM Group Ltd
Current assignee: QM Group Ltd
Priority date: 2001-05-05
Filing date: 2001-05-05
Publication date: 2002-12-04
Anticipated expiration: 2021-05-05
Also published as: GB2376051B; GB0111159D0

Abstract

A speed restricting mechanism for a rotational drive includes a rotor 6 for rotation with the rotational drive, a stationary cylindrical brake drum 2 and a braking member 4. The rotor 6 includes a pair drive pins (28, fig 13) that engage the braking member 4 to drive rotation thereof. The braking member 4 including two braking elements (18, fig 8), mounted for radial movement between a first position in which they engage the braking surface and a second position in which the braking surface is not engaged. The braking member 4 may be a planar elastomeric moulding with flexible elbows (16, fig 8). A latching element (22, fig 8) is engaged by the pins of the rotor 6 and latches the braking element in the second position when the rotor rotates in a first direction, and is unlatched when the rotor rotates in a second direction. The mechanism may form part of a sprung tape cartridge (figs 14 and 15) for a personal barrier.

Description

SPEED RESTRICTING MECHANISM The present invention relates to a speed restricting mechanism and in particular, but not exclusively, to a speed restricting mechanism for use in a tape cartridge that forms part of a personnel barrier system.

Personnel barrier systems that use retractable tapes are well known. Typically, a flat woven

tape is wound onto a spool in a cartridge. The spool is spring-biased for example using a ZD clock spring to rewind the tape into the cartridge after use.

Sometimes, a speed restricting mechanism is provided, to prevent the tape from rewinding too quickly. One such system described in US 5,967, 443 uses a centrifugal braking system in which a pair of brake blocks that rotate with the spool are urged outwards by centrifugal forces against a stationary brake drum when the spool rotates A disadvantage of this arrangement is that the mechanism is relatively expensive to produce and it suffers from excessive brake-wear. making use of the system less convenient.

It is an object of the present invention to provide a speed restricting mechanism that mitigates at least some of the aforementioned disadvantages.

According to the present invention there is provided a speed restricting mechanism for a rotational drive. the mechanism including a rotor device for rotation with the rotational drive, a stationary brake drum having a substantially cylindrical braking surface, and a braking member mounted for rotation relative to the rotor device, said rotor device including a driver element that is engageable with the braking member to drive rotation thereof, and said braking member including at least one braking element mounted for radial movement between a first position in which it engages the braking surface and a second position in which it does not engage the braking surface, and a latching element engageable by the rotor device for latching the braking element in said second position; the mechanism being constructed and arranged such that said braking element is latched in said second position when the rotor device rotates in a first direction, and is unlatched when the rotor device rotates in a second direction.

The latching mechanism allows the brakes to operate when the rotor rotates in the second direction, but prevents them operating when the rotor rotates in the ih'st direction. Thus. when installed in a tape cartridge for a personnel barrier-the mechanism is capable of restricting the speed at which the tape is rewound into the cartridge. However, when the tape is being drawn from the cartridge, the brakes do not operate, thus avoiding unnecessary

brake wear and making use of the system more convenient.

Advantageousty. the braking member inctudes a rotatahk arm and at) east one braking element that is connected to an end of thc rotatabk arm b\ means of a resilient elbow. This avoids the need tor a separate link mechanism, thus simplifying the de'ice. I he rotatable arm and the braking element may subtend an obtuse angle. tor example approximatC] y ! 35-Preferahly. the hraking member inciudes two braking elements attached to opposite ends of the rotatable arm. the braking member may be a moulded component and is preferabb. made of an elastomer.

Advantageous)}, thc braking member comprises a substantialb Hat piate. the iiiciii) ci- coiiiliri ; k : s i plate. The latching clement preferably includes a formation provided on a free end of said braking element. The latching element is preferably constructed and arranged to be engaged by the driver clement.

Advantageously. the rotor device comprises a rotatable arm and said driver element comprises at least one pin that depends from said arm.

According to a further aspect of the indention there is pro\ided a tape cartridge tor a personal barrier, said cartridge including a spool of tape. a housing, a return spring and a speed restricting mechanism according to any one ofthe preceding claims-said rotor device being connected to said spool for rotation therewith and said brake drum being connected

to said housing. to sal C7, An embodiment of the present invention will now be described, by way of example with reference to the accompanying drawings, in which : Figure 1 is a plan view of the speed restricting mechanism : Figure 2 is plan view of the mechanism in a second position :

Figure 3 is a cross-section on line Ill-Ill of Figure 2 ; Figure 4 is a plan view of the mechanism from below; Figure 5 is an isometric view of the mechanism from above; Figure 6 is an isometric view of the mechanism from below; Figure 7 is an exploded isometric view from above; Figure 8 is a plan view of a brake plate forming part of the mechanism; Figure 9 is a plan view of a rotor device forming part of the mechanism; Figure 10 is a side view of the rotor ; Figure 11 is a plan view of the rotor from below; Figure 12 is an isometric view of the rotor from above ; Figure 13 is an isometric view of the rotor from below ; Figure 14 is a side section through a tape cartridge that includes a speed restricting mechanism, and

Figure 15 is a cross-section through the tape cartridge of Fig. 14. t Z-1 The speed restricting mechanism is intended primarily for use in the tape cartridge of a personnel barrier system. In a typical tape cartridge, a spool of woven tape is mounted in a substantially cylindrical housing. Tape can be withdrawn through a slot in the housing, causing the spool to rotate. A clock spring is connected to the spool, which retracts the tape into the cartridge when the tape is released. An example of a tape cartridge that includes a speed restricting mechanism is shown in Figs. 14 & 15 and described below.

The speed restricting mechanism 1 includes three parts : a brake drum 2, a brake plate 4 and z : l a rotor device 6. Normally, the mechanism is mounted in the upper part of a tape cartridge, the rotor being mounted for rotation with the spool and a brake drum being connected to the housing of the cartridge, so that it does not rotate. The brake plate 4 is mounted for free rotation.

The drum 2 consists of a short cylindrical metal sleeve, for example having an internal diameter of 50mm and a height of) Omm.

The brake plate 4 comprises an elastomer moulding, for example of polyurethane, having a height of 2. ! 5mm.'the plate includes a centra) ring 8 having an interna) diameter of I : 1mm and tvm arms 1 () that extend outwards from the ring. Each arm I0 includes a rigid inner portion 12 that extends radially outwards from the ring 8 and has a mating formation ) 3 at its outer end. and an outcr portion] 4 that is connected to the inner-portion 12 hv a rekitivciy narrow. flexihie cfbow] o. The outer and inner portions of each arms subtend an obtuse angle (of approximately 135).

The outer arm portion 14 increases in width from the etbow ouhvards. the outer end (4'the outer arm portion being relatively thick and massi\e. the outer end inctudes a cur\ed braking surface 20 that is matched to the cur\ature of the inner wa !) of the brake drum 2.

A tatching formation 22 is pro\ided at the outer end of the outer arm portion ! 4.

The rotor device 6 includes a centra) boss 24 having a hexagonal bore 25 that. in use. fits over a projecting hexagonal shaft on the tape cartridge spoof The rotor device therefore rotates with the spoo) whenever tape is withdrawn from or retracted into the cartridge. A generally rhombic cross-arm 26 is attachecl to the upper end of the boss 24. From each end of this arm depends a short cylindrical drive pin 28.

In the assembled braking mechanism, the brake plate 4 fits into the brake drum 2 v\ith a smash clearance between the braking surfaces 20 and me inner surface of the brake drum. 'the rotor 6 is seated on top of the p) ate 4 with a smaH vertical clearance between the two. The boss 24 extends through the centra) ring 8 of the brake plate and is mounted on the shaft of the spool. Each drive pin 28 depends downwards between the outer end of the inner portion of one arm 10 and the outer end of the outer arm portion 14 of the other arm. In use, the rotor 6 rotates with the spool. whereas the brake plate 4 is free to rotate in either direction. between limits imposed by the drive pins 28. As the rotor rotates. the drive pins 28 engage either the mating formations 13 art the outer ends of the inner arm portions 12 (in z the case of clockwise rotation). or the latching formations 22 at the outer ends of the outer

arm portions 14 (in the case of anti-clockwise rotation). In both cases, the brake plate will then rotate with the rotor.

When the spool rotates rapidly clockwise (which it does when the tape is being retracted into the cartridge), the rotor and the brake plate also rotate clockwise and the relatively massive outer arm portions 14 spread outwards, owing to the centrifugal forces acting on them. This brings them into contact with the stationery brake drum 2, providing a braking effect that is proportional to the speed of rotation.

When the rotor rotates anti-clockwise (which it does when tape is withdrawn from the

cartridge), the drive pins 28 engage the latching formations 22 at the outer ends of the outer cartri arm portions 14. The brake plate 4 also then rotates with the rotor, but outwards movement of the outer arm portions 14 is prevented by the engagement of the drive pins 28 with the latching formations 22. A small clearance is therefore maintained between the braking surfaces 20 on the outer arm portions 14 and the inner surface of the brake drum 2. No braking effect is therefore produced, allowing the tape to be withdrawn easily from the cartridge and preventing wear of the brake surfaces.

A tape cartridge that includes a speed restricting mechanism is shown in Figs. 14 & 15. The tape cartridge 30 includes a spool 32 of woven tape 34 that is mounted in a substantially cylindrical housing 36. Tape can be withdrawn through a slot 38 in the housing, causing the spool 32 to rotate. A clock spring 40 is connected to the spool 32, which retracts the tape into the cartridge when the tape is released. The cartridge also includes a connector 42 to which the end of another tape may be connected.

The speed restricting mechanism 1 is mounted in the upper part of the housing 36, beneath an end cap 44. The rotor 6 is mounted for rotation with the spool 32 and the brake drum 2 is connected to the housing 36 of the cartridge, so that it does not rotate. The brake plate 4 is mounted for free rotation.

When tape is withdrawn or retracted, the spool 32 rotates and the rotor rotates with it. If the tape is withdrawn and then released, it is retracted into the cartridge by the spring 40.

The speed at which the tape is retracted is limited by the braking action of the speed restricting mechanism 1. For example, we have found that for a typical cartridge with a

fully withdrawn tapc. the retraction time is increased from iess than one second to approximatety 2-3 seconds.

Various modifications of the above described invention are of course possible, for exampte with regard to the shapes, dimensions and materials of the component parts,' ['he brake plate 4 may also be modiHed to include meta) weights in the outer arm portions 14. to increase the centhtuga) braking effect.

Further. the de\iee may be modiHed such that the outer arm portions 14 normaUv engage the brake drum 2. In this case. the latching formations 22 may be slightly modiHed in shape so that when those formations arl'engaged by the dri\ e pins 2S. the outer arm portions arl' drawn inwards, providing a smai) ciearance between the braking surfaces and me drum. the braking mechanism) s atso applicable to other uses apart from tape cartridges-sue)) as for examptc retractable measuring tapes and inertia ree) seat beh. s.

Claims

CLAIMS I A speed restricting mechanism for a rotational drive, the mechanism including a rotor device for rotation with the rotational drive, a stationary brake drum having a substantially cylindrical braking surface, and a braking member mounted for rotation relative to the rotor device, said rotor device including a driver element that is engageable with the braking member to drive rotation thereof, and said braking member including at least one braking element mounted for radial movement between a first position in which it engages the braking surface and a second position in which it does not engage the braking surface, and a latching element engageable by the rotor device for latching the braking element in said second position the mechanism being constructed and arranged such that said braking element is latched in said second position when the rotor device rotates in a first direction, and is unlatched when the rotor device rotates in a second direction.

2. A speed restricting mechanism according to claim 1, wherein the braking member Z7, includes a rotatable arm and at least one braking element that is connected to an end of the rotatable arm by means of a resilient elbow.

3. A speed restricting mechanism according to claim 2, wherein the rotatable arm and the braking element subtend an obtuse angle.

4. A speed restricting mechanism according to claim 2 or claim 3, wherein the braking member includes two braking elements attached to opposite ends of the rotatable arm.

5. A speed restricting mechanism according to any one of the preceding claims, wherein the braking member is a moulded component.

6. A speed restricting mechanism according to any one of the preceding claims. wherein the braking member is made of an elastomer.

7. A speed restricting mechanism according to any one of the preceding claims, Z=l wherein the braking member comprises a substantially flat plate.

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A speed restricting mechanism according to any one of the preceding claims.

wherein the latching element includes a formation provided on a free end or said braking element.

9. A speed restricting mechanism according to any one of the preceding claims. wherein the latching etement is constructed and arranged to be engaged bv the driver element.

H). A speed restrictmg mechanism according to any one of the preceding ctaims. wherein said rotor device comprises a rotatabie arm and said driver etement comprises at least one pin that depends from said arm.

11, A speed restricting mechanism suhstantially as described herein \\ith refcn.'1Ke to and as Hiustrated in the accompanying drawmgs.

12. A tape cartridge for a persona) barner. said cartndge including a spoo] of tape. a housing, a return spring and a speed restricting mechanism according to any one of the preceding claims, said rotor device being connected to said spool for rotation therewith and said brake drum being connected to said housing.