INTERNAL DISC BRAKING SYSTEM FOR CYCLES

This specification relates to the application of disc braking systems to bicycles and is applicable to all types of pedal-powered bicycle and tricycle as well as to motorised cycles.

Since the 1950s, almost all pedal-powered bicycle brake systems have used the principle of the Campagnolo side-pull design, in which two calipers are squeezed together by a cable running from the brake handles. Rubber brake blocks place an even pressure on either side of the wheel and are removed via a spring that centres them. When mountain bikes were introduced, improved braking was required and a cantilever system was introduced in which two "half calipers" were attached to each other via a separate cable which in turn was activated by the brake cable from the brake lever. Unless properly adjusted, this system could result in uneven pressures on either side of the wheel and a more suitable solution is the v-brake where the brake cable runs across the top and allows a greater leverage to apply increased force to the brake blocks and so improve stopping power.

Further increases in brake efficiency were provided by hydraulic systems, initially via drum brake technology, adapted from the motor cycle industry. Hub brakes are completely closed and unaffected by the weather. However, they can become overheated when used continuously on long, downhill sections. To improve efficiency and reliability, disc brakes were then developed and they provide significantly better resistance to brake fade, compared to the drum type of system.

As they are open to the air, disc brakes allow better cooling compared to that of drum brakes. Though they are exposed to the weather, water is readily flung off disc brakes. One problem with disc brakes is that their exposed location at the side of the wheel leaves them vulnerable to mechanical damage, e.g. if the bike is carelessly leaned against a wall, or falls over. An additional problem is that of grit becoming trapped between the disc and the brake pad. A further problem exists with disc brakes located at one side of the wheel. In the case of the front wheel, this causes an off-centred braking effect, which can cause the front wheel to twist out of the straight line along which the wheel was previously following. This effect causes uneven strain and fatigue on the forks, which are already highly stressed members, and could de-stabilise a bicycle.

There is thus a need for a disc brake system for bicycles, tricycles and motorised cycles where the discs are protected from inadvertent damage, are in the open air and so do not fade due to overheating and where the application of the brake does not cause a significant off-centred baking effect.

According to the invention, there is provided a braking system for bicycles, tricycles and motorised cycles comprising; i) a disc fast with a member(s) connected either directly or indirectly to the rim and tyre of the wheel and located within the space defined by the hub of the wheel and the two sets of spokes / other members connecting said hub to the rim of the wheel; ii) a braking means, engageable with the disc and fast with a non-rotatable member connected to a part of the frame of the bicycle, tricycle or motorised cycle; and iii) a means, operable by the rider, to cause the braking means to engage with / disengage from the disc; characterised in that when the rider operates the means to cause the braking means to engage with the disc, a braking force is applied to the disc and thence through the tyre to the surface on which the tyre bears to reduce rate of rotation of the wheel and thus slow / stop the bicycle, tricycle or motorised cycle and that when the means to cause the braking means to disengage is operated, the disc, rim and tyre are freed to rotate and the bicycle, tricycie or motorised cycle is able to move.

According to a first variation of the apparatus of the invention, the disc is fast with a sleeve located adjacent to the hub of the wheel and able to rotate about the axle of the wheel.

According to a second variation of the apparatus of the invention, the disc is fast with the rim of the wheel.

According to a third variation of the apparatus of the invention, the disc is located essentially at right angles to the axle of the wheel and in the plane of rotation of the wheel.

According to a fourth variation of the apparatus of the invention, the point of connection of the caliper support member to the non-rotating part of the hub is aligned with the plane of the centreline through the wheel.

According to a fifth variation of the apparatus of the invention, the centre of gravity of the assembly of the disc, braking means and members supporting the braking means is aligned with the centreline through the wheel.

According to a sixth variation of the apparatus of the invention, the disc is aligned to rotate in the plane of the centreline through the wheel.

According to a seventh variation of the apparatus of the invention, the means, operable by the rider, to cause the braking means to engage with / disengage from the disc is a cable arrangement.

According to an eighth variation of the apparatus of the invention, the means, operable by the rider, to cause the braking means to engage with / disengage from the disc is hydraulic.

According to a ninth variation of the apparatus of the invention, the means by which the rim of the wheel is connected to the hub is spokes.

According to a tenth variation of the apparatus of the invention, the means by which the rim of the wheel is connected to the hub is annular piates.

According to an eleventh variation of the apparatus of the invention, the annular plates connecting the rim of the wheel to the hub include removable panels giving access to the disc and braking means therein.

The principle of disc braking is well known and is that of a disc, fast with the rotatable wheel, being acted upon by friction pads, held in a caliper, fast with the frame of the bike. Disc brakes were invented for cars and are normally located within the plane of rotation of the car's wheels, which generally have a dished shape to join the rim to the part which is bolted to the hub. Because of the usual spoked arrangement of bicycle and motorised cycle wheels, the location of disc brakes within the plane of rotation of the wheel has hitherto not been possible. The result, when disc braking has been applied to bikes, is that the disc is located at the side of the wheel and thus vulnerable to the risk of damage.

The location of the disc brake at one side of the wheel causes off-centred braking. The off-centred braking can be corrected on high-powered motor bikes by using twin discs, one on either side of the front wheel. However, this is not practical on bicycles, as they are often leaned against walls, etc. when not in use and a disc on both sides would greatly increase the risk of damage. Side-mounted discs and calipers are also vulnerable to damage from minor collisions.

The principle of the invention is to locate the disc brake within the space bounded by the hub and the two sets of spokes on either side of the wheel. In a preferred design, the disc is mounted on a part of the hub fast with the rotating members and the brake caliper is fast with a non-rotating part of the hub. This requires a complex hub design, accurate machining and skilled assembly but the advantages are numerous and will be welcomed in specialised circles, e.g. cycle racing, where the extra performance, efficiency and reliability will justify the additional cost of manufacture.

For a clearer understanding of the invention and to show how it may be carried into effect, reference will now be made, by way of example only, to the following figures in which:-

Figure 1 is a part sectional, plan view of the basic concept of the invention showing the absence of the brake disc outside the plane of the spokes; Figure 2 is a front elevation of the wheel and fork arrangement, shown in Fig. 1 ;

Figure 3 is a side elevation of the wheel and forks shown in Figs. 1 and 2; Figure 4 is a rear elevation of the wheel and fork arrangement, i.e. opposite to the view in Fig. 2;

Figure 5 is a perspective view of the wheel, fork and hub arrangement of the disc brake of the invention;

Figure 6 is an enlarged view of the hub of the wheel shown in Fig. 5, showing the passage of the hydraulic pipe into the split hub; Figure 7 is an exploded perspective view of the lower fork and wheel assembly with the part square sectioned axle withdrawn; Figure 8 is a perspective view of the brake assembly fitted inside the divided hub assembly frame and showing the route of the hydraulic pipe; Figure 9 is a section through the wheel and disc brake assembly; Figure 10 is a section through the axle and brake assembly of the wheel shown in Fig. 9;

Figure 11 is a simplified section of the wheel, axle and disc brake assembly showing the principle of the invention and the centre of gravity of the brake, caliper and support assembly, but without extraneous details;

Figure 12 is similar to Fig. 11 but shows the option of attaching the disc to the wheel rim and a panel(s) allowing access to the disc and braking mechanisms;

Figure 13 is a sectional elevation showing the detail of the passage of the hydraulic brake pipe through the hub into the centre of the wheel; Figure 14 shows a perspective view of the hub and disc brake assembly shown sectionally in Fig. 13; and Figure 15 shows a perspective view of the application of the invention applied to a motor cycle wheel.

In the following description, the same reference numeral is used for the same part or for different parts fulfilling an identical function.

Referring to Figs. 1 - 5, the principle of the invention is shown with the disc 13 located essentially on the central plane 33 (Fig. 11) of wheel 19. Fig. 7 shows the fitting of forks 1, 2 around wheel 19 and the location of axle 3 and retaining bracket 4 secured 4A to fork 1 via iugs 4B. Axie 3 has a square section 3A to engage with hoies 3B in bracket 4 and 3B in fixed hub 12 (Fig. 14). The engagement of square section 3A with hole 3B in bracket 4 provides the reaction to the braking force. As axle 3 is fast with both forks 1 and 2, the reaction is passed equally to both sides of the forks and there is no off-centre braking effect. Figs. 6, 7, 8, 10, 11 and 12 show the location of disc brake 13 centrally between spokes 15 and Fig. 10 shows the engagement of caliper 7 on disc 13. Caliper 7 is mounted on holder 11 , which is secured 22 to fixed hub 12, fast 3B with axle 3 (not shown in Fig. 10). Bearings 14 permit spokes 15 and wheel 19 to rotate about fixed hub 12.

As shown, the hub 9, 10 is split; one section 9 is fast with sleeve 26 and carries disc brake 13, which is free to rotate via bearings 14B and 14C about machined sleeve 23, secured on fixed hub 12 by retaining means 18, e.g. a circlip. The other hub section 10 connects to fixed hub 12 via bearing 14A. The inner race of bearing 14A is located by spacer 16, secured 22 to fixed hub 12. The skilled man will appreciate the arrangement of locating shoulders, sleeves, spacers and circlip 18, which secure bearings 14 in their respective locations which are all clearly shown in Fig. 10.

Thus, wheel 19, i.e. spokes 15, rim 5 and tyre 20, are free to rotate via bearings 14 about fixed hub 12, carrying disc brake 13. Fixed hub 12 cannot rotate as it is held 3B (Fig. 14) by square section 3A (Fig. 7) on axle 3, which engages with hole 3B in bracket 4. Caliper 7 is fast with fixed hub 12.

Preferably, caliper 7 is operated from the handlebars (not shown) either by a conventional cable or hydraulic means, though pneumatic or electronic means are also possible. Hydraulic means are preferred as a greater braking force can be transmitted. Hydraulic fluid comes via pipe 21 from the brake-operating lever (not shown). Pipe 21 passes through groove 24 in fixed hub 12 and out through aperture 25 to connect 27 to caliper 7 (Figs. 13 and 14). Thus, when braking effort is applied via caliper 7 onto disc 13, the braking force acts to reduce the rotational speed of disc 13 which, via bearing sleeve 26, hub section 9 and spokes 15, exerts a braking force on rim 5 and tyre 20.

The reaction to the braking force passes through caliper 7, support 11 and bolts 22 into fixed axle 12 and thence to forks 1 and 2. To eliminate off-centre braking effects, bolts 22 should ideally be on wheel centreline 33 (Fig 11). However, this would mean moving disc 13 and caliper 7 to the right (Fig. 10) and into possible contact with spokes 15. A design compromise wouid be to shift boits 22 slightly to the left so that, for example, centre of gravity 34 of the disc 13, caliper 7 support and bolts 22 assembly was on centreline 33. Alternatively, bolts 22 could be shifted further to the left, so that disc 13 was on centreline 33. Though either of these alternatives would create a slight degree of off-centre braking, the effect would be negligible compared to that of present brake systems, located at the side of a wheel, beyond the plane of the spokes.

As has been explained, a number of spacers, e.g. 16, 26, are used to align the bearings 14 and disc 13. It is, thus, possible to alter the position of disc 13 axially along fixed hub 12.

The description above has been written with disc 13 located near fixed hub 12. However, an alternative position is for disc 13 to be fast with rim 5, as shown dashed 13A (Fig. 12). For clarity, caliper 7 and support 11 have been omitted, though clearly support 11 would have to be lengthened for this alternative.

The usual means of venting hydraulic systems are provided but not shown to avoid confusing detail on the Figures.

Fig. 8 shows how the hub assembly may be divided using two half members 28, 29, connected together 30, 3OA. This type of arrangement facilitates the assembly and maintenance of the disc brake of the invention. Members 28, 29 and connecting elements 3OA form a protective cage around the brake of the invention and would prevent damage, e.g. from a broken spoke.

The Figures show the location of the disc brake caliper 7 and support 11 above fixed hub 12. These members could equally well be located below hub 12. This would reduce the overall height of centre of gravity of wheel 19 (and of the whole cycle) and so improve stability.

Though spoked wheels 15 have been taught, a common wheel design is with annular panels 15A (Fig. 12). In this case, an annular access panel(s) 31 would be provided to maintain brake 7, 13. Panel(s) 31 would be secured, e.g. by screws, as indicated by centrelines 32 and bolts 34.

The application of the invention to bicycle, tricycle and motorised cycles adds a new dimension to the reliability of braking systems. Because of its location centrally between spokes 15, the brake is largely protected from any flying grit and water which tyre 20 might kick up. Hydraulic systems, such as described are essentially very reliable for this type of application, provided that they can be protected from mechanical damage. The location of disc 7 centrally within spokes 15 provides a step increase in the level of protection which is provided for this type of brake and so a further increase in the performance, efficiency, reliability and availability of the braking system for the bike.

Fig. 15 shows the application of the invention to the front wheel of a motorcycle. Here, an annular disc 7A, fast with rim 5A, is used and caliper 7A is located below the axle of the wheel.

As explained, there is an equal braking force on each of the two forks. This can give extra confidence to nervous riders. Because the position of the caliper does not obstruct the removal of the wheel, wider tyres can be fitted. The design permits both brake pads / caliper and tyres to be changed at the same time and this allows soft, high performance pads to be used, e.g. for racing. Quick-release, non-leak hydraulic connectors may be used to allow wheels to be removed.

The option of locating caliper 7 below the axle to give the bike a lower centre of gravity; and hence greater stability, is not an option for side-mounted disc brakes, as the caliper is more vulnerable to grit thrown up by the wheel or serious mechanical damage.

In wet weather, the action of the wheels is to spray water outwards and upwards. This will be directly towards side-mounted discs. However, discs located between the spokes will be largely unaffected and remain essentially dry, even when it is raining. Thus, the principle of the invention effectively gives dry weather brake performance even in the wet. By being in the open air, the disc gets a full cooling effect. As with other systems, double discs and / or double calipers may be used if additional braking is required.

The principle of the invention is applicable to both front and rear wheels of bicycles, tricycles and motorised cycles.

The skilled Mechanical Engineer will also be aware of many other detailed improvements, e.g. in weight saving, reduction in air resistance, etc., which are not appropriate to list here, but which, both individually and collectively, are significant in improving reliability, efficiency and performance of bicycles, tricycles and motorised cycles in what is a highly competitive field of sporting endeavour. Thus, the principle of the invention is highly innovative and a step improvement in cycle technology.