GB2485847A - Attachment of mudguard via demountable chain stay bridge - Google Patents

Abstract

An adjustable mudguard mounting of a cycle comprises a mounting plate 22 attached by screw-threaded fasteners 24 relative to the chain stays 16 of the cycle frame. Slots permit fore and aft movement to position the mudguard 21 close to the rear tyre. Easy mudguard removal and adjustment for rear axle position and tyre size is thereby provided.

Description

Improved Attachment for Cycle Mudguard This invention relates to an improved mudguard attachment for a cycle, and to a combination of cycle frame or portion thereof and the improved mudguard attachment.

Bicycle mudguards typically cover both front and rear wheels and shield the rider from water and mud thrown up by the tyres.

The rear mudguard is usually mounted to a small bridge' (either tubular or flat plate), which is permanently fixed between the chain stays of the frame. The chain stays comprise a pair of tubes running forwards from the rear fork ends to join to the bottom bracket shell, which defines the crank axis. The mudguard is typically also connected to a bridge permanently fixed between the seat stays (the pair of tubes running upwards and forwards from the rear fork ends, to join the frame at the junction of seat-and top-tubes, underneath the saddle. Additionally the mudguard is usually mounted to the rear fork end using wire stays extending from the mid and rear portions of the mudguard.

The problem with a permanently attached bridge of the chain stays is that it is attached afler the chain stays are mounted and aligned and is very close to the bottom bracket in order to give wheel clearance. Inevitably internal stresses and distortion are introduced in the chain stay portion in a plane where corrective action is not possible.

Furthermore the material of the chain stays may be adversely affected by the heat of welding or brazing.

What is required is an improved mudguard fixing which provides for adjustment of the forward end of a mudguard towards and away from the rear wheel, and can address the problems of chain stay distortion and material degradation close to the bottom bracket connection.

According to the invention there is provided in combination the chain stay portion of a cycle frame and a demountable rear mudguard mounting, said mounting extending in use substantially between the chain stays of the chain stay portion and including a fixing portion for the demountable attachment of the leading end of a rear mudguard.

The invention provides the following advantages: A permanently fixed chain stay bridge is not required. The conventional bridge, usually mounted (brazed or welded) close to the bottom bracket shell, does not add any structural strength to the frame. A demountable mounting according to the invention does not weaken the bicycle frame or introduce internal stresses in a plane where compensation is not possible.

The position of the mudguard in relation to the wheel may be adjusted. This allows the mudguard to remain close to the tyre for protection and aesthetic purposes. This is particularly useful on bicycles with horizontal fork ends, and when the position of the rear wheel is used to adjust the tension of the chain, and when a number of different tyre sizes (or even wheel sizes) may be used on the same frame.

The mudguard may be removed without removal of the rear wheel, something that is usually required with conventional mudguard mountings.

The chain stay portion of the frame may constitute a separate frame component, as is the case of a cycle with rear suspension, or more usually is rigidly attached to the front triangle of head, seat and top and down tubes, and forms with the seat stays the rear triangle of a conventional diamond frame.

In one embodiment, the frame is fitted with two spot brazed internally threaded bosses, on each chain stay. These bosses are typically provided to the underside of the chain stays, but could equally be on the top or on the sides. Spot brazed bosses introduce little heat related distortion or risk of change of material properties.

The rear mudguard mounting is preferably in the form of a plate, which is fitted to these bosses with threaded fasteners or other fixing device. Adjustment is provided by the slots in the plate. In one alternative, these are open-ended as to allow easier removal from the chain stays. The plate may be marked for ease of positioning and alignment, by for example inscriptions or indentations.

In certain circumstances, such as some small-wheeled bicycles where the position of the bridge is a significant distance from the bottom bracket, a fixed chain stay bridge' may be fitted for example with two holes (threaded or otherwise) or two studs, either largely in-line with the chain stays or largely perpendicular to them. In this embodiment, the advantages of being able to adjust and remove the mudguard are retained, together with a fixed chain stay bridge which has advantages for structural integrity in such a frame. In such a frame the fixed bridge is sufficiently far from the bottom bracket connection to avoid any significant effect on material properties or to impose an undesirable stress upon attachment by welding or brazing.

Other features of the invention will be apparent from the following description of a preferred embodiment shown by way of example only in the accompanying drawings, in which: Fig. 1 shows schematically a typical diamond frame of a bicycle, and wheels.

Fig. 2 shows the bottom bracket detail of Fig. 1, and the mudguard mounting of the invention.

Fig. 3 shows a perspective underside view of the mounting of Fig. 2.

With reference to the Fig. 1 a conventional diamond frame (10) of a bicycle comprises head tube (11), top tube (12), seat tube (13) and down tube (14), seat stays (15) and chain stays (16). The seat stays (15) and chain stays (16) are in pairs and extend on either side of the rear wheel (17). Front forks are not shown. Rear drop-out lugs (not shown) connect the seat stays and chain stays and define the mounting for the rear wheel axle. These drop-outs typically permit fore and aft adjustment of the wheel axle to allow setting of wheel alignment and chain tension.

Figs. 2 and 3 show a detail of Fig. I comprising the seat tube (13), down tube (14), bottom bracket (18) and chain stays (16). Also illustrated are the front portion of a rear mudguard (21) and a mounting plate (22) thereof The mounting plate (22) comprises a generally L' shaped bracket, one limb of which comprises an attachment to the chain stays, and the other of which comprises a mudguard fixing.

Each rear chain stay has a threaded boss spot brazed therein on the underside at an appropriate distance from the bottom bracket axis, typically in the range 50-100 mm.

As illustrated, the mounting plate (22) has slotted holes (23) to allow attachment to chain stays by socket headed screws (24). The slotted holes permit fore and aft adjustment of the plate (22). The mudguard (21) is attached to the mounting plate by threaded nut and bolt (25), but other kinds of fixing are possible -for example an upstanding post and mudguard socket. A releasable snap-fitting may be used.

As will be appreciated the mounting plate permits the slotted holes (23) to be sufficiently long to allow close fixing of the mudguard to the rear tyre after the rear axle position has been set. Furthermore the mudguard is easily removable without disturbing the rear axle position. The slotted holes may be open at one end so as to permit removal of the plate (22) without complete removal of the screws (24).

In small wheel bicycles having 16-20 inch wheels, the distance from the bottom bracket to the rear tyre is generally considerably greater than for a large wheel bicycle having 26-28 inch wheels. Frames for such cycles can be strengthened by means of a fixed chain stay bridge, typically 150-200 mm from the bottom bracket axis. In such circumstances the mudguard mounting of the invention may be attached to such a bridge, for example by screw-threaded fixings passing through aligned holes, or by threaded bosses or threaded studs of the fixed chain stay bridge. Fixing and adjustment of the rear mudguard mounting is by the method described above.

Some bicycles may incorporate a rear suspension whereby the chain stay portion of the frame is relatively movable, typically about the bottom bracket axis. The invention can also be used with such a frame arrangement.

A fixing to each chain stay is described. However a single sided fixing may be sufficient especially if the bracket wraps around or abuts against one chain stay so as to avoid angular movement thereof about the fixing axis.

Claims (15)

1. Claims 1. In combination the chain stay portion of a cycle frame and a demountable rear mudguard mounting, said mounting extending in use substantially between the chain stays of the chain stay portion and including a fixing portion for the demountable attachment of the leading end of a rear mudguard.
2. 2. The combination of claim I, wherein said chain stay portion includes for each chain stay an internal threaded boss to which said mounting is attachable.
3. 3. The combination of claim 2, wherein each threaded boss faces downwardly.
4. 4. The combination of claim 2 or claim 3, wherein said mounting is attached to the chain stay portion by screws associated one with each threaded boss.
5. 5. The combination of claim 1, wherein said chain stay portion includes a fixed bridge between the chain stays arid to which said mounting is attachable by threaded fasteners.
6. 6. The combination of any of claims 2-5, wherein said mounting is slotted for fore and aft adjustment relative to said chain stays.
7. 7. The combination of any preceding claim, wherein said fixing portion comprises an upstanding limb extending between the chain stays.
8. 8. The combination of claim 7, wherein said limb includes a through hole to receive a mudguard attachment.
9. 9. The combination of claim 7 or claim 8, and a rear mudguard attached to said upstanding limb.
10. 10. A method of adjusting the rear mudguard of a bicycle having a chain stay portion, a mudguard mounting and rear mudguard according to claim 9, and comprising the steps of: setting the rear wheel position in the chain stay portion, and positioning said rear mudguard close to the tyre of the rear wheel by means of said demountable rear mudguard mounting.
11. 11. A method according to claim 10, wherein said method further includes the steps of loosely mounting said rear mudguard mounting with respect to said chain stay portion; positioning said rear mudguard mounting with said mudguard attached thereto; and fixing said rear mudguard mounting to said chain stay portion against movement relative thereto.
12. 12. In combination a chain stay portion of a cycle frame and a demountable rear mudguard mounting substantially as described herein with reference to the accompanying drawings.
13. 13. A bicycle frame having a chain stay portion and a demountable rear mudguard mounting according to any of claims 1-7.
14. 14. A bicycle frame according to claim 13, wherein said chain stay portion is fixed with respect to the bottom bracket.
15. 15. A bicycle comprising a bicycle frame according to claim 14.