AU2011201239A1 - A Bicycle Suspension Swingarm - Google Patents

Abstract

An embodiment of the bicycle suspension swingarm 10 includes a pair of lower elongate members 11 & 12, each of which defines a proximal end that is connected to the first and second bodies 20 & 21 and a distal end that is connected to a pair of drop 5 outs 15. The lower surfaces of the proximal portions of elongate members 11 and 12 are fastened to the first body 20, for example by welding. The upper surfaces of the proximal portions of elongate members 11 and 12 are fastened to the second body 21. Hence, the proximal portions of the elongate members 11 and 12 are sandwiched intermediate the first and second bodies 20 and 21, which contributes to the stiffness 10 of the swingarm. Ct) (N. T rF'7 TIITAT T'17 /rr-7Tn'x7T T f\'7

Description

1 AUSTRALIA Patents Act 1990 (Cth) COMPLETE SPECIFICATION Applicant DEUBEL BICYCLES PTY LTD Title A BICYCLE SUSPENSION SWINGARM The invention is described in the following statement: 2 A BICYCLE SUSPENSION SWINGARM FIELD OF THE INVENTION The present invention relates to a swingarm for use upon suspended bicycles. 5 Embodiments of the present invention find application, though not exclusively, for use on suspended mountain bikes. BACKGROUND OF THE INVENTION A typical example of a prior art swingarm as used on mountain bikes is 10 illustrated in Figures 1 and 2. It comprises two divergent pairs of tubes 1 & 2 attached at their forward ends by a body 3 which is pivotally mounted at one end to the bicycle frame and at the other end to a shock absorber. The convergent pairs of tubes 1 & 2 are attached at their rearward ends to a pair of dropouts 4 that are adapted to receive the rear wheel axle. 15 It has been appreciated by the inventor that a relative lack of stiffness in at least some of the prior art swingarms may lessen the efficiency of transfer of motive force from the pedals to the rear wheel. The discussion of the prior art within this specification is not, and should not be taken as, an admission of the extent of common general knowledge in the field of 20 the invention in Australia or elsewhere. Rather, the discussion of the prior art is provided merely to assist the addressee to understand the invention and is included without prejudice. SUMMARY OF THE INVENTION 25 It is an object of the present invention to overcome, or substantially ameliorate, one of more of the disadvantages of the prior art, or to provide a useful alternative. A preferred embodiment of the invention provides a rear suspension swingarm that has an improved degree of stiffness in at least some directions, which may contribute to improved pedalling efficiency.

3 In one aspect of the present invention there is provided a bicycle suspension swingarm including: an elongate member defining a proximal end and a distal end, the elongate member further defining a first surface adjacent the proximal end and a second 5 surface adjacent the proximal end, the second surface being disposed opposite to the first surface; a first body disposed on the first surface; and a second body disposed on the second surface so as to sandwich a portion of the elongate member adjacent the proximal end intermediate the first and second 10 bodies. Preferably the first body is fastened to the first surface and the second body is fastened to the second surface. In one embodiment the fastening is by welding, whereas in another embodiment the fastening is by adhesive bonding. Preferably the swingarm includes another elongate member spaced apart from 15 the elongate member so as, in use, to straddle a bicycle wheel disposed there between. A preferred embodiment includes at least one further elongate member extending between the distal end and the second body so as to triangulate the swingarm. Preferably the first body is adapted in use for pivotal connection to a bicycle frame and the second body is adapted in use for pivotal connection to a shock 20 absorber. In a preferred embodiment at least one formation adapted to receive a bicycle wheel axel is disposed at, or adjacent to, the distal end. Preferably a surface of the first body to which the first surface is fastened has a shape corresponding to that of the first surface. Similarly, preferably a surface of the second body to which the second surface is fastened has a shape corresponding to that 25 of the second surface. Preferably the surface area of the surfaces whereby the elongate member is 2 fastened to the first and second bodies exceeds an area of 900 mm.

4 In one embodiment the portion of the elongate member adjacent the proximal end that is sandwiched intermediate the first and second bodies has a length of greater than 30 mm. Preferably the swingarm includes a brace extending between the elongate 5 member and the other elongate member and disposed adjacent the proximal end. In some embodiments the first and second bodies are fastened to each other; whereas in other embodiments the first and second bodies are formed as a single unitary component, to which the elongate member is fastened. According to a second aspect of the invention there is provided a bicycle 10 having a suspension system that includes a swingarm as described above. Preferably the suspension system is a rear suspension system. According to another aspect of the invention there is provided a bicycle suspension swingarm including an elongate member defining a proximal end and a distal end; and a body disposed on the proximal end so as to sandwich a portion of the 15 elongate member adjacent the proximal end. In one embodiment the elongate member, first body and second body are formed as a single unitary component. BRIEF DESCRIPTION OF THE DRAWINGS 20 Preferred embodiments of the invention will now be described, by way of non limiting example only, with reference to the accompanying drawings, in which: Figure 1 is a side view of a suspended mountain bike featuring a prior art rear suspension swingarm; Figure 2 is a perspective view of the prior art swingarm of figure 1; 25 Figure 3 is a perspective view of a preferred embodiment of the swingarm according to the present invention; Figure 4 is a partial perspective view of the preferred embodiment of figure 3; Figure 5 is a partial perspective exploded view of the preferred embodiment showing a pair of elongate members and a first and second body; 5 Figure 6 is a partial plan view of the preferred embodiment with the second body omitted so as to reveal otherwise hidden detail; Figure 7 is a perspective view of the second body; Figure 8 is a partial perspective view of the preferred embodiment in a 5 stripped-down state; Figure 9 is a partial perspective view of the preferred embodiment in a stripped-down state with only one elongate member being shown as connected to the first and second bodies so as to reveal otherwise hidden detail; Figure 10 is a partial perspective view of the prior art swingarm of figure 1 10 showing the surface area of the connection of one of the elongate members to the body; Figure 11 is a partial perspective exploded view of the preferred embodiment of the swingarm of the present invention showing the surface area of the connection of one of the elongate members to the body; and 15 Figure 12 is a perspective partial view of the preferred embodiment of the swingarm of the present invention showing the length of the sandwich connection of the elongate member to the body. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE 20 INVENTION Referring to the figures, the preferred embodiment of the bicycle suspension swingarm 10 is shown in its entirety in figure 3. It is preferably formed from a light weight and strong material such as aluminium or carbon fibre. The swingarm 10 includes a pair of lower elongate members 11 & 12 and a pair of upper elongate 25 members 13 & 14. Each of the elongate members 11, 12, 13 and 14 defines a proximal end that is connected to the first and second bodies 20 & 21 and a distal end that is connected to a bicycle wheel axle receiving formation in the form of a pair of drop outs 15. The first body 20 includes a pair of apertures 22 & 23 that are sized to respectively receive a pair of bearings 24 and 25, which mount a cylindrical pivot 26 30 for pivotal connection of the swingarm 10 to a bicycle frame. The second body 21 includes a pin 27 for pivotal connection of the swingarm 10 to a shock absorber. As indicated on figure 8, scalloped portions 36 & 37 are provided in the first body 20 and 6 scalloped portions 38 are provided in the second body 21 so as to remove excess material and thereby assist with weight minimisation. Each of the elongate members 11, 12, 13 and 14 is generally rectangular in cross section, with rounded edges. It will be appreciated that elongate members 5 having other cross sectional shapes may be employed in alternative embodiments. Each pair of elongate members 11 & 12 and 13 & 14 are spaced apart from each other so as to straddle a bicycle wheel that, in use, is disposed there between. The upper pair of elongate members 13 & 14 extend between the pair of drop outs 15 and the curved formations 34 & 35 of the second body 21. This creates a triangulated 10 swingarm structure. The connection of the respective proximal portions 19 & 27 of the two lower elongate members 11 & 12 to the first and second bodies 20 & 21 constitutes an important feature of the preferred embodiment of the present invention. This connection shall be described in detail with reference to elongate member 11, 15 however essentially the same connection methodology is used to connect the proximal portion of elongate member 12 to the two-part body 20 and 21. The lower surface of the proximal portion 19 of elongate member 11 is referred to herein as "first surface 17". The first body 20 is fastened to the first surface 17 by means of welding. The upper surface of the proximal portion 19 of 20 elongate member 11 is referred to herein as "second surface 18" and it will be appreciated that the second surface 18 is disposed opposite to the first surface 17. The second body 21 is fastened to the second surface 18, also by means of welding. Hence, the proximal portion 19 of the elongate member 11 is sandwiched intermediate the first and second bodies 20 and 21. 25 The means by which the elongate members 11 & 12 are fastened to the first and second bodies 20 & 21 is selected with reference to the material from which those components are made. For example, welding is one of the possible fastening means that may be utilised for some metals such as aluminium. However other fastening means may be more suitable for other materials. For example, adhesive bonding is 30 one of the possible fastening means that may be utilised for carbon fibre.

7 The surface 28 of the first body 20 to which the first surface 17 of the elongate member 11 is fastened has a shape corresponding to that of the first surface 17. In particular, the first surface 17 is substantially planar (with the exception of the rounded edges) and the surface 28 is also substantially planar. Similarly, the surface 5 29 of the second body 21 to which the second surface 18 is fastened has a substantially planar shape that corresponds to the substantially planar second surface 18. The portion 19 of the elongate member 11 that is adjacent the proximal end and which is sandwiched intermediate the first and second bodies 20 & 21 has a 10 length of greater than 30 mm. In particular, as shown in figure 12, the sandwich connection has a length of 58 mm. As best shown in figures 7 and 9, the second body 21 has a brace 30 depending there from. The brace 30 is disposed such that its edges 31 and 32 extend between the proximal portions of the elongate members 11 and 12. This allows the 15 edges 31 and 32 to be fastened to the proximal portions of the elongate members 11 and 12. Additionally, the I-shaped surface 33 at the base of the second body 21 is connected to the upper planar surface 28 of the first body 20 so as to fasten the first and second bodies to each other. It will be appreciated that these additional connections contribute further stiffness to the swingarm 10. 20 The sandwich-type of connection as described in the preceding paragraphs is typically considerably stiffer as compared to the analogous prior art connections that are known to the inventor as at the priority date of this patent application. One of the reasons for this improved stiffness is the length of the sandwich connection. Another contributor to the improved stiffness is the greater total surface area over which each 25 of the elongate members 11 & 12 is connected to the first and second bodies 20 & 21. As shown in figure 10, the total amount of this connection surface area in a typical 2 prior art swingarm is approximately 210 mm . In contrast, preferred embodiments of 2 the present invention can readily exceed a total connection surface area of 900 mm2 Some embodiments may exceed a total connection surface area of 1500 mm 2 . Indeed, 30 the total connection surface area for each of the elongate members 11 & 12 of the illustrated preferred embodiment is 2350 mm 2 , which comprises a surface area of 8 1100 mm 2 over which surface 18 is connected to surface 29 and 1250 mm2 over which surface 17 is connected to surface 28. These surface areas are illustrated in figure 11. An additional advantage that may be associated with an increased connection surface area is improved reliability due to a reduction in the stresses that 5 the connection must endure during usage due to the greater surface area across which the forces may be distributed. It has been appreciated by the inventor of the present invention that the improved stiffness arising from the sandwich-type connection allows the preferred embodiment to resist flexing in response to the torsional forces that are applied during 10 pedalling. This was supported by some computer-based modelling of the stiffness characteristics of the prior art swingarm as shown in figures 1, 2 and 10 as compared to the preferred embodiment of the present invention as shown in figures 3 to 9 and 11 to 12. This modelling calculated the deformation of the swingarms in response to applied pedalling torque and concluded that the preferred embodiment is 36% stiffer 15 than the prior art swingarm. This improved stiffness is likely to yield an improvement to the pedalling efficiency of the bicycle upon which the swingarm is used, which is a highly desirable outcome in almost all cycling contexts. In the preferred embodiment of the swingarm as described above the body is initially constructed in two separate pieces 20 & 21, which are connected together 20 along with the formation of the sandwich connection. However in an alternative contemplated embodiment (not illustrated) the body is initially formed as a single unitary component to which the elongate members 11 and 12 are fastened. In yet another alternative contemplated embodiment (not illustrated) the elongate members, first body and second body are all formed as a single unitary component. 25 In the illustrated embodiment the sandwich connection is oriented such that the sandwiching is aligned with the direction of swinging movement of the swingarm 10 as it pivots on pivot 26. However, it will be appreciated that in an alternative contemplated embodiment (not illustrated) the sandwiching may be aligned in other directions, including for example at right angles to the direction of swinging 30 movement of the swingarm.

9 Although not shown in the figures, in an alternative contemplated embodiment the upper pair of elongate members 13 & 14 may be connected to the second body 21 by means of a sandwich-type connection in a similar manner to that described above with regard to elongate members 11 & 12. This would be likely to further contribute 5 toward improved stiffness of such an embodiment of the swingarm. The illustrated embodiment is adapted for use with the single pivot type of suspension system. However, it will be appreciated that other contemplated embodiments (not illustrated) may be adapted for use with suspension systems having more than one pivot. 10 The swingarm of the present invention may be utilised upon any suspended bicycle, and most typically as a part of the rear suspension of a suspended mountain bike. However, it will be appreciated that the swingarm of the present invention may be utilised upon other types of suspended pedal-propelled vehicles, such as unicycles, tricycles and the like. Hence, the term "bicycle" as used in this document, including 15 in the claims, is to be construed broadly so as to include within its scope any type of suspended pedal-propelled vehicle. While a number of preferred embodiments have been described, it will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention without departing from the spirit or scope of the 20 invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (21)

1. A bicycle suspension swingarm including: an elongate member defining a proximal end and a distal end, the elongate member further defining a first surface adjacent the proximal end and a second 5 surface adjacent the proximal end, the second surface being disposed opposite to the first surface; a first body disposed on the first surface; and a second body disposed on the second surface so as to sandwich a portion of the elongate member adjacent the proximal end intermediate the first and second 10 bodies.

2. A swingarm according to claim 1 wherein the first body is fastened to the first surface. 15

3. A swingarm according to claim 1 or 2 wherein the second body is fastened to the second surface.

4. A swingarm according to claim 2 or 3 wherein the fastening is by welding or adhesive bonding. 20

5. A swingarm according to any one of the preceding claims including another elongate member spaced apart from the elongate member so as, in use, to straddle a bicycle wheel disposed there between. 25

6. A swingarm according to any one of the preceding claims including at least one further elongate member extending between the distal end and the second body so as to triangulate the swingarm.

7. A swingarm according to any one of the preceding claims wherein the first 30 body is adapted in use for pivotal connection to a bicycle frame. 11

8. A swingarm according to any one of the preceding claims wherein the second body is adapted in use for pivotal connection to a shock absorber.

9. A swingarm according to any one of the preceding claims wherein at least one 5 formation adapted to receive a bicycle wheel axel is disposed at, or adjacent to, the distal end.

10. A swingarm according to claim 2 wherein a surface of the first body to which the first surface is fastened has a shape corresponding to that of the first surface. 10

11. A swingarm according to claim 3 wherein a surface of the second body to which the second surface is fastened has a shape corresponding to that of the second surface. 15

12. A swingarm according to any one of the preceding claims wherein the surface area of the surfaces whereby the elongate member is fastened to the first and second 2 bodies exceeds an area of 900 mm2

13. A swingarm according to any one of the preceding claims wherein the portion 20 of the elongate member adjacent the proximal end that is sandwiched intermediate the first and second bodies has a length of greater than 30 mm.

14. A swingarm according to claim 5 including a brace extending between the elongate member and the other elongate member and disposed adjacent the proximal 25 end.

15. A swingarm according to claims 2 and 3 wherein the first and second bodies are fastened to each other. 30

16. A swingarm according to claim 1 wherein the first and second bodies are formed as a single unitary component and wherein the elongate member is fastened to the unitary body. 12

17. A bicycle having a suspension system that includes a swingarm according to any one of the preceding claims.

18. A bicycle according to claim 17 wherein the suspension system is a rear 5 suspension system.

19. A bicycle suspension swingarm including an elongate member defining a proximal end and a distal end; and a body disposed on the proximal end so as to sandwich a portion of the elongate member adjacent the proximal end. 10

20. A bicycle suspension swingarm according to claim 19 wherein the elongate member, first body and second body are formed as a single unitary component.

21. A bicycle suspension swingarm substantially as hereinbefore described with 15 reference to any one or more of the examples and/or the accompanying drawings.