Sealing device for a bicycle or motorcycle suspension

Abstract

A sealing device (20) for a shock absorbing fork sleeve is provided with a barrier (21) made of a metal material and an elastomer attachment layer (22). The elastomer attachment layer (22) comprises in turn a radially outer portion (23) forming a static seal with the sleeve wall (24) and at least one radially inner lip (25, 26) forming sliding contact with a moving part of the sleeve. An additional lip (29) forms a seal with the surface (24a) of the sleeve wall (24), thereby closing the pocket (V) of the elastomer attachment layer (22).

Description

Technical Field

[0001] This invention relates to a sealing device for bicycle or motorcycle suspensions. The sealing device is particularly suitable for use in bicycle or motorcycle forks that incorporate suspension (hereinafter also referred to as "shock-absorbing forks"). Background Technology

[0002] Bicycle or motorcycle suspensions typically function to cushion road imperfections and ensure that the wheels maintain continuous contact with the ground as much as possible. The suspension includes elastic load-bearing components such as air springs or coil springs, and hydraulic systems or shock absorbers that dampen vibrations caused by sudden changes in wheel position within the suspension.

[0003] In a bicycle, the fork is the front component of the frame that houses the front wheel. Its name comes from its shape: it consists of a tubular structure fixed to the frame and two arms supported at the front wheel hub (i.e., the center of the wheel). For many years, mountain bikes have utilized forks with pneumatic, hydraulic, or friction-based damping systems to facilitate cushioning against any uneven terrain with pneumatic, spring, or elastomeric suspension, much like motorcycles. Specifically, one arm of the bicycle fork contains an elastic component, typically an air spring, while the second arm contains a damping component, typically a hydraulic piston.

[0004] Motorcycle suspension works in a similar way. By using the suspension, the movement of the frame relative to the ground is controlled, and vibrations are damped and delayed by the shock absorber cartridges.

[0005] Although the invention also applies to motorcycle shock absorber forks, the remainder of this specification only explicitly refers to bicycle shock absorber forks.

[0006] In the arm of a bicycle fork, the damping component is constructed as a cartridge containing a hydraulic piston that moves within it. Within the cartridge chamber where the piston moves, a working fluid (typically oil) is present on both sides of the piston head. The cartridge must be sealed to prevent leakage of the working fluid, and a lubricating oil inlet is located on the fork arm outside the cartridge. If the two fluids (i.e., working oil and hydraulic oil) are the same, then a small amount of lubricating oil seeping into the cartridge is acceptable.

[0007] Regardless of the latter consideration, the sleeve must obviously be sealed from the outside world by a suitable sealing device.

[0008] The sealing device in the prior art is a standard type of oil seal mounted on a moving rod. Figure 1 An example of such a sealing device is shown in an axisymmetric diagram centered on the axis x of the moving rod (not shown). The sealing device 10 includes a screen 11 made of metallic material and an elastomer coating 12, the screen 11 preferably being L-shaped. The elastomer coating 12 has a portion 13 forming a static seal on the housing 14 of the sleeve. The coating 12 also has a first lip 15 and a second lip 16, respectively approaching (or facing) the inner side (upper part) and outer side (lower part) of the sleeve, forming a dynamic seal radially inward (i.e., sealing on the moving rod) (hereinafter also referred to as the "inner seal"). The inner seal is further provided with an elastic member 17 that pushes the first lip 15 and the second lip 16 radially inward.

[0009] Despite its long-standing reputation, this known approach still presents problems during the compression process of a hydraulic piston. Existing sealing devices are optimized to function correctly only at relatively low, specific pressures. As pressure increases, the frictional forces acting on the dynamic seal also increase, as discussed later.

[0010] In fact, as mentioned earlier, the sleeve of the fork is a hydraulic shock absorber. The compression and expansion phases create either high or low oil pressure acting on the dynamic seal lip. In particular, the high pressure (approximately 1.5 MPa) present in the pores V of the elastomer attachment layer creates a high radial load on the main lip constituting the dynamic seal, leading to high friction. Moreover, if a strong impact is transmitted through the suspension, the peak friction can be extremely high. In other words, the oil pressure acting on the main lip has a significant impact on the friction felt by the user. High friction is a problem overall, but the peak friction is even more problematic.

[0011] Furthermore, due to intensifying global competition, customers are constantly demanding continuous technical and economic improvements to sealing devices. In particular, customers require the reduction of friction and friction peaks as much as possible, with a particular focus on the latter. Therefore, ideally, this type of sealing device should be "insensitive" to pressure effects.

[0012] Therefore, it is necessary to define a sealing device that provides a reliable seal from beginning to end while avoiding the problems mentioned above. Summary of the Invention

[0013] To significantly overcome the aforementioned technical problems, one object of the present invention is to define a new design that gives the sealing device an additional sealing lip (hereinafter referred to as "additional lip") that functions as a one-way valve.

[0014] As pressure increases, the additional lip takes full advantage of the pressure peak, sealing the pores in the elastomer attachment layer by being pressed against a dedicated surface by the fluid. This ensures that the lips forming a dynamic seal, approaching the inner and outer sides of the sleeve, are not exposed to the pressure peak; and, as a further advantage, high contact pressure between the main lip and the moving rod is avoided, thereby reducing friction between them. As the pressure level decreases during shock absorber expansion, the additional lip returns to its initial position. Furthermore, when the pressure within the shock absorber cavity falls below the pressure in the pores of the elastomer attachment layer, the additional lip separates from the dedicated surface, thereby restoring pressure balance to the system.

[0015] Therefore, the present invention provides a sealing device for bicycle or motorcycle suspension, having the features described in the independent technical solutions appended to this specification.

[0016] Further preferred and / or particularly advantageous embodiments of the invention are described in accordance with the features shown in the accompanying dependent technical solutions. Attached Figure Description

[0017] The present invention will now be described with reference to the accompanying drawings, which show non-limiting embodiments of the invention, wherein:

[0018] Figure 1 This is a cross-sectional schematic diagram of a sealing device for a suspension sleeve used in bicycles or motorcycles in the prior art;

[0019] Figure 2 A cross-sectional schematic diagram of a sealing device for a bicycle or motorcycle suspension sleeve according to a specific embodiment of the present invention; and

[0020] Figure 3 for Figure 2 Enlarged view of details (detail Y) of the sealing device shown. Detailed Implementation

[0021] The invention is described below by way of non-limiting embodiment, with reference to a sealing device for a sleeve in a bicycle shock absorber fork. As described above, the sealing device of the present invention is also applicable to motorcycle suspensions. See also Figure 2 and 3 The sealing device 20 includes:

[0022] - Partition 21, made of metal, preferably L-shaped;

[0023] - Elastomer attachment layer 22.

[0024] The elastomeric attachment layer 22 has a radially outer portion 23 that forms a static seal on the sleeve wall 24. The elastomeric attachment layer 22 also has a first lip 25 and a second lip 26 that form a dynamic seal on the radially inner side. That is, the first lip and the second lip form sliding contact with the moving parts of the sleeve (e.g., the piston rod of a shock absorber) at positions approaching the inner and outer sides of the sleeve, respectively.

[0025] The dynamic seal on the radially inner side is further provided with an elastic component 27 that pushes the first lip 25 and the second lip 26 radially inward. A gasket 28 ensures that the sealing device 20 is properly positioned.

[0026] Because of the greater pressure inside the sleeve, the first sealing lip 25, which forms a dynamic seal with the moving rod inside the sleeve, has a sharp edge. Conversely, because of the lower pressure, the second sealing lip 26, which forms a dynamic seal with the moving rod on the outside of the sleeve, has a rounded angle.

[0027] The sealing device 20 is characterized by an additional lip 29 that acts as a one-way valve. When pressure increases, the additional lip 29 is pressed against the housing wall of the damper, thereby forming a seal on the surface 24a of the housing 24. As pressure increases, the additional lip 29 fully utilizes the pressure peak, sealing the pores V in the elastomer attachment layer by being pressed against the dedicated surface 24a by the fluid. This ensures that the lips 25, 26, which form dynamic seals on the inner and outer sides of the sleeve, are not exposed to high-pressure peaks; and, as a further advantage, the contact pressure between the main lip and the moving rod is avoided, thereby reducing friction between them.

[0028] When the pressure decreases during the expansion phase, the additional lip 29 separates from the surface 24a of the cylinder wall 24, so the oil pressure in the cavity V between the lips 25, 26 and the additional lip 29 becomes the same as the oil pressure present in the entire system.

[0029] In a preferred embodiment, the inlet ramp 24B of the sealing device 20 (forming part of the cylinder wall 24) should be given a larger diameter than the radially outer chamfer 29a of the additional lip 29 to ensure that the additional lip can be properly inserted into the cylinder wall 24. This is because the sealing device 20 is installed in the cylinder wall 24 from the bottom up, so the cylinder wall 24 must have a sufficiently wide ramp to allow the additional lip 29 to fit within it. Therefore, dimension a, defined as half the difference between the diameter of the inlet ramp 24a of the cylinder wall 24 and the diameter of the radially outer chamfer 29a of the additional lip 29, must be greater than zero.

[0030] The additional lip 29 must also provide radial interference with the cylinder wall 24 to ensure the sealing of the cavity. Therefore, it is advantageous that dimension b, defined as half the difference between the diameter of the radially peripheral chamfered section 29a of the additional lip 29 and the diameter of the radially peripheral contact point 24c of the cylinder wall 24, must be between 0 and 1 mm.

[0031] Furthermore, the surface 24a of the cylinder wall 24 must form an angle β with the axial direction defined by the axis x, so that the pressure acting on the additional lip 29 generates friction, causing the additional lip 29 to remain in place rather than bend back. Therefore, it is advantageous that the angle value of β is between 5° and 30°.

[0032] Finally, angle α, defined as the difference between the inclination angle of the additional lip 29 relative to the axial direction and the inclination angle β of the cylinder wall 24 as defined above, must cause the additional lip 29 to move at its edge. This causes an increase in the contact pressure of the radially peripheral chamfered surface 29a of the additional lip 29, thereby resulting in a stronger oil seal. Therefore, it is advantageous that angle α be between 10° and 30°.

[0033] When angles α and β are set in this manner, the result is that, as demonstrated by finite element testing, the additional lip 29 deflects but does not bend completely radially inward, as the latter would cause separation from the surface 24a of the cylinder wall 24. This ensures that the additional lip can function.

[0034] Finally, the advantage of the proposed solution lies in the fact that the sleeve can provide constant friction, avoiding friction peaks in any state of the fork (compression, extension). Therefore, the almost constant frictional resistance value can be optimized during the design phase because it now has a very limited value range.

[0035] It should be understood that, in addition to the specific embodiments of the invention described above, many other variations of the invention exist. It should also be understood that these specific embodiments are provided by way of example only and are not intended to limit the subject matter, application, or possible constructions of the invention. On the contrary, although the above description enables those skilled in the art to practice the invention according to at least one specific embodiment, it should be understood that various variations of the described components are possible without exceeding the scope of protection of the invention as defined by the appended claims, whether interpreted literally or by their legal equivalents.

Claims

1. A sealing device (20) for a shock-absorbing fork sleeve, the device (20) comprising: - The partition (21) is made of metal. and - An elastomer attachment layer (22) further includes a radially peripheral portion (23) that forms a static seal with the sleeve wall (24) and at least one radially inner lip (25, 26) that forms a sliding contact with the moving part of the sleeve. The sealing device (20) is characterized by an additional lip (29) which forms a seal with the surface (24a) of the cylinder wall (24) by closing the pores (V) of the elastomer attachment layer (22); In the radial direction, the cavity (V) is located between the partition (21) and at least one radially inner lip (25, 26) of the elastomeric attachment layer (22).

2. The sealing device (20) according to claim 1, characterized in that: Dimension a, half the difference between the diameter of the inclined surface (24b) of the cylinder wall (24) and the diameter of the radially peripheral chamfered section (29a) of the additional lip (29) is greater than 0.

3. The sealing device (20) according to claim 2, characterized in that: Size b, half the difference between the diameter of the radial outer chamfered section (29a) of the additional lip (29) and the diameter of the radial outer contact point (24c) of the cylinder wall (24), is between 0 and 1 mm.

4. The sealing device (20) according to any one of the preceding claims, characterized in that: The angle β formed between the surface (24a) of the cylinder wall (24) and the axial direction defined by the axis (x) is between 5° and 30°.

5. The sealing device (20) according to claim 4, characterized in that: Angle α, the difference between the angle of inclination of the additional lip (29) relative to the axial direction defined by the axis (x) and angle β, is between 10° and 30°.

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