TECHNICAL FIELD

The present subject matter described herein in general relates to a suspension system for a vehicle and in particular relates to a telescopic front fork assembly for a two-wheeled vehicle.

BACKGROUND

A telescopic front fork assembly is employed in a two-wheeled vehicle to act as a shock absorbing means or suspension means, and to facilitate effective braking and handling of the vehicle. Shock absorbers are necessary to keep a rider isolated from the road jerks and vibrations, thereby making the ride comfortable. In addition, effective braking and handling of the vehicle is important for safety reasons. Typically, the telescopic front fork assembly connects the front wheel of the two-wheeled vehicle with the handlebar and in this way shares the load of the vehicle.

The telescopic front fork assembly includes two parallel placed fork tubes, each of which has an identical construction. These tubes, in particular, dampen the vibrations felt by a rider. The telescopic front fork assembly facilitates upward and downward displacements of the front wheel to absorb jerks and vibrations caused due to a rough and uneven road while the vehicle is in motion. In addition, the telescopic front fork assembly ensures a firm ground contact of the front wheel for better control and steerability.

Generally, variable dampening characteristics are required to be exhibited by the telescopic front fork on the basis of varying road conditions. As an example, the amount of dampening required when the vehicle is driven on a smooth road surface is very low. Contrary to this, the amount of dampening required on a rough and uneven road is very high. To suit different kinds of road surfaces, the dampening characteristics of the telescopic front fork need to be varied. However, conventional telescopic front fork assemblies provide a constant, non-variable dampening characteristic. The constant non-variable dampening characteristic is mainly due to the non-variable size and the number of the compression and extension orifices located on the circumference of the pistons provided inside the front forks of the telescopic front fork.

These orifices are of a circular cross-section and are identical in shape and diameter. This provides a constant, non-variable dampening characteristic to the conventional telescopic front fork assembly, since the flow of a dampening fluid through these orifices during the compression and the extension cycles takes place in a predetermined way.

More recently, telescopic front fork assemblies, such as cartridge type dampening systems, which provide adjustable dampening, have been developed to achieve the variable dampening characteristics. However, these telescopic front fork assemblies with adjustable dampening design employ substantially higher number of additional components as compared to the conventional assemblies. The additional components, which include pneumatic valves, adjustment rods, spring discs, elastomeric pads etc., make the design complex and the structure considerably heavy. The presence of the large number of components requires additional serviceability. Moreover, the manufacturing and the maintenance costs associated with such telescopic front fork assemblies are high..

SUMMARY

The subject matter described herein is directed to a telescopic front fork assembly for a two-wheeled vehicle. In accordance with one embodiment of the present subject matter, the telescopic front fork assembly includes a pair of telescopic struts. The telescopic struts include an outer tube and an inner tube, and each tube has a first end and a second end. The second end of the inner tube is capable of axially sliding through the first end of the outer tube, towards the second end of the outer tube. Furthermore, a piston having a first end and a second end is concentrically disposed inside the inner tube. A number of extension dampening holes are disposed circumferentially towards the first end of the piston. Likewise, a number of compression dampening holes are disposed circumferentially towards the second end of the piston. An annular space between the second end of piston and outer tube acts as an area of storage of dampening fluid.

Further, the telescopic struts include an adjustable dampening mechanism for adjusting the dampening characteristics of the front fork assembly. The adjustable dampening mechanism includes a sleeve that is concentrically disposed between the inner tube and the piston. The adjustable dampening mechanism also includes a rotating mechanism for rotating the sleeve. The sleeve is rotated such that the sleeve is enabled to selectively cover the compression dampening holes and the extension dampening holes, located on the piston. Thus, the hole opening size or number of holes or both are selectively controlled depending upon the portion or number of the holes covered by the sleeve. Furthermore, the hole opening size or the number of holes is directly proportional to the volume of the dampening fluid flowing across the holes. Accordingly, the selective control of the hole opening size or the number of holes increases the resistance towards the flow of the dampening fluid across the holes, thereby increasing the dampening characteristics.

The present subject matter proposes a solution to adjust the dampening characteristics of the telescopic front fork assembly according to the road conditions as well as different rider weights thereby enhancing the rider comfort. Further, the adjustable dampening system as proposed herein is light in weight and is cost effective.

These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features, aspects and advantages of the subject matter will be better understood with regard to the following description, appended claims, and accompanying drawings, where:

FIG. 1 shows a perspective view of a telescopic front fork assembly for a two-wheeled vehicle, according to one embodiment of the present subject matter. FIG. 2A shows a sectional view of a telescopic strut of the telescopic front fork assembly of FIG. 1.
FIG. 2B shows a perspective view of a piston of the telescopic strut shown in FIG. 2 A.
FIG. 2C shows a perspective front view of the piston of FIG. 2 A. FIG. 2D shows a perspective side view of the piston of FIG. 2A showing a keyway.

DETAILED DESCRIPTION

The present subject matter is directed to a telescopic front fork assembly with an adjustable dampening mechanism for a two-wheeled vehicle, such as a motorcycle. The present subject matter proposes a user controlled adjustment of the dampening characteristics of the telescopic front fork assembly, also referred to as the assembly hereinafter, depending upon the varied road conditions.

According to one embodiment of the present subject matter, the assembly includes a pair of telescopic struts. Each of the telescopic struts includes an outer tube and an inner tube, and each tube has a first end and a second end. The inner tube is operably connected with the outer tube in a manner such that the inner tube axially slides through the first end of the outer tube towards the second end of the outer tube.

A spring is operably and axially disposed between the first end of the inner tube and a first end of a piston. The piston is concentrically disposed inside the inner tube. A number of extension dampening holes and the compression dampening holes are disposed circumferentially towards two different ends of the piston. An annular space between the piston and outer tube acts as a storage-area of damping fluid. When the front fork assembly is at rest, the fluid lies in the annular space over the second end of the piston.

As and when the vehicle encounters a jolt due to the uneven road, the wheel either displaces upwards or downwards. In case of the upward displacement, the telescopic strut also moves upwards along with the wheel. Similarly, the telescopic strut moves downwards during the downward displacement. In both scenarios there is a relative motion between the inner tube and the outer tube. This relative motion enables axial slide of inner tube along the outer tube, thereby compressing or extending the spring lying there between.

The inward sliding of the inner tube pressurizes the dampening fluid in the annular space over the second end of the piston. Accordingly, the inward sliding of the inner tube forces the pressurized dampening fluid to flow into a chamber of the piston through the compression dampening holes. The inward flow of the dampening fluid opposes the compression forces exerted on the spring, thus dissipating the compression forces. Consequently, the dampening fluid absorbs the impact of the jerk.

Immediately after the jerk is overcome, the compressed spring tends to extend so as to release a potential energy that gets stored by virtue of compression. The extension of the spring makes the inner tube to slide back to its initial position, thereby causing the fluid present inside the chamber of the piston to flow back towards the annular space, over the second end of the piston, through the extension dampening holes. The outward flow of the dampening fluid opposes the extension of the spring, thus dissipating the extension forces. Consequently, the oscillations of the spring are damped by the flow of the dampening fluid through the aforementioned dampening holes.

Thus, the dampening characteristic of the assembly, i.e., the extent of absorption of the impact of a jerk, is determined by various factors such as the spring constant of the spring and the amount of dissipation provided by the flow of dampening fluid. In order to allow variation in the dampening characteristics, the assembly includes a mechanism to adjust the dampening characteristics of the front fork assembly.. Such mechanism may be referred as an adjustable dampening mechanism. The adjustable dampening mechanism includes a sleeve, which is concentrically disposed between the inner tube and the piston.

In addition, a rotating mechanism is provided within the adjustable dampening mechanism for rotating the sleeve. In case a variation in the dampening characteristics is required, the sleeve circumscribing the piston is rotated. A user controlled rotation of the sleeve facilitates selective control the hole opening size or number of the extension and the compression dampening holes. Accordingly, the flow of the dampening fluid through aforementioned dampening holes is controlled. Conclusively, the dampening characteristics of the vehicle may be adjusted or varied.

Either one or both of the telescopic struts of the telescopic front fork assembly may include the adjustable dampening mechanism. In addition, the dampening mechanism may be either user controlled or automated or a combination of both.

FIG. 1 shows a perspective view of a telescopic front fork assembly 100 for a two-wheeled vehicle.

In one embodiment of the present subject matter, the telescopic front fork assembly 100 comprises a pair of telescopic struts 102. Each of the telescopic struts 102 includes an outer tube 104 having a first end 106 and a second end 108. Further, an inner tube 110 is slidably and operably disposed within the outer tube 104. The inner tube 110 also includes a first end 112 and a second end 114.

The second end 114 of the inner tube 110 is operable to axially slide into the outer tube 104, through the first end 106 of the outer tube 104 towards the second end 108 of the outer tube 104. Specifically, the inner tube 110 is operable to slide back and forth inside the outer tube 104.

FIG. 2A depicts a sectional view of the telescopic strut 102 of the front fork assembly 100.

In one embodiment, a piston 200 having a first end 202 and a second end 204 is concentrically and operably disposed inside the inner tube 110. The second end 204 of the piston 200 is fastened to the second end 108 of the outer tube 104 through a bolt 206. A spring 207 is operably disposed between the first end 112 of the inner tube 110 and the first end 202 of the piston 200. A sleeve 212 is also concentrically disposed between the inner tube 110 and the piston 200. The sleeve 212 is preferably made from a metallic or a polymeric material.

Further, an annular space between the piston 200 and the outer tube 104 defines a continuous space for the storage of a dampening fluid therein. When the front fork assembly 100 is at rest, the annular space over the second end 204 of the piston 200 stores the dampening fluid. The dampening fluid may include any fluid including oil, gas or a mixture thereof. Further, a rotating mechanism including a first bevel gear 214, operably and rigidly engaged with the sleeve 212, and a second bevel gear 216 operably engaged with the first bevel gear 214, is provided for rotating the sleeve 212. The operation of the rotating mechanism has been elaborated later.

FIG. 2B shows a perspective view of the piston 200 of the telescopic strut 102 shown in FIG. 2A.

A plurality of extension dampening holes 208 and a plurality of compression dampening holes 210 are provided on the piston 200. In one embodiment, the holes are circular in shape and of different sizes, i.e., have different bore diameters. However, the holes may have different shapes such as oval, rectangular and so on.

In one embodiment, the plurality of extension dampening holes 208 are located circumferentially towards the first end 202 of the piston 200, whereas the plurality of compression dampening holes 210 are located circumferentially towards the second end 204 of the piston 200.Without limiting the scope of present subject matter, in another embodiment, the location of the extension dampening holes 208 and the compression dampening holes 210 on the piston 200 may be varied.

In operation, when the telescopic front fork assembly 100 is subjected to a jerk, the telescopic strut 102 moves either upwards or downwards along with a wheel of the vehicle, producing a relative motion between the inner tube 110 and the outer tube 104. This relative motion enables the second end 114 of the inner tube 110 to axially slide through the first end 106 of the outer tube 104 towards the second end 108 of the outer tube 104. The axial sliding of the inner tube 110 compresses the connected spring 207.
FIG. 2C shows a perspective front view of the sleeve 212 of the telescopic strut 102 shown in FIG. 2A.

A plurality of extension dampening control slots 230 and a plurality of compression dampening control slots 235 are provided on the sleeve 212. In one embodiment, the extension dampening contrbl slots 230 are located circumferentially towards the first end 218 of the sleeve 212. Likewise, the compression dampening control slots 235 are located circumferentially towards the second end 220 of the sleeve 212.

Without limiting the scope of present subject matter, in another embodiment, the location of the extension dampening control slots 230 and the compression dampening control slots 235 on the sleeve 212 may be varied. As explained earlier, the axial sliding of inner tube 110 inside the outer tube 104 compresses the spring 207. The inward sliding of inner tube 110 pressurizes a dampening fluid located at the annular space over the second end of the piston 200 to flow inside the chamber (not shown) of the piston 200 through the compression dampening holes 210 provided on the piston 200. However, the inward flow of the dampening fluid through the compression dampening holes 210 opposes the compression of the spring 207, thus dissipating the compression forces. Accordingly, the dampening fluid absorbs the impact of the jerk.

As soon as the vehicle overcomes the jerk, the compressed spring 207 tends to extend. The extension of the spring 207 makes the inner tube 110 to slide back to its initial position, thereby pressurizing the dampening fluid. Accordingly, the fluid present inside the chamber of the piston 200 is pressurized to flow back into the annular space over the second end 204 of the piston 200. Again, the outward flow of the dampening fluid through the extension dampening holes 208 opposes the expansion of the spring 207, thus dissipating the extension forces. Accordingly, the oscillations of the spring 207 are dampened by the flow of the dampening fluid through the extension dampening holes 208 and the compression dampening holes 210.

As explained earlier in FIG. 2A, the sleeve 212 inside the telescopic strut 102 is concentrically disposed between the inner tube 110 and the piston 200. In addition, the sleeve 212 can be rotated by means of the rotating mechanism. The rotation is imparted so as to selectively align the control slots 230 and 235 of the sleeve 212 correspondingly with the extension dampening holes 208 and the compression dampening holes 210 located circumferentially on the piston 200. Specifically, the rotation of the sleeve 212 facilitates superposition of the extension dampening control slot 230 over one or more of the extension dampening holes 208. Likewise, the compression dampening control slot 235 gets superposed over one or more of the compression dampening holes 210.

As explained earlier, the compression dampening holes 210 and the extension dampening holes 208 have different bore diameters. Accordingly, the superposition of the slots 230 and 235 with a selected pair of holes out of the plurality of the extension dampening holes 208 and the compression dampening holes 210 facilitates selective controlling of the hole opening sizes or the number of the compression dampening holes 210 and the extension dampening holes 208. This sort of selective control of the extension dampening holes 208 and the compression dampening holes 210 either resists or favours the flow of the dampening fluid through the aforementioned dampening holes on the piston 200.

Specifically, the resistance posed towards the flow of the dampening fluid through aforementioned dampening holes is directly proportional to the value of dampening. As discussed before, the selective resistance to the flow of the dampening fluid is accomplished by the rotation of the sleeve 212. Accordingly, a particular value of dampening force is achieved for a particular position of the sleeve 212. Conclusively, the dampening characteristics of the vehicle may be adjusted by rotating the sleeve 212. As an example, if a rider of the two-wheeled vehicle encounters a highly rough road ahead that is full of potholes, he/she may adjust the dampening characteristic of the telescopic strut assembly to a high dampening mode. However, when the rider is convinced that the road ahead is smooth enough, he/she may adjust the dampening characteristic to a low dampening mode. In addition, if the rider is carrying a heavy load on the two-wheeled vehicle or if a pillion rider is there, then the rider may adjust the dampening characteristic to the high dampening mode even on the smooth road. In one embodiment, the aforesaid rotating mechanism may include a first bevel gear 214 and a second bevel gear 216. The first bevel gear 214 is operably engaged with the sleeve 212, whereas the second bevel gear 216 is operably engaged with the first bevel gear 214. Rotating the second bevel gear 216 either manually or through any electrical mechanism results in the corresponding rotation of the first bevel gear 214. The rotation of the first bevel gear 214 consequently results in the rotation of the sleeve 212. A keyway 240, as shown in FIG. 2D, operably engages the first bevel gear 214 with the sleeve 212. In one embodiment, the keyway 240 may be substituted with a splined piston. Other rotating means, such as a pair of worm and worm gear or a cam, may also be used.

In another embodiment, the adjustable mechanism of the present telescopic front fork assembly does not require any human intervention and may be achieved by employing an automated mechanism. Specifically, the value of dampening may be altered with respect to a sensing mechanism installed within the automated mechanism provided in a two-wheeled vehicle. The sensing mechanism may be any electronic vibration sensing means that senses the condition of the road. Accordingly, the adjustable mechanism may automatically adjust the dampening value with respect to the encountered road conditions on the basis of the inputs from the sensing mechanism.

In another embodiment, the shape and size of the holes on the piston and the slots on the sleeve may be varied so as to enable either discreet or continuously varying control of the fluid path. This type of control of the fluid path enables discreet change or smooth continuous change in damping characteristics.

The previously described versions of the subject matter and its equivalent thereof have many advantages, including those which are described below:

The telescopic front fork assembly 100 of the present subject matter facilitates user-enabled adjustability of the underlying dampening mechanism. The user can exercise his control over the adjustable dampening mechanism with the help of a rotatable valve type switch. If the present dampening mechanism is electrically actuated, the user can set the level of desired dampening by means of an electrical control/switch.

Further, the present adjustable dampening mechanism involves a sleeve and the bevel gears to adjust the hole opening size of the dampening holes lcoated on the piston 200. In terms of overall weight and space occupation, the telescopic front fork assembly 100 scores over various conventional adjustable front fork assemblies such as conventional assemblies which have cartridge type of construction. Also, the overall manufacturing cost of the telescopic front fork assembly 100 is considerably less as it employs less number of components than usual. Moreover, due to a simpler design, the upkeep and the maintenance costs associated with the telescopic front fork assembly 100 is low.

Although the subject matter has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present subject matter as defined.

We claim:

1. A telescopic front fork assembly (100), said front fork assembly (100) comprising:

a pair of telescopic strut (102), at least one of said telescopic struts (102) comprising:
an outer tube (104) having a first end (106) and a second end (108);

an inner tube (110) having a first end (112) and a second end (114), wherein said inner tube (110), is capable of axially sliding into said outer tube (104); and

a piston (200) having a first end (202) and a second end (204) concentrically disposed inside said inner tube (110), wherein a plurality of extension dampening holes (208) and

a plurality of compression dampening holes (210) are disposed towards said first end (202) and said second end (204) of said piston (200), respectively characterized in that,

an adjustable dampening mechanism operable to adjust the dampening characteristics by selectively controlling hole opening size or number of said extension dampening holes (208) and said compression dampening holes (210), thereby controlling the flow of a dampening fluid through said extension dampening holes (208) and said compression dampening holes (210).

2. The telescopic front fork assembly (100) as claimed in claim 1, wherein said adjustable dampening mechanism comprises a sleeve (212) concentrically disposed between said inner tube (110) and said piston (200) and wherein a plurality of extension dampening control slots (230) and a plurality of compression dampening control slots (235) are located circumferentially towards a first end (218) and a second end (220) of said sleeve (212), respectively.

3. The telescopic front fork assembly (100) as claimed in claim 2, wherein said adjustable dampening mechanism comprises a first bevel gear (214) and a second bevel gear (216), for rotating said sleeve (212) to align said extension dampening control slots (230) and said compression dampening control slots (235) with said extension dampening holes (208) and said compression dampening holes (210), respectively.

4. The telescopic front fork assembly (100) as claimed in claim 3, wherein said first bevel gear (214) is operably engaged to said sleeve (212) and said second bevel gear (216) is operably engaged to said first bevel gear (214) and wherein said second bevel gear (216) is operable to rotate said first bevel gear (214), such that rotation of said first bevel gear (214) causes rotation of said sleeve (212).

5. The telescopic front fork assembly (100) as claimed in claim 4, wherein said first bevel gear (214) is operably engaged to said sleeve (212) through a keyway (240).

6. The telescopic front fork assembly (100) as claimed in claim 4, wherein said first bevel gear (214) is operably engaged to said sleeve (212) through a splined shaft.

7. The telescopic front fork assembly (100) as claimed in claim 4, wherein said second bevel gear (216) is manually rotatable.

8. The telescopic front fork assembly (100) as claimed in claim 4, wherein said second bevel gear (216) is rotatable by an automated mechanism.

9. The telescopic front fork assembly (100) as claimed in claim 1, wherein an annular space between the piston (200) and outer tube (104) acts as an area of storage of damping fluid.

10. The telescopic front fork assembly (100) as claimed in claim 9, wherein said dampening fluid is one or more of oil, gas or a mixture of oil and gas.

11. A two-wheeled vehicle comprising a shock absorbing system, wherein said shock absorbing system comprises a telescopic front fork assembly (100) as claimed in any of the preceding claim.

12. A two-wheeled vehicle of claim 11, wherein said front fork assembly (100) includes a single telescopic strut (102).