Claims:We claim,
1. An anti-dive front fork suspension (1000) for two wheeler motor vehicle comprising
an outer tube (100),
an inner tube (200) telescopically slidable within the outer tube (100),
a seat pipe (110) fixed on its one end (110a) to the outer tube (100) by a hollow bolt (105),
a main spring (130) resting on the seat pipe (110) at its one end (130a) and on a spacer tube (135) on its other end (130b),
the spacer tube (135) further interacts with a fork bolt (140) which is affixed it to the inner tube (200) and the anti-dive front fork suspension (1000) characterised by,
the seat pipe (110) having a seat pipe internal chamber (145), the seat pipe (110) having a damping orifices (110x, 110y) positioned within the seat pipe internal chamber (145), the seat pipe internal chamber (145) has a resting face (155a) and the seat pipe (110) having a stepped portion (145a).
2. An anti-dive front fork suspension (1000) for two wheeler motor vehicle as claimed in claim 1, wherein the seat pipe internal chamber (145) has an opening (115) in the resting face (155a) to allow a mechanical link (125) to pass through the opening (115).
3. An anti-dive front fork suspension (1000) for two wheeler motor vehicle as claimed in claim 2, wherein the mechanical link (125) passing through the opening (115) is connected to a seat pipe internal piston (150) at a linking position (150b) provided on the seat pipe internal piston (150) within the seat pipe internal chamber (145).

4. An anti-dive front fork suspension (1000) for two wheeler motor vehicle as claimed in claim 3, wherein the seat pipe internal piston (150) is provided with a passage (150a) which aligns with the damping orifice (110x) when the seat pipe internal piston (150) is in its resting position.
5. An anti-dive front fork suspension (1000) for two wheeler motor vehicle as claimed in claim 3, wherein the damping orifice (110y) is not covered by the seat pipe internal piston (150) body when the seat pipe internal piston (150) is in its resting position.
6. An anti-dive front fork suspension (1000) for two wheeler motor vehicle as claimed in claim 3, wherein the mechanical link (125) is connected to a braking lever which is also connected with a lever operated braking system.
, Description:FIELD OF INVENTION
The invention relates to front fork suspension utilised in two wheeler motor vehicles. It more particularly relates to anti-dive mechanisms that can be provided in front fork suspensions.
BACKGROUND OF THE INVENTION
Weight transfer from rear axle to front axle in motor vehicles during braking is commonly known as diving. As such it leads to dropping of the front portion of the motor vehicle which is required to be managed as it affects passenger comfort and vehicle stability and control. A makeshift solution for managing effects of this phenomenon in two wheelers includes stiffening the suspension of the two wheeler. But, doing so negatively affects the stability of the two wheeler during cornering and braking. This naturally implies that suspension settings need to change according to the situation to provide the rider maximum stability, control and comfort.
Numerous attempts have been made in the past to provide a suspension capable of changing its characteristics in accordance with the situation. While some suspension device dealing with the phenomenon have attempted to alter the damping during braking to resist diving, others have functioned by altering the main spring’s compression during braking to achieve the suspension characteristics required to better resist diving. These anti-diving mechanisms either are purely mechanical or a combination of mechanical and electronic components. As far as mechanical anti-dive mechanisms go, chiefly hydraulic mechanisms have been utilised in the suspensions developed.
Mechanical anti-dive mechanism have primarily utilised hydraulic systems to either alter the damping or change the spring’s load to better resist diving. In this regard one may consider the suspension unit disclosed by Japanese patent publication JP62191209A. The shock absorber (10) (refer Figure 1a) is connected by bypasses (20) and (21) to a dive modulator (9). The dive modulator (9) has a valve member (22) which comes to rest on a valve seat (28) when brake fluid pressure in the chamber (23) increases. After the valve member (22) comes to rest on the valve seat (28) during application of brakes, the damping force produced increases as the damping fluid thereafter can only flow through the orifice (17a) provided on the piston. It may be noted here that this suspension unit may fail if bypasses (20) and (21) and anti-dive modulator (9) are damaged due to external elements. Damage to these components can drain out the damping fluid present within the shock absorber (10). The braking system is also rendered vulnerable to failure if the hydraulic connection provided to the chamber (23) of anti-dive modulator (9) is damaged. Furthermore, it may also be noted that the anti-dive modulator (9) increases the bulk of the suspension unit. Therefore, such a system is also not compact enough to be utilised in a two wheeler motor vehicle.
In another example of an anti-dive suspension disclosed by UK Patent Application GB2073680A, diving is resisted by increasing the loading of the main spring. The suspension unit disclosed utilises a hydraulic mechanism to compress the main spring during braking. During the braking operation, the piston (33) (refer Figure 1b) forces out the hydraulic fluid present within the cylindrical portion (31) and through the hose (36) and the passageway (42) into the chamber formed on top of the front fork. This displaced hydraulic fluid then exerts a force on the piston (38) which then moves to compresses the main spring thereby increasing its loading. Even though this suspension unit is not vulnerable to failure due to damage to the anti-dive mechanism, but still the anti-dive mechanism itself can still fail if external elements damage the pump unit (32) and the hose (36). Such damage would drain out the hydraulic fluid present within the anti-dive mechanism rendering it non-operational.
Suspension units with electronic and mechanical components are known to be capable of changing their suspension characterises in different situations but they may not be cost effective to allow for their use in every two wheeler motor vehicles. This has hence lead to a situation in which anti-dive feature is provided only in high end motorcycles whose buyers do not mind the increase in cost. Therefore, in light of the cited limitations and the vulnerabilities of the prior art suspension units, there is a requirement of an anti-dive front fork suspension which is economical.
It is another objective of the present invention to provide an anti-dive front fork suspension which is not vulnerable to failure due to leaking out of the hydraulic fluid from a damaged anti-dive mechanism.
It is yet another objective of the present invention to provide an anti-dive front fork suspension which houses the anti-dive mechanism within the front fork suspension itself.
It is still another objective to provide an anti-dive front fork suspension which has a simple and compact construction.
One more objective of the present invention is to provide an anti-dive front fork suspension that can be readily utilised in two wheeler motor vehicles.
SUMMARY
An anti-dive front fork suspension is provided comprising an outer tube, an inner tube telescopically slidable within the outer tube, a seat pipe fixed on its one end to the outer tube by a hollow bolt, a main spring resting on the seat pipe at its one end and on a spacer tube on its other end, with the spacer tube further interacting with a fork bolt which is affixed to the inner tube. The anti-dive front fork suspension provided is characterised by the seat pipe having a seat pipe internal chamber with two damping orifices positioned within said seat pipe internal chamber. The seat pipe internal chamber also has a resting face and a stepped portion. An opening is provided to the seat pipe internal chamber to allow a mechanical link to pass through it.
Typically, the mechanical link passing through the opening to the seat pipe internal chamber is connected to a seat pipe internal piston at a linking position provided on the seat pipe internal piston within the seat pipe internal chamber.
Typically, the seat pipe internal piston is provided with a passage which aligns with a damping orifice provided within the seat pipe internal chamber when the seat pipe internal piston is in its resting position.
Typically, the other damping orifice provided within the seat pipe internal chamber is not covered by the seat pipe internal piston body when the seat pipe internal piston is in its resting position.
BRIEF DESCRIPTION OF DIAGRAMS
Figure 1a illustrates a known anti-dive suspension unit.
Figure 1b illustrates another known anti-dive suspension unit.
Figure 2 illustrates the outer view of the anti-dive front fork suspension as per an embodiment of the current invention.
Figure 3 illustrates a cross sectional view of the anti-dive front fork suspension as per an embodiment of the current invention.
Figure 4 illustrates the magnified cross sectional view of the anti-dive mechanism as per an embodiment of the current invention.
Figure 5 illustrates the exploded view of the anti-dive mechanism as per an embodiment of the current invention.

DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiment of an anti-dive front fork suspension will now be described in detail with reference to accompanying drawings. The preferred embodiment must not be viewed as restricting the scope and ambit of the disclosure.
The suspension units disclosed in the patent publication JP62191209A (shown in Figure 1a) and the patent application GB2073680A (shown in Figure 1b) are respectively capable of resisting diving. But the mechanisms disclosed in them are vulnerable to damage from external elements. The damaged anti-dive mechanisms may leak hydraulic fluid rendering them, the suspension unit or the braking system ineffective. In case of the suspension unit disclosed in JP62191209A, the suspension unit may lose its damping fluid due to damage to the anti-dive modulator (9) and the bypasses (20) and (21). The braking system may also be affected if the connection provided to the chamber (23) is damaged by external elements. Even though suspension unit disclosed by GB2073680A is not as vulnerable as that disclosed by JP62191209A, its anti-dive mechanism may also lose its hydraulic fluid if external elements damage the pump unit (32) or the hose (36). In order to overcome these shortcomings and other stated limitations, an anti-dive front fork suspension (1000) with an anti-dive mechanism is hereon described.
The anti-dive front fork suspension (1000) for two wheeler motor vehicle in accordance with an embodiment of the current invention is shown in Figure 2. It comprises of an outer tube (100), an inner tube (200) telescopically slidable within the outer tube (100). A hollow bolt (105) (indicated in figure 3) provided on the outer tube (100) fixes the seat pipe (110) to the outer tube (100). The outer tube (100), the hollow bolt (105) and an axle portion (120) have an opening (115) which proceeds though the resting face (155a) into the seat pipe (110) (indicated in Figure 4). The opening (115) is so positioned so at allow a mechanical linkage (125) to enter inside the seat pipe’s (110) hollow structure from its one end (110a). A main spring (130) rests on the seat pipe (110) at it’s another end (130a) and on its other end (130b) on a spacer tube (135). The spacer tube (135) is connected with the inner tube (200) by a fork bolt (140). These sub components can be observed in Figure 3. The seat pipe (110) has three damping orifices (110x, 110y and 110z). The damping orifices (110x and 110y) are located close to the one end (110a) of the seat pipe (110), while the damping orifice (110z) is located close to the other end (110b) of the seat pipe (110). The components namely the inner tube (100), the outer tube (200), the main spring (130), spacer tube (135), fork bolt (140) and seals, washers and O-rings (provided as per requirement) function similarly to their corresponding components as provided in any other conventional front fork.
The seat pipe (110) is structurally different from the seat pipes provided in any other conventional front fork. The seat pipe (110) (as shown in Figure 4) has a seat pipe internal chamber (145) whose limits are defined by a stepped portion (145a) provided within the seat pipe (110) and the opening (115). The damping orifices (110x and 110y) are located in the seat pipe internal chamber (145). A seat pipe internal piston (150) provided within the seat pipe internal chamber (145) interacts with a bush (155) provided along the one end (110a) with the hollow bolt (105) via a seat pipe internal spring (160). A surface of the bush (155) provides a resting face (155a) (indicated in Figure 4) for resting one end of the seat pipe internal spring (160). The other end of the seat pipe internal spring (160) rests on the seat pipe internal piston (150). Also, as indicated in figure 4 the seat pipe internal piston (150) is linked with the mechanical linkage (125) passing through the opening (115) at a linking position (150b). The seat pipe internal piston (150) as indicated in Figure 4 is in its resting position. The seat pipe internal piston (150) is so located inside the seat pipe internal chamber (145) such that damping orifice (110x) perfectly aligns with a passage (150a) provided from within the seat pipe internal piston (150) while the seat pipe internal piston (150) is in its resting position. The damping orifice (110y) is located close to the stepped portion (145a) in the seat pipe internal chamber (145) such that it is not covered by the seat pipe internal piston (150) in its resting position.
When the rider operates the front wheel braking lever (165) (observable in figure 2) the mechanical linkage (125) is also pulled. This in turn causes the seat pipe internal piston (150) connected with the mechanical link (125) to retract towards the one end of the seat pipe (110a). This further leads to the passage (150a) losing its alignment with the damping orifice (110x). The seat pipe internal piston (150) hence blocks the damping orifice (110x), now allowing the damping fluid to flow only though the damping orifice (110y). This increases the damping force generated during the compression of the main spring (130) while the front wheel braking lever (165) is being operated. The increase in damping force generated retards the rate at which the main spring (130) is compressed thereby controlling the dive of the two wheeler motor vehicle.
The seat pipe internal spring (160) gets compressed when the seat pipe internal piston (150) retracts towards the one end (110a). When the rider ceases operation of the front wheel braking lever (165), the seat pipe internal piston (150) returns to its resting position under the action of the seat pipe internal spring (160). With both damping orifice (110x) and (110y) being open in the resting position of the seat pipe internal piston (150), the values of damping force generated in the anti-dive front fork suspension (1000) return to normal. The anti-dive front fork suspension (1000) thereon functions like a conventional front fork with two compression damping orifices (when the front wheel brake lever (165) is not being operated).
The anti-dive mechanism provided in the anti-dive front fork (1000) as indicated in the dotted portion (500) of figure 3 comprises of the seat pipe (110), the seat pipe internal piston (150) and the seat pipe internal spring (160). The bush (155) and a washer (170) are also provided in the anti-dive mechanism to ensure proper linkage of the seat pipe of the seat pipe (110) with the outer tube (100). The bush (155) also provides a base for the seat pipe internal spring (160). An O-ring (175) is fitted into a groove (150c) provided on the seat pipe internal piston (150) to provide proper sealing. Figure 5 gives an exploded view the anti-dive mechanism as provided in the anti-dive front fork (1000). The anti-dive front fork suspension (1000) comprising the mechanical linkage (125) may be used in a two wheeler motor vehicles with any lever operated braking system. This is possible because the mechanical linkage (125) is separately connected to and operated directly by a braking lever. The braking system is therefore effectively isolated from the anti-dive front fork suspension’s (1000) mechanisms even though both are actuated at the same time by a braking lever. The lever operated braking system may be an Anti-lock Braking System (ABS) or a Combined Braking System (CBS) or any other braking system that may be operated by a braking lever.
The anti-dive front fork suspension (1000) has a simple and compact construction which allows it to be utilised in any two wheeler motor vehicle. The anti-dive front fork suspension (1000) is hence very economical to provide given that it can be mass manufactured. Also, the components of the anti-dive mechanism provided in the anti-dive front fork suspension (1000) are contained within the front fork itself. The anti-dive mechanism is hence well protected from being damaged by the external elements by the outer tube and the inner tube. The anti-dive mechanism being operated via a mechanical linkage (125) is also not vulnerable to failure due to leakage of a hydraulic fluid. The possibility of the anti-dive front fork suspension (1000) itself failing due to leakage of damping fluid through the anti-dive mechanism is also eliminated. Furthermore, even the braking system is protected from a possible leakage of its hydraulic fluid due to damage to the anti-dive mechanism. While it has been shown that the mechanical linkage (125) is linked with the front wheel brake lever (165) it may also be linked with a rear wheel brake lever by making minor changes. Any changes that may have to be carried to the anti-dive front fork to allow it to be linked to the rear wheel brake lever lie within the scope of the invention.

List of reference numbers
100……Outer tube
200……Inner tube
105……Hollow bolt
110……Seat pipe
110a…..One end of the seat pipe
110b…..Other end of the seat pipe
110x…..Damping orifice one
110y…..Damping orifice two
110z…..Damping orifice three
115……Opening
120……Axle portion
125……Mechanical Linkage
130……Main Spring
130a…..One end of the spring
130b…..Other end of the spring
135……Spacer tube
140……Fork bolt
145……Seat pipe internal chamber
145a…..Stepped portion