DESC:FRONT FORK WITH SAFE DAMPING ARRANGEMENT
Field of the invention:
The present invention relates to a front fork and more particularly it relates to an arrangement for safe damping in a front fork.
Background of the invention:
Telescopic Front forks are designed to have a fixed damping force through-out its stroke, which is controlled by hole size and number of holes in piston. Fork will continue to travel to end of the stroke in the same speed and suddenly comes to a halt which makes rider to come to dead stop which creates a situation to bend beyond designed angle towards front wheel and gets imbalanced due to shift in CG of the vehicle. The existing designs can take care of bottoming i.e., only end cushioning called oil lock force. Even though anti breaking systems (ABS) are introduced in most of the vehicles and also which is becoming mandatory, still there are chances of rider / vehicle toppling while brakes are applied at high speed instances. Conventional telescopic front forks are designed with sufficient strokes to take care of front suspension effect of rebounding and compressing while accelerating and applying brakes respectively. These front suspensions have a uniform damping effect through-out the stroke of the front fork, which continuously moves the Center of the gravity towards front. Rebounding is mainly controlled by Coil spring, but while braking action in other words during compression movement, Rider leans forward with a braking inertia and also with a higher speed. Even with the latest ABS technology, Rider has a fear of toppling while applying brake, since the suspension movement during compression remains same.
Accordingly, there exists a need to upgrade function of suspension system to support advancements in braking features and also to meet safety requirements of large selling ABS mounted Motor cycles and Scooters.
Objects of the invention:
An object of the present invention is to provide a safe damping arrangement in a front fork, to avoid rider toppling.
Another object of the present invention is to provide a safe damping system a front fork to avoid sudden stroke ends and provide Rider a confidence of safe braking operation.
Yet another object of the present invention is to provide a safety feature in a two wheeled vehicle in addition to the anti-braking system.
Summary of the invention
Accordingly, the present invention provides a front fork with safe damping arrangement providing controlled cushioning at the stroke end. The front for consists of an outer tube, an inner tube mounted within the outer tube; a fork tube slidably received within the inner tube having upper end closed with a bolt cap and partially filled with working oil and a piston having lower end fixed to the bottom of the inner tube and upper end extending into the fork tube. The piston is configured with a piston bore there within and piston holes on the piston body for passage of oil there through. A damping spring is incorporated within the piston bore with one end fixed to the inner bottom of the piston and other end having a bush loaded thereon. A fork spring is fixed to a spacer below the bolt cap of the fork tube. The fork spring under compression extends between the spacer and the upper end of the piston. Further, a plunger mechanism is mounted within the fork spring which is having its upper end secured to the spacer and lower end provided with a plunger head. The plunger head is configured with relief slots thereon for releasing oil there through during compression stroke.

During normal compression stroke, when the fork tube slides down, the plunger head is not in contact with the bush and allows oil passage through piston holes achieving the desired damping force. During the extreme stroke condition, i.e. when a sudden brake is applied at high speed, the fork tube comes to a desired compressed condition and the plunger moves forward to push the bush in lower direction resulting in overlapping one of the piston holes (30A) and restricting the oil passage, thereby increasing the damping force to create a cushioning effect. At this condition, only a small amount of oil is released through the relief slots on the plunger head. Thus, the present invention provides a controlled cushioning at the stroke end. About 25% to 30 % of the stroke is tuned to generate a higher damping and take up forceful compression so that stroke end banging is eliminated.
Brief description of the drawings:
The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1shows a cross sectional view of a front fork assembled with a safe damping arrangement, in accordance with the present invention.
Detailed description of the embodiments:
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
When a sudden brake is applied at high speed, the fork moves at a speed and comes in fully compressed condition where the rider is lifted from the seat and bends towards the front wheel. The present invention provides a safe damping arrangement for a front fork of a two wheeled vehicle. The present invention provides a controlled cushioning at the stroke end. About 25% to 30 % of the stroke is tuned to generate a higher damping and take up forceful compression so that stroke end banging is eliminated. The front fork comprises of an outer tube, an inner tube fitted in the outer tube, a fork tube slidably fitted there-within, a piston fitted to the bottom of inner tube and extending into the fork tube, and a fork spring suspended within the inner tube between a spacer at the top and the piston. The piston is configured with a rebound hole and a piston main bore for passage of oil there through. In present invention, a plunger mechanism is incorporated within the fork tube for safe damping arrangement. A plunger is mounted on the top side of the fork spring which is a fixed end, and a spring loaded bush is mounted inside the piston bore. During normal compression stroke, when the fork tube slides down, the piston holes ow oil passage through them normally achieving the desired damping force thereby. During the extreme stroke condition, i.e. when a sudden brake is applied at high speed, the fork tube comes to a desired compressed condition and the plunger moves forward to push the bush in lower direction resulting in overlapping one of the piston holes (30A) and restricting the oil passage, thereby increasing the damping force to create a cushioning effect. At this condition, only a small amount of oil is released through the relief slots on the plunger head.
The present invention is illustrated with reference to the accompanying drawings, wherein numbers indicated in the bracket represent the components of the invention throughout the description. The table 1 below lists the components and their respective reference numbers:
Table 1:
Ref No Component Ref No Component
10 Outer tube 35 Fork spring
15 Inner tube 40 Plunger
20 Fork tube 45 Plunger head
25 Piston 50 Bush
25A Piston bore 60 Damping spring
30A, 30B Piston holes 65 Spacer
Referring to Figure 1, a cross sectional view of a front fork (100) assembled with a safe damping arrangement is shown. The front fork (100) comprises of an outer tube (10) having lower end closed and the upper end open and an inner tube (15) mounted there within. A fork tube (20) having upper end closed with a bolt cap (not shown), is slidably received within the inner tube (15). The fork tube (20) is partially filled with working oil.
A piston (25) fixed to the bottom of the inner tube (15) and extending into the fork tube (20) is configured with piston bore (25A) therein and at least two piston holes (30A and 30B) configured thereon for passage of oil there through. A damping spring (60) incorporated within the piston bore (25A) is fixed to the inner bottom of the piston (25) with a bush (50) loaded thereon.
A fork spring (35) is fixed to a spacer (65) below the bolt cap in the fork tube (20). The fork spring (35) mounted under compression is extending between the spacer (65) and the upper end of the piston (25).
A plunger (40) secured to the spacer (65) is mounted within the fork spring (35) in such a way that in normal condition, a plunger head (45) is not in contact with bush (50). The plunger head (45) is configured with relief slots thereon.
In normal compression stroke, when the fork tube (20) slides down, the piston holes (30A and 30B) allow oil passage through them thereby achieving the desired damping force. In this condition, the plunger head (45) is not in contact with the bush (50).
At the extreme stroke condition, i.e. when a sudden brake is applied at high speed, the fork tube (20) comes to fully compressed condition and the plunger (40) pushes the bush (50) in lower direction, closing one of the piston hole (30A) thereby blocking the oil flow. This increases the damping force creating a cushioning effect. At this condition, only a small amount of oil is released through the relief slots on the plunger head (35).
Advantages of the invention:
• The safe damping arrangement in a front fork (100) of the present invention provides an economic and safe solution to avoid sudden stroke ends which in turn avoids major accidents due to rider toppling.
• The safe damping arrangement in a front fork (100) of the present invention provides a safety feature in addition to the existing anti-braking systems in motorcycles, eliminating the fear of rider toppling while applying sudden brake.
• The safe damping arrangement in a front fork (100) of the present invention is inbuilt to the existing front fork without much structural change.
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the scope of the invention.
,CLAIMS:CLAIMS
We claim:
1. A front fork (100) with safe damping arrangement, consisting of an outer tube (10), an inner tube (15) mounted within the outer tube (10); a fork tube (20) slidably received within the inner tube (15) having upper end closed with a bolt cap and partially filled with working oil;
a piston (25) configured with a piston bore (25A) therein and piston holes (30A, 30B) thereon, the piston (25) having lower end fixed to the bottom of the inner tube (15) and upper end extending into the fork tube (20), wherein oil passes through piston holes (30A, 30B) during normal compression stroke thereby achieving desired damping force;
a damping spring (60) incorporated within the piston bore (25A) with one end fixed to the inner bottom of the piston (25) and other end having a bush (50) loaded thereon;
a fork spring (35) fixed to a spacer (65) below the bolt cap and extending between the spacer (65) and the upper end of the piston (25); and
a plunger mechanism (40) mounted within the fork spring (35) and having upper end secured to the spacer (65) and lower end provided with a plunger head (45) wherein the plunger head (45) blocks a piston hole (30A) in fully compressed condition of fork tube (20) thereby blocking the oil passage through the piston hole (30A), increasing the damping force and creating a cushioning effect.
2. The front fork (100) with safe damping arrangement as claimed in claim 1, wherein the plunger head (45) is not in contact with bush in normal condition.
3. The front fork (100) with safe damping arrangement as claimed in claim 1, wherein the plunger head (45) is configured with relief slots for releasing oil there through during compression stroke.
Dated this 22nd day of January, 2018

Prafulla Wange
(Agent of Applicant),
(IN/PA-2058)