Claims:We Claim:

1. A versatile front fork assembly (1000) for a vehicle comprising of an inner tube (100), an outer tube (200), an outer main spring (300), an inner main spring (400), a sealing assembly (500), a seat pipe (600), an inner tube valve assembly (700), and a bump rubber (800)
wherein,
- the outer main spring (300) is located between a spring seat (205) on the outer surface of the outer tube (200) and a bracket (105) fixed to the outer surface of the inner tube (100);
- the inner main spring (400) is located between one end of the inner tube (100) closed by a fork bolt (110) and a piston (605) given on one end of the seat pipe (600);
- the other end of the seat pipe (600) is attached to the outer tube (200) by a bolt (210), a bump rubber (800) is concentrically located with and fixed at the other end of the seat pipe (600);
- the seat pipe (600) has an inner recessed portion (608) within which a tube (610) is fitted, the tube (610) has a longitudinal recess (610A) running along its length;
- orifices (610AB1, and 610AB2) are given at the same horizontal plane on the cylindrical curved surface of the tube (610) above the location of the longitudinal recess (610A) on the tube (610);
- orifice (610AB3) is given below the location of the longitudinal recess (610A) on the tube (610);
- orifices (610AB4 and 610AB5) are given at the same horizontal plane on the tube (610) angularly displaced from one end of the longitudinal recess (610A); and
- the inner valve assembly (700) located at the open end of the inner tube (100) is provided with an adjustment tube (705), a check valve plate (710A) with a spring (710B) and a top cap (715).

2. The versatile front fork assembly (1000) for a vehicle as claimed in claim 1, wherein the outer main spring (300) is configured to have two different spring rating; the upper portion of the outer main spring (300) has the spring rating ‘k1’ whereas lower portion has the spring rating ‘k2’; wherein,
- the ratio of spring ratings (k2/k1) is in the range of 1.6 to 2.0; and
- the length of lower portion of the outer main spring having spring rating ‘k2’ is in the range of 0.35x to 0.50x.

3. The versatile front fork assembly (1000) for a vehicle as claimed in claim 2, wherein the seat pipe (600) has orifices (600AB1, 600AB2, 600AB3, 600AB3’, 600AB4 and 600AB5) mandatorily overlapping over the orifices (610AB1, 610AB2, 610AB3, 610AB4 and 610AB5) given on the tube (610).

4. The versatile front fork assembly (1000) for a vehicle as claimed in claim 2, wherein the seat pipe (600) has a plurality of orifices (600AB1, 600AB2, ….., ……, 600ABn) that mandatorily overlaps over the respective set of orifices (610AB1, 610AB2, …., …., 610ABn) given on the tube (610).

5. The versatile front fork assembly (1000) as claimed in claim 3 or 4, wherein the seat pipe (600) further has a set of orifices (600AB6 and 600AB7), each of the orifices located at either ends of the longitudinal recess (610A) given on the tube (610).

6. The versatile front fork assembly (1000) as claimed in claim 5, wherein a protrusion (610B) located at one end of the cylindrical curved surface of the tube (610) to rotationally lock the tube (610) with a matching depression (600B) given on the seat pipe (600).

7. The versatile front fork assembly (1000) as claimed in claim 6, wherein a rebound spring (410) is located between an upper face of the top cap (715) and the bottom face of the piston (605).

8. The versatile front fork assembly (1000) as claimed in claim 7, wherein the adjustment tube (705) has two curved slots (705A, 705B) in its cylindrical walls which travel along its length and an orifice (705O) on its curved surface which is interlinked with one of the curved slot travelling along its length.
9. The versatile front fork assembly (1000) as claimed in claim 8, wherein the sealing assembly (500) has at least a bush (525), a washer (520), an oil seal (515), a circlip (510), and a dust seal (505) positioned and assembled in this order at the open end of the outer tube (200).

10. The versatile front fork assembly (1000) as claimed in claim 9, wherein a bush (105A) is fitted at the lower end outside surface of the inner tube (100).

11. The versatile front fork assembly (1000) as claimed in claim 10, wherein the said assembly is configured to passively adapt to extreme operating conditions and wide range of front axle load ranging from 35 to 300 kg on its own without needing any user input and any modification / customization.

Dated this 22nd day of March 2021 , Description:FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

TITLE OF THE INVENTION
“VERSATILE FRONT FORK ASSEMBLY FOR A VEHICLE”

Endurance Technologies Limited
E-92, M.I.D.C. Industrial Area, Waluj,
Aurangabad – 431136, Maharashtra, India

The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of Invention

[001] The present invention is related to suspension system for a motor vehicle. More particularly, the invention is related to front fork assembly for a vehicle, wherein the assembly has more than one main spring and a staged damping mechanism to allow it to be utilized for a wider range of load without any design changes and/or customization.

Background of the Invention

[002] Suspension is one of the important systems of the vehicle architecture as it contributes to vehicle handling and provides safety and comfort by keeping the vehicle user comfortably isolated from road bumps and vibrations. Various forms of Suspension Systems have been proposed and developed for bikes, scooters and three wheelers over the period of time. The most common form of front fork assembly of the suspension system comprises a pair of telescopic assemblies between which the front wheel is mounted. Each telescoping assembly comprises an outer tube, and an inner tube which is free to move in and out of the outer tube and is cushioned in some manner, as by springs and/or a hydraulic System.

[003] A typical front fork suspension assembly for a two wheeler comprises of a main springs for absorbing the impact of vehicle travelling over a surface irregularity and a damping mechanism to dissipate the energy of the main spring as it expands and contracts to maintain levelled movement over the road surface. The front fork suspension typically available in the market are specifically designed for a predetermined load range (categorizing in form of two wheeled vehicle and three wheeled vehicle), damping force and suspension unit size requirements. If the predetermined load range is exceeded, the front fork suspension risks bottoming out at the slightest impact with the road surface irregularity. The damping system too risks being overwhelmed as it tries to dampen oscillations of a larger load than its designed capacity.

[004] In the prior art, such problems have been resolved at vehicle designing stage (depending on the type of vehicle being whether it is two wheeled or three wheeled) by switching over to a separate spring and damper unit suspension construction for motor vehicles carrying greater loads. Though the outer spring of different spring rating are known to be used in the suspension system, a single spring with two different spring rating have not been known in the prior art to make the front assembly versatile so as to make it usable from load to high load on the front axle. The document No. DE202004017869U1 describes front wheel suspension for a two or three-wheeler, characterized by the combination of a fork in which the front wheel is rotatably supported by means of a wheel bearing and a wheel axle, which fork with the front wheel cross-part with a frame of the two- or three-wheeled by a handlebar which is damped relative to the frame by means of a shock absorber. Another document no. CN103359240B discloses a hydraulic shock absorber suitable for use as a front fork or the like of a motorcycle or bicycle in which in order to prevent the outer tube and the inner tube from being caused by a lateral force based on a resistance received by a wheel from the road surface during travel and scraping each other, a spiral oil groove is provided in an inner surface of the outer tube, so that the inner tube is supported on the inner surface of the outer tube via an oil film.

[005] One issue with such engineering solutions is that they are not universal with respect to the category of load (category of the vehicle) and typically require significant customization and alteration when the suspension unit has to be applied to a new class of motor vehicles (i.e. from two wheeler to three wheeler and vice-versa). The front fork assembly therefore designed for a two wheeler would not be implementable in workable form on a three wheeler directly without doing desired customization and vice-versa. In such cases, even proven suspension designs have to be mandatorily revalidated as per the standard leading to requirement of more resources (time and cost).

[006] Therefore, there exists a long pending unmet need of providing a versatile front fork assembly for a vehicle that can passively adapt to its usage in vehicles having different load bearing requirements without needing any redesigning, customization and revalidation thereof.

Objectives of the Invention

[007] The main object of the present invention is to provide a versatile front fork suspension assembly for vehicles.

[008] Another object of the present invention is to provide a versatile front fork suspension assembly that can passively adapt to change in its loading irrespective of the category of the vehicle, i.e. two wheeler or three wheeler.

[009] Still another object of the present invention is to provide a versatile front fork suspension that does not need redesigning or any kind of customization when fitted on different vehicles (i.e. two wheeler or three wheeler) with different load bearing and damping requirements.

[0010] Yet the object of the present invention is to provide a front fork suspension assembly with wider utility and applicability than that of a typical front fork suspension made for a specific vehicle.

[0011] It is yet another objective of the invention to provide a brake actuating system that provides the superior suspension performance while keeping the cost of production low and maintaining the quality of damping irrespective of the vehicles selected from two wheeled and three wheeled.

[0012] Further, the objective of the invention to provide a versatile front fork assembly with at part suspension characteristics so that the end user can drive the vehicle with enhanced ride comfort and safety.
Summary of the Invention

[0013] With above objectives in view, the current invention provides a front fork assembly for a motor vehicle comprising of an inner tube, an outer tube, an outer main spring, an inner main spring, a sealing assembly, a seat pipe, an inner tube valve assembly, and a bump rubber wherein, the outer main spring is located between a spring seat on the outer surface of the outer tube and a bracket fixed to the outer surface of the inner tube; the inner main spring is located between one end of the inner tube closed by a fork bolt and a piston given on one end of the seat pipe; the other end of the seat pipe is attached to the outer tube by a bolt, a bump rubber is concentrically located with and fixed at the other end of the seat pipe; the seat pipe has an inner recessed portion within which a tube is fitted, the tube has a longitudinal recess running along its length; orifices are given at the same horizontal plane on the cylindrical curved surface of the tube above the location of the longitudinal recess on the tube; an orifice is given below the location of the longitudinal recess on the tube; orifices are given at the same horizontal plane on the tube angularly displaced from one end of the longitudinal recess; and the inner valve assembly located at the open end of the inner tube is provided with an adjustment tube, a check valve plate with a spring and a top cap.

[0014] Typically, the seat pipe has orifices which are located above the orifices given on the tube. The seat pipe further has orifices located above one end and the other end respectively of the longitudinal recess given on the tube. Typically, a protrusion given on the cylindrical curved surface of the tube rotationally locks the tube with a matching depression given on the seat pipe. A rebound spring is located between an upper face of the top cap and the bottom face of the piston.

[0015] Typically, the adjustment tube has two curved slots in its cylindrical walls which travel along its length and an orifice on its curved surface which is interlinked with one of the curved slot travelling along its length. The sealing assembly has at least a bush, a washer, an oil seal, a circlip, and a dust seal positioned and assembled in this order at the open end of the outer tube. Typically, a bush is fitted at the lower end outside surface of the inner tube.

Brief Description of the Drawings

[0016] This invention is illustrated in the accompanying drawings, throughout which like reference letters / numerals indicate corresponding parts in the various figures. The embodiments herein and advantages thereof will be better understood from the following description when read with reference to the following drawings, wherein

[0017] Figure 1 illustrates a fully assembled front fork in accordance with an embodiment of the present invention.

[0018] Figure 2 illustrates a cut section diagram of a front fork in accordance with an embodiment of the present invention.

[0019] Figure 3 illustrates a magnified cut section diagram of a front fork in accordance with an embodiment of the present invention.

[0020] Figure 4a & 4b illustrate operating conditions a front fork in accordance with an embodiment of the present invention.

[0021] Figure 5 illustrates the magnified cut section diagram of a sealing assembly for a front fork in accordance with an embodiment of the present invention.

[0022] Figure 6a & 6b illustrates a seat pipe and its cut section in accordance with an embodiment of the present invention.

[0023] Figure 7a & 7b illustrate the tube and its cut section in accordance with an embodiment of the present invention.

[0024] Figure 8a & 8b illustrate an adjustment tube and its cut section in accordance with an embodiment of the present invention.

[0025] Figure 9 shows the exploded view of the outer main spring of the front fork assembly in accordance with the present invention.

Detailed Description of the Present Invention

[0026] The invention will now be described in detail with reference to the accompanying drawings which must not be viewed as restricting the scope and ambit of the invention.
[0027] Referring to Figs. 1, 2 and 3, the front fork (1000) in accordance with an embodiment of the present invention comprises of an inner tube (100), an outer tube (200), an outer main spring (300), an inner main spring (400), a sealing assembly (500), a seat pipe (600), an inner tube valve assembly (700), and a bump rubber (800) wherein, the outer main spring (300) is located between a spring seat (205) on the outer surface of the outer tube (200) and a bracket (105) fixed to the outer surface of the inner tube (100); the inner main spring (400) is located between one end of the inner tube (100) closed by a fork bolt (110) and a piston (605) given on one end of the seat pipe (600), a spacer (shown but not specifically indicated in Fig. 2) can optionally be provided below the fork bolt (110) to reduce the length of the inner main spring (400); the other end of the seat pipe (600) is attached to the outer tube (200) by a bolt (210) and a bump rubber (800) is concentrically located with and fixed at the other end of the seat pipe (600).

[0028] Referring Fig. 3, 6a, 6b , 7a, 7b , 8a and 8b; the seat pipe (600) has an inner recessed portion (608) within which a tube (610) is fitted, the tube (610) has a longitudinal recess (610A) running along its length, orifices (610AB1, and 610AB2) are given at the same horizontal plane on the cylindrical curved surface of the tube (610) above the location of the longitudinal recess (610A) on the tube (610) and orifice (610AB3) is given below the location of the longitudinal recess (610A) on the tube (610), orifices (610AB4 and 610AB5) are given at the same horizontal plane on the tube (610) angularly displaced from one end of the longitudinal recess (610A), the seat pipe (600) has orifices (600AB1, 600AB2, 600AB3, 600AB3’, 600AB4 and 600AB5) located above the orifices (610AB1, 610AB2, 610AB3, 610AB4 and 610AB5) given on the tube (610), the seat pipe (600) further has orifices (600AB6 and 600AB7) located above one end and the other end of the longitudinal recess (610A) given on the tube (610), a protrusion (610B) located at one end of the cylindrical curved surface of the tube (610) rotationally locks the tube (610) with a matching depression (600B) given on the seat pipe (600); and the inner valve assembly (700) located at the open end of the inner tube (100) is provided with an adjustment tube (705), a check valve plate (710A) with a spring (710B) and a top cap (715), the adjustment tube (705) has two curved slots (705A, 705B) in its cylindrical walls which travel along its length and an orifice (705O) on its curved surface which is interlinked with a curved slot travelling along its length.

[0029] Further referring to Figs. 2 and 5, the sealing assembly (500) of the front fork (1000) is located at the open end of the outer tube (200). The sealing assembly (500) has at least a bush (525), a washer (520), an oil seal (515), a circlip (510) and a dust seal (505) which are located in a space given at the open end of the outer tube (200) and are also assembled in this order.

[0030] During normal full length compression in low load condition/use in a low weight motor vehicle category viz. two wheeler (referring Fig. 4a), when the wheel of the motor vehicle hits a big road surface irregularity, the front fork (1000) is so compressed such that the adjustment tube (705) at the open end of the inner tube (100) travels up to and partially covers the orifices (600AB4, 600AB5 and 600AB7). During such compression the outer main spring (300) and the inner main spring (400) are partially compressed. During initial stages of compression, when the orifices (600AB4, 600AB5 and 600AB7) are not partially covered, the damping fluid flows through the orifices (600AB1, 600AB2 and 600AB4 and 600AB5) and through the corresponding orifices (610AB1, 610AB2, 610AB4 and 610AB5) and into the seat pipe (600) and then out of the orifice (610AB3) and its corresponding orifice (600AB3). The damping fluid entering through the orifice (600AB7) travels in the damping fluid channel formed by the longitudinal recess (610A) and the seat pipe (600) and then exits through the orifice (600AB6). The flow through orifice (600AB6) happens only it is not obstructed by the solid portions of components of the inner valve assembly (700). The curved slots (705A) and (705B) on the adjustment tube (705) allow significant quantities of damping fluid to flow through them only when the damping fluid pressure rises sufficiently to compress the spring (710B) and thereby lifting the check valve plate (710A). In normal operating circumstances only minor leakage of damping fluid happens to flow past the check valve plate (710A). Some amount of damping fluid also flows out from the orifice (705O). This damping fluid thereby proceeds to flow through a corresponding orifice on the inner tube (100) and between the minor clearance between the inner tube (100) and the outer tube (200) until it reaches the oil seal (510) of the sealing assembly (500). This ensures the lubrication of curved surfaces below the oil seal (510) i.e. of the bush (505), the inner curved surface of the outer tube (200) and the outer curved surface of the inner tube (100), up till the bush (105A) that is fitted on the lower end outer surface of the inner tube (100).

[0031] When the lower end of the adjustment tube (705) reaches orifices (600AB4, 600AB5 and 600AB7) during compression and partially covers them, the flow of damping fluid through these orifices (600AB4, 600AB5 and 600AB7) is partially obstructed and therefore the resulting damping force created due to the damping fluid flow through them and the orifices (600AB1 and 600AB2 of seat pipe (600), and 610AB1 and 610AB2 of tube (610)) rises significantly. For this reason, when the motor vehicle has a lower weight or is not fully loaded, the orifices (600AB4, 600AB5 and 600AB7) form the maximum limit up to which the inner tube (100) can travel within the outer tube (200).

[0032] When the vehicle is heavily loaded/ vehicle itself is very heavy (say it is a three wheeler), during compression, the adjustment tube (705) proceeds to cover the orifices (600AB4, 600AB5 and 600AB7) and then moves further down until it reaches the orifices (600AB1 and 600AB2 of seat pipe (600)). After the orifices (600AB4, 600AB5 and 600AB7) are covered, the damping fluid can flow into the seat pipe (600) through the orifices (600AB1 and 600AB2 of seat pipe (600), and 610AB1 and 610AB2 of tube (610)) and then out through the orifices (610AB3 and 600AB3). Here again the curved slots (705A) and (705B) on the adjustment tube (705) allow significant quantities of damping fluid to flow through them only when the damping fluid pressure rises sufficiently to compress the spring (710B) and thereby lifting the check valve plate (710A). Once the orifices (600AB1 and 600AB2 of seat pipe (600)) are covered by the adjustment tube (705) the damping force rises greatly. As the damping fluid can now flow out only through the curved slots (705A) and (705B) on the adjustment tube (705), the damping force’s magnitude reaches its maximum possible extent. Further compression below the level of the orifices (600AB1 and 600AB2 of seat pipe (600)) happens very slowly. When bottoming condition has been reached, the bump rubber (800) acting as a secondary spring absorbs the residual energy remaining after full compression of the front fork (1000) (refer Fig 4b). The bump rubber (800) does so by compressing under the force applied by the lower end of the inner tube (100).

[0033] It is to be noted that as the adjustment tube (705) fitted on the lower end of the inner tube (100) travels into the outer tube (200), the damping force’s magnitude increases in stages defined by extent of compression achieved. There are three notable stages. The first stage of damping exists from fully extended condition up until the time the adjustment tube (705) partially covers the orifices (600AB4, 600AB5 and 600AB7). The second stage of damping starts when the adjustment tube (705) partially covers the orifices (600AB4, 600AB5 and 600AB7) and continues until the adjustment tube (705) covers the orifices (600AB1 and 600AB2 of seat pipe (600)). The third stage of damping starts when the orifices (600AB1 and 600AB2 of seat pipe (600)) are fully covered and ends when the adjustment tube (705) fitted on the lower end of the inner tube (100) reaches the bump rubber (800). The maximum damping force magnitude is achieved by the front fork (1000) in the third stage.

[0034] Thus, the front fork assembly (1000) of the invention can passively adapt to extreme operating conditions and wide range of front axle load ranging from 35 kg (in case of unladen condition of two wheeler) to 300 kg (in case of laden condition of three wheeler) on its own without needing any user input and any modification/customization to it as well. The staged damping feature and provision of two main springs, namely the outer main spring (300) and the inner main spring (400) also allows the front fork (1000) to be used in motor vehicles of higher load category (three wheeler) without needing any redesigning, modification, customization and rearrangement of its structural assembly and/or sub-components. The outer main spring (300) is configured to have two different spring ratings as shown in Fig. 9. The ratio of the spring ratings (k2/k1) for a spring of the assembly varies from1.6 to 2.0. The upper portion of the outer main spring (300) has the spring rating ‘k1’ whereas lower portion has the spring rating ‘k2’. Assuming the length of the outer main spring as ‘x’, the length of lower portion of the outer main spring having spring rating ‘k2’ is in the range of 0.35x to 0.50x.

[0035] During expansion the order of damping fluid flow is reversed. The damping force created also decreases in stages when expansion is happening. Initially, during re-expansion of the front fork (1000) after reaching bottoming condition, whatever limited fluid flow happens, happens due to leakage that happens past the check valve plate (710A) and through curved slots (705A and 705B). Once the orifices (600AB1 and 600AB2 of seat pipe (600)) are uncovered by the upward movement of the adjustment tube (705), the damping fluid starts to flow in from the orifice (610AB3 and 600AB3), through the seat pipe (600) and out of the orifices (600AB1 and 600AB2 of seat pipe (600)). Then as the adjustment tube (705) moves past and uncovers the orifices (600AB7), damping fluid starts flowing in from the orifices (600AB6) via the flow path created by inner surface of the seat pipe (600) and the longitudinal recess (610A) in the tube (610) and out of the orifice (600AB7). The orifice (600AB4 and 600AB5) are also uncovered when the orifice (600AB7) is uncovered. This allows damping fluid reaching within the seat pipe (600) from the orifices (600AB3 and 610AB3) to flow out from the orifice (600AB4 and 600AB5) as well. The return to fully extended condition (refer Fig. 3) after the orifices (600AB4, 600AB5 and 600AB7) have been uncovered by the adjustment tube (705) happens when the upper opening of the top cap (715) reaches the level of the orifice (600AB3). Once the upper opening of the top cap (715) has reached the level of the orifice (600AB3), the rebound spring (410) located between the upper face of the top cap (715) and the bottom face of the piston (605) absorbs the remaining energy, slows down further expansion and prevents hard metal to metal contact from happening between the upper face of the top cap (715) and the lower surface of the piston (605).

[0036] During the operation of the front fork (1000), the bushes (525 and 105A) prevent tilting of the inner tube (100) with respect to the outer tube (200) during reciprocating telescopic motion of the inner tube (100) within the outer tube (200). This prevents damage to the outer curved surface of the inner tube (100). This in turn helps in preventing damage to the sealing assembly (500) from the outer curved surface of the inner tube (100). The lips of the oil seal (510) of the sealing assembly (500) function to retain the damping fluid below it. The oil seal (515) allows only minimal leakage past itself for lubrication of the sub-components leading up to the dust seal (505).

[0037] The technical advancements and advantages derived from the novel features of the versatile front fork suspension assembly of the present disclosure are as follows:
- The front fork suspension assembly of the invention imparts versatility to make it use on two wheeler (low load condition of 35 kg on front axle) as well as on three wheeler (high load condition of 300 kg of the front axle) as and when required and in as such form without demanding for any modification / customization in its assembly structure.
- The front fork assembly (1000) of the invention enables passive staged increase and decrease in damping force during its compression and expansion respectively. This helps in smoothening the oscillations caused by the wheel’s movement over a road surface irregularity, thereby giving the rider a better quality ride comfort and safety.
- The front fork assembly (1000) of this disclosure can be used in different types of vehicles (two wheeler, three wheelers) and different operating conditions without any major modifications to its sub-assemblies / sub-components and their arrangement.
- The front fork assembly (1000) of the invention can function without user input to change its performance as per requirement which enhances its utility as well.

[0038] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.