DESC:TELESCOPIC FRONT FORKS WITH HARDENED INNER TUBE
Field of the invention
The present invention relates to a front fork suspension system of an automobile and more particularly, the induction hardening of front fork inner tube at the under bracket mounting area for increased stability.
Background of the invention
The typical motorcycle has a pair of fork tubes for the front suspension. A telescopic front fork essentially consists of two tubes, arranged symmetrically with respect to the median plane of the wheel, on which is fixed the axis of the wheel. Each has an inner tube sliding through the outer tube, which further comprises of a hydraulic damping device, an elastic device which is most often a helical spring and a lubricant.
Conventionally front fork inner tube surface is either chrome plated or nickel chrome plated to improve wear and corrosion. This coating will provide a surface hardness which can withstand external surface abuses like sliding wear out, stone hitting on roads. But the concern of one side rubbing and oil seal failure leading to oil leakage exists in almost all the front forks except inverted front forks. In most of the cases during riding, bumps can cause lateral displacement of wheels and the long lever arm causes high bending movements in front fork legs and steering head. Hence its geometrical accuracy conditions are to be controlled and processed. There is a need to address this phenomenon of inner tube rubbing and oil seal replacement as servicing option.
Accordingly, there is a need of an inner tube with requisite hardened zone at the under-bracket mounting area where maximum load is exerted, that overcomes the above mentioned drawbacks of the prior art.
Object of the invention
An object of the present invention is to improve the core hardness of inner tube at the under bracket mounting area,
Another object of the present invention is to avoid bending action of inner tube which in turn reduces the load impact on sliding parts that is inner tube and outer tube.
Summary of the invention
The present invention provides a telescopic front fork suspension constructed to be incorporated between a wheel hub and handle means of a vehicle consisting of an outer tube having one end connected to the wheel hub and an inner tube having one end slidingly received in the outer tube and other end connected to the handle means of the vehicle through an under bracket mounting. The under bracket mounting area inside the inner tube is induction hardened thereby avoiding bending action of inner tube and reducing the load impact on inner tube and outer tube. In addition to basic inner tube induction hardening Nickel and Chrome plating is also processed. This ensures structural and surface hardness to eliminate the wear out concern.
Brief description of the drawings
The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,
Figure 1 shows an under bracket mounted front fork suspension system, in accordance with the present invention; and
Figure 2 shows an inner tube of the front suspension with its load exerted position where induction and tempering zone is identified, in accordance with the present invention.
Detail description of the invention
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 embodiment.
The present invention provides a telescopic front forks with hardened inner tube at the under bracket mounting area, which avoids bending action of inner tube which in turn reduces the load impact on sliding parts, that is inner tube and outer tube of the telescopic front forks.
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. Reference numbers and corresponding components are listed in Table 1 below:
Table 1:
Ref No Description Ref No Description
100 Front fork suspension 12 No hardening zone
10 Outer tube 13 Transition zone
20 Inner tube 14 Threading side
30 Under bracket 15 Induction hardened zone
11 Under bracket mounting area

Referring to Figures 1 and 2, a telescopic front fork suspension (100) (hereinafter, “the suspension (100)”) in accordance with the present invention is shown. The suspension (100) constructed to be incorporated between a wheel hub and handle means of a vehicle is mounted using under bracket (30). The suspension (100) mainly consists of two forks, each consisting of an outer tube (10) having one end connected to the wheel hub and the other end slidingly receiving an inner tube (20). Free end of the inner tube (20) is connected to the handle means of the vehicle through an under bracket mounting (30). In a specific embodiment, the under bracket mounting area (11) of the inner tube (20) is induction hardened where maximum load is exerted.
Referring to Figure 2, the inner tube (20) includes 3 zones; a no hardening zone (12), a transition zone (13) and an induction hardened zone (15). The improved design for increasing the stability of inner tube (20) is achieved by induction hardening and tempering process at the defined zone i.e., under bracket zone (11) or mounting area.
In the present invention, hardening is carried out first in the under bracket mounting zone (11), where first the feed rate and power level are controlled along with quench water cooling. The duration of heating or heat intensity will decide the penetration of hardness and case depth. The harden ability depends on the material thickness and composition mainly carbon content. Part of the under bracket mounting zone (11) will be passing through the scanner (coil) with a specified feed rate and the part passes through tempering with a defined time gap online immediately after hardening cycle. The heating portion of part along with start and end position is controlled by CNC program which ensures repeatability and linear dimensional accuracy.
There are two methods of hardening the under bracket zone (11) of inner tube (20), either keeping the inner tube as stationery and moving the heat coils along the required length or passing inner tube (20) through a center less process keeping the coil fixed. Here the process is considered by passing the inner tube through a center less mechanism, keeping hardening coil temperature in the range of 900 degree to 950 degree and tempering coil at 200 degree to 250 degree temperature. The federate of the part passing through heating coils would be around 1.5 m/ min to 2 m/min.
SAE 1541 is the material with medium carbon content which supports the hardening and tempering treatment, alternate and equivalent material available also can be investigated and processed. Hardness and penetration is presently done by destructive method by hardness checking equipment. The induction hardening process improves the internal hardness of tube material which withstands the bending forces exerted during front fork operation. Bending phenomenon may be due to normal up & down movement, while braking and abnormal movements during humps, pot holes and rough roads.
By induction hardening and tempering process one side rubbing and wear-out of inner tube is eliminated. Side rubbing phenomenon is generated during bending of inner tube (20) under load conditions and vehicle running / braking actions. In the earlier processes does not have hardening, the part is only nickel hard chrome plated to overcome wear and corrosion. In addition to basic inner tube (20) induction hardening, nickel and chrome plating is also processed. This ensures structural and surface hardness to eliminate the wear out concern. Thus by induction hardening of inner tube (20) at the under bracket zone (11) or mounting area, avoids bending action of inner tube (100) which in turn reduces the load impact on sliding parts, that is inner tube and outer tube.
Advantages of the invention
1. The present invention provides, induction hardening of inner tube at the under bracket zone or mounting area, which avoids bending action of inner tube which in turn reduces the load impact on sliding parts, that is inner tube (100) and outer tube.
2. The present invention provides, improved product life.
3. The present invention provides, reduced servicing of replacing oil seal for inner tube abnormality.
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 scope of the invention.
,CLAIMS: CLAIMS
We claim:
1. A telescopic front fork suspension (100) constructed to be incorporated between a wheel hub and handle means of a vehicle consisting of an outer tube (10) having one end connected to the wheel hub and an inner tube (20) having one end slidingly received in the outer tube (10) and other end connected to the handle means of the vehicle through an under bracket mounting (30);
characterized in that, an under bracket mounting area (11) inside the inner tube (20) is induction hardened thereby avoiding bending action of inner tube and reducing the load impact on inner tube (20) and outer tube (10).
Dated this 22nd day of January, 2018

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