|Title of Invention||
TELESCOPIC FRONT FORK OF A MOTOR CYCLE
|Abstract||Telescopic front fork of a motorcycle compnsmg an oil filled compression chamber enclosing a second oil filled chamber housing a piston, at the base of the second chamber is a spindle taper (piece oil lock) having circumferential holes on which a tight-fitting flexible 0-ring is circumferentially seated, such that the 0-ring normally remains closed oyer the said holes under fluid pressure in the Compression chamber during the compression stroke; a flow path for oil within the second chamber leading to the said holes, whereby on the completion of the compression stroke and the commencement of the extension stroke, oil from the second chamber is drawn into the compression chamber through the said flow path and the said holes, under fluid pressure thrusting the 0-ring away from the said holes.|
This invention relates to a telescopic front fork of a motorcycle, which is rendered noise free during operation.
In the conventional telescopic front forks of motorcycles known to the art, the piece oil lock (spindle taper) is used for generating high damping force in the full bump condition to avoid the metal-to-metal contact at the bottom. However, this system produces noise at the beginning of the extension stroke due to creation of vacuum in the compression chamber?. This phenomenon is prominent when the stroke of the fork is more," such that the inner tube crosses over the compression damping holes and reaches spindle taper.
This problem is solved by this invention by allowing sufficient oil in the compression chamber at the beginning of the extension stroke. This is achieved by providing an O-ring arrangement. During the compression stroke, by reason of the high pressure the O-ring will close the holes on the spindle taper, thus closing the oil flow path. During the
extension stroke, when the inner tube is still on the outer diameter of the spindle taper (compression holes on; the piston are not yet exposed), a low pressure is generated in the compression chamber tending to vacuum. Under this condition, the O- ring will expand creating a
path for the oil to fl
w from the inside of the piston (second chamber) to the compression chamber, thereby eliminating the vacuum.
This invention will now be diescribed with reference to the accompanying drawings, which illustrate by way of example, and not by way of limitation, one of its possible embodiments wherein
Fig. 1 illustrates the assembly of the front fork
Fig. 2 illustrates a view in detail of what is
shown \r\ Fig.l
Fig. 3 illustrates the piston
Fig.4 illustrates the 0-r\ng
And f ig.5 illustrates piece oil lock (soindle
When the compressicjn stroke takes place, once the inner tube passes the compression damping holes, there will be high pressure In the compression chamber C as there is very restricted path for oil to flow from the clearance of inner tube inner diameter and spindle taper outer diameter. This is intentionally maintained to develop adequate oil lacking force. The O-ring will be kept compressed Jon the holes on account of fluid pressure, thusj closing the holes on the spindle taper in compression stroke.
In the conventional fork, at the end of compression stroke, the inner tube I will start to move back- creating more volume in the compression chamber C but oil supply being very restricted; it will start creaYmg vacuum. As this happens in very small interval of time, a vacuum noise gets created. To avoid the noise from occurring it is necessary to have some means of providing adequate oil supply at that moment.
This is achieved by providing a flow path P for oil from inside the second chamber S to the chamber C as shown by the arrows A in fig: 2. The flow of oil takes place due to the pressure differential on both sides of the O-ring, resulting in expansion of the 0- ring, providing oil flow path P through holes H for oil to flow into the compression chamber C during the extension stroke.
Thus by avoiding the vacuum in the compression chamber and ensuring adequate oil supply at right time through creation of path way for oil flow, the noise can be eliminated.
This invention proposed herein has advantages viz. design is very simple and requires little modification in the existing telescopic fork design, is cost-effective & has no moving parts thus avoiding additional source of noise.
Current designs use additional check valve, which is fixed in inner tube assembly below the regular check valve. This mechanism avoids vacuum formation and hence noi&e in extension stroke.
The other existing manifestation of this has been providing a similar metallic checjk valve on the spindle taper. Such designs are complex, difficult to manufacture and costly. Additionally the
metallic check valve is likely to generate noise due to its motion.
It will be appreciated that various other embodiments of this invention are possible without departing from the sjcope and ambit thereof.
1. Telescopic front fork of a motorcycle compnsmg an oil filled compression chamber enclosing a second oil filled chamber housing a piston, at the base of the second chamber is a spindle taper (piece oil lock) having circumferential holes on which a tight-fitting flexible 0-ring is circumferentially seated, such that the 0-ring normally remains closed oyer the said holes under fluid pressure in the Compression chamber during the compression stroke; a flow path for oil within the second chamber leading to the said holes, whereby on the completion of the compression stroke and the commencement of the extension stroke, oil from the second chamber is drawn into the compression chamber through the said flow path and the said holes, under fluid pressure thrusting the 0-ring away from the said holes.
2. Telescopic front fork of a motorcycle substantially as herein described with reference to, and as illustrated in, the accompanying drawings,
|Indian Patent Application Number||447/CHE/2008|
|PG Journal Number||07/2013|
|Date of Filing||22-Feb-2008|
|Name of Patentee||TVS MOTOR COMPANY LIMITED|
|Applicant Address||"JAYALAKSHMI ESTATES", NO. 24, (OLD NO. 8), HADDOWS ROAD, CHENNAI-600 006.|
|PCT International Classification Number||B 62 K 25/08|
|PCT International Application Number||N/A|
|PCT International Filing date|