FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
1. TITLE OF THE INVENTION
MULTI START ISO METRIC TRAPEZOIDAL THREAD FOR CAM
CHAIN TENSIONER
2.APPLICANT
(a)NAME:ADVIK HI-TECH PVT LTD
(b)NATIONALITY: Indian Company
Plot No. B-5. Chakan Industrial Area.
(c)ADDRESS:Phase II, Village VasulL Taluka Khed.
District Pune: Pin Code-410501.State
Maharashtra, Country India.

TECHNICAL FIELD
[001 ] The present invention relates to a tensioner that imparts a predetermined tensile force to a force transmitting member such as a chain or timing belt that drives a camshaft of an engine mounted in a vehicle for e.g. four wheeler automobile or a two wheeled vehicle.
BACKGROUND ART
[002] Conventional tensioner used in automobiles protrude at a very slow pace from the body to maintain the tension on the chain. It is indeed very important for the chain tensioner to maintain a constant tension on the chain in case of chain slackness or over tightness. In case the chain receives insufficient tension it is ver likely that the vaive timings of the engine may change thereby affecting the engine. Hence, it becomes necessary to overcome the drawback of the prior art.
DISCLOSURE OF THE INVENTION
[003] The present invention relates to a cam chain tensioner consisting of body. screw, nut, spring, thrust member, o-ring. bearing, cirelip. cap element, cap pin and a stopper. Screw consists of threads formed externally while nut consists of internal threads. Screw and nut are threaded])*' engaged with each other. Spring is used to provide rotary force to the nut threadediy engaged with the screw. One end of the spring is hooked in the slit provided in the screw while other end of spring is hooked in the slot provided in the tensioner body. Stopper is used to retract the nut and restricts its forward movement. Upon release of stopper from the body, the energy stored in the spring is released which causes the screw to rotate. Rotation of the screw translates into linear motion of the nut on account of across flat provided on the nut and the bearing. Bearing has projections extending from, the top which rest in the slots provided in the tensioner body. Bearing is secured to the bod)' with the help of a cirelip. Screw provided is a multi-start thread specifically a three start thread.
[004] It is an object of the present invention to provide a screw with multi-start threads.

[005] ft is an object of the present invention to overcome the shortcomings mentioned in the prior art.
BRIEF DESCRIPTION OF DRAWINGS
[006] Fig. 1 shows a sectional view of a tensioner [007] Fig. 2 shows multi-start screw used in tensioner [008] Fig. 3 shows multi-start nut used in tensioner [009] Fig. 4 shows geometry of multi-start thread.
DESCRIPTION OF THE DRAWINGS [010] List of elements
1)Body
2)Screw
3)Nut
4)Spring
5)Bearing
6)Thrust Member
7)O-ring

8)Stopper
9)Circlip
10)Cap Element
11)Cap pin
[011] Figure 1 illustrates a tensioner having body, screw, nut, spring, bearing. thrust member, O-ring. Stopper, circlip, cap element and cap pin. Body 1 has an opening at one end to allow forward movement of the nut 3. Body 1 has slots in the bottom portion to allow the stopper to engage with the screw7 2. One end of the spring 4 is hooked in the slit of the screw 2._ which is threadedly engaged with the nut 3, while other end of the spring 4 is hooked in the slot provided in the body 1. The screw 2 on being rotated by the stopper 8 causes the spring 4 to rotate as well.

When the stopper 8 is released from the body 1, the energy stored in the spring 4 is released which in turn results in rotation of the screw 2. The rotation of the screw 2 results in linear motion of the nut 3 on account of across flat provided on the nut 3. The three start thread provided on the screw 2 ensures fast travel of the nut 3 to ensure that the nut 3 maintains contact with the tensioning rail. Screw 2 has a provision for resting the nut 3,
[012] Figure 2 shows a multi-start threaded screw used in tensioner. Multi-start screw used in tensioner provides a swift motion to the nut when the same is being moved by the screw on being energized by the spring.
[013] Figure 3 shows a multi-start threaded nut used in tensioner.
[014] Figure 4 shows geometry of multi-start thread. Figure illustrates lead, lead angle and included angle. The lead angle of the thread can be 10,11 or 12 degrees. The included angle is less than 40 degrees. The lead of the thread can be 4.44 mm or 4.95 mm or 5.34 mm.

CLAIMS
1) A tensioner that converts a rotary force of the screw into an impulsive force in an
axis line direction of a nut. the tensioner comprising:
a case;
screw being rotatably received in the case in such a state that movement thereof it
the axis Sine direction is caused to be restrained;
the nut being engaged with the screw, said nut being movable in the axis line
direction, and rotation thereof with respect to the case being caused to be
restrained, and on said nut a load from a force transmitting member is adapted to
act in the axis line direction; and
a spring being stored in an inner portion of the case, which imparts the rotary
force to the screw:
characterized in that:
screw has a means for resting the nut.
2)A tensioner as claimed in Claim 1, wherein the means for resting the nut is a circumferential solid surface having thickness of at least 1 mm.
3)A tensioner as claimed in Claim 1. wherein means for resting is provided between the head of the screw7 and thread of the screw.
4)A tensioner that converts a rotary force of the screw into an impulsive force in an
axis line direction of a nut, the tensioner comprising:
a case:
screw being rotatably received in the case in such a state that movement thereof ir
the axis line direction is caused to be restrained:
the nut beina threadediv encased with the screw, said nut beina movable in the
axis line direction, and rotation thereof with respect to the case being caused to be
restrained, and on said nut a load from a force transmitting member is adapted to
act in the axis line direction: and
a spring being stored in an inner portion of the case, which imparts the rotary
force to the screw7:
characterized in that:
screw has a means for providing swift motion to the nut.
5)A tensioner as claimed in Claim 4, wherein the screw having means for providing swift motion to the nut are in the form of multi-start threads formed on the screw and the nut.
6)A tensioner as claimed in Claim 4, wherein the lead angle of the multi -start thread is 11 ± 1 degree.
7)A tensioner as claimed in Claim 4. wherein the included angle of the multi-start thread is less than 40 degrees.
8)A tensioner as claimed in Claim 4, wherein the lead of the multi-start thread is 4.44 mm or 4.95 mm or 5.34 mm.