DESC:FIELD OF THE INVENTION
The present invention relates to the field of tyre building drum. More particularly, the present invention relates to a tyre building drum with a mildly convex contour. Advantageously, the present invention relates to a tyre building drum with improved tyre performance for internal quality and improved service performance.

BACKGROUND OF THE INVENTION
A two-wheeler bias ply tyre building machine, has a cylindrical drum, referred generally as a ‘drum’, to assemble various components of the tyre in a sequential manner called the tyre building or tyre assembling process. The drum is mounted on the tyre building machine such that the drum axis is parallel to the ground. The width of the drum which is specific to the tyre being built, is called the drum set or drum width. Drums normally function in a collapsed and expanded condition. Tyre assembly or building is done when the drum is in a partially expanded or fully expanded condition. Depending on drum designs, when expanded, drums can have gaps between adjacent segments or no gaps if the segments are aligned adequately.

Traditionally, the drum set portion is designed as a flat surface,
US2007095481A1 discloses a tyre belt drum. Belt drum, particularly for shaping a belt layer and/or a tread layer or another tyre component provided with metal parts and the like into a circumferential whole, wherein the drum is rotatable about a centre line, comprising a number of support members having a rigid support surface for the tyre component and situated at the circumference of the drum.

JP2012081660A discloses a molding drum for belt tread assembly and method of manufacturing tyre using the same. The molding drum for molding a belt tread assembly produced by winding tread rubber on the outer circumference of the belt prepared by covering a metal cord with rubber. A method of forming a belt-shaped surface of a forming drum by a straight central formed contour having a length of 15 to 50% of a drum axial center length, and an outer forming contour line having a convex arc shape in the outer peripheral surface of the outer peripheral surface.

EP2572872A1 discloses a tyre building drum with a solid deck surface. A rotatable tyre building drum comprising a pair of axially and radially moveable bead locks and a radially expandable center building deck assembly. The center building deck assembly is configured for forming a 360 degree solid deck surface when radially expanded. The building drum is particularly useful for building motorcycle tyres.

US3932256A discloses a tyre building drum. A tyre building drum, in particular useful for applying a tread to a previously built uncured tyre carcass, having a large number of segments, e.g. 36, which can move radially to expand and to contract the drum. Each cover plate is longitudinally coextensive with its two associated segments and has a fixed longitudinal edge rigidly affixed to one of said segments and a free longitudinal edge overlying the other of said segments, the plate having an arched contour convex outwardly of the axis. The working surface of the tyre building drum can be more nearly a regular circular cylinder over a greater range of drum diameter change than has heretofore been available.

US6723195B1 discloses an adjustable tyre building contour drum and method of building tyre thereon. The segmental tyre building drum for laminating tyre components having a plurality of circumferentially spaced, radially movable base segments each having a secondary segment radially movable relative to the base segment for providing a cylindrical flat surface to support each of the tyre components as it is applied and spliced on the building drum and to compensate for thickened edges of the tyre components applied to the tyre building drum.

US20060102272A1 discloses a tyre building drum and tyre building method. The tyre building drum and tyre building method, capable of assembling tyre component members with high accuracy. A tyre building drum is used, which includes at least one core body, which is disposed at an axial inside of a pair of bead lock means, and which comprises a plurality of sheets of rigid support members disposed in a toroidal shape and adapted to be displaced and thereby expanded or contracted.

US4683021A discloses a tyre building drum. A tyre building drum has a central shaft and a pair of end drum assemblies mounted for axial movement along the shaft. The end drum assemblies include a main sleeve slideable on the shaft and an annular housing mounted on the sleeve to form an annular chamber surrounding the sleeve which houses an annular piston. There is an annular expansion means (bead seating segments) mounted on the housing \ which are moved radially by a ramp means attached to the piston. This ramp means have a cam surface thereon comprising an inclined radially outer portion and a convex arcuate radially inner portion.

Accordingly, there exists a need for a tyre building drum with a mildly convex contour across the drum width for removing the trapped air between tread and casing at the time of assembly.

OBJECTS OF INVENTION
It is the primary object of the present invention to provide a tyre building drum system designed with a mildly convex contour.

It is another object of the present invention to provide a tyre building drum with a mildly convex contour for removing the trapped air between tread and casing at the time of assembly.

It is another object of the present invention to reduce rejections, defects / tyre repair and field complaints resulting from bias tyre building process.

It is another object of the present invention to improve the tyre performance for internal quality and improved service performance.

SUMMARY OF THE INVENTION
One or more of the problems of the conventional prior art may be overcome by various embodiments of the present invention.

It is the primary aspect of the present invention to provide a tyre building drum, comprising:
a convex drum profile unit [1];
a center convex spacer [2]; and
side segments [3],
wherein the building drum system comprises of a mildly convex contour, and
the tyre building drum is in convex shape for removing the trapped air between tread and casing/plies at the time of assembly and the air is pushed out from a central portion of the drum to the sides when the drum is contoured.

It is another aspect of the present invention, wherein the convex drum profile unit [1] comprises of an elastomeric top cover [10], covering a convex right part [11], a convex left part [12], and center spacer made of metal and the like.

It is another aspect of the present invention, wherein the convex right part [11], the convex left part [12] and the center convex spacer [2] are integrated as a single piece made of suitable metal, non-metals and the like, where the adjacent segments have no gaps when expanded, and no cover is needed

It is another aspect of the present invention, wherein the tyre building drum with a mildly convex contour is designed to improve defect performances.

BRIEF DESCRIPTION OF THE DRAWINGS:
So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawing, which form a part of this specification. It is to be noted, however, that the drawing illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of the invention's scope as it may admit to other equally effective embodiments.
Figure 1: illustrates the sectional view of the tyre building drum designed with a mildly convex contour according to one embodiment of the present invention.
Figure 2: illustrates the sectional view of the structural components of tyre building drum designed with a mildly convex contour according to one embodiment of the present invention.
Figure 3: illustrates the improvements from present invention having tyre building drum designed with a mildly convex contour showing greater and easy removal of entrapped air when compared with regular flat profile in which air is trapped.
Figure 4: illustrates the tyre building drum with side segments and centre spacer integrated as one piece and no elastomeric cover, according to another embodiment of the present invention.

DETAILED DESCRIPTION OF INVENTION:
It is to be understood that the present disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The present disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

The present invention relates to the field of tyre building drum. More particularly, the present invention relates to a tyre building drum with a mildly convex contour. Advantageously, the present invention relates to a tyre building drum with improved tyre performance for internal quality and improved service performance.

Thus according to the invention, the tire building drum according to the present invention is designed with a mildly convex contour. This convex profile helps in removing the trapped air between tread and casing at the time of assembly.
Figure 1 illustrates the sectional view of the tyre building drum designed with a mildly convex contour according to one embodiment of the present invention.

Referring to the Figure 2, sectional view of the structural components of tyre building drum designed with a mildly convex contour is shown. The tyre building drum comprises a convex drum profile unit [1] with a convex top cover [10], convex right part [11], convex left part [12]; a center convex spacer [2]; and an inner segment [3]. Top cover [10] is made of elastomer and convex right part, convex left part; a center convex spacer is made of mild steel (M.S.).

Figure 3 a) illustrates the improvements from present invention having tyre building drum designed with a mildly convex contour showing greater and easy removal of entrapped air when compared with b) regular flat profile in which the possibility of air trap is higher. The defects are caused by air locks, and a convex drum according to the invention facilitates easy removal of air during spinner movement. When the drum is flat the turned-up ply ends act as a step to trap the air that is being removed. When the drum is contoured, and as the air is pushed out from the central portion to the sides, there is a gap between the tread and the plies to remove air before sealing occurs.

The tyre building drum designed with a mildly convex contour according to the present invention shows improvements in defect performance of 17 diameter tyre sizes and 18 diameter tyre sizes when compared with flat drum defect performance and from Table 1 and Table 2 it is clear that the improvements are due to the changing from regular drum to convex drum.

In one scenario, the drum comprises of one or more side segments, central portion and a top cover [10]. The top cover [10] used to cover gaps in between expanded drum segments, is made of elastomer and the like. The elastomer top cover [10] between adjacent segments provides a continuous backing for assembling the tyre components. In another scenario the convex right part [11], the convex left part [12] and the center convex spacer [2] are integrated as a single piece made of suitable metal, non-metals and the like and can be used for suitably designed drums that do not have any gaps on expanded condition (not shown in figure). The tyre building drum with a mildly convex contour is designed to improve defect performances.

The present invention by itself is basically true for any tyre building drum that has been changed from ‘flat’ to ‘convex’ profile, including ones that don’t have any gaps (and hence don’t need an elastomeric cover) but have been accorded a convex profile. Such drums may have surfaces made of metal or non-metal and the like.

Referring to the Figure 4, the tyre drum with no gaps between adjacent segments that does not require an elastomeric top cover according to another embodiment of the present invention is illustrated. The drawing effectively indicates how the profile is designed. The curvature is defined and is achieved by providing appropriate design limits. The drum represents an integrated side segments/centre spacer type. However, the basic idea behind the invention is that a contoured drum is likely to be better than a flat drum. The drum shown in the drawings is just one of the types that can be used. Mild Steel is the most preferred metal because of availability, economical cost and long life under sustained daily use. Other conventional materials that satisfy these requirements can be used.

There is no change in the actual assembly or sequence of manufacture of the tyres between the flat drum and convex drum. The change of contour is the only innovation. However, the general sequence of operation is as below:
(i) Apply plies one after another
(ii) Affix beads and turn up plies
(iii) Affix tread
(iv) Apply down spinners – this is the operation that consolidates the tread to the plies (casing), and also removes air in the process.

Table 1 shows 17 Diameter Tyre Sizes Flat Drum vs Convex Drum – Defect Performance.

17 Diameter Tyre Sizes
110/80-17
90/90-17
3.00-17
2.75-18

Table 1
Size 1 Size 2 Size 3 Size 4
DRUM TYPE Flat Drum Convex Drum Flat Drum Convex Drum Flat Drum Convex Drum Flat Drum Convex Drum
Minor
Defect Index Lower - Better 100 53 100 56 100 33 100 55
Scrap Index Lower - Better 100 28 100 11 100 47 100 36

Table 2 shows 18 Diameter Tyre Sizes- Flat Drum vs Convex Drum – Defect Performance
18 Diameter Tyre Sizes
80/100-18 (3 different patterns)
90/90-18
3.00-18

Table 2
Size 1 Size 2 Size 3 Size 4 Size 5 Size 6
DRUM TYPE Flat Drum Convex Drum Flat Drum Convex Drum Flat Drum Convex Drum Flat Drum Convex Drum Flat Drum Convex Drum Flat Drum Convex Drum
Minor
Defect Index Lower -Better 100 1 100 43 100 21 100 38 100 56 100 10
Scrap Index Lower - Better 100 0 100 20 100 4.5 100 72 100 0 100 20

Although, the invention has been described and illustrated with respect to the exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention. ,CLAIMS:WE CLAIM:
1. A tyre building drum, comprising:
a convex drum profile unit [1];
a center convex spacer [2]; and
one or more segment [3],
wherein the building drum system comprises of a mildly convex contour, and
the tyre building drum is in convex shape for removing the trapped air between tread and casing/plies at the time of assembly and the air is pushed out from a central portion of the drum to the sides when the drum is contoured.

2. The tyre building drum as claimed in claim 1, wherein the convex drum profile unit [1] comprises of an elastomeric top cover [10], covering a convex right part [11], a convex left part [12], and center spacer made of metal and the like.

3. The tyre building drum as claimed in claim 1, wherein the convex right part [11], the convex left part [12] and the center convex spacer [2] are integrated as a single piece made of suitable metal, non-metals and the like.

4. The tyre building drum as claimed in claim 1, wherein the tyre building drum with a mildly convex contour is designed to improve defect performances.