Expandable forming drum, and process for building tyres

Patent metadata

Field	Value
Publication number	US-10611110-B2
Application number	US-201415104731-A
Country	US
Kind code	B2
Filing date	Dec 22, 2014
Priority date	Dec 23, 2013
Publication date	Apr 7, 2020
Grant date	Apr 7, 2020

Abstract

A toroidal forming drum and a process for budding tyres. The toroidal forming drum is expanded within a shaped carcass sleeve for supporting the carcass sleeve against an abutment surface externally provided by the forming drum. An elementary semi-finished product is applied around the shaped carcass sleeve by pressing the elementary semi-finished product toward the abutment surface. The abutment surface has circumferential rows of solid portions alternated with hollow portions. The solid portions, arranged along axially opposite circumferential edges of the abutment surface, have a transverse size between 10% and 60% of a transverse size presented by the solid portions arranged in proximity to an axial centreline plane of the abutment surface.

First claim

The invention claimed is:

1. An expandable toroidal forming drum for building tyres, comprising:
circumferentially consecutive sectors radially moveable between a contracted condition in which said sectors are approached with respect to a geometric rotation axis of the forming drum, and an expanded condition in which the sectors are radially moveable away from said geometric axis in order to define a radially external abutment surface,
wherein, in the expanded condition, the abutment surface has circumferential rows of solid portions alternated with hollow portions, and
wherein the solid portions arranged along axially opposite circumferential edges of the abutment surface have a transverse size between 10% and 60% of a transverse size presented by the solid portions arranged in proximity to an axial centreline plane of the abutment surface.

2. The drum as claimed in claim 1 , wherein the transverse size of the solid portions arranged along axially opposite circumferential edges of the abutment surface ranges between 20% and 50% of the transverse size presented by the solid portions arranged in proximity to the axial centreline plane of the abutment surface.

3. The drum as claimed in claim 1 , wherein the transverse size of the solid portions is detectable in a radial plane of the forming drum.

4. The drum as claimed in claim 1 , wherein each sector has circumferentially opposite coupling portions, each comprising elongated projections alternated with circumferentially extended cavities, wherein the projections of each sector are slidably engaged in respective cavities of circumferentially adjacent sectors.

5. The drum as claimed in claim 4 , wherein said solid portions and hollow portions are respectively defined on said projections and by said cavities.

6. The drum as claimed in claim 4 , wherein each of said cavities is axially delimited between lateral walls of two axially consecutive projections.

7. The drum as claimed in claim 4 , wherein at least some of said projections have substantially plate-like structure and lie according to planes parallel to a circumferential extension direction of the abutment surface.

8. The drum as claimed in claim 6 , wherein said lateral walls are extended according to planes substantially perpendicular to a geometric rotation axis of the forming drum.

9. The drum as claimed in claim 6 , wherein at least some of said cavities are axially delimited, each between the lateral walls of two axially consecutive projections.

10. The drum as claimed in claim 4 , wherein, in each sector, projections belonging to one of said coupling portions are offset with respect to projections belonging to the other coupling portion.

11. The drum as claimed in claim 4 , wherein axially terminal cavities arranged along the axially opposite circumferential edges of the abutment surface are each delimitated between a base surface and a lateral wall, respectively converging, both carried by an axially terminal projection arranged along said circumferential edge.

12. The drum as claimed in claim 11 , wherein said lateral wall is oriented according to a plane substantially perpendicular to the geometric rotation axis of the forming drum.

13. The drum as claimed in claim 11 , wherein said base surface is oriented in a manner substantially parallel to the geometric rotation axis of the forming drum.

14. The drum as claimed in claim 4 , wherein first axially terminal projections arranged along the axially opposite circumferential edges of the abutment surface are interconnected, substantially on an entire length, each with an axially adjacent projection.

15. The drum as claimed in claim 4 , wherein first axially terminal projections arranged along the axially opposite circumferential edges of the abutment surface, each have a base surface converging with respect to a lateral wall of an axially adjacent projection, for delimiting one of said cavities between two axially contiguous solid portions of the abutment surface.

16. The drum as claimed in claim 4 , wherein second axially terminal projections arranged along the axially opposite circumferential edges of the abutment surface, each have a base surface and a lateral wall, respectively converging, delimiting a respective solid portion of the abutment surface.

17. The drum as claimed in claim 4 , wherein second axially terminal projections arranged along the axially opposite circumferential edges of the abutment surface, each have, at a respective base surface, a substantially arched longitudinal edge.

18. The drum as claimed in claim 4 , wherein, in the contracted condition, the projections are inserted in the cavities according to a measure at least equal to 80% of a length of the cavities.

19. The drum as claimed in claim 4 , wherein, in the expanded condition, the projections are extracted from the cavities according to a measure at least equal to 80% of a length of the cavities.

20. The drum as claimed in claim 4 , wherein, at least in proximity to an axial centreline plane of the forming drum, each projection has an axial size between about 4 mm and about 15 mm.

21. The drum as claimed in claim 5 , wherein the hollow portions in the expanded condition have a circumferential size between about 30 mm and about 60 mm.

22. The drum as claimed in claim 1 , further comprising radial movement devices for simultaneously moving the sectors between the contracted condition and the expanded condition.

23. The drum as claimed in claim 22 , wherein said radial movement devices comprise transmission mechanisms operatively engageable by actuator devices and configured for simultaneously translating the sectors from the contracted condition to the expanded condition.

24. The drum as claimed in claim 23 , wherein said transmission mechanisms comprise driving levers, each driving lever hinged to one of said sectors and to at least one driving collar slidably fit along a central shaft.

25. The drum as claimed in claim 24 , wherein the driving collar is operatively connected to a threaded bar rotatably engaged in the central shaft.

26. The drum as claimed in claim 24 , comprising two driving collars slidably engaged on the central shaft in axially opposite positions with respect to the sectors, and engaging the threaded bar at respective right hand and left hand threads.

27. The drum as claimed in claim 1 , wherein the sectors are carried by respective telescopically extendable guide members, radially extending from a central shaft.

28. The drum as claimed in claim 1 , having, in expanded condition, a curvature ratio between about 0.15 and about 0.45.

Assignees

• Pirelli

Inventors

• Montanari Silvio
• Marchini Maurizio
• Haupt Oliver
• Mariani Mario
• Conti Davide Lupo

Classifications

• B29K2021/00

  Use of unspecified rubbers as moulding material · CPC title

• B29D30/12 Primary

  Cores · CPC title

• B29D2030/105

  the cores being movable · CPC title

• B29D30/10

  on round cores, i.e. the shape of the core is approximately identical with the shape of the completed tyre · CPC title

• B29D30/245

  Drums for the single stage building process, i.e. the building-up of the cylindrical carcass and the toroidal expansion of it are realised on the same drum (expansion to a toroidal shape B29D30/36) · CPC title