1. Field
The invention relates to the technical field of vehicle tires and, in particular, to that of the manufacture of tires comprising fibres injected in a given direction into one of the rubber components of which said tire is made.
2. Description of Related Art
Publication EP 1 213 130 provides a specific idea of this type of tire, in which short reinforcing fibres, or inserts, are embedded in the tread in an oriented fashion so as to improve the mechanical properties of this part of the tire in a given direction.
Publication EP 1 213 383 proposes a means for embedding said inserts into a rubber component intended to be assembled to form a tire tread structure.
This device comprises a hollow needle capable of penetrating the rubber component, and inside which the reinforcing fibre runs, a moving support capable of performing a reciprocating movement and supporting said needle, a cutting blade for cutting off the fibre to be embedded, and at least two clamping means for maintaining and adjusting the position of the fibre. However, these clamping means have the effect of placing the reinforcing fibre under compression.
Application PCT/EP2010/062907, not published, describes an apparatus and a method for overcoming this compression problem.
This device for embedding an insert into a rubber profiled element in a given direction comprises:                a means for feeding the thread continuously,        a moving support capable of moving on a structure in a rectilinear reciprocating movement between a raised position and a lowered position,        a hollow needle comprising a channel inside which said thread is able to run, which needle is fixed by one of its ends to the base of the moving support and comprising at its other end a tip capable of penetrating said rubber profiled element,        a cutting means arranged on the structure, comprising a blade capable of cutting off the thread on each cycle of the reciprocating movement of the needle, when said tip is in a raised position so as to release a given length of thread constituting a tail at the outlet of the needle.        
Still according to this publication, there is described a method of operating the device which comprises the following steps:                A—when the needle is in a raised position above the surface of the profiled element, a given length of thread is released on the tip side of said needle so as to constitute a tail,        B—the needle is lowered so as to cause the tip of said needle to penetrate the profiled element to a given depth,        C—the needle is extracted from the profiled element while allowing the thread to run inside the needle,        D—the tip of the needle is raised by a given height above the surface of the profiled element so as to release a length of thread between the tip of the needle and the surface of the profiled element,        E—the thread is cut off at the surface of the profiled element so as to release a new tail of given length.        
On each cycle, the tail situated outside the needle on the tip side is driven into the profiled element. As the needle is raised again, the tail is held in position in the bottom of the perforation produced in the rubbery material which grips it, and which prevents the thread contained in the needle from rising back up, such that the raising movement allows the thread to be made to run along inside the needle.
During this movement, the portion of thread contained between the inlet of the needle and the tail is kept under tension. The thread is pulled through the needle rather than pushed as was proposed in the apparatus forming the subject matter of publication EP 1 213 383.
However, it is observed that, to make the needle penetrate the rubber profiled element, it is necessary to develop considerable forces which are not without consequence on the dimensioning of the needle and for the mechanisms to be employed to bring about its reciprocating movement. The effect of these forces is to deform the surface of the profiled element at the point of penetration of the needle, and they can moreover cause the needle to break, in particular when the angle of penetration of the needle into the profiled element is less than 90°.