VISCOUS FLUID

DESCRIPTION

Technical sector

The present invention relates to a method and apparatus for the application of a highly viscous fluid.

Prior art

As is known, a tyre comprises a toroidal carcass, which has two annular beads and supports an annular tread. Between the carcass and the tread, a tread belt is interposed, which comprises a number of tread plies. Within the carcass ply, an innerliner is arranged which is airtight, constitutes an inner lining and has the function of retaining the air within the tyre in order to maintain the inflation pressure of the tyre itself over time.

In recent years, tyre development has been directed towards tyres with an inner lining that is manufactured with a sealing agent that is intended to seal any punctures. Typically, the sealing agent has high viscosity in order to ensure both the sealing action in relation to any holes and the stability thereof within the internal cavity regardless of the conditions of the tyre.

The sealing agent is applied to a pre-vulcanized tyre and preferably to the innerliner within the area of the tyre that comes into contact with the road (or the area of the tyre in which punctures may potentially occur). In particular, the sealing agent is applied at the tread and at least partially at the sidewalls.

Typically, the process for applying the sealing agent provides for the positioning of the pre-vulcanized tyre on a frame, whereupon it is blocked by means of lateral rails in such a way as to prevent any lateral translation of the tyre itself.

In response to an operator command, the sealing agent application process is started by inserting a sealing agent applicator device into the internal cavity of the tyre in a position directly facing a surface of the internal cavity itself. The applicator device is conveniently implemented by means of a movable arm provided at one end of a nozzle and is intended to apply a substantially uniform bead of sealing agent to the inner surface of the cavity. In particular, the applicator device is intended to apply a bead of sealing agent by means of a reciprocating movement between the two lateral ends of the internal cavity; in particular, the arm moves within a plane that is perpendicular to the equatorial plane of the tyre. The tyre is brought into rotation by the support by means of motorized rollers; and the movement of the arm and the rotation of the tyre combined lead to the application of the sealing agent, which must be as uniform as possible.

The applicator device is connected to a sealing agent delivery circuit comprising a tank that is preferably manufactured from a metal material and contains the sealing agent, a conduit that is preferably heated and that originates from the tank and is in hydraulic communication with the applicator device, and a pumping device that draws the sealing agent from the tank and delivers it under pressure to the applicator device. In particular, an extractor element is provided at one end of a movable scoop intended to move with an alternating movement so as to draw the sealing agent inside the tank and feed it to the pumping device.

The extraction of the sealing agent from the tank may, however, be particularly complex due to the high viscosity thereof. In particular, when reducing the amount of sealing agent contained within the tank, the sealing agent itself may have difficulty flowing from the side wall of the tank towards the extraction point, causing phenomena similar to cavitation phenomena; in other words, an empty cavity is generated near the extractor element that leads the pumping device to work at idle with increased strokes per minute that may damage the pumping device itself in the long run.

Description of the invention

The aim of the present invention is to provide a method for the application of a highly viscous fluid that is both free from the disadvantages of the prior art and that is, in particular, easy and inexpensive to implement.

A further aim of the present invention is to provide an apparatus for the application of a highly viscous fluid that is both free from the disadvantages of the prior art and that is, in particular, easy and inexpensive to implement.

According to the present invention, a method and an apparatus are provided for the application of a highly viscous fluid as set forth in the appended claims. Brief description of the drawings

The present invention is now described with reference to the attached drawings, which illustrate several non-limiting exemplary embodiments, wherein:

- Figure 1 is a front schematic view, with parts removed for clarity, of a system that has been implemented for the application of a sealing agent to the surface of the internal cavity of a tyre;

- Figure 2 is a schematic view of a portion of the system of Figure 1 implemented in accordance with the present invention; and

- Figure 3 is a block diagram showing a control method implemented in accordance with the present invention and implemented by an electronic control unit of figure 1.

Preferred embodiments of the invention

With reference to Figure 1, the numeral 1 denotes a system 1 in its entirety configured for the application of a sealing agent to the surface 2 of the inner cavity 3 of a tyre 4. It is to be understood that the phrase "profile of the inner cavity 3 of a tyre 4," refers to a surface profile of the tyre 4.

The tyre 4 is arranged on a frame 5 that is suitable for supporting, and bringing into rotation about the central x axis thereof, the tyre 4 by means of motorized rollers 6. The system 1 comprises a sealing agent applicator device 7 conveniently implemented by means of a robot provided with a movable arm 8 and intended to apply a substantially uniform bead of sealing agent to the surface 2 at the portion of the tyre 3 that is intended to come into contact with the road, i.e., at the tread and, at least partially, at the sidewalls. According to a preferred variant, in order to perform the non-contact application of the sealing agent in the semifluid state, the applicator device 7 is implemented by means of a nozzle 9; the nozzle 9 is preferably arranged at one axial end of the movable arm 8.

A sealing agent delivery circuit 10 is connected to the applicator device 7. The system 1 also comprises an electronic control unit ECU that supervises the operation of the applicator device 7 and/or the delivery circuit 10, as better described within the discussion that follows.

As illustrated in Figure 2, the delivery circuit 10 comprises a new sealing agent collection device 11, a new sealing agent delivery device 13, a recycled sealing agent collection device 11*, and a recycled sealing agent delivery device 13*. The assembly defined by the new sealing agent collection device 11 and the new sealing agent delivery device 13 is substantially identical to the assembly formed by the recycled sealing agent collection device 11* and the recycled sealing agent delivery device 13*; only one of said assemblies will therefore be described in the following discussion.

The sealing agent collection device 11 comprises a collection tank 14, preferably made of a metal material and in particular of steel, that collects the sealing agent therewithin.

The tank 14 is defined by a cylindrical tubular casing 15 (or drum) that is closed at the bottom by a bottom wall 16 and open at the top (i.e., it is not provided with an upper wall or lid). The tank 14 has a variable volume collection chamber C, which has a cylindrical symmetry about an axis of rotation and is laterally delimited by the casing 15.

In contrast, the sealing agent delivery device 13 comprises a pumping device 17 that is connected to the electronic control unit ECU by which it is actuated, and that is suitable for drawing the sealing agent from the tank 14 and supplying it, under pressure, to the applicator device 7 by means of a sealing agent delivery conduit 18. The sealing agent delivery conduit 18 is preferably heated, originates from the tank 14 and is in hydraulic communication with the applicator device 7. According to a preferred variant, a number of shut-off valves (not shown) that control and regulate the flow of sealing agent are also located along the delivery conduit 18, downstream of the pumping device 17.

The pumping device 17 is preferably implemented by means of an extraction pump (known per se and not described in detail), in particular of the tyre type and specifically for highly viscous materials.

The sealing agent delivery device 13 then comprises a pair of extractor devices 19 arranged externally to the tank 14. In particular, the two extractor devices 19 are implemented by means of a pair of hydraulic extractor cylinders 19 arranged laterally in relation to the tank 14. The two extractor cylinders 19 are diametrically opposite in relation to the tank 14. The two extractor cylinders 19 are of a known type and are each provided with a relevant cylinder 20 comprising a hollow cylindrical body, a movable piston (not shown) that slides within the cylinder 20 due to the effect of the pressure exerted by the fluid contained within the cylinder 20 itself, and a rod 21 having a first end connected to the piston and a second, outer end connected to the cylinder 20. In particular, the rods 21 are connected at a second end to a thrust plate 22. The thrust plate 22 is provided with a through-hole 23 formed at a substantially central position. At an upper surface 24 (i.e., facing outward and not facing the collection device 11), the thrust plate 22 carries, connected at a substantially central position, the pumping device 17. At an inner surface 25 (i.e., in a position directly facing the collection device 11), the thrust plate 22 carries, connected at a substantially central position, an assembly A formed by a piston 26 that delimits at the perimeter the collection chamber C and a rod 27 connecting the piston 26 and the thrust plate 22.

In particular, the thrust plate 22 and the assembly A may move downwards (in other words towards the bottom wall 16) in such a way as to exert a substantially constant pressure against the sealing agent as the amount of sealing agent within the tank 14 varies.

In use, the thrust plate 22 and the assembly A are movable between an upper end-of- travel position (shown in Figure 2), in which the volume of the collection chamber C is at a maximum, and a lower end-of-travel position, which substantially corresponds to the complete emptying of the tank 14, in which position the volume of the collection chamber C is at a minimum and the piston 26 is arranged substantially at the bottom wall 16.

Both the piston 26 and the rod 27 are internally hollow, i.e., they are provided with respective through holes that are arranged, when in use, facing each other and in communication with each other in such a way as to define a channel for the passage of an extractor element 28. In addition, the opening formed in the rod 27 is facing, and in communication with, the through-hole 23. The extractor element 28 is provided at one end with a movable scoop 29 intended to move with a reciprocating motion in such a way as to draw the sealing agent within the collection chamber C in the vicinity of the piston 26 and to deliver said sealing agent to the pumping device 17.

Furthermore, the delivery circuit 10 comprises a position sensor 30, in particular a linear position transducer (for example a Hall effect sensor) intended to detect the position of the piston 26. The position sensor 30 is preferably arranged externally to the tank 14 and to the pair of extractor cylinders 19. The position sensor 30 is connected to the electronic control unit ECU to which it transmits signals indicative of the position of the piston 26. In other words, the position sensor 30 is arranged at a position facing the piston 26 so as to detect the displacements thereof over a predetermined interval of time. In particular, the position sensor 30 transmits signals indicative of the position of a bracket 32 connected to the thrust plate 22 (and, consequently, to the piston 26). According to a preferred variant, the position sensor 30 is supported by a bracket 31, preferably L-shaped.

In addition, the delivery circuit 10 comprises a solenoid valve 33 connected to the electronic control unit ECU. The solenoid valve 33 is preferably of the proportional and pressure-controlled type; the solenoid valve 33 allows for precise control of the pressure exerted by the piston 26 upon the sealing agent.

Finally, the delivery circuit 10 comprises a solenoid valve 34 connected to the electronic control unit ECU. The solenoid valve 34 is preferably of the proportional type; the solenoid valve 34 makes it possible to precisely control the rate of extraction of the sealing agent from the tank 14 by controlling the rate of the reciprocating motion of the extractor element 28.

According to a preferred variant, also provided is a heating device 12 housed at the bottom wall 16 or alternatively at the piston 26 and provided with a heating element 35 intended for heating the sealing agent, preferably implemented by means of an electrical resistance connected to the electronic control unit by which it is controlled. The electrical resistance, in order to heat the sealing agent, is preferably embedded within a disc element of reduced thickness. Alternatively, the heating element is implemented by means of a conduit or a coil wherein a heating fluid circulates that is supplied by a delivery circuit.

The method implemented by the electronic control unit ECU to control the application of the sealing agent is described below.

The electronic control unit ECU acquires a plurality of input data that are processed in order to control the application of the sealing agent.

In the first instance, the electronic control unit ECU acquires the weight W of the applied sealing agent, expressed in kg, during the last application (typically, the weight of the applied sealing agent is calculated from the difference between the weight of the tyre 4 detected after the application of the sealing agent, and the weight of the tyre 4 detected before the application of the sealing agent).

The block indicated with CORR in Figure 3 seeks to cancel out an error in the weight W of the applied sealing agent, i.e. a difference between the weight W of the applied sealing agent and the average weight WAVG of the applied sealing agent duringthe last n applications (with n being variable). Based upon the weight W of the applied sealing agent and the average weight WAVG of the sealing agent applied during the last n applications, a sealing agent flow correction factor FCF, expressed in pulses per minute, (pls/min) is calculated. According to a preferred variant, the number of applications n is greater than 50.

According to a preferred embodiment, said correction factor FCF is calculated from the ratio between the average weight WAVG of the sealing agent applied during the last n applications (with n being variable) and the theoretical (or ideal) weight WT of the sealing agent to be applied. This ratio is then further corrected by multiplying it by a gain index (in order to adjust the amount of correction).

The block indicated with CRPS in Figure 3 instead makes it possible to calculate the target extraction rate of the pumping device 17, expressed in pulses per minute, and the target extraction rate of the pumping device 17*, expressed in pulses per minute.

In particular, the electronic control unit ECU receives as an input the target value RRSP of the ratio between the recycled sealing agent and new sealing agent (expressed as a percentage, where a target value of 15% indicates that it is desired to obtain 15% recycled sealing agent based upon the total and 85% new sealing agent based upon the total); and the target value SSP of the total sealing agent extraction rate (expressed in pulses per minute) obtained both by means of the pumping device 17 and by means of the pumping device 17* (for example, 100 pls/min).

From the product of the target value RRSP and target value SSP it is possible to determine the target extraction rate S17* of the pumping device 17*; while the target extraction rate S17 of the pumping device 17* is obtained simply from the difference between the target value SSP of the total extraction rate and the target extraction rate S17* of the pumping device 17*. For example, with the data reported in the previous discussion, a target pumping device 17* extraction rate S17* equal to 15 pls/min and a target pumping device 17 extraction rate S17 equal to 85 pls/min would be obtained.

Finally, the block indicated with CF in Figure 3 receives the following parameters as input data:

- dimensions DD of the casing 15 defining the tank 14 (in particular, the inner diameter of the cylindrical tubular casing 15) expressed, for example, in mm;

- flow correction factor FCF expressed in pulses per minute (pls/min);

- position of the piston 26 provided by the position sensor 30 and preferably expressed in mm; and

- the position of the piston 26* provided by the position sensor 30* and preferably expressed in mm.

By means of these input data and knowing the geometry of the tank, the electronic control unit ECU is designed to determine:

- the effective value RRA of the ratio between new sealing agent and recycled sealing agent (expressed as a percentage, wherein an effective value of 5% indicates that the recycled sealing agent is 5% of the total sealing agent and the new sealing agent is 95% of the total sealing agent);

- the volume V, V* of sealing agent extracted from each pumping device 17, 17* during a predetermined interval of time; and

-the effective flow rate P, P* of each pumping device 17, 17* expressed in kg per minute.

In the event that the deviation between the effective value RRA of the ratio of new sealing agent to recycled sealing agent and the target value RRSP of the ratio between the recycled sealing agent and the new sealing agent is greater than a limit value (variable and predetermined at a preliminary set-up stage) - for example ±5%

- the electronic control unit is designed to send an alarm signal.

The preceding discussion explicitly refers to a system for the application of a sealing agent to the surface 2 of the inner cavity 3 of a tyre 4; however, the system and the method described may find advantageous application with any highly viscous fluid.

The preceding discussion therefore explicitly refers to a system for the application of a new sealing agent and a recycled sealing agent; the system and method described may however find advantageous application with any combination of highly viscous fluids.

The advantages of the system 1 described in the preceding discussion are evident. In particular, the system 1 makes it possible to optimize the flow of the sealing agent, and makes it possible to simplify the extraction of the sealing agent from the tank 14 and, in this way, prevent damage to the pumping device 17 and allow for the complete emptying of the tank 14.

List of reference numbers in the figures

1 sealing agent application system

2 surface

3 internal cavities

4 tyre

5 frame

6 motorized rollers

7 applicator device

8 arm

9 nozzle

10 delivery circuit

11, 11* collection device

12 heating device

13, 13* delivery device

14 tank

15 casing 16 bottom wall

17, 17* pumping device

18 delivery conduit

19 extractor device

20 cylinder

21 rod

22 thrust plate

23 opening

24 upper surface

25 lower surface

26, 26* piston

27 rod

28 extractor element

29 scoop

30, 30* position sensor

31 bracket

32 bracket

33 solenoid valve

34 solenoid valve

35 heating element

X central axis

ECU control unit

C collection chamber

A assembly

DD tank dimensions

W sealing agent weight

WAVG average sealing agent weight

FCF correction factor

RRSP ratio target value

SSP rate target value

S17, S17* extraction rate

RRA effective ratio value V, V* sealing agent volume

P, P* sealing agent flow rate