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

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

The sealing agent is applied to a pre-vulcanized pneumatic tyre and preferably to the innerliner within the area of the pneumatic tyre that comes into contact with the road (or the area of the pneumatic tyre wherein punctures can 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 pneumatic 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 pneumatic 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 pneumatic 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 pneumatic tyre. The pneumatic tyre is brought into rotation by the support by means of motorized rollers; the movement (continuous or alternatively stepped) of the arm, combined with the rotation of the pneumatic tyre, results in the application of the sealing agent, which must be as uniform as possible. Documents <CIT>, <CIT> and <CIT> relate to sealing agent application processes and apparatuses of the known type. The sealing agent has a high specific weight, and even a small change in the amount of sealing agent applied to the inner surface of the pneumatic tyre can cause a significant variation in the weight of the pneumatic tyre, leading to an imbalance (i.e., an eccentricity) of the overall mass of the pneumatic tyre. It has been observed that known, and currently used, application systems do not make it possible to obtain elevated uniformity in relation to the thickness of the sealing agent that is applied to the surface of the internal cavity, i.e., the thickness of the sealing agent that is applied to the surface of the internal cavity can present appreciable variations from area to area.

The object of the present invention is therefore to provide a method for applying a sealing agent to the surface of an internal cavity of a pneumatic tyre that is free from the disadvantages of the state of the art and that is, in particular, easy and inexpensive to implement.

A further object of the present invention is accordingly to provide a system for applying a sealing agent to the surface of an internal cavity of a pneumatic tyre that is free from the disadvantages of the state of the art and that is, in particular, easy and inexpensive to manufacture.

According to the present invention a method and a system are provided for applying a sealing agent to the surface of an internal cavity of a pneumatic tyre according to what is determined within the attached claims.

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

With reference to <FIG>, the numeral <NUM> denotes a system <NUM> in its entirety for the application of a sealing agent to the surface <NUM> of an internal cavity <NUM> of a pneumatic tyre <NUM>. It is to be understood that the phrase "profile of the internal cavity <NUM> of a pneumatic tyre <NUM>", refers to a surface profile of the pneumatic tyre <NUM>.

The pneumatic tyre <NUM> is arranged on a frame <NUM> that is suitable for supporting, and bringing into rotation around a central X axis thereof, the pneumatic tyre <NUM> by means of motorized rollers <NUM>. The frame <NUM> is designed to bring pneumatic tyres <NUM> into rotation at a substantially constant speed and preferably between <NUM> and <NUM>/min. Preferably, the pneumatic tyre <NUM> is housed within the frame <NUM> in such a way as to prevent any lateral translation of the pneumatic tyre <NUM> itself during the rotational movement around the x axis.

As shown in <FIG>, the system <NUM> comprises a sealing agent applicator device <NUM>, which is conveniently implemented by means of a robot with an arm <NUM> that is movable and intended to apply a substantially uniform bead of sealing agent to the surface <NUM>.

The applicator device <NUM> is intended to apply a bead of sealing agent by means of a reciprocating movement between the two lateral ends of the internal cavity <NUM>; in particular, the arm <NUM> moves in a plane that is substantially orthogonal to the equatorial plane of the pneumatic tyre <NUM>. The rotation of the frame <NUM> around the axis X and the movement of the arm <NUM> results in an application with a helical progression. More specifically, the applicator device <NUM> is intended to apply a bead of sealing agent at the portion of the pneumatic tyre <NUM> that is intended to come into contact with the road, i.e., at the tread and, at least partially, at the sidewalls.

The applicator device <NUM> is connected to a sealing agent supply circuit <NUM> comprising a tank <NUM> that is preferably manufactured from a metallic material and contains the sealing agent, a conduit <NUM> that is preferably heated and that originates from the tank <NUM> and that is in hydraulic communication with the applicator device <NUM>, and a pumping device <NUM> that extracts the sealing agent from the tank <NUM> and supplies it under pressure to the applicator device <NUM>.

According to a preferred variant, the applicator device <NUM> is implemented by means of a nozzle <NUM> in order to perform the non-contact application of the sealing agent in the semifluid state; the nozzle <NUM> is preferably arranged at one axial end of the movable arm <NUM>.

The applicator device <NUM> is implemented in such a way as to make the distance between the nozzle <NUM> and the surface <NUM> substantially constant. It should be emphasized that by holding the distance between the nozzle <NUM> and the surface <NUM> substantially constant it is possible to implement a more uniform application in terms of the thickness and width of the bead and in terms of the precision of the sealing agent application area.

According to a first embodiment, provided upstream of the frame <NUM> is a weighing station <NUM>, which includes a number of load cells <NUM>, wherein each thereof comprises a known type of measuring device connected to a control unit <NUM>, which in turn comprises a signal processing device <NUM>. The signal processing device <NUM> is configured in such a way as to receive, before the application of the sealing agent, signals from the load cells <NUM> that are indicative of the weight of the pneumatic tyre <NUM>.

Provided upstream of the frame <NUM> is a further weighing station <NUM>, which in turn comprises a number of load cells <NUM>, wherein each thereof comprises a known type of measuring device connected to the control unit <NUM>. The signal processing device <NUM> is configured in such a way as to receive, after the application of the sealing agent, signals from the load cells <NUM> that are indicative of the weight of the pneumatic tyre <NUM>.

According to a second embodiment, corresponding to the position of the frame <NUM>, a weighing station <NUM> is provided, which comprises a number of load cells <NUM>, wherein each thereof comprises a known type of measuring device connected to the control unit <NUM>. The signal processing device <NUM> is configured in such a way as to receive signals from the load cells <NUM> that are indicative both of the weight of the pneumatic tyre <NUM> before the application of the sealant and the signals that are indicative of the weight of the tyre <NUM> after the application of the sealing agent.

In both embodiments, the signal processing device <NUM> is therefore implemented in such a way as to calculate the quantity of sealing agent applied from the difference between the weight of the pneumatic tyre <NUM> after the application of the sealing agent and the weight of the pneumatic tyre <NUM> before the application of the sealing agent.

The data in relation to the quantity of sealing agent applied for each pneumatic tyre <NUM> (calculated from the difference between the weight of each pneumatic tyre <NUM> after the application of the sealing agent and the weight of the same pneumatic tyre <NUM> before the application of the sealing agent) are stored within a one-dimensional array <NUM> or short-term vector within a memory buffer <NUM> within the control unit <NUM>. The short-term vector <NUM> defines a short-term memory buffer <NUM>.

It is important to highlight that the quantity of sealing agent to be applied is variable as a function of the reference features (in particular as a function of the dimensions/size) of the pneumatic tyre <NUM>. According to a first variant, a plurality of short-term vectors <NUM> is stored within the short-term memory buffer <NUM>, wherein each short-term vector <NUM> corresponds to a different type of pneumatic tyre <NUM> whereupon the layer of sealing agent being processed by the system <NUM> can be applied.

According to a second and preferred variant, the data in relation to all of the different types of pneumatic tyre <NUM> to which the layer of sealing agent being processed by the system <NUM> can be applied, are stored within a single short-term vector <NUM> within the short-term memory buffer <NUM>. The reference quantities of sealing agent to be applied for each of the different types of pneumatic tyre <NUM> being processed by the system <NUM> are stored within the control unit <NUM>. The reference quantities of sealing agent to be applied for each of the different types of pneumatic tyre <NUM> are preferably determined during an experimental fine-tuning step of the system <NUM> as a function of the reference characteristics (in particular as a function of the dimensions/size) of each of the different types of pneumatic tyre <NUM>. Preferably, the reference quantities of sealing agent to be applied for each of the different types of pneumatic tyre <NUM> being processed by the system <NUM> are fixed and are not modified during the operation of the system <NUM>.

Once the type of pneumatic tyre <NUM> to be processed has been selected, the control unit <NUM> is configured to compare the quantity of sealing agent applied to each pneumatic tyre <NUM> with the respective reference quantity. In particular, the control unit <NUM> is configured to calculate the difference between the quantity of sealing agent applied for each pneumatic tyre <NUM> and the respective reference quantity. The differences between the quantity of sealing agent applied to each pneumatic tyre <NUM> and the respective reference quantity are stored within the short-term vector <NUM>. It appears evident that in this way the data contained within the short-term vector <NUM> are independent of the reference characteristics (in particular as a function of the dimensions/ size) of the pneumatic tyre <NUM> and data relating to different types of pneumatic tyres <NUM> can be stored. The control unit <NUM> is therefore able to assess both the direction/orientation of the deviation in relation to the reference quantity of sealing agent to be applied (i.e., if, compared to the reference quantity of sealing agent to be applied, the tendency is to apply a greater or lesser quantity of sealing agent) and the absolute value of the deviation in relation to the reference quantity of sealing agent to be applied (i.e., by how much the quantity of sealing agent to be applied deviates from the reference quantity of sealing agent to be applied).

The short-term vector <NUM> comprises a number of cells between <NUM> and <NUM>, preferably between <NUM> and <NUM>, in particular equal to <NUM>. The short-term vector <NUM> is preferably handled using FIFO logic (first in first out).

Similarly, the data in relation to the quantity of sealing agent applied for each pneumatic tyre <NUM> (calculated from the difference between the weight of each pneumatic tyre <NUM> after the application of the sealing agent and the weight of the same pneumatic tyre <NUM> before the application of the sealing agent) are stored within a one-dimensional array <NUM> or long-term vector within the memory buffer <NUM>. The long-term vector <NUM> defines a long-term memory buffer <NUM>.

According to a first variant, a plurality of long-term vectors <NUM> is stored within the long-term memory buffer <NUM>, wherein each long-term vector <NUM> corresponds to a different type of pneumatic tyre <NUM> whereupon the layer of sealing agent being processed by the system <NUM> can be applied.

According to a second and preferred variant, the data in relation to all of the different types of pneumatic tyre <NUM> to which the layer of sealing agent being processed by the system <NUM> can be applied, are stored with a single long-term vector <NUM> within the long-memory buffer <NUM>. The reference quantities of sealing agent to be applied for each of the different types of pneumatic tyre <NUM> being processed by the system <NUM> are stored within the control unit <NUM>. The reference quantities of sealing agent to be applied for each of the different types of pneumatic tyre <NUM> are preferably determined during an experimental fine-tuning step of the system <NUM> as a function of the reference characteristics (in particular as a function of the dimensions/size) of each of the different types of pneumatic tyre <NUM>. Preferably, the reference quantities of sealing agent to be applied for each of the different types of pneumatic tyre <NUM> being processed by the system <NUM> are fixed and are not modified during the operation of the system <NUM>.

Once the type of pneumatic tyre <NUM> to be processed has been selected, the control unit <NUM> is configured to compare the quantity of sealing agent applied to each pneumatic tyre <NUM> with the respective reference quantity. In particular, the control unit <NUM> is configured to calculate the difference between the quantity of sealing agent applied for each pneumatic tyre <NUM> and the respective reference quantity. The differences between the quantity of sealing agent applied to each pneumatic tyre <NUM> and the respective reference quantity are stored within the long-term vector <NUM>. It appears evident that in this way the data contained within the long-term vector <NUM> are independent of the reference characteristics (in particular as a function of the dimensions/size) of the pneumatic tyre <NUM>, and data relating to different types of pneumatic tyres <NUM> can be stored. The control unit <NUM> is therefore able to assess both the direction/orientation of the deviation in relation to the reference quantity of sealing agent to be applied (i.e., if, compared to the reference quantity of sealing agent to be applied, the tendency is to apply a greater or lesser quantity of sealing agent) and the absolute value of the deviation in relation to the reference quantity of sealing agent to be applied (i.e., by how much the quantity of sealing agent to be applied deviates from the reference quantity of sealing agent to be applied).

The long-term vector <NUM> comprises a number of cells of between <NUM> and <NUM>, preferably between <NUM> and <NUM>, in particular equal to <NUM>. The long-term vector <NUM> is preferably handled using FIFO logic (first in first out).

Finally, the data in relation to the quantity of sealing agent applied for each pneumatic tyre <NUM> (calculated from the difference between the weight of each pneumatic tyre after the application of the sealing agent and the weight of the same pneumatic tyre before the application of the sealing agent) are stored within a one-dimensional array <NUM> or historical memory vector within the memory buffer <NUM>. The historical memory vector <NUM> defines a historical memory buffer <NUM>. The historical memory buffer <NUM> collects the production data of approximately <NUM>,<NUM> pneumatic tyres. In addition to the data in relation to the quantity of applied sealing agent, for each pneumatic tyre <NUM>, within the historical memory buffer <NUM>, additional production data are also stored such as, for example, the time of year wherein the production of the pneumatic tyre <NUM> occurred, the type of nozzle <NUM> used for the production of the pneumatic tyre <NUM>, etc..

As shown in <FIG>, a predictive algorithm <NUM> is stored within the control unit <NUM> that receives at the input, inter alia, the data provided by the short-term memory buffer <NUM>, by the long-term memory buffer <NUM> and by the historical memory buffer <NUM>.

In particular, the predictive algorithm <NUM> receives the following input data:.

On the basis of all of the input data received, the predictive algorithm <NUM> produces a short-term compensation factor KST and a long-term compensation factor KLT.

The predictive algorithm <NUM> consists in a mathematical model wherein the different previously processed input data are used to calculate the short-term compensation factor KST and the long-term compensation factor KLT.

The short-term compensation factor KST and the long-term compensation factor KLT are determined as follows: <MAT> wherein (a) - (g) represent the different input data input and ki (with i = <NUM>, <NUM>,. <NUM>) represent the weights attributed to each input datum.

The weights ki are not constant but depend upon the compensation factor that is being calculated, distinguishing between short-term compensation factor KST and the KLT compensation factor. In the case wherein the short-term compensation factor KST is being calculated, a weight is attributed that is greater that the data (a) and (b) taken from the short-term memory buffer <NUM>; whilst, in contrast, in the case wherein the long-term compensation factor KLT is being calculated, a weight is attributed that is greater than the data (c) and (d) taken from the long-term memory buffer <NUM>.

Finally, the control unit <NUM> comprises a module <NUM> for calculating the compensation parameters that it receives at the input from the predictive algorithm <NUM>, both the short-term compensation factor KST and the long-term compensation factor KLT, together with further production data (generically indicated with REP, "recipe extrusion parameters") such as, for example, the dimensions of the pneumatic tyre <NUM> being processed, the type of nozzle <NUM>, the extrusion speed, etc..

Based on the short-term compensation factor KST or the long-term compensation factor KLT, provided by the predictive algorithm <NUM>, and on the REP production data, the calculation module <NUM> produces an extrusion process correction factor KEA.

The calculation module <NUM> consists of a mathematical model for calculating the correction factor KEA. In particular, the correction factor KEA is determined as follows: <MAT> wherein KST / KLT and REP have the meanings introduced previously and pi (with i = <NUM>, <NUM>) represent the weights attributed respectively to the short-term compensation factor KST or else to the long-term compensation factor KLT and to the REP production data. The weights pi are preferably constant.

The short-term compensation factor KST and the long-term compensation factor KLT from predictive algorithm <NUM> are not used simultaneously but exclusively within the formula to determine the correction factor KEA.

During the normal production process, the short-term compensation factor KST is used within the formula to determine the correction factor KEA. In contrast, the long-term compensation factor KLT is used within the formula to determine the correction factor KEA in the case wherein the system <NUM> is, for example, restarted after a production shutdown period.

Hereinafter there will be described the method of operation of the system <NUM>, which includes, in succession, the following steps:.

The advantages of the system <NUM> described in the preceding discussion are evident.

Claim 1:
Method for applying a sealing agent to a surface (<NUM>) of a inner cavity (<NUM>) of a pneumatic tyre (<NUM>); the method comprises the step of applying a strip of sealing agent to the surface (<NUM>) of the inner cavity (<NUM>) by means of an applicator device (<NUM>) whilst the pneumatic tyre (<NUM>) is brought into rotation around an axis (X) thereof;
the method is characterized in that it comprises the further steps of:
- measuring the weight of the pneumatic tyre (<NUM>) before the application of the sealing agent application to the surface (<NUM>);
- measuring the weight of the pneumatic tyre (<NUM>) after the application of the sealing agent application to the surface (<NUM>);
- calculating the quantity of sealing agent applied to the surface (<NUM>) from the difference between the weight of the pneumatic tyre (<NUM>) after the application of the sealing agent to the surface (<NUM>) and the weight of the pneumatic tyre (<NUM>) before the application of the sealing agent to the surface (<NUM>);
- calculating the difference between the quantity of sealing agent applied to the surface (<NUM>) and a reference quantity of sealing agent to be applied to the surface (<NUM>) that varies as a function of the type of pneumatic tyre;
- storing said difference within a short-term memory buffer (<NUM>) and a long-term memory buffer (<NUM>) having a greater number of cells than the short-term memory buffer (<NUM>);
- determining a short-term compensation factor (KST) and a long-term compensation factor (KLT) as a function of both the short-term memory buffer (<NUM>) and the short-term memory buffer (<NUM>);
- calculating a correction factor (KEA) using, alternately, the short-term compensation factor (KST) or else the long-term compensation factor (KLT);
- using said correction factor (KEA) to actuate the applicator device (<NUM>) during the subsequent step of applying the strip of sealing agent to the surface (<NUM>).