WO2013150459A1

WO2013150459A1 - High performance shock pad, method of manufacture thereof and its use

Info

Publication number: WO2013150459A1
Application number: PCT/IB2013/052656
Authority: WO
Inventors: Pedro Miguel PEREIRA MARQUES
Original assignee: Biosafe Industria de Reciclagens SA
Current assignee: Biosafe Industria de Reciclagens SA
Priority date: 2012-04-03
Filing date: 2013-04-03
Publication date: 2013-10-10
Anticipated expiration: 2014-10-03

Description

HIGH PERFORMANCE SHOCK PAD, METHOD OF MANUFACTURE THEREOF AND ITS USE

DESCRIPTION

Technical domain of the invention

This invention regards high performance shock pads with flexible densities that can be adjusted depending on the interests of the end user and the intended application. These adjustments may be made by varying the pressure that is applied and the amount of material used, namely rubber granules and binder.

These high performance shock pads can be used in many types of flooring, particularly sports flooring (synthetic turf pitch, wooden indoor floors, running tracks and tennis courts) , comfortable flooring (under layers of wooden floors, comfort mats, mats for spas and surrounding areas) and safety floors (playgrounds and / or similar) .

Summary of the invention

The aim of this invention is to describe a high performance shock pad which has between 80% and 97% of rubber and has between 20% and 3% of a binder, all in weight.

In one preferred embodiment of this invention, the high performance shock pad is produced using recycled rubber.

In another preferred embodiment of this invention, the high performance shock pad has perforations.

In one preferred embodiment of this invention, the high performance shock pad has circular perforations. In another preferred embodiment of this invention, the high performance shock pad has its periphery composed of semicircles with rounded shape edges.

In one preferred embodiment of this invention, the high performance shock pad has connectors (1) made of the same high performance shock pad's composition.

In another preferred embodiment of this invention, the high performance shock pad has connectors (1) made of vulcanized rubber mixture composed of equal parts of virgin SBR ( Styrene-butadiene rubber) and recycled rubber.

In one preferred embodiment of this invention, the high performance shock pad has connectors (1) made of a composition based on vulcanized rubber mixtures with a formula composed of 25% to 75% of virgin SBR and 75% to 25% of recycled rubber, all in weight.

In another preferred embodiment of this invention, the high performance shock pad is porous when applied upon of a drainage system.

In one preferred embodiment of this invention, the high performance shock pad has a network of small channels that connect all the perforations.

In another preferred embodiment of this invention, the high performance shock pad has a geotextile or other drainage mesh over it.

In one preferred embodiment of this invention, the high performance shock pad has a geotextile or other drainage mesh to be placed in a final phase of production, for example by gluing or hot gluing.

In another preferred embodiment of this invention, the high performance shock pad is applied under a wooden floor.

Another aim of this invention is to describe a method of producing the high performance shock pad with the connections comprising the following steps:

- Mixing the rubber granules with the binder;

- Placing the mixture in a mould;

- Applying pressure, temperature and time to the material in the mould to mould and cure the high performance shock pad;

- Mixing rubber granules with the virgin SBR;

- Placing the mixture in a mould;

- Applying pressure, temperature and time to the material in the mould to mould and cure the connectors;

- Joining together the high performance shock pad with the connectors ;

- Packing the pieces;

- Identifying the packages;

- Shipping the product.

In one preferred embodiment of the present invention, the method to obtain the high performance shock pad comprises the mixture of the rubber and the binder for 3 to 6 minutes .

In another preferred embodiment of this invention, the method to obtain the high performance shock pad comprises a curing process lasting 3 to 10 minutes at temperatures of between 80°C and 160°C. In one preferred embodimentof this invention, the method to get the high performance shock pad comprises the application of between 0.1 and 25 MPa of pressure.

In another preferred embodiment of this invention, the method to obtain the high performance shock pad uses a polyurethane resin as the binder.

Background to the invention

The shock pads for sports flooring were created to enhance the playability performance of synthetic turf pitches and reduce player's injuries. These surfaces can be made of different kind of materials and in various ways. Most shock pads are made of recycled rubber granules that can be installed "in-situ" or by installing pre-moulded pads. These pads have some problems of stability, logistics and guarantees that the surface is homogenous all over the flooring .

This lack of homogenisation leads to surfaces with varying densities, or in the case of surfaces made "in-situ" with excessive playing loads causing the material to slip to areas with less use, or in the case of surfaces made with continuous mats where uncontrolled size expansion joints can appear and cause uneven surfaces in the sports pitches .

This is why some alternatives have recently appeared on the market that try to overcome these defects, namely, virgin and/or recycled foam surfaces, rolls of continuous mats of recycled rubber and rolls of foam. In surfaces where the aim is the transmission of comfort to users, the shock pads make the floor softer and more comfortable .

Safety surfaces, particularly surfaces for children's playgrounds or equivalent, reduce the risk of injury from falling from heights and HIC or critical fall height, according to Standard EN 1117 is the most important parameter to measure. The most common materials used for reducing the risk of injury are loose sand or recycled rubber granules bound together with a binder.

There are three ways of producing these rubber surfaces : 1- "In-Situ"

The recycled rubber granules and binder are mixed on site and applied like a traditional screed surface, implying great movements of equipment and resins that are sensitive to climatic conditions.

One of the most important requirements for a good application is that the underlying base is completely dry and do not have any contaminants and that the temperature is not under 10°C, thus limiting its use during periods of higher humidity or low temperatures.

As it is a bulk application, it can be adapted to all existing equipments and there is the possibility of constructing images and coloured figures as desired with pigmented granules of recycled or virgin rubber.

Typically to increase HIC, the thickness of the surface is increased and can be as much as 15 cm thick. This solution would not be economically viable if the surface was made purely of virgin materials, particularly granules of ethylene propylene diene (EPDM) rubber. In an attempt to reduce costs, a shock pad is made with recycled black rubber granules and only a layer of around 1 cm on top is made with coloured granules.

The HIC values depend on the skill of the applier and their professionalism meaning work' s owner cannot previously guarantee this value to the awarding authority. This guarantee is only given after the surface that was applied has been certified.

In terms of labour, this process becomes expensive and slow because of the need to clean and dry the underlying base, limiting this application on damp or cold days. Once the black sub-base has been applied, the applier have to wait until it is solid enough to apply the final layer.

2- Pre-moulded surfaces.

This kind of application consists of mounting the pads in a clean and dry surface. This has to be made with cement or asphalt to enable the pads to be firmly fixed to the under- surface .

These pads are subject to wear by so much friction that they have to be compacted during its production to minimise this effect, losing some of their impact absorption capability .

In order to make them stable, these pads have to be interconnected with plastic pins or glued to one another. They also need an expansion joint around the entire surface, which is often forgotten by the applier and when exists is a preferable place to the accumulation of residues .

Taking into account the scientific data available regarding heat expansion of the material the pads are made of, mainly SBR, it is estimated that the heat expansion will vary between 1.4% and 1.8% over an 80°C temperature range.

When it is not possible to control the heat expansion of a no waterproof surface, the pads typically lift on hot days and cracks open on colder days. This has been the biggest problem these pre-moulded surfaces have had to cope with. Various manufacturers have tried to mitigate this effect by super-gluing the surfaces to the subsurface and connecting them together with plastic pins. Even so, it is not possible to control the appearance of cracks between the j oints .

Due to the compacting, described above, all the pads on the market have more or less evident variations in density and different HIC values all along the pads and in their interconnections .

The use of pre-moulded pads in playgrounds is most frequent for the following reasons:

- The pads are produced in controlled conditions where they can guarantee HIC certificates;

- Depending on the shapes made by each manufacturer, the pad will drain a greater or lesser amount of water, though in real situations the most of the water drains away through the joints;

- They are quicker to install and need less logistics. These surfaces may be as much as 10 cm thick and are not easy to adjust to existing equipment as they need electrical cutting tools like jigsaws.

3- "In-Situ" with shock pads in plates.

This process is identical to the "in-situ", but instead of making the sub-surface using the same process, pre-moulded shock pads are used to make the sub-surface that is then covered with 1 cm of the finishing product.

Some appliers have already opted for the joint solution of "in-situ" and pre-moulded pads, with which they can give some previous guarantees to the work' s owner and reduce labour. These shock pads can be made from recycled rubber, polyurethane foam and polystyrene.

As there is no control of the heat expansion of the shock pads, they are strongly glued to the subsurface and to the upper layer. This makes the process slower and more expensive .

Some appliers using this method also install a reinforcing mesh .

This invention intends to overcome the problems found in the solutions presented above and presents some advantages that the existing products do not offer. These advantages are particularly clear in some kinds of applications such as sports, comfort and safety flooring.

This invention was driven by the following needs:

^•S To create a shock pad that could be adapted to different kinds of sports, comfort and safety floors. ^•S To create a more economical and effective solution than those currently on the market.

^•S To create a composition that, due to the nature of the industry, where the developer works, has to include recycled rubber granules. To tackle directly the problems associated with the use, with this composition.

General description of the invention

This invention regards high performance shock pad with flexible densities that can be adjusted depending on the interests of the end user and the intended application. These adjustments may be made by varying the pressure that is applied and the amount of material used, namely rubber granules and binder.

This high performance shock pad has many advantages regarding the prior art, namely:

- Control of heat expansion;

- Elimination of drainage surface;

- Ease of transport;

- Ease of application;

- Maintenance of technical characteristics over time;

- Equal performance at all points of the surface;

- Creation of an air box to prevent any degradation of wood, when it is used;

Elimination of dampness by creating an air box allowing the air to circulate; - Improved chemical and antibacterial resistance;

- Possibility of surface colouring;

- Greater HIC with less surface thickness;

Elimination of the need to dry the underlying surface ;

Possibility of repairing or replacing the upper layer without the need to change the shock pad.

These high performance shock pads can be applied to countless kinds of paving sports flooring (synthetic turf pitches, wooden indoor floors, running tracks and tennis courts) , comfortable flooring (comfort mat, mats for spas and surrounding areas) and safety floors (playgrounds and / or similar) .

Brief description of the figures

Figures have been attached to make this invention easier to understand, showing preferred embodiments but which do not in any way limit the scope of this invention.

Figure 1 shows a production diagram to obtain the high performance shock pad.

Figure 2 shows how the high performance shock pad behaves under pressure.

Figure 3 shows how the high performance shock pad behaves depending on the size of the rubber granule.

Figure 4 shows a force diagram. Figure 5 shows how the high performance shock pad behaves on impact .

Figure 6 shows a profile of the high performance shock pad showing the network of small channels.

Figure 7 shows a way of installing the high performance shock pads, where the number 1 represents the connecting link .

Figure 8 gives a detailed view of the high performance shock pad where the number 1 represents the connecting link .

Figure 9 shows the connecting link and a cross section.

Figure 10 shows a detail of the high performance shock pad, particularly one of its rounded edges.

Figure 11 shows a three dimensional image of the assembly of the high performance shock pad.

Detailed description of the invention

This invention regards high performance shock pad with flexible densities that can be adjusted depending on the interests of the end user and the intended application. These adjustments may be made by varying the pressure that is applied and the amount of material used, namely rubber If this kind of high performance shock pad is applied in sports surfaces such as synthetic turf pitches, there is a flexible density shock pad that can be adjusted to the interests of synthetic turf suppliers.

FIFA regulations state that the certification can only be obtained by a system that is composed of a shock pad, synthetic turf and filler that can be sand and/or rubber. As there are countless kinds of turf and its suppliers, this high performance shock pad is important as it allows, in conjunction with the synthetic turf suppliers, to certify a specific system. Thus, the supplier can adjust the shock pad to boost the performance of a particular kind of synthetic turf.

The fundamental characteristics of this application are the vertical deformation and impact absorption. As this invention means it is possible to control the density variation, as described earlier, it is thus possible to control vertical deformation and the capacity to absorb impacts in a particular system.

The certification of a system, earlier described, implies two fundamental tests, which are vertical deformation and impact absorption. The kind of high performance shock pad composition here presented means that it is possible to get different vertical deformations and different impact absorptions just by altering the compaction and/or size of granule, i.e. just altering the density.

The high performance shock pad composition is between 80% and 97% of recycled rubber and 20% to 3% of a binder, all in weight. This kind of solution means that it is possible to alter the amount of material per square metre associated with the pressure and temperature applied during production. The mixture is then placed in a mould at a temperature of between 80°C and 160°C and cured for between 3 and 10 minutes under a pressure of 0.10 to 25 MPa.

The shock pads on the market cannot do this so easily because the reaction of the foam needs a specific pressure to develop according to a specific characteristic, i.e. the alteration of this parameter in the production is critical to get the intended result.

When speaking of recycled foams, the production technology is identical to that used in the shock pads, but as there is a huge variety of foams the final thicknesses of the final plates cannot be controlled and the homogeneity of the density cannot be guaranteed throughout the plate.

Shock pads produced "in-situ" cannot offer the work's owner any guarantees before the final certification of the system. As a football pitch can be as big as 10,000 m², the loss would be incalculable if the demands of work' s owner are not met.

The market also offers the possibility of using shock pads in continuous layered mats of recycled rubber. It cannot realistically be used to improve the performance of a specific system as it has to be relatively thin, no more than 12 mm, and its composition may alter along with its density which may not be enough once it is flat and massive . Heat expansion control

This may be it is the best advantage of this invention - the ability to control the heat expansion while maintaining its characteristics over the surface.

Synthetic turf pitches are normally used outdoors and are therefore subject to a range of temperatures throughout the day and the year. In some cases, the difference may be as much as 80°C.

When this kind of temperature range exists the rubber will expand by about 1.5%, which over a 100 metre football pitch means an expansion of about 1.5 metres. If the shock pad does not foresee this situation the surface can lift or uncontrolled cracks can appear in the shock pad.

At the moment there is no shock pad that has this kind of expansion parameter.

A product's dimensional stability is the ability of the product to maintain its dimensions after suffering heat expansion. Heat expansion, on the other hand, is the change in size a product goes through when subjected to different temperatures .

This invention forecasts the control of heat expansion by its design and by the connectors between the shock pads.

Three aspects are fundamental in the design of this invention that gives it stability inside the shock pad and between shock pads . The first fundamental aspect is the perforation of the surface, which can take place when it is made by using a mould with this format or be perforated later on site according to the customer' s demands and the kind of application. The perforation can have any shape, but it should preferentially be circular. This perforation allows the surface to expand inwards in case of extreme expansion.

The second fundamental aspect is its external shape. The periphery of the high performance shock pad was designed in form of semi-circles, i.e. half of the perforation configuration. This shape and the rounded shape edges will provide expansion joints between the high performance shock pads. The developer had calculated that this joint alone is not wide enough to absorb extreme expansion so to overcome this situation connectors were created as described below, and in cases of extreme expansion, the high performance shock pads will touch and as the edges are rounded and fairly flexible, they will fit into one another.

The third fundamental aspect of the design, are the connectors. These connectors were designed and created to complement the success of this invention by controlling heat expansion. One possibility is to produce the shock pads with them already included, made of the same composition. Another possibility is to produce the connectors from a different material. The connectors could then be made from a composition based on vulcanized rubber mixtures with 25% to 75% of virgin SBR and 75% to 25% of recycled rubber, all in weight.

Ideally the proportion would be 50% of SBR to 50% of recycled rubber in weight. This latter solution, virgin SBR plus recycled rubber, has the advantage that the user can properly control the final dimensions and alter them as necessary .

The size of the connectors is of extreme importance, as they ensure that there is an expansion joint and they are easy to assemble. These dimensions may vary both in overall size as the distance between the centres of the holes and the holes' size.

In the case of negative heat expansion, the expansion joint may increase in size.

These expansions are accompanied by the connectors as their composition is very similar to the plate (SBR and recycled rubber) with the added advantage that they are fairly elastic materials.

Theoretical case:

Considering, in an extreme situation, where the high performance shock pad is 1000x500 mm against another of the same size where there is a 4 mm expansion joint. If all the expansion occurs on the 1000 mm dimension and only towards the joint, if there is 1.5% heat expansion, this means the joint has to absorb 30 mm. In extreme cases, the plates can fit into one another through half the circumference of the perforation, and so only with this process it is possible to absorb 24 mm of expansion, and so only 6 mm has to be absorbed by internal deformation. Since the internal deformation obtained needs to be between 20% and 40%, the internal deformation needed for a surface is 0.6%, which is an extremely small amount. It can be therefore concluded that the high performance shock pad presented in this invention manage to control the heat expansion they may be subject to without lifting off the subsurface.

Elimination of the drainage surface

All synthetic turf pitches need systems to drain water from rain and irrigation systems. The different shock pad systems described above use porous surfaces that only use drainage systems that are installed under the shock pads.

With this invention, there will be no need to install underlying drainage systems or camouflaged drainage systems and otherwise the base shall be insulated to recover the water for other purposes.

Apart from providing a high performance shock pad, this invention also provides an extremely effective rain and irrigation water drainage system.

A network of small channels was created connecting all the holes in each high performance shock pad with the following advantages :

- Prevents stagnant water in the holes;

- Increases drainage capacity.

In real situations, the artificial turf pitches filling sand has small grains and is carried away by water that flows through the synthetic turf water drainage holes. To avoid the contamination of the high performance shock pads with sand, a geotextile or other drainage mesh can be placed over them. Ease of transport

Logistics questions of works are becoming more and more important and can dictate the success or failure of a product's competitiveness.

The logistics of the manufacturing of high performance shock pads for synthetic artificial turf pitches is similar to shock pads in plates, but comparing rolls or "in-situ" processes, this solution is cheaper.

A quick comparison of these last two last solutions lets us see it is necessary to move more equipment, more raw materials and more labour.

The high performance shock pads are packed in pallets with the maximum weights allowed in land and sea transport. On site the surfaces can be moved on the same pallets or divided into smaller units as the customer decides. The surfaces are light-weight and small enough that an applier can carry them without any special transport at the work site .

There are shock pads with different weights and sizes on the market, but normally two persons are necessary to carry them.

When the work' s owner chooses to use shock pads in rolls to try to reduce transport costs, they end up having transport problems on site as these rolls are too heavy to be moved manually .

If they go for an "in-situ" process they need to move large amounts of raw materials and other loads that require careful storage conditions. If the material is applied using specialised equipment, this too must be moved to the site, which can be complicated as in some countries the movement of machinery is limited and controlled.

Easy to apply

This invention will simplify assembly in comparison with other pre-moulded shock pad solutions available on the market .

In the shock pads that exist on the market there are male/female connectors that have to be connected in the right order and in the right hole. This is no longer necessary with this invention as the applier only has to be concerned with the three identical connection points, which are identified and strategically mounted giving further possibility to the applier of assembling the surface after turning it 90 ° .

If they choose to use shock pads in rolls, the appliers have to pay attention to some important parameters. They have to check the alignment of the mat, ensure the expansion joint is uniform, which is humanly impossible without the aid of some kind of tool and in the case of any correction they have to manhandle dozens of square metres at a time.

In comparison with shock pads in rolls, this invention is notable for its light weight and ergonomically designed dimensions that simplify assembly. It only requires one person and all she needs to concern is with fitting them together at the proper points as the expansion joints and alignment are guaranteed by the connectors. In comparison with the "in-situ" solutions, the main differences are the possibility of the shock pads being applied without any specialised labour and synthetic turf can be immediately applied after the shock pads' surface is ready .

Guarantee of keeping its technical characteristics over time

The high performance shock pads are manufactured using recycled rubber granules that take more than 600 years to break down, bound together using a binder. The binder may be a polymer resin such as single-component polyurethane, which has long been used in children' s playground surfaces and which has proven they are durable.

There are no studies into the specific durability of all the different raw materials. When taking into account the experience that the developer gained from playgrounds and knowing that high performance shock pads will always be out of Ultra Violet rays and direct contact aggression, the developer can state that the durability will increase exponentially.

In order to certify that the performance of the high performance shock pads' surface will not be affected by solid particles carried by leachates, a geotextile or other drainage mesh can be incorporated on the upper face acting as a filter.

With "in-situ" shock pads, there are some sports surfaces with many hours of play a day where the drainage between areas of greater or lesser play become noticeable quite quickly .

Performance guarantee across the surface

One of the concerns of this invention is to guarantee uniform performance across the high performance shock pads and between its connectors.

For this propose the periphery shape of the high performance shock pads is a great contribution. This geometry means that in production it is possible to guarantee in the joint the same conditions of density and quantities of material that exist on the inside.

Some shock pads on the market try to include a drainage system by making some tears, others try to create a drainage net, creating different densities throughout the surface and consequently different behaviour, due to the size of the drainage channels. Because of these processes used in the prior art, the density of the joints is always different in each work.

The creation of a net of small, uniform channels and its outside geometric shape means for the high performance shock pads that the density is homogenous. The small channels are essential for the performance of the surface, acting as a spring, i.e. it is as if the surface was sitting on countless small springs.

In applying this kind of high performance shock pads on indoor wooden or derivatives floors the user finds the following data. Control of heat expansion

The high performance shock pads are made of rubber granules join together with rubber connections, which is why their elasticity and impact absorption is better than other techniques known in the prior art.

The indoor wooden and/or derivative floors are subject to controlled temperatures, but in many cases the pavilions do not have air conditioning and those that do have, only use it on days when there are official games meaning there are great temperature differences over the year.

For this application the ability to control heat expansion is extremely important for maintaining all the performance characteristics over the surface for a long period of time.

Installing the high performance shock pads in this kind of floor is made under the wood and it is confined to the size of the field.

Easy application

The ease of application was described earlier, here the developer shall just comment on the differences/advantages.

Installing the shock pads in rolls of foam requires care in checking the alignment and control of the joints. When being applied, there is a tendency for the corners to rise up if they are not fixed down. If pre-moulded surfaces are used the foam has connectors that have to be connected in a specific order and in the right hole. If the applier installs rubber pins under the floor he have to ensure that they are all the same distance from each other, which is a time-consuming and difficult task.

Creation of an air box to stop the wood from rotting

In the case of a wooden and/or derivative floor, even if the surface has been treated, it is still a natural compound and can rot without proper air circulation.

Due to the porous composition, the perforations and the small channels, surprisingly the high performance shock pads create an excellent circulation of air avoiding the appearance of moulds or fungus.

The foam on the market that is normally used does not offer this kind of air circulation. In the case of rubber pins, this kind of air circulation is possible.

Elimination of dampness

One of the serious problems that arise when using foams is the accumulation of dampness and its transfer to the wooden floor .

This invention creates an extremely effective air box so the circulation of the air eliminates this dampness.

Guarantee of maintaining the technical characteristics over a long period of time

One of the serious problems with foam surfaces is the degradation over time. It is part of their nature to lose elasticity after being used many times. Another fact that was noticed by appliers of this kind of surface is a notable dip in the surface in areas of greater use .

The nature of the composition of this invention means that this does not happen, or will only do so after many decades .

Athletics tracks and tennis courts

Adapting the density to improve athlete's performance

There are some kinds of sports where the surface has a very direct influence on athlete's performance and playability.

Shock pads for high performance flooring have to be able to be adapted to specific requirements.

Athletics tracks and tennis courts need to be hard and elastic .

Due to the high compaction capacity during the production of the high performance shock pads, high densities can be achieved that offer fairly high hardness, while its distinct shape means it is considerably elastic. In this kind of use, the present invention allows the elimination of the base drainage net.

Comfort surfaces

In this kind of surface, this invention stands out because of the use of recycled materials and lower costs to reach the same end. Safety surfaces

Playgrounds and/or similar

As the high performance shock pad is completely perforated, it is substantially lighter than existing shock pads for the same effect, as the others are practically solid.

The resin curing process uses heat. It is well known that rubber is a terrible heat conductor, but if the heat can be transmitted directly into the inside of the piece, curing times would be significantly shorter, and that is only possible by adopting the shape of this invention.

As it was previously said, the durability of this kind of pieces with this composition depends on the pressure used in the production. If this surface was not perforated it could not be pressed and it would not be possible to get low densities, leading to early degradation.

Another way to achieve the durability of this invention would be to use higher percentages of resin which would be much more expensive.

In summary, the shape that was adopted is essential for the success of this invention as regards the costs, given the reduction in the material applied.

Greater HIC with less thickness

In preliminary tests, the figures that were obtained mean there is a greater HIC with less thickness. Practical case

According to the technical data for surfaces known in the prior art with similar thicknesses, the HIC is 0.8 metres, while for this invention the figures are never less than 1.2 metres, 33% more. This result is only possible because of the shape that was adopted for this invention. The small channels help to support the impact acting as springs, and as the holes deform in all directions following the impact behave like shock absorbers, absorbing a significant amount of the impact forces.

Elimination of the need to dry the structural base

One of the limitations on applying this kind of surface is excessive dampness, which reacts with the binder quite quickly, reducing the performance and durability.

With this invention, there is no need to wait for the structural base to be dry since it is not recommended that this surface is glued to the base.

To apply the upper layer and taking into account that this will not be applied directly on the base, it can be done normally even if the structural base is damp. As with all good practice, the base must be clean so the surface is as regular as possible.

The maintenance or replacement of the upper layer does not imply that the shock pad has to be changed. With this invention, the shock pad works independently of the upper layer. This is only partially glued by the run-off of the glue that is incorporated in the mixture for the upper layer. Therefore it is fairly easy to separate the upper layer from the shock pad. The first step in the development of this invention involved defining the primary aspects and starting to make the idea come true. Here, the kind of composition was generically defined.

Then the adaptability of the shock pad to different kinds or requirements was defined.

After conducting some preliminary tests in moulds for ceramics, the developer came to the conclusion that the behaviour of the final piece was directly related with the granule size and pressure as shown in Figures 2 and 3.

Finding an optimum balance between elasticity and density is a constant objective. Point A in the two charts shown in Figures 2 and 3 gives us the best balance between Pressure and Granule size. Various shock pads were tested with different grain sizes of recycled rubber granules and different pressures, which were assessed by their impact absorption and deformation capacity.

Influence of the geometry in the performance

For the performance is highlighted from the prior art, it is necessary to consider that the objective is to create a piece that acts as the most efficient spring/shock absorber possible .

The fact that the developer was looking at a product produced from recycled rubber granules indicates that the elasticity of the rubber itself can be used for the spring effect, but some way has to be found to make it act like a shock absorber. In analysing some pieces made of the same material the developer noticed that the vertical deformation that it suffers does not dissipate the energy but returns it when it goes back to its original shape.

As it is illustrated in Figure 5, impact force ( Fi ) causes a deformation (a) in a piece with a thickness (e) and causes various forces of energy restitution and as we can see all point towards the centre of the body. As the restitution forces (F_n) are vectors when there is an angle, energy is dissipated.

Depending on the angle ( ) , the dissipated force (F₂) increases or decreases, as illustrated in Figure 4. The calculation is governed by the rules of trigonometry. I.e. the objective will be to find a way to make F₂ as big as possible .

The way to reach that objective is to have a shock pad that is completely perforated, with holes of any geometric configuration but equidistant and so the developer designed and produced a prototype.

Figure 4 represents extreme situations were only one or a few holes are mechanically strained. In reality this situations do not happen, because the size of the bodies that are going to be protected are big enough to always cover more than one hole and the diameter of the hole is small enough for this effect. Another reason is that this shock pad is used under another surface which will distribute the impact of the force over various holes as shown in Figure 5. With this design of the high performance shock pads, the shock absorber effect is managed by greater dissipation of energy than any other known prior art shock pads.

After studying some known prior art pieces with this kind of materials, the developer verified that different geometries and different thicknesses influenced a series of different elastic behaviours. In order to get the greatest homogenisation of densities throughout the piece, the developer opted for an innovative geometry with holes and a specific periphery shape as mentioned earlier.

Study into the influence of the geometry on production costs

As the high performance shock pad is completely perforated it manages to have a volume that is substantially lower than other existing surfaces for the same effect, since the other known prior art shock pads are practically solid.

One of the most important factors for the process is the time to cure the resins used as binders, which is directly related with the transfer of heat between the mould and the inside of the piece. It is well known that rubber is a bad heat conductor, but if the heat can be transmitted directly into the inside of the piece, curing times would be significantly shorter, and that is only possible by adopting the design of this invention.

In summary, the design that was adopted is essential for the success of this invention as regarding the processing costs, when compared with the costs of known state of the art shock pads . Ergonomic study

a. Weight factor

Depending on the thicknesses and densities that are requested, each square metre can weigh between 4 kg and 42 kg, with each high performance shock pads weighing no more than 21kg. b. Dimension factor

The dimensions depend on the interest of the final customer, however for ease of handling the maximum size is 1 square metre and in order that the floor can be laid by just one applier the developer opted for the dimensions of 1000x500 mm.

The preferential dimensions are:

- 500x500

- 1000x500

- 1000x1000

Packaging study

The product will be packed on palettes with the maximum square metres and wrapped in plastic film. The number of square metres per palette depends on the thickness of each plate .

The second step in the development of this invention was the water drainage study. Knowing that most of the floors that will be built on top of this shock pad will be outdoors, there is a need to build a water drainage system. Since the shock pad is completely perforated, it makes sense to create a net of small channels to connect all the holes. The small channels can be various shapes but it is preferably to make them half-round since being curved they would not create any localised tension in the pieces.

Surprisingly, adding these small channels was fundamental for the elasticity of the surface, making it more comfortable .

The third step in the development of this invention was the expansion control study. While studying prior art shock pads the developer noted a difficulty in overcoming the heat expansion of the materials.

One condition to create in order to overcome this difficulty is an expansion joint between the pieces, but as the kind of material used can present a considerable heat expansion, the expansion joint would have to be several centimetres, which meant that when the final layer is installed this joint would be visible with lower finish and could even behave in an undesirable manner.

To solve this situation and overcome the current problems, it was designed a high performance shock pad with a periphery of semi-circles and rounded edges which, in extreme cases of expansion allows that they can fit into one another.

A junction of a few millimetres is made by the connectors and, in conjunction with the geometry of a "half" of the geometric figures of the inside of the high performance shock pad s and the rounded edges, allows that in the case of great expansions, they touch each other and as they are made of elastic rubber, they start to fit into one another.

As was calculated and stated earlier, there can be high expansion between two surfaces.

Apart from the geometric shape of the periphery of the high performance shock pad, the high performance shock pad is completely perforated, allowing for internal expansion caused by the compression of the internal holes.

The forth step in the development of this invention was the study of the connections between the high performance shock pads. The connection of the high performance shock pad s has to be very easy to guarantee the distance of the expansion joint and at the same time be elastic enough to mould to heat expansion.

To meet these requirements, a new geometry comes up. As it was previously said, initially these pieces were to be integrated into the production of each high performance shock pad, but because of the complexity of the moulds and not having any guarantee of reliable production due to the different thicknesses, the developer decided to produce the connectors separately and then fix them on later.

The fifth step in the development of this invention was the study and inclusion of a geotextile or other drainage mesh. To make sure that the performance of the high performance shock pads is not affected by solid particles carried on leachate, a geotextile or other drainage mesh can be incorporated on the upper surface to act as a filter. If these solid particles block up the free spaces its performance will be diminished significantly.

The geotextile or other drainage mesh will be attached at the final production phase, for example through gluing or hot gluing.

The sixth step in the development of this invention was the optimisation of the density by modifying the geometry of the zones in contact with the structural base.

The seventh step in the development of this invention is its characterisation. This step will include all the characterisation studies so they can be included in the specifications .

The following claims highlight additional ways to the invention was made.

Claims

1. High performance shock pad comprising a perforated surface, with 97% to 80% of rubber to between 3% to 20% of binder, in weight and a net of small channels on its base that connect all the perforations and connectors (1) .

2. High performance shock pad according to the previous claim, wherein is used recycled rubber.

3. High performance shock pad according to the previous claims, comprising perforations with circular shape.

4. High performance shock pad according to the previous claims, comprising a periphery composed of semicircles with rounded shape edges.

5. High performance shock pad according to the previous claims, wherein the connectors (1) are made of the same high performance shock pad composition.

6. High performance shock pad according to the claims 1 to 4, wherein the connectors (1) are made of a composition based on vulcanized rubber mixture composed of equal parts in weight of virgin SBR and recycled rubber.

7. High performance shock pad according to the claims 1 to 4, wherein the connectors (1) are made of a vulcanized rubber mixtures with 25% to 75% of virgin SBR to between 75% to 25% of recycled rubber, in weight.

8. High performance shock pad according to the previous claims, comprising a geotextile or other drainage mesh on top of it.

9. The method for obtaining a high performance shock pad as described in claims 1 to 8, using the following steps:

- Mixing the rubber granules with the binder;

- Placing the mixture in a mould;

Applying pressure, temperature and time to the material in the mould and produce the shock pad;

- Mixing rubber granules with the virgin SBR;

- Placing the mixture in a mould;

Applying pressure, temperature and time to the material in the mould to produce the connectors;

- Joining together the shock pad with the connectors, producing the high performance shock pad;

- Packing the pieces;

- Identifying the packages;

- Shipping the product.

10. The method for obtaining a high performance shock pad according to the previous claim, comprising an additional step of placing a geotextile or other drainage mesh in the final phase of production.

11. The method for obtaining a high performance shock pad according to the previous claims 9 and 10, comprising the mixture of rubber and binder for between 3 and 6 minutes .

12. The method for obtaining a high performance shock pad according to claims 9 to 11, comprising a curing process lasting 3 to 10 minutes at temperatures of between 80°C and 160°C.

13. The method for obtaining a high performance shock pad according to claims 9 to 12, wherein is applied pressure between 0.1 and 25 MPa.

14. The method for obtaining a high performance shock pad according to claims 9 to 13, wherein the binder is a polyurethane resin.

15. Use of the high performance shock pad described in claims 1 to 8, applied under a wooden floor, safety and comfort surfaces, athletics tracks and tennis courts .