GB2540373A

GB2540373A - Abrasion durability testing device

Info

Publication number: GB2540373A
Application number: GB1512295.5A
Authority: GB
Inventors: John Bayes Thomas; James Armitage Zachary; Roger Smith David
Original assignee: Satra Tech Centre
Current assignee: Satra Tech Centre
Priority date: 2015-07-14
Filing date: 2015-07-14
Publication date: 2017-01-18
Also published as: WO2017009643A3; WO2017009643A2; GB201512295D0

Abstract

An abrasion durability testing device 100 for circulating abrasive particles in a liquid stored in a housing of an abrasion durability test system, the device comprising a body 105 having perforated sections 120, each perforated sectioncomprising an air inlet and an air outlet, air being drawn in from the air inlet and driven out from the air outlet to generate a stream of bubbles in the liquid for circulating the abrasive particles, the walls of at least some of the perforated sections are shaped such that the air outlets have wider openings than those of the air inlets. Preferably, the walls are sloped downwards from the outlets towards the inlets. The distance between two adjacent perforated sections is preferably such that, in use, the abrasive particles fall into the perforated sections without settling on the surface of the body; adjacent walls of two perforated sections may form a chevron shape. The walls are preferably at least partially concave and angled at about 45o to the surface of the body. Some of the perforated sections may have a frustoconical shape, a funnel shape or an octagonal shape. Also claimed is a system and method using such a device.

Description

Abrasion Durability Testing Device

FIELD OF INVENTION

This invention relates to an abrasion durability testing apparatus, system and a method for testing abrasion durability of a wearable element.

BACKGROUND OF INVENTION

Footwear, in particular hiking footwear and trainers, are subject to industry standard methods of testing to assess its water resistance and durability. Immersed flexing is a well-known industry wide used method to assess the water resistance of footwear under various conditions. During this test, the immersion level for the water and number of flexing cycles are varied in a systematic manner. The number of flexes can be equated to the distance moved.

However, the water used in immersed flexing testing is distilled water, and although this allows for the generation of reliable and repeatable results from routine testing, it is not representative of some of the harsh conditions encountered by high performance footwear such as military boots, hiking footwear and trainers worn for cross-country or off-road running. These types of footwear are often exposed to long periods of immersion in muddy water, and subject to the ingress of sand and grit particles as well as water. This attack by sand and grit can introduce abrasive elements into the footwear, greatly accelerating wear and tear.

SUMMARY

There is a need to test the footwear in harsher environments. The inventors have developed a test technique that recreates the effect of immersed flexing in muddy or silty water to establish footwear durability under conditions that could greatly accelerate wear due to abrasion.

According to one aspect of the invention, there is provided an abrasion durability testing device for circulating abrasive particles in a liquid stored in a housing of an abrasion durability test system, the device comprising: a body comprising perforated sections, each perforated section comprising an air inlet and an air outlet. The device is configured such that air is drawn in from the air inlet and air is driven out from the air outlet to generate a stream of bubbles in the liquid for circulating the abrasive particles. Walls of at least some of the perforated sections through a thickness are shaped such that the air outlets have wider openings than those of the air inlets.

The walls may be sloped down from the air outlets towards the air inlets. In other words, the walls of the perforated sections are slanted in respect of a longitudinal surface of the body. The perforated sections are formed across the longitudinal surface of the body and the abrasive elements or particles may try to settle (but they substantially do not) on the longitudinal surface. The body may be shaped such that there are no perforated sections (or cells) on a vertical surface (along the thickness of the body) transverse to the longitudinal surface so that air is flown substantially vertically to the longitudinal surface of the body.

The lateral distance between two adjacent perforated sections on a surface of the body may be such that, in use, the abrasive particles fall into the perforated sections without settling on the (longitudinal) surface of the body. The lateral distance between at least some of two adjacent perforated sections on the surface of the body may be such that adjacent walls of said two perforated sections form a substantially chevron shape. It is possible that all the perforated sections may have chevron shaped edges or some of the perforated sections have the chevron shaped edges and some have substantially flat edges (but with a minimal distance). Advantageously, the chevron shaped edge for the lateral distance between the two perforated sections enable the abrasive element to always fall into the perforated section’s air inlet so that the abrasive element can be substantially continuously circulated. It would be appreciated that the lateral distance between two air outlets may not have a chevron shape. In such a case the lateral distance may be sufficiently small that the abrasive material falls onto the air inlet using the slanted walls of the perforated sections. In this example (when the edges are not exactly the chevron shaped), the lateral distance between two perforated sections may be between about 1 mm and about 2.5 mm, preferably between about 1.5mm and about 2mm. The combinational effect of the sufficiently small lateral distance (or almost no lateral distance by having chevron edges) and the slanted walls may enable the abrasive material to fall onto the air inlets so that the abrasive material can be thrown up by the even stream of bubbles generated by the testing device. This may enable the abrasive material to be continuously circulated in the water tank to conduct the abrasion durability test on a wearable element such as footwear.

The walls may be angled about 45° in respect of a surface of the body. It would be appreciated that other angles are also possible but a substantially right angle should be avoided.

The lateral dimension of the air inlet may be controlled to provide an air pressure for circulating the abrasive particles. The lateral dimension of the air inlet is about 0.7 mm, preferably it may be between about 0.6 mm and 0.8mm.

The device may be configured to produce an air pressure of about 2.5 bar. Although other air pressure amount may be applicable.

The walls may be at least partially concave. The slanted walls may not have a substantially straight shape but can also have a concave shape.

At least some of the perforated sections may have a substantially frusto-conical shape in which a base of the frusto-conical shape corresponds to the air inlets of the perforated sections. Alternatively, at least some of the perforated sections may have a substantially funnel shape in which the narrow opening of the funnel shape corresponds to the air inlets of the perforated sections. Alternatively, at least some of the perforated sections may have a substantially octagonal shape. The perforated sections may have a substantially circular shape. It would be appreciated that the perforated sections can have other types of shapes as long as they have air inlets with narrower opening than that of the air outlets.

The device may further comprise a base section coupled with the body. The device may further comprise an end section coupled with the base section and the body.

The end section, the base section and the body may be attached to one another using an adhesive material.

The base section may comprise a recessed portion such that when the base section and body are coupled together an air chamber is formed between the recessed portion and the air inlets of perforated sections of the body.

The end section may comprise a hole for supplying air through the end section and when the body, the base section and the end section are coupled together the hole is connected to the air chamber so that air can be drawn in from the hole of the end section through the air chamber to the air inlets of the perforated sections of the body to generate the stream of bubbles. The hole may have a L shape so that an air outlet of the hole connects to the air chamber.

The end section may comprise a surface adjacent to the air outlets of the perforated section, the surface of the end section being angled in the substantially same angle as the walls of the perforated sections of the body. This enables the abrasive elements to fall into the perforated sections rather than settling on the surface of the end section. It is also possible to dissemble the device by separating the body, base section and end section which helps to clean the device more efficiently.

The device may further comprise a weight attached to the base section. The weight may be strips of lead roof flashing. The weight enables the testing device to be kept at the bottom of the water tank.

In embodiments there is also provided an abrasion durability test system for a wearable element. The system comprising: a housing at least partially filled with a liquid; abrasive particles mixed with the liquid; the abrasion durability testing device described above, the device being located on a base surface of the housing or forming a base surface of the housing; and an air supply regulator for supplying air through the abrasion durability testing device to generate a stream of bubbles to continuously circulate the abrasive particles throughout the liquid stored in the housing.

The system may further comprise a plurality of air conduits connected between the air supply regulator and the testing device.

The housing may comprise a water tank and the liquid may be water and the volume of the liquid may be about 10 litre.

The abrasive particles may comprise aluminium oxide powder. The weight of the aluminium oxide powder may be about 600 gram.

The system may further comprise a plurality of the abrasion durability testing devices located on the base surface of the housing. The dimension of the surface of the housing is adjusted to adequately fit the plurality of testing device with no gaps remaining there between.

The system may be configured to generate an even stream of bubbles. The even stream of bubbles is capable of generating a sufficient force to carry the abrasive material upwards in the tank. When the abrasive material tends to fall down towards the surface of the device due to the gravitational force of the abrasive material, the even stream of bubbles can carry them upwards again to ensure continuous circulation throughout the water.

The abrasion durability testing device may be attached with the base surface of the housing by means of an adhesive material.

When the abrasion durability testing device forms the base surface of the housing, walls of the housing may be integrated with the abrasion durability testing device.

The walls of the housing may comprise the same material as that of the abrasion durability testing device.

In embodiments, the invention also providesa method for manufacturing an abrasion durability testing device for circulating abrasive particles in a liquid stored in a housing of an abrasion durability test system, the method comprising: forming a body; forming perforated sections through the body, each perforated section comprising an air inlet and an air outlet so that air can be drawn in from the air inlet and driven out from the air outlet to provide a stream of bubbles in the liquid for circulating the abrasive particles; shaping walls of at least some of the perforated sections through a thickness such that the air outlets have wider openings than those of the air inlets.

The method may further comprise forming a base section comprising a recessed section.

The method may further comprise forming an end section. The method may further comprise attaching the end section, the base section and the body to one another using an adhesive material. The method may further comprise forming an air chamber between the recessed portion and the air inlets of perforated sections of the body when the base section and body are coupled together. The method may further comprise forming a hole on the end section for supplying air through the end section and when the body, the base section and the end section are coupled together the hole is connected to the air chamber so that air can be drawn in from the hole of the end section through the air chamber to the air inlets of the perforated sections of the body to generate the stream of bubbles.

The body, base section and the end section may be manufactured using a 3D printing technique. The perforations of the air inlets may be formed using a hand-drill.

Alternatively the body, base section and the end section may be manufactured using a computer numerical control (CNC) machine.

Alternatively the body, base section and the end section may be manufactured using a moulding technique.

In embodiments, the invention also provides a method of testing abrasion durability of a wearable element using the abrasion durability test system as described above, the method comprising the following steps in sequence: positioning the abrasion durability testing device at the base surface of the housing; switching the air supply regulator on; filling the housing with a predetermined amount of water; adjusting the testing device with a predetermined air pressure; pouring a predetermined amount of abrasive particles into the water; placing the wearable element at a predetermined height into the water and abrasive particles in the housing; adding a predetermined amount of foam suppressant to the water to minimise foaming; and running the test for a predetermined number of cycles so that the wearable element is flexed during the test.

The foam suppressant may be vegetable oil.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described in more detail and, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1a to 1d illustrate computer aided drafting (CAD) representations for top, perspective, side and cross-sectional views of an abrasion durability testing device;

Fig.2 illustrates a schematic representation of the geometrically spaced perforations through a thickness of a body of the abrasion durability testing device;

Fig.3 shows an alternative CAD representation of the abrasion durability testing device of Fig. 1;

Fig.4 shows a printed abrasion durability testing device and a 3D printer’s support board;

Fig.5 shows an assembled unit of the abrasion durability testing device;

Fig.6 shows pneumatic tubes, with cable-tied junctions for supplying air through the testing device;

Fig.7 shows a hole on the abrasion durability testing device in which a pneumatic tube can be fitted to supply air through the testing device;

Fig.8 shows a plan view of the geometrically spaced perforated sections on the abrasion durability testing device;

Fig.9 illustrates an abrasion durability testing system in which a water tank with the testing devices are in place, and an air supply is switched on;

Fig 10 shows air being diffused through the testing device generating a stream of bubbles;

Fig 11 shows footwear before and after a period of immersed flexing with circulating grit/abrasive particles;

Fig 12 illustrates a magnified view of the effects of the abrasive grit/particles on a footwear material;

Fig 13 illustrates a mesh panel of the footwear product being worn through as a result of a flexing action of a foot, compounded by the presence of the grit/abrasive material in the water and also between the footwear and a hose;

Fig 14 shows a considerable amount of grit being collected inside the shoe during the test;

Fig 15 shows un-tested and tested footwear, showing the discoloration that has taken place, as well as the general fraying of textiles;

Fig 16 shows laces on an un-tested and a tested trainer, and

Fig 17 shows an alternative embodiment of the abrasion durability testing device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Description of the Abrasion Durability Testing Device

Fig. 1a to 1d illustrate computer aided drafting (CAD) representations for top, perspective, side and cross-sectional views of an abrasion durability testing device. Here the abrasion durability testing device can also be referred as a bubble baffle bed. The device 100 includes a geometrically arranged series of cells or perforated sections 120 across a longitudinal surface of a body (or an upper bed) 105. The perforated sections 120 extend in a substantially transverse direction to the longitudinal surface and extend through a thickness of the body 105. The device 100 also includes a base section (or a lower bed) 110. The base section 110 includes a recessed section (not shown) such that that when the body 105 is fitted on top of the base section 110 a chamber (not shown) is created between the body 105 and base section. The device also includes an angled end section 125 with a fixture 130 being fitted to a side of both body 105 and base section 110. The angled end section 125 includes an L shaped hole 115 shaped to accept an air supply and to diffuse it in the chamber to turn it into an even stream of bubbles.

Fig. 2 illustrates a schematic representation of the geometrically spaced perforation sections through a thickness of the body of the abrasion durability testing device. Each perforation section (or cell) includes an air inlet 180 and an air outlet 190. The lateral dimension of each air outlet 190 is higher than that of each air inlet 180. Walls 165 of each perforated section are sloped or slanted down from the air outlet 190 towards the air inlet 180. The walls 165, 185, 195 are shaped such that each perforated section is tapered from the air outlet 190 to the air inlet 180. The lateral distance between at least some of two adjacent perforated sections on a surface 205 of the body is such that adjacent walls 185, 195 of said two perforated sections form a substantially chevron shape. The lateral distance between two adjacent perforated sections on the surface of the body is such that, in use, the abrasive particles or elements fall into the perforated sections without settling on the surface 205 of the body. This enables the abrasive elements to be circulated in the water tank continuously. It would be appreciated that for some of the perforated sections, the lateral distance between two adjacent sections may not be substantially zero (or not having the chevron shape), but the lateral distance is generally sufficiently low so that the abrasive elements do not have sufficient space to settle on the surface 205. The sloped or slanted walls of the perforated sections further enables the abrasive elements to fall into directly on the air inlet from where bubble streams are generated. Thus the bubble streams are capable of continuous circulations of the abrasive element throughout the water tank (or housing).

Manufacturing of the Abrasion Durability Testing Device

It is desirable that some means of introducing movement in the water tank to keep the grit/abrasive element in circulation during the flex testing of a wearable element (e.g. footwear, gloves etc). The proposed test is intended as follows - during the flex testing, a quantity of abrasive element/grit (aluminium oxide, as used in several industry standard abrasion tests) would be kept circulating in the water tank by means of air diffused into the water through a plurality of (three) pneumatically fed abrasion durability testing device (or “bubble baffles”) placed at the bottom of the water tank.

In one example, the abrasion durability testing device is designed using a CAD technique. Fig. 3 shows an alternative CAD representation 200 of the abrasion durability testing device of Fig. 1. After generating CAD files for the designs of the devices (baffles), the models are 3D printed in Acrylonitrile-Butadiene-Styrene (ABS) material in sections so that they could be cleaned thoroughly (e.g. by jet washing) and for the air inlet (cavity) within the baffles to be thoroughly cleared of any debris before being assembled. ABS is a production grade thermoplastic used in various industries for prototyping using 3D printers. Fig.4 shows a printed abrasion durability testing device 300 placed on a 3D printer’s support board 310. When the 3D printed files are physically printed, the cells do not have perforated air inlets. The air inlets can be achieved by using a hand-drill.

According to one embodiment of the invention, three of these testing devices or “bubble baffles” are provided and are placed side by side to fill the floor of the tank. Although three baffles are used in the current application the number of baffles varies depending on the actual size of the baffles and the water tank. In this example, two of the bubble baffles are 120 mm wide and one is 130 mm wide. The bubble baffles sizes can be varied to minimise the number of joints.

Fig. 5 shows an assembled unit of the abrasion durability testing device 100. The body (upper bed) 105, the base section (the lower bed) 110 and the (angled) end section 125 are bonded together with two-part epoxy resin 150. Other types of waterproof adhesives such as cyanoacrylate can be used to assemble the unit.

Fig. 6 shows pneumatic tubes 505, with cable-tied junctions for supplying air through the testing device. A pneumatic air supply is fed through a small regulator, and from there it is split into three small-bore tubes 505 (approximately 4mm external diameter) which fit into corresponding holes 115 (see Fig. 6) in each of the 3-D printed baffle base sections 110. These tubes 505 supply air to fill the chambers within, and this becomes a stream of small, diffused bubbles. Fig.7 shows a hole 115 on the abrasion durability testing device in which a pneumatic tube can be fitted to supply air through the testing device.

Test Scenario

Some initial tests showed that simply adding sand or an abrasive material to the water tanks is ineffective as it quickly falls out of suspension and settles at the bottom of the tank. The aim of the proposed testing is to introduce movement in the water tanks and to keep the grit in circulation during the flex testing such that the density of the grit in the water is kept substantially constant.

Fig. 8 shows the abrasion durability testing device in which a plan view of the perforated sections (or cells) 120 are shown. The perforated sections 120 comprise air inlets 160. In one example, the air inlets 160 are circular holes, each one hand finished with a hand drill to ensure a perfect circulation of air. The movement of the grit in the water depends on air supply and size of the air inlets in the perforated sections of the baffles. Unless the inlets (holes) are suitably sized to allow easy circulation and cleaning, and the air pressure is maintained at a suitable level, they can become blocked with grit. This would ultimately mean that the circulation of grit would be impaired, leading to further material falling out of suspension and greater build-up on top of or in the baffle holes. In order to overcome this, the size (or lateral dimension) of the air inlets (holes) can be about 0.7mm in diameter. The design of the bubble baffles prevent the settling of the grit or the abrasive material on the bed. In the perforated section (cell) 120, the edges 175 are inclined at an angle of about 45 degrees or more with respect to a horizontal surface of the bed. The edges 175 between the perforated sections (cells) can be substantially sharp (or chevron shaped) such that the grit does not settle on the edges 175. In one example, the pressure on the air supply is set between at 2.5 bar (250kPa), as this can be a suitable pressure for keeping the grit in circulation whilst minimising splashing and overflows. The air pressure value can vary depending on the size of the cavities or type of the abrasive material used. In embodiments, other abrasive materials can also be used, for example, sand (or sharp sand), various abrasive powders such as carbides and oxides. The abrasive material can also be concrete dust.

In order to create the required concentration of waterborne grit, 600g of aluminium oxide powder is added to a tank full of 10 litres of water. This gives a good degree of opacity as well as abrasive feel to the water, although this ratio could be adjusted and tailored to individual requirements. Other types of abrasive material with higher abrasive power such as builders’ sharp sand could also be used.

Fig. 9 illustrates an abrasion durability testing system in which a water tank 900 with the testing devices 905 are in place, and an air supply 910 is switched on. The system also includes water 915 filled in the water tank and abrasive element mixed with the water 915. Fig. 10 shows air being diffused through the bubble baffles bed generating a bubble stream 1010.

The ABS material from which these baffles are printed may float in the water, more so when the air supply is engaged and the air inlets are filled with air. In order to counteract this natural buoyancy, strips of lead roof flashing were cut to the appropriate size and then adhered to the underside of each section of baffle. This ensures that the baffles remained at the bottom of the tanks. The bubble baffles can be made from any material for example, aluminium, or material used to build the water tank itself. In examples, two types of materials can be used, i.e. a transparent acrylic and a fiberglass. The transparent acrylic material can be used readily to the incorporation of the testing device (bubble baffles).

During the testing, the stream of bubbles produced cause the water to become very turbulent, which may cause a great deal of splashing. This is not necessarily a problem for the footwear (or a wearable element) being tested, as this test is not intended as a leak resistance test but this splashing needs to be guarded against the equipment itself. Additionally, there are a number of metal fixtures and electronic components near the top of the water tank, these needs protecting against splashes of water especially as the water contains abrasive and potentially corrosive elements.

To overcome the splashing problem mentioned above, a natural foam suppressant (vegetable oil) is added to the water, which greatly reduces the severity of the foaming and bubbling and the degree to which water and contaminants are splashed onto the equipment. Whilst it is possible that the addition of an oil to the test water may have additional effects on the aesthetics of the test footwear, it is presented at such a low concentration (5ml per 10 litres) that any effect it will have on the footwear will likely be vastly outweighed by the effect of the abrasive grit present in the water. It would be appreciated that other foam suppressant materials can also be used.

Fig. 11 to 16 show the effects of waterborne abrasive elements on a trainer, used for early test verification. Fig. 11 shows footwear before 1110 and after 1115 a period of immersed flexing with circulating grit. As it can be seen from the figures the shoe 1115 is covered with grit after testing. Fig. 12 illustrates a magnified view of the effects of the abrasive grit/particles on the footwear material. Fig. 13 illustrates a mesh panel 1310 of the footwear product being worn through as a result of a flexing action of a foot, compounded by the presence of the grit/abrasive material in the water and also between the footwear and a hose. Fig. 14 shows a considerable amount of grit 1410 being collected inside the shoe during the test. Fig 15 shows un-tested 1510 and tested footwear 1515, showing the discoloration that has taken place, as well as the general fraying of textiles. The footwear that is tested had its insock removed before testing. This test can be used to assess footwear’s colour fastness under conditions of use in dirty or muddy water. Fig. 16 shows laces on an un-tested 1610 and a tested trainer 1615. The inventors anticipate that longer term testing would cause abrasive damage sufficient to snap the laces.

Fig. 17 shows an alternative embodiment of the abrasion durability testing system in which water tank 600 is shown with integrated abrasion durability testing device (bubble baffle bed) 600 with substantially circular perforated sections (cells) 610 with air inlets (cavity) 615. This bubble baffle bed is made from the same material as the water tank and does not require any lead plates at the bottom. The edges joining the adjacent perforated sections (cells) are sharper in comparison to the sections (cells) with square shaped perforations. The objective of the bubble baffle bed is such that the grit should not settle on the bubble baffle bed. This design reduces (minimises) the surface area of the flat surfaces on the bed and prevents the settling of the grit. The air is pumped at the bottom of the tank through the side of the tank as this arrangement reduces (eliminates) the use of small bore tubes. It will be noted that Fig. 17 is a schematic representation of the plan view of the circular perforated sections - it is not to be scaled. The plan view shows some overlapped edges between two perforated sections. The overlap is the representation of the reduced (or minimised) space between two perforated sections so that the abrasive material cannot settle on the surface of the device.

During the test, some of the grit may fall out of suspension despite the airflow, and some lodges in small gaps between the side of the tank and the edges of the baffles. Some of the baffles can be slightly shorter in length, so that they may not entirely span the width of the water tanks, leaving fewer small gaps in which sediment can become trapped. Larger gaps should allow the sediment to move back into circulation.

There is a considerable evaporative loss of water during the course of the test due to the bursting of bubbles and spraying of water. The tank will need topping up periodically. The bubble baffles with the air inlet (cavity) size with the diameter of 0.7 mm are sufficient to run the test up to 3 to 4 days since the cavities do not clog up during this period.

During initial testing, it showed that there was a significant take-up of grit/abrasive material by the footwear and hose, as evidenced by clearer water towards the end of such testing. This suggests that mass gain measurements would be a most useful accompaniment to the results from this testing work. Such measurements would give manufacturers a most useful insight into the product’s ability to resist the ingress of contaminants.

During regular testing to TM 230, water ingress into the footwear is usually minimal. In this test, however, the water level is very high, leading to almost immediate saturation of the footwear. Thus, a waterproof cover is required for the test foot-form and for the associated mechanism.

It should be pointed out that this test does not assess the footwear’s leak resistance, as the water is not static at a pre-determined level above the featherline or vamp (as in standard testing) but the water is frothing and foaming. In this particular case, water will inevitably work its way up and into the footwear, unless it is very high legged, which would not ordinarily happen during standard immersed flexing tests. In this proposed testing, the footwear’s ability to withstand abrasion and other associated damage caused by immersed flexing, and the action of the grit circulating within the turbid water is being tested.

Test results would cover aspects such as the extent of wear, whole shoe aesthetics, the continued functionality of any closure system, durability of stitching, sole adhesion and perhaps the ease of cleaning after use.

One possible method of testing the footwear is as follows: 1. Set up the test equipment (STM 505) as per the requirements of TM230, but do not yet put the test footwear onto the footform. 2. Place a suitably durable waterproof cover on the footform that will be used. A waterproof sock is ideal, but tough plastic bags may suffice. 3. Weigh the footwear to the nearest 0.1g. 4. Fit the test footwear to the footform, and fasten as appropriate. 5. Position the bubble baffles in place at the bottom of the tank, and connect each branch of the airline to the corresponding hole in each baffle. 6. Switch on the pneumatic air supply and check that all fittings are secure and that there are no leaks. 7. Fill the tank with 10 litres of tap water. 8. Adjust the air pressure for the baffle supply to about 2.5 bar, and ensure that each baffle is functioning correctly, and that all fittings are secure. 9. Carefully pour 600g of aluminium oxide powder into the tank, distributing it equally across the baffles. 10. Lower the footwear into the tank and start the test in the usual way. 11. After a few minutes, add 1tsp of suitable foam suppressant material (e.g. vegetable oil) to the water, to minimise foaming. 12. Run the test for the desired number of cycles. 13. Raise the shoe from the water after every 10,000 cycles, and visually inspect the shoe without removing it from the footform. Note any obvious damage each time. 14. Monitor the water level throughout the test, and top up the tank with water if necessary. 15. At the end of the test period, remove the footwear and inspect if for damage, recoding anything of note. Take photographs as appropriate. 16. Condition the test footwear at laboratory conditions for 24 hours, and then weigh it. Note any mass gain. 17. Empty the water from the tanks after each test, and thoroughly clean the tanks, baffles and pipework to remove any leftover grit.

In the above steps, the term “footform” refers to a means of flexing the toe of the footwear capable of achieving an angle of up to (25+2)° with respect to a base at a rate of (60 ± 6) flexes per minute. The toe at rest lies at (6 ± 2)° with respect to the base. The flexing mechanism applies a vertically upwards moment of (37 ± 5) Nm to the fore part of a sample about a flexing line.

The method and apparatus described here can be applicable to other types of protection wear such as footwear for military shoes, beach shoes, mountain shoes, hand gloves and footwear for marine applications.

Footwear for watersports such as kayaking and canoeing is manufactured to be lightweight, quick-drying, and with robust fastening devices to promote a snug fit, so as to exclude water-borne contaminants. Testing of this nature, with mass-gain measurements, would be most useful for this kind of footwear.

It would be appreciated that STM505 (mentioned in the description above) refers to a dynamic footwear water resistance tester and TM230 is a whole-shoe test designed to assess the completed footwear for resistance to water penetration into the volume occupied by the foot.

No doubt many other effective alternatives will occur to the skilled person. It will be understood that the invention is not limited to the described embodiments and encompasses modifications apparent to those skilled in the art lying within the scope of the claims appended hereto.

Claims

CLAIMS:

1. An abrasion durability testing device for circulating abrasive particles in a liquid stored in a housing of an abrasion durability test system, the device comprising: a body comprising perforated sections, each perforated section comprising an air inlet and an air outlet, wherein the device is configured such that air is drawn in from the air inlet and air is driven out from the air outlet to generate a stream of bubbles in the liquid for circulating the abrasive particles; wherein walls of at least some of the perforated sections through a thickness are shaped such that the air outlets have wider openings than those of the air inlets.

2. The device according to claim 1, wherein said walls are sloped down from the air outlets towards the air inlets.

3. The device according to claim 1 or 2, wherein the lateral distance between two adjacent perforated sections on a surface of the body is such that, in use, the abrasive particles fall into the perforated sections without settling on the surface of the body.

4. The device according to claim 3, wherein the lateral distance between at least some of two adjacent perforated sections on the surface of the body is such that adjacent walls of said two perforated sections form a substantially chevron shape.

5. The device according to any preceding claim, wherein said walls are angled about 45° in respect of a surface of the body.

6. The device according to any preceding claim, wherein said walls are at least partially concave.

7. The device according to any preceding claim, wherein the lateral dimension of the air inlet is controlled to provide an air pressure for circulating the abrasive particles.

8. The device according to claim 7, wherein the lateral dimension of the air inlet is about 0.7 mm.

9. The device according to claim 7 or 8, being configured to produce an air pressure of about 2.5 bar.

10. The device according to any preceding claim, wherein at least some of the perforated sections have a substantially frusto-conical shape in which a base of the frusto-conical shape corresponds to the air inlets of the perforated sections.

11. The device according to any one of claims 1 to 9, wherein at least some of the perforated sections have a substantially funnel shape in which the narrow opening of the funnel shape corresponds to the air inlets of the perforated sections.

12. The device according to any one of claims 1 to 9, wherein at least some of the perforated sections have a substantially octagonal shape.

13. The device according to any preceding claim, further comprising a base section coupled with the body.

14. The device according to claim 13, further comprising an end section coupled with the base section and the body.

15. The device according to claim 14, wherein the end section, the base section and the body are attached to one another using an adhesive material.

16. The device according to any one of claims 13 to 15, wherein the base section comprises a recessed portion such that when the base section and body are coupled together an air chamber is formed between the recessed portion and the air inlets of perforated sections of the body.

17. The device according to claim 16, wherein the end section comprising a hole for supplying air through the end section and when the body, the base section and the end section are coupled together the hole is connected to the air chamber so that air can be drawn in from the hole of the end section through the air chamber to the air inlets of the perforated sections of the body to generate the stream of bubbles.

18. The device according to any one of claims 14 to 17, wherein the end section comprises a surface adjacent the air outlets of the perforated section, said surface of the end section being angled in the substantially same angle as the walls of the perforated sections of the body.

19. The device according to any one of claims 13 to 18, further comprising a weight attached to the base section.

20. An abrasion durability test system for a wearable element, the system comprising: a housing at least partially filled with a liquid; abrasive particles mixed with the liquid; the abrasion durability testing device according to any preceding claim, the device being located on a base surface of the housing or forming a base surface of the housing; and an air supply regulator for supplying air through the abrasion durability testing device to generate a stream of bubbles to continuously circulate the abrasive particles throughout the liquid stored in the housing.

21. The system according to claim 20, further comprising a plurality of air conduits connected between the air supply regulator and the testing device.

22. The system according to claim 20 or 21, wherein the housing comprising a water tank and the liquid is water and the volume of the liquid is about 10 litre.

23. The system according to claim 20, 21 or 22, wherein the abrasive particles comprising aluminium oxide powder.

24. The system according to claim 23, wherein the weight of the aluminium oxide powder is about 600 gram.

25. The system according to any one of claims 20 to 24, further comprising a plurality of the abrasion durability testing devices located on the base surface of the housing.

26. The system according to any one of claims 20 to 25, wherein the system is configured to generate an even stream of bubbles.

27. The system according to any one of claims 20 to 26, wherein the abrasion durability testing device is attached with the base surface of the housing by means of an adhesive material.

28. The system according to any one of claims 20 to 27, wherein when the abrasion durability testing device forms the base surface of the housing, walls of the housing are integrated with the abrasion durability testing device.

29. The system according to claim 28, wherein the walls of the housing comprise the same material as that of the abrasion durability testing device.

30. A method for manufacturing an abrasion durability testing device for circulating abrasive particles in a liquid stored in a housing of an abrasion durability test system, the method comprising: forming a body; forming perforated sections through the body, each perforated section comprising an air inlet and an air outlet so that air can be drawn in from the air inlet and driven out from the air outlet to provide a stream of bubbles in the liquid for circulating the abrasive particles; shaping walls of at least some of the perforated sections through a thickness such that the air outlets have wider openings than those of the air inlets.

31. The method according to claim 30, further comprising forming a base section comprising a recessed section.

32. The method according to claim 31, further comprising forming an end section.

33. The method according to claim 32, further comprising attaching the end section, the base section and the body to one another using an adhesive material.

34. The method according to claim 33, further comprising forming an air chamber between the recessed portion and the air inlets of perforated sections of the body when the base section and body are coupled together.

35. The method according to claim 34, further comprising forming a hole on the end section for supplying air through the end section and when the body, the base section and the end section are coupled together the hole is connected to the air chamber so that air can be drawn in from the hole of the end section through the air chamber to the air inlets of the perforated sections of the body to generate the stream of bubbles.

36. The method according to any one of claims 32 to 35, wherein the body, base section and the end section are manufactured using a 3D printing technique.

37. The method according to claim 36, wherein the air inlets are formed using a hand-drill.

38. The method according to any one of claims 32 to 35, wherein the body, base section and the end section are manufactured using a computer numerical control (CNC) machine.

39. The method according to any one of claims 32 to 35, wherein the body, base section and the end section are manufactured using a moulding technique.

40. A method of testing abrasion durability of a wearable element using the abrasion durability test system of any one of claims 20 to 29, the method comprising the following steps in sequence: positioning the abrasion durability testing device at the base surface of the housing; switching the air supply regulator on; filling the housing with a predetermined amount of water; adjusting the testing device with a predetermined air pressure; pouring a predetermined amount of abrasive particles into the water; placing the wearable element at a predetermined height into the water and abrasive particles in the housing; adding a predetermined amount of suppressant material to the water to minimise foaming; and running the test for a predetermined number of cycles so that the wearable element is flexed during the test.

41. The method of claim 40, wherein the suppressant material comprises vegetable oil.

42. An abrasion durability testing device, an abrasion durability test system, a method for manufacturing the abrasion durability testing device, substantially as hereinbefore described with reference to and as illustrated, in the accompanying drawings.