GB2321224A

GB2321224A - Device for testing tyre beads

Info

Publication number: GB2321224A
Application number: GB9721834A
Authority: GB
Inventors: Klaus Hanebuth; Klaus Kleinhoff
Original assignee: Continental AG
Current assignee: Continental AG
Priority date: 1996-10-23
Filing date: 1997-10-16
Publication date: 1998-07-22
Anticipated expiration: 2017-10-16
Also published as: GB2321224B; GB9721834D0; FR2754896A1; DE19643762A1; DE19643762C2

Abstract

In a device for testing the bead characteristic of a vehicle tyre by measuring the radially-acting resistive force exerted by the tyre bead on annularly-disposed radially movable segments 4 the segments have surfaces 5 provided for contact with the seat surface 6 of the tyre bead which extend at an inclination # to the axial direction A. This inclination preferably corresponds to that of the seat surface 6 of the tyre and/or the contact surface of the rim upon which the tyre is to be mounted. The radially inner ends of the surfaces 5 have stops 9 to locate the tyre beads as segments 14.1, on to which the tyre is placed by carrying means 15, are raised. At least part of the surface of the stops 9 may be inclined with respect to the radial direction, for example by 15 degrees (Figure 10).

Description

2321224 Device for Testing the Bead Characteristic of a Vehicle Tyre The

invention relates, according to the preamble of claim 1, to a device for testing the bead characteristic of a vehicle tyre by measurement of the radially-acting resistive force exerted by the tyre bead on the at least 3, preferably 6 to 9, spreadable segments of the device located in a ring shape, in dependence on the displaceable - diameter of the ring segments and thus of the bead expansion, the segments having a surface extending at an inclination to the axial, which is provided for contact with the likewise roughly axiallyextending seat surface of the tyre bead. The movements of the segments radially outwards, i.e. the spreading of the segment ring, compels the tyre bead to adopt a larger inner diameter; it responds to this compulsion with a compressive effect radially inwards.

The power/deformation diagram constructed as always in detail - as a rule the sum of all radial forces applied via the respectively set bead inner diameter is entered is known as the bead characteristic. The person skilled in the art recognises, after a glance at the bead characteristic of a tyre, the placing of the same in the - 2 area of the competitive requirements "throw -off security" and "burst pressure" on the one hand and ",ease of assembly" on the other hand. Furthermore, the bead characteristic enables assessment of the alteration in these competitive properties via alterations in the rim diameter and thus influences the tolerance requirements imposed on the rim manufacturers.

If the bead seat is %'too taut" i.e. if its pressure on the rim is too great, then the tyre is either difficult to fit or incapable of being fitted; the worst case in this direction is that in which a fitter pushes the tyre with such force over the rim flange or the hump that the carcase layers constructed under the rim core are damaged.

If the bead seat is "too loose" then in the case of powerful braking, the tyre can rotate relative to the rim, so that the balancing is no longer true, or in particular in connection with abrasions on kerb stones or incorrect air pressure, the tyre can be thrown off from the rim.

Generally, more rim tolerance can be coped with if the power increase extends in a flatter curve via the deformation, i.e. the expansion behaviour of the bead and thus in particular of the bead core is gentler. However, 3 then also the clear inner diameter of the bead must be selected as smaller, so that in all circumstances sufficient pressure on the rim is maintained in the tolerated range of rim diameter.

Frequently during running in of a different or entirely new tyre series in an existing line of manufacturing devices, or after the introduction of new manufacturing devices for tyres, the characteristic of each bead is tested, until the measurements in core winding, carcase construction, bead covering with rubber and selection of rubber hardness and adjustment thereof are co-ordinated with one another in such a way that the characteristic is correct and corresponds both to the safety and to the fitting requirements.

It is known from DE-PS 38 14 646 C2 to impart to the clamp jaws which have to spread the bead, a crosssectional profile in the manner of a rim which is suitable for fitting with the tyre to be tested. As known, rims for automobiles have an inclination of roughly S' and those for most trucks one of about 150 to the axial. With the friction pairings available for some time now, with the 15' inclination, slippage of the tyre beads axially inwards occurs. With both inclinations, also the 5' inclination, reproducibility of the test position is poor. Consequently, upon repeated measurement of the same bead, slightly different characteristics repeatedly occur.

Therefore, the inventors have set themselves the object of improving the reproducibility of measurements of bead characteristics. In addition, they follow the aim of rendering these measurements less expensive and/or faster.

In order to achieve this object, firstly many different imaginable sources of error had to be pursued; in particular it was firstly believed that during introduction into and extraction from the testing devices or during the other handling of the test pieces the bead would become deformed and this would lead to poor reproducibility. Evidence for this was that from measurement to measurement in a statistical average, the pressure at a specific diameter became increasingly less; this would be typical for an expansion of the bead core.

In opposition to the current consensus, the inventors persistently maintained this belief, and finally proposed a new solution, which in the interim has been confirmed in tests.

This solution is characterised in that the inclined contact surface of at least two - preferably all - - 5 segments have on their radial inner end a roughly radially extending stop surface. This serves to simplify definition of the exact position of the test piece relative to the device.

Devices according to the invention are in fact more complex to manufacture, yet this contra-indication against this invention could be considerably mitigated by a further development according to claim 9, according to which the segments have axially extending receiving surfaces, adapters wedge-shaped in cross-section being however connected or drawn at or on these receiving surfaces, the radial outer surfaces of said adapters being designed as a contact surface with the inclination known per se relative to the axial and a stop surface according to the invention on the radial inner end of the substantially axially extending seat surface. Accordingly it is not necessary to provide entirely new test devices; it is only necessary to connect new segments with a contact surface according to the invention - preferably in axial stacking - to the old segments.

Conversion with radial stacking of the adapters becomes slightly more complex, i.e. during their arrangement radially outwith the old segments, because then either the otherwise occurring enlargement in diameter by previous rotation of the old segments about the central adapter thickness must be counteracted (the segments are hardened), or it must be accepted that a test device reequipped according to the invention is no longer suitable for the original tyre size provided, but for a larger one (so that a new device would have to be provided for the smallest). For this purpose in this type of conversion the protruding lever length of the segments is unaltered relative to their guides, so that no increased stress 10 occurs in the slideways of these segments.

According to claim 2, in order to test automobile tyres and light truck tyres, which are used on rims with a seat surface inclination of 50, the inclination of the contact surface of their segments to the axial should likewise be 5'; but even with an inclination in the vicinity of this, for example 4' or 6', practically the same good reproducibility of measurement results is achieved, and only after angular deviations between bead seat surface and segment contact surface of more than 2' is there an appreciable impairment in the reproducibility.

The seat surfaces of tyre beads frequently have, in the area of the bead toe, a slightly greater inclination; it is accordingly possible to incline also the inclined contact surfaces of the segments of the test device to a greater degree in the corresponding axial area.

This is however preferably avoided, i.e. a constant inclination is used. This simpler construction appears to bring no disadvantages in reproducibility.

In accordance with what was stated above and with the same tolerance range of +/- 2' according to claim 3, in a device according to the invention for testing truck tyres and light truck tyres which are used on rims with a seat surface inclination of 15', the inclination of the contact surface of this segment should come to 150 to the axial.

With a construction according to the invention of the spreadable segments or the adapters located therein with a stop, no further high friction engagement is necessary; on the contrary it was recognised that then even the setting of as low a friction contact as possible is advantageous. Such a preferred further development of the invention according to claim 4 is characterised in that their inclined contact surfaces are coated in order to reduce friction, preferably with polyethylene terephthalate (PM, Teflon) or with polyurethane (PU).

Basically each device according to the invention must be so formed that the respective test piece can also be drawn on to the test device. This is more appropriately effected - as is known and conventional - in the furthest - 8 possible retracted position of the segments which are spreadable by a radial movement. In this position the capacity for being drawn on can be ensured in various ways:

The greatest freedom in dimensioning and placing the stops is achieved if, according to the particularly preferred construction according to claim 5, the stop surfaces of all the segments for fitting and withdrawing the test piece are removable or may be folded aside. Insofar as the outer diameter to be measured at the radial inner end of the contact surface is smaller than the smallest tolerated clear inner diameter of the tyre beads to be tested - a condition which was logically also to be required for the previously known test devices with a cylindrical contact surface, the test pieces may be mounted and conversely removed again at least with the axial outer side of the respective bead to be tested leading. The advantage of this design resides in the fact that on the one hand large stop surfaces are possible and on the other in the fact that the segments need not be retracted very far together, so that in the spread condition the slots occurring between the segments remains small. The latter is agreeable, in that in this way the pressure maximal on the segment edges remain particularly small.

- 9 The disadvantage of such a construction resides naturally in the high number of movable parts, which makes the device more expensive and more liable to breakdown, and in addition, due to increasing play, could gradually impair the precision in a sequence of several thousand tests.

These disadvantages can be mitigated, if however accepting a restriction in the specific advantages, if not all but only some of the stops may be folded away, for example over two-thirds of the circumference, and the test pieces are raised away eccentrically and/or in a gyrating fashion over the stops which have remained in position. However, according to previous research, the restriction of the advantages of stops which may be folded way appears to have a more profound effect than the restriction of the associated disadvantages.

Remaining with the fitting device last described, the inventors have discovered that at least for most tyres, particularly also for the tyres of heavy trucks with their 15' seat surfaces, a very small radial height h of the stops is achieved, in order axially to fix the bead to be tested without excessive pressure against this stop. For 20 inch tyres for example, a stop height of only 3.5 mm has proved acceptable. The radial minimum travel path inwards is thus increased compared to the construction described before only by this amount; actually nothing need be altered in the travel path of the current test devices, as they in any case offer a sufficient travel path in an inward direction.

The inventors have utilised this recognition for the particularly preferred device according to claim 6, which is characterised in that the greatest radial height h of the stops is so measured that the outer diameter D to be measured at that point in the furthest possible retracted position of the segments is smaller than the clear inner diameter of the smallest tolerated tyre bead. Thus each bead to be tested can be mounted and/or withdrawn over the stops, i.e. may be mounted and again withdrawn with its axial outward side leading.

In addition or instead of this however the capacity for drawing on with the axial inner side of the bead to be tested leading can be enabled; this purpose is served by a device according to claim 7 which is characterised in that the outer diameter d. to be measured at the radial outer end of the contact surface in the furthest possible retracted position of the segments is smaller than the clear inner diameter of the smallest tolerated tyre bead.

Thus the test bead may be fitted and/or withdrawn over the end of the device, where the radial end of the segments lies.

A device which makes possible both mounting directions at least for one of the two beads, can by means of two rings of segments with contact surfaces test both beads of a tyre simultaneously, as explained in more detail in claims 14 to 16 in variants.

As is known per se from DE-PS 38 14 646 C2, according to claim 8, in devices according to the invention also the axis of rotational symmetry should lie vertically. In this way the possible tilting effects during fitting and withdrawing are as small as possible, as in this way gravity and the frictional force initiated thereby do not systematically engage on one end.

The radially acting resistive force of the bead against its spreading is preferably determined in a way known per se by measuring the fluid pressure in the hydraulic cylinders causing the segments to spread, according to claim 10. This leads to an extremely precise and costeffective measurement of the pressure applied over the entire bead surface, with high reliability and a low outlay on servicing.

More differentiated, if however more expensive information regarding the property of the tyre is obtained with the variant according to claim 11 according to which the radially active resistive force of the bead against its spreading is determined by measurement of the pressure on one or a plurality of surface sections of the contact surface or the entirety of the contact surface, by means of one or a plurality of piezo crystals, as is known per se from DE-PS 17 73 367. Thus any errors are not only detected but also localised.

The receiving device according to the invention for the beads of the test pieces with stops on the radial inner end of the seat surface slightly inclined with respect to the axial, is suitable for integration in a larger test system and is easily automated. The integration of one or two receiving devices according to the invention in test systems and their appropriate design is the subjectmatter of the further claims 12 to 18 which will be described in more detail in the following. Such a test system with a receiving device according to the invention is simply identified in the following as device or test device.

Such a test device should comprise a device for guiding the test piece, briefly known as a test piece guide in the following. The most important mechanical part of such a test piece guide is an axially movable, onepiece or segmented disc. The test piece guide should in addition recognise arrival of the test piece at the test - 13 position, and then initiate spreading of the segments. Furthermore, a member should be present which recognises the final spread position or the maximum spreading force, i.e. the termination of the actual test, and then retract the segments again, in order to release the test piece; this member is regarded for reasons of simplicity in the following as belonging to the test piece guide, without this latter requiring an arrangement in a common framework or casing.

Of particular importance is the similarly precise and reliable detection of the test position. In the case of cylindrical receiving surfaces this however was of almost no importance, because the cylinder had the same diameter everywhere, therefore only oblique positionings were to be avoided so that the bead was not expanded elliptically; in the case of the conical receiving surfaces according to the invention, the correct axial association now plays a decisive part.

In this case the preferred procedure is such that the bead to be tested is firstly positioned slightly axially outwith the provided test position; in this position the segments together with their stops are spread until they would prevent the bead from moving over them and axially inwards, then the bead to be tested is moved precisely as far as the stops lying flush with one another, so that - 14 the axial position is defined, and only then are the segments spread in order to record the bead characteristic until they gradually expand the bead.

Specifically, such a test device according to claim 12 can be so designed that it comprises a test piece guide, which firstly guides the test piece, upon a sufficiently retracted position of the segments, with the bead to be tested leading over the stops on the segments, which then spreads the segments until on the one hand the stops prevent the bead to be tested from moving back over the stops but on the other hand the contact surfaces are not yet in contact with the seat surfaces of the test piece, which then return the test piece until the axially inner delimiting surface of the bead comes into contact with the radially extending stop surface, so that the axial position of the test piece is defined relative to the segments, which then waits for the actual test, during which time the segments are further spread, which, after termination of the test, retracts the segments again until their outer diameter above the stops is again smaller than the clear inner diameter of the smallest tolerated tyre bead, and which thereafter returns the test piece.

Thus only one of the two beads of the tyre is tested. As a rule, the second bead is in a mirror-image configuration to the first; in this case the second bead can be tested with the same device, if according to claim 13 the test piece guide after termination of the test of one bead causes it to return and turns it over, so that, assuming the preferred vertical test piece guide, the previously upper bead now becomes the bottom one, according to which in the same way the other tyre bead is tested. Turning over of the tyre is in fact difficult to automate and in previous prototypes still require a certain amount of manual labour; the investment cost is in this way however as small as possible and upon introduction of a tyre series a high component of personnel experienced in manual work also has an aspect of quality assurance; the two human eyes thus involved, and sensitive hands, can recognise many and other opportunities for improvement still existing. If on the other hand both beads are differently designed from one another, the test piece after testing one bead is either to be brought to another correspondingly dimensioned test device or, after removal of the test piece from the test device, after testing of the first bead, the said test device must be re-equipped and the test piece thereafter re-introduced, now for testing of the second bead. Re- 16 equipping is particularly simple to imagine with a construction according to claim 9.

For a more intense, if possible 100% monitoring of manufacturing of a large series, a method is rather considered where the test piece is not turned over, nor need be brought to another point, and wherein the test device need not be re-equipped. As the beads need not be congruent, but in any case can be in a mirror-image configuration, this is only achievable with two rings of segments, i.e. a ring for one bead and another ring for the other bead.

With the preferred use of two rings of segments, not only is the handling requirement on the test piece capable of reduction, but in addition both beads can be tested simultaneously, which further reduces the time consumed.

Claims

Claims 16 to 18 contain specifically embodiments with two rings of segments to be spread. These constructions (as in fact the entire invention) are not restricted to the fact that the mounting and removal of the test piece is effected in the vertical, nor to the fact that the two beads are in a mirror image; rather, all other mounting and removal devices are possible and a greater variety of both beads is possible, particularly also different diameters. If tyres are to be tested both beads of which - 17 deviate from one another in diameter, the segment ring for testing the smaller bead should first "dive" into the test piece or be ""swallowed" by it. In the meantime it should not be forgotten that for a long time all massproduced tyres have had beads of identical size, and feed paths deviating from the vertical bring no decisive advantages; thus these, at least for a long time, have been special cases. Not to restrict the protective scope of claims 14 to 16, but only in order to simplify understanding, these three constructions are shown in the following without taking into account the special cases; thus in this simplification the test piece is conveyed from the top downwards into the test device located below, and the beads of the test pieces are similar, apart from their mirrorimage configuration. For the two rings of segments it further applies according to claim 6 that the beads can be guided over said stops in the retracted conditions of the segment ring precisely to be traversed. Furthermore, it is at least required for the first segment ring reached, that according to claim 7 it can be traversed also on the side of the tyre bead facing away - 18 from the stop in the furthest possible retracted position of the segments. Based on these conditions, the device according to claim 14 with the said simplifications is characterised in that it has an upper and a lower ring of segments, of which the lower serves to test the lower bead and the upper to test the upper bead of the test piece, and in that it comprises a test piece guide, if necessary with an electronic control unit, which firstly guides the test piece, at a position of the segments of the upper ring retracted until both its outer diameter d at the radially outer end and also its outer diameter D measured above the stops is smaller than the smallest tolerated clear diameter of both tyre beads, and with sufficiently retracted position of the segments of the lower ring, with the lower bead leading over the entire upper ring of segments and over the stops to these lower segments, which then spreads these lower segments until on the one hand the stops prevent the first bead to be tested from moving back over the stops but on the other hand the contact surfaces are not yet in contact with the seat surfaces of the test piece, which then returns the test piece until the axially inner delimiting surface of the lower bead comes - 19 into contact with the radial stop surface of the lower segments, so that the axial position of the lower bead is defined relative to the lower segments, which then waits for actual testing of the lower bead, while the segments of the lower segment ring are further spread, which, after termination of testing, retracts segments of the lower ring until their outer diameter d at the radially outward end of the contact surface is smaller than the smallest tolerated clear inner diameter of the tyre beads, which then guides the test piece further downwards, while the segments of the second upper ring are retracted until their outer diameter d at the radially outer end of their contact surface is smaller than the smallest tolerated clear inner diameter of the tyre beads, which, after crossing the heel of this upper bead, then spreads these upper segments until on the one hand their stops prevent the upper bead from moving downwards over the stops but on the other hand the contact surfaces are not yet in contact with the seat surfaces of the test piece, guiding the test piece until the axially inner delimiting surface of this upper bead comes into contact with the radial stop surface of the upper segments, so that the axial position of the upper bead is defined relative to the upper segment, which then waits for actual testing of the upper bead, while the segments of the upper segment ring are further spread, which, after termination of testing of the upper bead, retracts the segments of the upper ring until their outer diameter d at the radially outer end of the contact surface is smaller than the smallest tolerated clear inner diameter of the tyre beads and both their outer diameter d at their radially outer end and also their outer diameter D measured above the stops is smaller than the smallest tolerated clear inner diameter of the tyre bead, and retracts the segments of the lower ring until both their outer diameter d at their radial outward end and their outer diameter D measured above the stops is smaller than the smallest tolerated clear inner diameter of the tyre bead, and which thereafter returns the test piece upwards. According to claim 15 the abovenamed device may also be further developed in that the two rings of spreadable segments have such an actual spacing from stop surface to stop surface that the latter at least approximately coincides with the mouth width of the rim, for which the test piece is provided. Control of this device may be - 21 altered in that both tyre beads are tested simultaneously instead of in succession. In this way the test duration is scarcely half of what it was. In this way one arrives at a device according to claim 16 whose design and function is described in more detail in the sequence of Figures 4 to 9. The invention will be described in more detail in the 10 following with reference to some Figures, which show: Figure 1: a conventional truck tyre as a test piece in cross-section, Figure 2: on a smaller scale and in cross-section a test device according to the invention with a test piece ready to be fed into the test device, Figure 3: on the same scale as Figure 2, in plan view, the most important parts of the test device in the same position ready for introduction of a 20 test piece, Figure 4: on the same scale as Figure 2, in crosssection, a test device according to the invention during the first phase of introduction of the test piece into the test device, Figure 5: similarly to Figure 4, a test device according to the invention during a second phase of Figure 7: Figure 8: - 22 introduction of the test piece into the test device, Figure 6: similarly to Figure 4, a test device according to the invention during a third phase of introduction of the test piece into the test device, similarly to Figure 4, a test device according to the invention during a fourth phase of introduction of the test piece into the test device, similarly to Figure 4, a test device according to the invention after completion of introduction of the test piece into the test device, and during testing of the bead characteristic, and Figure 9: on the same scale as the preceding Figures 2 to 8, in a plan view to be compared with Figure 3, the most important parts of the test device in the same position ready to test or testing as Figure 8. The removal of the test piece from the test device may be read off filmfashion upon following Figures 7 to 2 in reverse sequence, and is not separately shown in order to 25 avoid repetition. 23 - Figure 10: shows in a cross-section on a larger scale the re-equipping of a previously known segment to form a test piece receiving means having a stop. The sequence of Figures 11 to 21 shows the function of another device according to the invention, i.e. with two rings of spreadable segments and with a single piece-disc for positioning the test piece; thus on the same scale as 10 Figures 2 to 9, the following are shown: Figure 12 Figure 13: Figure 14: Figure 11: the test piece suspended concentrically above the test device, the first phase of introduction into the test device and release of the test piece from the crane-like carrier device, removal of the carrier device, the initiating alignment of the lower bead on the lower ring of segments, Figure 15: a connecting phase of the alignment of the lower bead on the lower ring of segments, Figure 16: the next phase of alignment of the lower bead on the lower ring of segments with termination of the axial alignment, Figure 17: the final phase of alignment of the lower bead on the lower ring of segments with termination of the radial alignment, - 24 Figure 18: a first phase of alignment of the upper segment ring on the upper bead core, Figure 19: a second phase of alignment of the upper segment ring on the upper bead core, Figure 20: a third phase of alignment of the upper segment ring on the upper bead core with termination of the axial alignment, and Figure 21: the final phase of alignment of the upper segment ring on the upper bead core with termination of the radial alignment. Finally the following is shown: Figure 22: a measurement graph shown by way of example from a test of bead characteristic. Figure 1 shows in cross-section a known truck tyre 2 with beads 3, within which there is respectively located a bead core 3.1 of steel wire. The cross-sectional surface of the bead core 3.1 has in a conventional way a hexagonal configuration. The bead 3 has on its radial inner side a roughly axially extending seat surface 6. "Roughly axial" means in this case inclined through 150 to the axial and in such an orientation that by following it, one moves axially inwards and radially inwards, as is conventional. In the case of automobile tyres this inclination conventionally is 50. In some tyres the - 25 inclination at the toe is increased by up to 3' in order to increase pressure. The axial inner end of the seat surface 6 is called the bead toe 12. The axially outer end of the seat surface 6 is called the bead heel 13. The conventional single-ply carcase of steel wire cords is indicated by a continuous line. Illustration of the ply layers, core riders and various rubber layers has been omitted, in order not to detract from what is essential for this invention. Figure 2 shows in cross-section on a smaller scale the same tyre 2 in the form of a test piece lying horizontally above a device 1 according to the invention. Here however, for increased concentration on the essential, illustration of the carcase has been omitted. The device 1 shown here has a ring of spreadable segments 4. The axis of rotational symmetry A is entered as a dashed-dotted line. In this Figure the segments 4 are in the furthest possible retracted position. The smallest inner diameter (= clear diameter) of the tyre beads 3 is indicated here by the reference mark Di. It is to be measured at the bead toe 12, the axially inner end of the seat surface 6. An essential factor is that the greatest radial height h of the stops 9 is selected to be so small that the outer diameter D - 26 measured above the stops 9 of the segments 4 is smaller than the clear diameter Di of the tyre beads 3. The spreadable segments 4 are oriented around in such a way that the radially inner ends 7 and the stops 9 arranged in the same way are located at the top. The stop surfaces 9a thus avoid slippage of the tyre bead upwards during spreading of the segments 4. As indicated in the following, the stop surfaces 9a also serve as aids for introduction and positioning, so that the bead toe 12 and thus the entire bead 3 comes to lie correctly on the spreadable segments 4. For this purpose the stops 9 preferably have a radial extension h of 2 to 5 mm. If operation is with only one ring of segments 4, as is shown in this example, the orientation shown here of the inclination of the contact surface 5 is the best, as in this way gravity, even if not strong enough on its own, counteracts slippage of the bead during the actual testing, i.e. during the elastic expansion; in the inverse arrangement on the other hand, the gravitational force would reinforce slippage, which would require a larger minimum dimension of the stops 9 (see also upper ring in Figures 11 to 21). Further evidence in favour of this orientation is that, with support of the test device on the ground and supply - 27 and removal of test pieces from above or upwards, the insertion movement of the test piece 2 above the mandrill-like projecting test device 1 is smaller than in the reverse orientation of inclination of the contact surfaces 5 and arrangement of the stops 9 on the under side. Thus the test device 1 need not project so far forward. More expensive, even if also possible, would be a suspended attachment of the test device on the roof of the test area and supply and removal of the test pieces 2 from below or downwards. The suspended attachment itself is already much more difficult to set up, as the ceiling height comes at most to 4 meters, so that the device would need to be constructed extremely long, in order to be reachable by employees, and the positioning of the test pieces during the phase in which the tyre beads 3 are not yet clamped on the segments 4, would be more difficult to design. However, this arrangement would make it easier to keep the laboratory clean. In the preferred arrangement shown in Figure 2 the bead positioning is effected before spreading and clamping by a disc 14 located beneath the ring of segments 4. This disc 14 can be of a one-piece construction, as in the sequence of Figures 11 to 21 shown later, or likewise may be divided into segments 14.1, as shown in this Figure - 28 and in the Figures up to Figure 9 belonging to the same sequence of Figures. What is involved is that the disc 14 or the disc segments 14.1 are vertically adjustable to such an extent that the test piece 2 can be brought into the respective correct axial position. For this purpose it is possible to mount the disc 14 to be axially adjustable relative to the foundation, which allows the design of the same to be one-piece (see the later sequence of Figures 11 to 21), or adjustable axially relative to the segments 4 (i.e. vertically adjustable), as shown here. In the variant shown here, the disc segments 14.1 must also follow the radial movements of the segments 4, for which purpose they can be unconnected, forming an uninterrupted ring. The single-piece plate construction shown in the sequence of Figures 11 to 21 appears of particular advantage for testing the smaller automobile and light truck tyres, because in this way the number of movable parts is smaller, and the one shown here in Figure 2 appears to be more favourable for the larger truck tyres, as here in order to avoid tilting, - guide lengths cannot be made of any optional length with a view to the masses to be moved - is offered in any case without segmentation in order to reduce the lever arms, which could lead in the case of a random increase in friction on one side to jamming of the guide, i.e. to tilting. otherwise, intermediate joints - 29 would possibly require to be provided between the means driving the lifting movement and the singlepiece disc. The segmentation shown here permits guidance and support of the disc segments 14.1 directly on the segments 4 of the test device. In this way control of the required position of the test piece 2 may be carried out particularly directly and rigidly. In this phase the tyre 2 is held by a carrying means 15 engaging from the inside in the upper bead 3. After a small further lowering of the test piece 2, this latter lies on the said disc 14, which then takes on the further axial positioning; the lifting means 15 is retracted a small distance upwards. Figure 3 shows, on the same scale as Figure 2, the same device as Figure 2, but without the tyre and without the carrying means, in a plan view from above in the furthest possible retracted position. Figure 4 shows in the same type as illustration as Figure 2 the tyre 2 lowered until the bead toe 12, the narrowest part of the test piece 2 with the clear diameter Di, just passes the stop 9 with a diameter D in the retracted condition of the ring of segments 4. In this Figure also the segments 4 are in the furthest possible retracted - 30 position. It will be seen that the relationship D < Di already mentioned in the description of Figure 2, is a condition for the success of the passage shown here. During this passage, in this embodiment the test piece 2 is already lying on the axially movable plate 14. This latter is then lowered further together with the test piece 2: Figure 5 shows in the same type of illustration as the previous Figure the test piece 2 lowered until its toe 12 is located slightly beneath the stop surface 9a. Otherwise this Figure coincides with the preceding ones. After reaching this axial position the segments 4 are spread until the radial outer ends of the stops 9 lie further radially outwards than the bead toe 12, on the other hand however are so little spread that the seat surface 6 of the bead 3 does not yet come to lie on the conical contact surface 5 of the segments 4. This partial spreading is shown in Figure 6, which otherwise coincides with the previous Figure. As Figure 7 shows, according to this the test piece 2 is displaced upwards by means of a slight lifting of the plate 14, until the bead toe 12 presses slightly, preferably with about half a thousandth part of the - 31 carrying capacity of the respective test piece, against the stop surface 9a. As Figure 8 shows, thereafter the ring of segments 4 is spread until contact surface 5 and seat surface 6 come to line one on the other without play. Figure 9 shows in a similar form of illustration to Figure 3, i.e. on the same scale as the preceding Figures and in a plan view from above, the disposition of the device 1. The unavoidable slots between the spread segments 4 are small enough to avoid damage to the radial inner side of the test piece 2 previously shown in the Figures, i.e. the seat surface 6 of its bead 3, during the subsequent expansion. BY means of further spreading of the segments 4, in a way known per se, at least one, as a rule two, sometimes also three, specific diameter(s) Di for the tyre bead are set and the required spreading forces are measured. The alterations in diameter during the actual test, i.e. the segment spreading under load, are in a view true to scale so low that they are less than the thickness of the line; therefore a separate view of the spreading phases under load has been omitted. Proceeding from the final position and testing shown in Figure 9, the removal of the test piece by following Figures 8 to 2 in reverse sequence can be observed. According to its construction, the test piece is to be turned over in such a way that the previously lower bead is now the upper one. In this turned-over position the test piece again goes through the sequence of Figures from 2 to 9 and back, in order to record and test the characteristic of the second bead. Thereafter the device is ready for the next test piece. Figure 10 shows, likewise true to scale, yet on a much larger scale, a detail of an individual segment 4 according to the invention, which comprises substantially one segment 4a with a receiving surface 5a in the manner of a cylinder cutout, and an adapter 10, which is supported with its surface 10.1 on the previous test piece receiving surface 5a. This adapter 10 for the first time displays the slightly conically extending contact surface 5, which now serves to receive the test piece. The adapter 10 is held by a bolt 10.2 with a slight press fit both opposite a corresponding bore 10.3 in adapter 10 and also opposite a bore 4a.1 in the previously known segment 4a. In the throat 21, which is formed by the stop surface 9a according to the invention on the one hand and the 33 conical contact surface on the other hand, a small incision 21 is machined in order to ensure defined surface ends. The throat diameter Dk is defined as the diameter to be read at the imagined sharp intersecting edge of the surfaces 9a and 5. For simplification of the logistics, the adapter 10 is so designed that the diameter Dk in the throat 21 coincides with the diameter D, of the previously known segment 4a. Thus each of the old bead characteristic testing devices are in fact still usable for the tyre sizes for which they were originally built. Preferably, as can only be shown in this larger scale, either the entire stop surface 9a according to the invention or better still, as shown here, only a radial outer area 9b of the stop surface 9a is slightly inclined to the radial, particularly preferably, as shown here, by 5. This slightly conical design according to claim 18 simplifies axial positioning of the bead toe relative to the throat 21. In favourable cases this can enable separate axial positioning to be omitted; the radial positioning by spreading of the segments is then capable to a certain degree of pressing the respective bead to be tested into the correct axial position. This certain degree is naturally the greater the greater the angle's inclination is and the greater the height - 34 proportion of the inclined area 9b of the stop surface 9a; the inclination on the other hand must be so small that the friction does not lead to self-jamming or to an ill-defined stumbling of the bead toe on the surface 9b. In actual measurement of the bead characteristic, as a rule two different ring radii are initiated in accordance with the tolerance range of the associated rim, and the forces reacting on the segments are measured. With a conventional hydraulic drive, this can be effected by measurement of oil pressure. The construction shown here shows the possibility of measuring the pressure on the segment itself by arrangement of one or a plurality of piezo crystals 22 in each segment. This is advantageous because specific fluctuations in the local bead pressure over the circumferential direction are characteristic for many structural faults. Such fluctuations are recognisable in this way. In a similar film-fashion like the sequence of Figures 2 to 9, the sequence of Figures 11 to 21 shows the method of operation of another device according to the invention. For reasons of clarity the same scale of illustration is used as in the previous sequence and the same tyre is shown as a test piece. - 35 Figure 11 shows in cross-section similarly to Figure 2 the test piece 2 lying horizontally above this second device 1 according to the invention. The second device 1 shown here has two rings of spreadable segments 4, a lower 1, which corresponds to the single ring of the first device previously described, and which serves to test the lower tyre bead 3, and an upper one with stops 9 and contact surfaces 5, located in a mirror image to the lower one, on its segments 4. The axis of rotational symmetry A is shown as a dashed-dotted line. In this Figure, the segments 4 of both rings are shown in the furthest possible retracted position. As already explained for Figure 2, it is essential that the greatest radial height h of the stops 9 is selected to be so small that the outer diameter D measured above the stops 9 of the segments 4 is smaller in both rings than the clear diameter Di of the tyre beads 3. It is necessary that this condition be fulfilled, but in this second device not yet sufficient: for the capacity of the test piece 2 to be introduced and extracted, there must be added fulfilment of the further condition, i.e. that also the outer diameter d of the upper segment ring, which is measured at the radial outer end 8 is, in the further possible retracted condition, smaller than the clear bead inner diameter Di. The same requirement is not made of the lower ring, as long as, as preferred and here shown, both the introduction and removal of the test piece are effected from above or upwards. In any case it involves no recognisable advantage to enlarge the contact surface 5 of the lower segments, in any case not so long as both tyre beads 3 are axially symmetrical with one another. Accordingly in this case both rings of segments 4 are designed to be symmetrical with one another. In order to permit the greatest possible retracted position and in this way to keep as small as possible the necessary radial travel paths of the segments 4, i.e. for purposes of maximum simplicity, the outer diameter D above the stops 9 is further equal to the outer diameter d above the respective radial outer end 8 of both rings of segments 4 in the furthest retracted position. In the meantime should the long-known tyres with differing beads in the inner and outer vehicle sides become popular, a proposal which for a long time has been refused by the automobile industry for purposes of logistic simplicity, then use should be made of the fact that the said second requirement need only be directed at the upper segment ring. In such a case therefore, (maintaining the introduction and removal of the test piece from the top or upwards), the segment ring with the larger diameter would be located below and the larger above. The spreadable segments 4 of the lower ring are oriented around in such a way that the stops 9 are located above. The stop surfaces 9a thus avoid slippage of the tyre bead upward during spreading of the segments 4. Conversely, the spreadable segments 4 of the upper ring are so orientated that the stops 9 are located below. The stop surfaces 9a thus avoid slippage of the tyre bead downwards during spreading of the segments 4. In this case it must accepted that the gravitational force reinforces the slippage of the upper ring to be avoided, a fact which, at least on the upper ring, requires a slightly enlarged minimum dimension of the stops 9. Figure 11 shows the first phase of the testing procedure: the test piece 2 has just been positioned coaxially with the axis of rotational symmetry of the device 1 by a crane-like carrying means 15, which engages from inside into the upper bead 3. The device 1 has a foundation 16, and vertically adjustable relative thereto, there is mounted a single-piece disc 14. After the phase shown in Figure 11, the crane-like carrying device 15 together with the test piece suspended - 38 therein is lowered until the tyre 2 comes to lie with its lower side wall on the disc 14. During the lowering procedure, the lower bead 3 firstly traverses the radially outer edge of the segments 4 of the upper ring, then the stops 9 of these upper segments 4 and finally the stops 9 of the segments 4 of the lower ring. The axial spacing W between the stop surfaces 9a of the two rings during these first phases of introduction of the test piece is preferably appreciably smaller than the clear axial dimension w between the two bead toes 12, in order in this way to allow the gripper arms 15.1 of the carrier device 15 sufficient room for pivoting radially inwards. After the test piece 2 is deposited on the disc 14, the gripper arms 15.1 move radially inwards and thus release the test piece 2. This phase is shown in Figure 12. The vertically-adjustable disc 14 undertakes guidance of the test piece until, at the end of the testing procedure, the gripper arms 15.1 again grip by spreading behind the upper bead of the tested tyre 2, and remove it. Figure 13 shows the removal of the carrier device 15 in an upward direction. As it does not move in the - 39 following sequence of Figures, it is no longer shown in the following Figures. While Figure 13 shows the phase in which the lower toe 12 is just traversing the lower stop 9, Figure 14 shows the further lowering of the test piece, so that the lower bead toe 12 comes to rest just beneath the stop surface 9a. For the lower bead, this phase corresponds to that in Figure 5 of the preceding sequence of Figures. As an alternative to the lowering of disc 14, it would naturally also have been possible to design the lower ring of segments 4 (also) as vertically adjustable, and in order to achieve the only interesting relative position between the lower segment ring and the lower bead 3, to raise this lower ring of segments 4 correspondingly. As the possibility of such a kineticreversal is common knowledge to the average person skilled in the art, it is regarded as unnecessary to represent it in its own Figure; this variant is of course also intended to belong under the protective scope. The division shown here of the axial movements so that only the upper segment ring is vertically adjustable and not the lower, for that purpose also however the disc 14, avoids constructive zones of excessive functional thickness and is thus more cost-intensive in procurement, servicing and maintenance. Figure 15 shows, analogously to the earlier Figure 6, the spreading of the segments 4 to this extent of the lower ring, that now the diameter D above the lower stops 9 is greater than the clear diameter Di of the lower bead 3. This spreading is so small that the seat surface 6 of the lower bead 3 does not yet come to rest on the conical contact surface 5 according to the invention of the lower segments 4. Apart from this partial spreading of the lower segments 4, Figure 15 coincides with Figure 14. The drive means 17, indicated as hydraulic cylinders, whose respective longitudinal axes lie radially to the axis of rotational symmetry A, serve to spread the segments 4. Analogous drive means must naturally also be present in the simpler device according to the sequence of Figures 2 to 9; at that point however they are not shown, in order to direct the eye of the observer to the principal method of operation. Naturally, other drive mechanisms are also possible, for example threaded spindles instead of the hydraulic cylinders. It is further possible to impose, on the segments 4 of the ring by means of a cone located coaxially with the axis of rotational symmetry A, a spreading uniform on all - 41 sides; for this purpose there is imparted to the respective central cone by means of a centrally engaging drive means, an axial movement which is transferred by sliding on its peripheral surface into an axial movement of the segments. A hydraulic cylinder or a threaded spindle are again preferably considered as such a central drive means. Figure 16 shows, analogously to Figure 7, raising of test piece 2 until the lower bead toe 12 abuts against the lower stop surface 9a. In this phase the correct relative axial position of the lower bead 3 relative to the lower ring of segments 4 is already reached. The contact surface 5 of the segments 4 however has not yet reached the seat surface of the lower bead 3. As already explained for Figure 14, instead of raising the test piece, the lower ring of segments 4 might naturally also be lowered, in order to achieve the same relative position between the lower bead 3 and the lower segment ring; the lowering facility of the lower ring of segments 4 necessary for this however seems more expensive than the raising facility of the disc 14, in view of the fact that the upper ring of segments 4 must be vertically adjustable, as is visible in Figures 18 and 20. - 42 Thereafter the segments 4 of the lower ring are spread until the contact surface 5 of the segments 4 reaches the seat surface 6 of the lower bead 3. Figure 17 shows the position thus reached. From this position, the characteristic of the lower bead could already be recorded by further spreading of the lower ring of segments. Due to the high rigidity of the tyre beads, the spreading paths thus achieved are however so small that they cannot be shown true to scale. As this further spreading however is known to the specialist in the cylindrical test devices, a separate illustration of the spreading of the segments under load has been omitted. Preferably, the lower bead 3 is firstly tensioned only so slightly that during the subsequent introduction of the upper bead into the upper ring of segments 4, it does not slip off again. While the upper ring of segments 4 has until now been waiting unchanged in its furthest possible retracted and furthest lowered position, it is now, as Figure 18 shows, raised into a position in which the upper stop surface 9a comes to rest just beneath the bead toe 12 of the upper bead. The sensors for detecting the position of the upper bead toe 12 are not shown for reasons of clarity. Figure 19 shows that thereafter the upper ring of segments 4 is spread until thereafter the diameter D, measured above the upper stops 9, is greater than the clear diameter Di of the upper bead, without the seat surface 6 of the upper bead 3 contacting the conical contact surface 5 according to the invention of the upper segments 4. This spreading, exactly like that shown in Figure 21, is preferably effected by similar drive means 17 as already discussed for the lower ring of segments in the second and third paragraph of the description of Figure 15. In order to avoid mechanical power transmission members extending to the foundation 16, these drive means 17 are preferably not supported relative to the foundation 16 but directly relative to the vertically extending pillar 18, relative to which the upper segments 4 are also guided. Preferably, the supply line 20 (preferably two tubes for supply and removal of oil pressure, but if an electrically driven threaded spindle were used, an electrical conduit would be considered) extends within the column 18, where it is undisturbed and well protected. The necessary vertical mobility of the column 18 is ensured by a flexible intermediate piece (i.e. in the case of hydraulic drive, two hoses) 20a. In order that all the supply lines may be shown in summary in one Figure, in Figure 19 the substantially rigid supply 19 to a drive means 17 of a segment 4 of the lower ring is shown; from this point further supply lines should branch in an annular fashion to the drive means for the other segments 4 of the lower ring. In the further Figures, for reasons of clarity, the supply lines are not shown. Figure 20 shows that thereafter the upper ring of segments 4 is moved higher by a small amount until the upper bead toe 12 presses slightly against the upper stop surface 9a. In the subsequent spreading, this stop 15 surface serves as a guide for the upper tyre bead. Figure 21 shows the phase in which also the upper ring of segments 4 has come into full contact with the tyre bead 3 associated therewith. The actual testing of the upper 20 bead can begin now from this position. The characteristic of the upper and of the lower bead are preferably recorded simultaneously. Figure 22 shows by way of example a diagram recorded in this way. The person skilled in the art will firstly look at the pitch; - 45 if it is too steep, the test piece reacts too sensitively to fluctuations in the actual rim dimensions from the required rim dimensions, i.e., even at a small plus tolerance of the rim diameter, the tyre can no longer be fitted and even at a small minus tolerance the security of seat is no longer sufficient, if it is too flat, this can be an indication of too few wire windings in the bead core or even particularly when during return to the less expanded diameter, the spreading force is smaller than during first initiation of this diameter - for a wire breakage. Further, the specialist will observe the correct absolute height of the measuring curve, i.e. the fact that, at the smallest acceptable rim diameter, the pressure is still sufficient for safety requirements and at the largest acceptable rim diameter the pressure is still small enough for fitting. As is known, within narrow limits a false height of the measurement curve can be removed by correction of the passage through zero, which is possible by application of or removal of rubber radially inside the bead cores. - 46 Proceeding from a bead characteristic testing device with spreading segments, whose contact surfaces 5 have a small inclination, which deviates preferably at most by 30 from the inclination of the seat surface on the rim on which the test piece will be fitted later, the invention in summary proposes, in order to avoid slippage of the tyre beads from the spreading segments, the arrangement of stops 9 at the radial inner end of the slightly inclined contact surfaces. The invention provides great progress in the precision of reproduction of bead characteristic tests and in addition enables extensive automation of this testing. is L-i-1 Claims:

1. Device (1) for testing the bead characteristic of a vehicle tyre (2) by measuring the radially-active resistive force (F) exerted by the tyre bead (3) on the at least 3, preferably 6 to 9 ring-shaped spreadable segments (4) of the device (1), in dependence on the displaceable - diameter of the ring of segments (4) and thus of the rim expansion, the segments (4) having a surface (5) extending at an inclination (0) to the axial (A), said surface being provided for contact with the likewise roughly axially extending seat surface (6) of the tyre bead 3, characterised in that the inclined contact surface (5) of at least two - preferably of all segments (4) has on its radially inward end (7) a roughly radially extending stop surface (9a) for simplifying the precise definition of the axial position of the test piece (2) relative to the device (1).

2. Device (1) according to claim 1 for testing automobile and truck tyres with a bead diameter up to 16 inches inclusive, characterised in that the inclination (0) of the contact surface (5) of its segments (4) comes to 50 to the axial (A) 400

3. Device (1) according to claim 1 for testing automobile tyres and truck tyres of a bead diameter of greater than 16 inches, characterised in that the inclination (p) of the contact surface (5) of its segments (4) to the axial (A) is 15'.

4. Device (1) according to claim 4, characterised in that its inclined contact surfaces (5) are coated in order to reduce friction, preferably with polyethylene terephthalate (PM, Teflon) or with polyurethane (PU).

5. Device (1) according to claim 1, characterised in that the stop surfaces (9a) of at least some preferably all - segments (4) are removable or may be folded aside in order to raise and withdraw the test piece (2).

6. Device (1) according to claim 1, preferably not according to claim 7, characterised in that the largest radial height (h) of the stop surface (9a) is of such dimensions that the outer diameter (D) to be measured at that point in the furthest possible retracted position of the segments (4) is smaller than the clear inner diameter of the smallest tolerated tyre bead (3), so that the test piece (2) can be lifted and/or withdrawn over the stop (9).

44- Cl

7. Device (1) according to claim 1, preferably not according to claim 7, characterised in that the outer diameter (d) to be measured at the furthest possible retracted position of the segments (4) is smaller than the clear inner diameter of the smallest tolerated tyre bead (3), so that the test piece (2) can be raised and/or withdrawn over the end of the device, where the radial outer end (8) of the segments (4) lie.

8. Device (1) according to one of the preceding claims, characterised in that in a known way its axis of rotational symmetry (A) lies vertically.

9. Device (1) according to one of the preceding claims, characterised in that the segments (4) have axially extending receiving surfaces (5a), and in that, at or on these receiving surfaces (5), there are connected or drawn on adapters (10) which are wedge-shaped in crosssection, and whose radial outer surfaces are designed as the contact surface (5) with an inclination (0) known per se relative to the axial (A) and with a substantially radially extending stop surface according to the invention at the radially inward end of the substantially axially extending seat surface.

10. Device (1) according to one of the preceding claims, characterised in that, in a known way, the radially- ' 0 active resistive force (F) of the bead (3) against its spreading is determined by measurement of the fluid pressure in the hydraulic cylinders causing spreading of the segments (4).

11. Device (1) according to one of the preceding claims, characterised in that the radially-active resistive force (F) of the bead (3) against its spreading is determined by measurement of the pressure on one or a plurality of surface sections of the contact surface (5), or the entire contact surface (5) is determined by means of one or a plurality of piezo crystals.

12. Device (1) according to claims 1 and 6, preferably alsoaccording to claim 10, characterised in that it (1) comprises a test piece guidance system, which firstly guides the test piece (2), upon a sufficiently retracted position of the segments (4) with the bead (3) to be tested, ahead over the stops (9) to the segments (4), which then spreads the segments (4) so far apart hat on the one hand the stops (9) prevent the bead (3) to be tested from moving back over the stops (9), but on the other hand the contact surfaces (5) are still not in contact with the seat surfaces (6) of the test piece (2), 5' 1 which then returns the test piece (2) until the axially inner delimiting surface (11) of the bead (3) comes into contact with the radially- extending stop surface (9a), so that the axial position of the test piece (2) is defined relative to the segments (4), which then waits for the actual testing, while the segments (4) are spread further apart, which, after the end of testing, again retracts the segments (4) until their outer diameter (D) above the stops (9) is again smaller than the clear inner diameter of the smallest tolerated tyre bead (3), and which thereafter returns the test piece (2).

13. Device (1) according to claim 12, characterised in that the test piece guidance system, after termination of testing of one bead (3) and its return, turns the test piece over, and then in the same way also tests the other tyre bead (3).

14. Device (1) according to claims 1, 6 and 7. preferably also according to claim 8, characterised in that it (1) has, axially stacked (i.e. preferably located one above the other) two rings of segments (4) of which the first (preferably the lower) is set up to test the first (preferably r) bead (3), and the second (preferably upper. -,t the second (preferably upper) iE 11 bead (3) of the same test piece (2), and which (1) comprises a test piece guidance system: which firstly guides the test piece (2) when the position of the segments (4)of the second (preferably upper) ring is retracted so far that both its outer diameter (D) on its radially outer end (8), and also its outer diameter (D) measured above the stops (9) is smaller than the smallest tolerated clear inner diameter of the first (lower) tyre bead (3) and, when the position of the segments (4) of the first (preferably lower) ring is retracted sufficiently far, leads the test piece (2) firstly with the first (preferably lower) bead (3) to be tested over the entire second (preferably upper) ring of segments (4) and over the stops (9) on these first segments (4) (preferably from the top downwards), which then spreads these first (preferably lower) segments (4) so far apart that on the one hand the stops (9) prevent the first bead (3) to be tested from moving back over the stops (9) but on the other hand the contact surfaces (5) are not yet in contact with the seat surfaces (6) of the test piece (2), which then returns the test piece (2) until the axial inner delimiting surface (11) of the first bead (3) to be tested comes into contact with the radial stop surface (9a) of the first segments (4), so that the axial position of the first bead (3) to be tested is defined relative to the segments (4), S 5 which then waits for the actual testing of the first (preferably lower) bead (3), during which time the segments (4) of the first (preferably lower) segment ring spread further, which, after termination of testing, returns the segments (4) of the first (preferably lower) ring together, so that their outer diameter (d) at the radial outer end (8) of the contact surface (5) is smaller than the smallest tolerated clear inner diameter of this first tyre bead (3), which then guides the test piece (2) further (preferably downwards), while the segments (4) of the second (preferably upper) ring are retracted so far that their outer diameter (d) at the radially outer end (8) of their contact surface (5) is smaller than the smallest tolerated clear inner diameter of this second tyre bead (3). which, after traversing the heel (13) of this second bead (3), then spreads these second segments (4) until on the one hand their stops (9) prevent the second bead (3) from moving (downwards) over the stops (9) but on the other hand the contact surfaces (5) are not yet in contact with the seat surfaces (6) of the test piece (2), guiding the test piece (2) until the axially inner delimiting surface (11) of this second bead (3) to be tested comes into contact with the radial stop surface (9a) of the second segment (4), so that the axial s it position of the last bead (3) to be tested is defined relative to these second segments (4), which then waits for the actual testing of the second (preferably upper) bead (3), during which time the segments (4) of the second (preferably upper) segment ring are further spread, which, after termination of testing of this second bead (3), retracts the segments (4) of the second (preferably upper) ring until their outer diameter (d) at the radial outer end (8) of the contact surface (5) is smaller than the smallest tolerated clear inner diameter of the second tyre bead (3) and both its outer diameter (d) at its radially outer end (8), and its outer diameter (D) measured above the stops (9) is smaller than the smallest tolerated clear inner diameter of the first tyre bead (3), and which retracts the segments (4) of the first (preferably lower) ring until both their outer diameter (d) at the radial outer end (8) and also their outer diameter (D) measured above the stops (9) is smaller than the smallest tolerated clear inner diameter of the first tyre bead (3), and which thereafter returns the test piece (2) (preferably upwards).

15. Device (1) according to claims 1, 6 and 7, preferably also according to claim 8, characterised in 5lb that it (1), like the device according to claim 16, has two rings of segments (4) with the same fitting possibilities for the tyre beads above these rings of segments (4) in their inserted position, these two rings however in addition having such an axial spacing (W) from stop surface (9a) to stop surface (9a), that the former (W) at least approximately agrees in its rim mouth width of such a rim, for which the test piece (2) is provided, and, deviating from claim 16, both tyre beads are tested simultaneously instead of in succession.

16. Device (1) according to claims 1, 6 and 7, preferably also according to claim 8, characterised in that it (1) has, axially stacked (i.e. preferably located one above the other) two rings of segments (4), of which the first, (preferably the lower) is set up to test the first (preferably lower) bead (3), and the second (preferably upper) for testing the second (preferably upper) bead (3) of the same test piece (2), these two rings having such an axial spacing (W) from stop surface (a) to stop surface (9a), that the former (W) at least approximately coincides with the rim mouth width of such a rim as is provided for the test piece (2), and which (1) comprises a test piece guidance system, - which firstly, when the segments (4) of the second (preferably upper ring) are so far retracted that both their outer diameter (d) at their radial outer end (8) 6 b and their outer diameter (D) measured above the stop (9) are smaller than the smallest tolerated clear inner diameter of the first (lower) tyre bead (3), and with a sufficiently far inserted position of the segments (4) of the first (preferably lower) ring, first leads the test piece (2) ahead over the entire second (preferably upper) ring of segments (4) and over the stops (9) on the first segments (4) (preferably from the top downwards), and which at least roughly simultaneously, in a preferably unaltered position of the segments (4) of the second (preferably upper) ring, axially positions the second tyre bead (3) in such a way that its seat surface (6) comes to rest slightly further axially inwards than the associated contact surface (5), - which then spreads the segments (4) of both rings, preferably simultaneously, to such a distance that on the one hand the respective stops (9) prevent a movement of the respective bead (3) over the stops (9) into the axial interior of the test piece (2), but on the other hand the contact surfaces (5) of both segment rings are not yet in contact with the respective seat surfaces (6) of the respective bead (3), which then axially positions the test piece (2) and/or the segment rings so that the axially inward delimiting surface (11) of both beads to be tested comes into contact with the radial stop surface (9a) of the respective segment (4), so that the axial position of ;j both beads (3) is defined relative to the respective segments (4), which then waits for the actual, preferably simultaneous testing of both beads (3), during which time the segments (4) of both segment rings are further spread, which, after termination of testing of both beads, retracts the segments (4) of both rings as already described for the introduction system for the test pieces, so that the test piece can again be extracted, reversing the introductory movement, and which thereafter lifts or retracts the test piece (2) (preferably upwards) again out of the testing device (1).

17. Device (1) according to claims 8 and at least one of claims 12 to 16, characterised in that it grasps the lower bead (3) of the test piece (2) after introduction from above and the test piece (2), preferably alone, is held on the test piece guidance system by its weight.

18. Device (1) according to one of the preceding claims, preferably according to claim 16, characterised in that the stop surfaces (9a) of at least one ring of segments (4), where referring to claim 18 preferably of the upper ring, is slightly conical in form with a conical angle of j C3 less than 300. in order to simplify introduction of the toes of the beads (12).