METHOD AND APPARATUS FOR MAKING A TRUED SPOKE WHEEL

Abstract: What is disclosed is a method and a device (1) for manufacturing a spoke wheel (2), wherein spokes are placed in a spoke wheel, brought under a mechanical tension and subjected to a stabilising operation, wherein a final trueing operation of the spoke wheel takes place after at least one stabilising operation of the spokes, and wherein both operations are carried out in one and the same device. This leads to an enhanced quality of the spoke wheel (2) that is produced and means a saving in terms of labour. Several interim trueing operations of the spoke wheel can simply be alternated with one or more interim stabilising operations in the same device so as to obtain a more uniform distribution of the tension in the spokes.

Description: METHOD AND APPARATUS FOR MAKING A TRUED SPOKE WHEEL The present invention relates to a method for manufacturing a spoke wheel, wherein spokes are placed in a spoke wheel and brought under a mechanical tension. The present invention furthermore relates to a device which includes means for stabilising spokes in a spoke wheel. A method and a device of this kind are known from EP-A-0 360 355, which discloses a method and a device wherein spokes in a spoke wheel, which are usually not tensioned, are subjected to a stabilising operation, wherein the spokes are pre-stretched and thus strengthened, so that they will bed more correctly in to the spoke openings in the rim and the axle flange of the spoke wheel. This is done in an attempt to partially eliminate the need for re-trueing after a short period of use. After the stabilising operation, the spoke wheel is taken out of the prior art device so as to be moved to a next device, such as a device for final tensioning of the spokes. One drawback of the prior art method is the fact that comparatively labourious operations are required in order to obtain a technically satisfactory end product in the form of a spoke wheel that must not necessarily be re-trued after a short period of use. In order to accomplish that objective, the method according to the invention is characterized in that a final trueing operation of the spoke wheel takes place after at least one stabilising operation of the spokes, and in that both operations are carried out in one and the same device; the device according to the invention is furthermore characterized in that it also includes trueing means for trueing the spoke wheel in axial and/or radial direction. The present invention is based on the insight that, in order to obtain a really good end product, the interaction between said at least one stabilising operation and said final trueing operation, whereby misalignments in the rim are corrected by changing the tension in one or more spokes, is of major practical importance with a view to obtaining a high-quality end product, which operations are best carried out in one and the same device, so that it will no longer be necessary to successively place the spoke wheel into the respective devices and take it out again. Not only does this lead to more compact, less extensive machinery, but furthermore less labour is needed and less time is wasted, which in addition will result in an increased output of the device according to the invention, which is thus multifunctional. Further it has become apparent that tensioning of the spokes prior to the stabilising operation is important in practice in order to make said stabilisation effective. Since the method according to the invention makes it possible to have even more than one trueing and stabilising cycle precede the eventual trueing operation, it thus provides, in a relatively simple manner, the basis for achieving a higher degree of uniformity in the distribution of the various tensioning forces in the spokes of the spoke wheel than could previously be the case. As a result, peaks in the tensioning force, which invariably resulted in local deformation of the rim after a certain period of use and which made re-trueing necessary after a short time, will occur less quickly than previously. It is noted here that a method and a device for trueing a rim of a spoke wheel are known per se from EP-A-0 476 749, which method and device are so complex, however, that there can be absolutely no question of any multifunctionality. In one embodiment of the method according to invention, in order to achieve a higher-quality end product which does not need re-trueing neither in radial direction nor in axial direction, even after a somewhat longer period of normal use, one or more interim trueing operations of the spoke wheel are alternated with one or more interim stabilising operations. Surprisingly, the quality in terms of the need for re-trueing and the length of the periods therebetween appears to improve strongly, which is of vital importance especially for the still growing professional cycle market segment. The extent to which the tension in a spoke wheel must be readjusted at the time of the final trueing operation will decrease when interim operations are used, whilst on the other hand the operational characteristics of the end product on the other hand will be maintained at a higher level for a longer period of time, in particular when more than one trueing and stabilising cycle precedes the final trueing operation, which can be realised at low cost but in a more efficient manner by means of the present combined stabilisation/trueing device. Although it is preferable to increase the average mechanical tension during a trueing operation, starting from a minimum value, so as to eliminate the play and the rim deviations that have developed during the stabilising operation (s) , the momentaneous mechanical tension in an individual spoke can be increased or decreased during the trueing operation, in order to obtain the most uniform possible distribution of tension over the spokes after the final trueing operation, wherein axial and radial deviations in the form of the spoke wheel, also during later use, will be more stable and remain within narrow bounds, even after prolonged normal use. Preferably, the average of the mechanical tension in the spokes of the spoke wheel is therefore increased with every trueing operation - of several combinations of successive stabilising/trueing operations - so that first the larger and gradually the smaller deviations in the shape of the spoke wheel can thus be corrected. In practice, the degree to which the average minimum mechanical tension in the spokes of the spoke wheel is increased will depend on the effect of the immediately preceding stabilising operation on the respective momentaneous mechanical tension. Said effect will be greater with the first stabilising operation than with a next stabilising operation, so that also the precision with which gradually decreasing deviations in the shape are corrected will increase. One embodiment of the device according to the invention is characterized in that the device includes processor means connected to at least part of the stabilising and trueing means for driving said stabilising and trueing means. The invention and its further advantages will now be explained in more detail with reference to the appended drawing. The figure shows a preferred embodiment of a device 1, which now makes it possible to tension spokes S and S' of a spoke wheel 2 by means of spoke tensioning means (schematically indicated) , which inter alia include a nipple wrench 3, in such a manner that deviations both in axial and in radial direction in the rim 4 of spoke wheel 2 are eliminated. The spokes S and S', which are slightly mechanically biassed between a flange 5 disposed near the clamped-down axle 6 and the rim 4, are tensioned or relaxed by means of the rotary nipple wrench 3 during trueing of the spoke wheel 2. Spoke wheel 2 is moved in one direction during said trueing, or alternately in one direction and the other, the latter being preferred in connection with a saving of the time needed for trueing that can be achieved in that case. In the illustrated embodiment of the device 1, the nipple wrench 3 can be rotated by means of a rotary motor 7. Nipple wrench 3 can be moved by means of an element 8, which is fixedly mounted on a beam 9 which is capable of pivoting movement about two pivots A and B. Connected to pivots A and B are two further beams 10 and 11, which are also pivot-mounted on pivots C and D, which pivots are mounted in a block beam 12. Beams 9 - 11 and block beam 12 with respective pivots A, B, C and D together form a positioning mechanism for the nipple wrench 3. Beam 9 can be moved by means of a shifting element 13 mounted between beam 10 and block beam 12, which may for example be a linear motor, and which functions to set the desired angle between spoke S, S' and nipple wrench 3, which is usually about 90 degrees, independently of the type of spoke wheel 2. Block beam 12 can be moved as a whole by means of vertical positioning element 14 for the purpose of adjusting the height, which depends on the location and the type of rim 4 of spoke wheel 2. One movable beam 9 is shorter than the other part on block beam 12, which extends between pivots C and D. In the illustrated embodiment, the shorter beam 9 of the positioning mechanism, which at some point is trapezoidal, is positioned near spoke wheel 2. Device 1 possesses a positioning element 15, by means of which the nipple wrench can be moved along spoke S, S' to the nipple in question. The positioning mechanism comprising the four pivots thereby provides optimum vertical adjustment and angle-maintaining characteristics, so that the nipple wrench 3 will properly fit at the correct square angle on the nipples in question. The figure furthermore shows that setting mechanisms are disposed to the left and to the right of the spoke wheel 2 for the purpose of correctly tightening nipples which are present on groups of spokes S and S' which extend at different angles relative to rim 4. A rim driving unit, usually comprising at least one stepping motor 16, causes the spoke wheel 2 to rotate about the axle 6 which is to be clamped down. It stands to reason that each of the elements 8 and 13 - 15 is driven at successive, programmed times to a degree adapted to the type of spoke wheel, the rim and the number of spokes by programmable processor means (not shown) . Device 1 furthermore includes stabilising means 17, by means of which spokes S and S' are stretched in order for said spokes to bed in to flange 5 and rim 4 of spoke wheel 2. The illustrated stabilising means 17 are in the form of pressure pieces, for example of plastic material, which are capable of movement in a direction towards each other, which pressure pieces exert a prescribed pressure force on spokes S and S' when spoke wheel 2 is stationary, which pressure force is supplied by a cylinder 18 connected to said processor means. In this embodiment, the stabilising means 17 are fixed to a spring construction 19, which ensures that spoke wheel 2 will remain in the centre and can be stabilised on both sides simultaneously by the stabilising means, without this leading to deformation or to unacceptable forces being exerted, for example at the location where axle 6 is clamped down. It is not necessary for a construction of this kind to spring in order to achieve this, however . Spokes S and S', which are usually under a minimum mechanical bias, are initially stabilised by the stabilising means 17, whereby the first undesirable burrs in openings in rim 4 and flange 5, in which the spokes are present, are forced aside and the spokes are pre-stretched. Following that, a final trueing operation of spoke wheel 2 could take place in device 1. Several interim trueing and stabilising operations may alternately be carried out in the same device 1 prior to the final trueing operation. The momentaneous mechanical tension in a spoke is increased or decreased during a trueing operation in order to enable correct trueing of the spoke wheel 2. Usually, but not necessarily so, the average of the mechanical tension in the spokes of spoke wheel 2 is increased with each trueing operation. The degree of said increase of the average minimum mechanical tension in each spoke of the spoke wheel may depend on the effect of the stabilising operation on the respective momentaneous mechanical tension. The setting of the aforesaid angle of about 90° between spokes S, S 1 and the nipple wrench 3 takes place on the basis of preceding measurements carried out by measuring means (not shown) , wherein the following values are measured or determined: the diameter of the spoke wheel 2, the spacing between the two flanges 5 on axle 6, the type of wheel, that is, a rear wheel or a wheel with multiple sprockets, and the rim height. The rim height may for example be determined by placing sensors on either side of the spoke wheel 2, which will continue to transmit a shift command to positioning element 14 until one of the sensors switches, whereby said shift is measured by a pulse counter, for example, from which the rim height can be derived.

Claims: CLAIMS 1. A method for manufacturing a spoke wheel, wherein spokes are placed in a spoke wheel, brought under a mechanical tension and subjected to a stabilising operation, characterized in that a final trueing operation of the spoke wheel takes place after at least one stabilising operation of the spokes, and in that both operations are carried out in one and the same device. 2. A method according to claim 1, characterized in that one or more interim trueing operations of the spoke wheel are alternated with one or more interim stabilising operations. 3. A method according to claim 1 or 2, characterized in that the spokes, after being placed into the spoke wheel, are subjected to a minimum mechanical tension. 4. A method according to claim 3, characterized in that the momentaneous mechanical tension in a spoke is increased or decreased during the trueing operation 5. A method according to any one of the claims 1 - 4, characterized in that the average of the mechanical tension in the spokes of the spoke wheel is increased with every trueing operation. 6. A method according to claim 5, characterized in that the degree to which the average minimum mechanical tension in the spokes of the spoke wheel is increased depends on the effect of the immediately preceding stabilising operation on the respective momentaneous mechanical tension. 7. A device for manufacturing a spoke wheel, which device includes means for stabilising spokes in spoke wheels, characterized in that said device also includes trueing means for trueing the spoke wheel in axial and/or radial direction. 8. A device according to claim 7, characterized in that the device includes processor means connected to at least part of the stabilising and trueing means for driving said stabilising and trueing means .

Inventors: BEST BOB, BOSNJAK MLADDEN, BEST, BOB, BOSNJAK, MLADDEN
Applicants: BEST BOB, BEST MACHINE DEV V O F, BOSNJAK MLADDEN, BEST MACHINE DEVELOPMENT V.O.F., BEST, BOB, BOSNJAK, MLADDEN
Application year: 1999
Main classification: B60B31
IPC codes: B60B31