A tread ring transfer apparatus for use in a green tyre building system

Abstract: A tread ring transfer apparatus for use in a green tyre building system adapted for holding and transferring a tyre component which is formed in a cylindrical shape has a ring shaped holder frame (20); and a plurality of holding segments (22) provided along a circumferential direction of the holder frame (20) and radially movable inwardly and outwardly to hold and release the tyre component respectively. Each holding segment (22) has at least one contact member (28) for pressing contact with the tyre component when the holding segments are moved radially inward. One contact member (28) of one of the plurality of holding segments is different in height from another contact member.

Description: This invention relates to a tread ring transfer apparatus for use in a green tyre building system to hold and transfer a tyre component in the form of a cylinder. Conventionally, in a green tyre building system, there is provided a pair of forming drums disposed opposite to each other with a tread ring transfer apparatus (hereinafter merely referred to as a "transfer apparatus") interposed therebetween. One of the forming drums is a tread ring forming drum, and the other is a tyre building drum. A tread ring in the form of a cylinder comprising belt, bandage, and material for tread is formed on the tread ring forming drum, from where the tread ring is transferred to a position around carcass plies in the form of a cylinder placed on the tyre building drum by the transfer apparatus, thereby building complete a green tyre. Generally, the transfer apparatus is provided with a plurality of holding segments arranged around its circumference at equal intervals. The segments are movable in radial inner and outer directions of the transfer apparatus. Each segment has a holder portion (contact member). The contact member comes into pressing contact with the tread ring, when the segments are moved in their radial inward direction, to thereby hold and allow transfer of the tread ring to the tyre building drum. The above-constructed transfer apparatus has suffered the following problems. When the contact members of these segments are provided equally spaced in the circumferential direction the tread ring is formed with recesses on its outer circumferential surface thereof, at positions corresponding to the contact members. These recesses in the tread ring increase Radial Force Variations (referred to as "RFV" hereinafter) in the higher modes, thus generating undesirable noise during driving of an automotive vehicle at high speeds. "RFV" is one of the measured quantities of the force variation of the tyre; they are namely LFV, RFV, and TFV, representing the rigidity of the tyre in the respective directions; namely the lateral direction, the radial direction, and the tangential direction with respect to the circumference of the tyre. "RFV" in particular is a variation of the measured force (in units of Kg) under application of the force such that the tyre (or green tyre) undergoes deformation in the radial direction by the specific amount. To solve the above problem, recently, there has been proposed in EP-A-0633130 a transfer apparatus provided with contact members in the spaced apart circumferential direction thereof by a varied interval to thereby reduce RFV of a tyre in the higher modes. The term "higher mode" hereinafter used has some thing to do with the higher frequencies; which in turn has some relation to the rotational speed of the tyre when equipped to a automobile. Thus the higher mode in the certain respect simulates a faster rotational speed of the tyre. The aforementioned transfer apparatus can not completely solve the problem because the freedom of interval variation among the contact members for some instance is constrained by the structural limitations of the holding segments. Accordingly, sufficient reduction of RFV is not always found without changing the size or structure of the holding segment in some instance, leading to a drastic design change, not favoured by the industry, and thus there is room for further improvement. The above-constructed transfer apparatus has another problem. Although it is effective in reducing RFV, providing contact members at varied intervals makes standardisation much harder for the industry as the number of parts increases, leading to an inconvenience in maintaining and administrating of the parts. In view of this, there is a demand for a novel transfer apparatus in which the structure of each segment can be made identical as much as possible while, at the same time, reducing RFV in the higher modes. In view thereof, it is an object of this invention to overcome the above-mentioned drawbacks residing in the prior art. It is another object of this invention to provide a tread ring transferring apparatus capable of reducing RFV of tyre in higher modes with a simplified construction. Accordingly one aspect of the present invention provides a tread ring transfer apparatus for use in a green tyre building system adapted for holding and transferring a tyre component which is formed in a cylindrical shape, comprising a holder frame in the form of a ring; and a plurality of holding segments provided along a circumferential direction of the holder frame and radially movable inward and outward to hold and release the tyre component respectively, each holding segment including at least one contact member which is adapted for pressing contact with the tyre component when the holding segments are moved radially inwards, characterised in that a contact member of one of the plurality of segments is different from another projection of the other segment in height in the radial direction. According to this invention, recesses formed on the tyre component in a holding state of tyre component by the pressing contact with the contact members of the respective segments have varied depths along the circumferential direction of tyre. RFV of tyre is affected by the recesses of different depths. Because varying the radial heights of the contact members leaves outer configuration of the tyre component unevenly recessed and in turn unevenly peaked along the circumferential direction thereof. Assuming there are eight contact members in the holder frame; they have equal radial heights and are arranged at equal intervals in the circumferential direction of the holding segment. When these contact members press against the tyre component, it would result in producing the recesses and in turn peaks at eight points at the same interval respectively along the circumferential direction of the tyre component. With the tyre component thus constructed, it is known that these equally distanced and projected peaks on the outer surface of the tyre component will facilitate formation of the higher RFV along the circumferential direction thereof. Therefore, varying the projected amount of the contact members (even if they are at the same interval along the circumferential direction of the holder frame) unevenly along the circumferential direction of the holder frame, when pressed against the tyre component, produces the peak points on the outer configuration of the tyre component which are shifted away from the equally distanced points along the circumferential direction of the tyre. As a result, there can be avoided the phenomenon where the same level of RFV is generated in a short period of time (cycle), as in the tyres produced with use of the conventional transfer apparatus in which projections are provided in the circumferential direction at the same intervals. Thus, RFV in the higher modes can be reduced. In one aspect of this invention, the holding segments are provided along the circumferential direction of the holder frame at the same interval, and the contact members of the holding segments are provided along the circumferential direction of the holder frame at the same interval when the holding segments are radially moved inward to hold the tyre component. With this arrangement, the construction of each segment can be made common to one another in an effective way. In another aspect of this invention, the height of the contact member is set such that the contact members adjacent to each other along the circumferential direction of the holder frame are different in height. Preferably, the height of the contact member is set in the range of 0.5 to 4.0 mm. With this arrangement, RFV of the tyre in the higher modes can be effectively reduced. The above and other objects, features and advantages of the present invention will become more apparent upon a reading of the following detailed description and drawings by way of example: FIG. 1 is a front view of a green tyre building system including a tread ring transferring apparatus according to the invention; FIG. 2 is a side view of the tread ring transferring apparatus; FIG. 3 is a diagram showing an arrangement of projections (contact members); and FIG. 4 is a graph showing a relationship between RFV and variation modes. FIG. 1 is a diagram schematically showing a green tyre building system incorporated with a tread ring transfer apparatus (hereinafter merely referred to as a "transfer apparatus") embodying the invention. Reference numeral 10 denotes the green tyre building system. The system 10 comprises a first forming drum (tread ring forming drum) 12 and a second forming drum (tyre building drum) 14 , and a transfer apparatus 16. The first and second forming drums 12 and 14 are arranged spaced apart from each other by a specified distance with the transfer apparatus 16 interposed therebetween. The transfer apparatus 16 is reciprocally slidable between the first and second drums 12 and 14 along a pair of parallel rails 18 in the directions shown by the arrows in FIG. 1. In the green tyre building system 10, the transfer apparatus 16 transfers a tread ring, formed by the first forming drum 12, to the second forming drum 14 around which carcass plies are wound. Then, the tread ring and the carcass plies are integrally formed to build a green tyre. More specifically, on the first forming drum 12, tyre constituent members such as belt, bandage, and rubber material for the tread are assembled one over another to form a sub-assembly Wa (tread ring) in the form of cylinder. On the second forming drum 14, a plurality of carcass plies are assembled one over another to form a second sub-assembly Wb also in the form of cylinder. The transfer apparatus 16 removes the sub-assembly Wa formed on the first forming drum 12 therefrom and transfers it to the second forming drum 14 on which the second sub-assembly Wb is held. Then, on the second forming drum 14, the sub-assembly Wa,Wb are integrally formed to build a finished green tyre. FIG. 2 is a diagram showing the construction of the transfer apparatus 16 in detail. The transfer apparatus 16 has a holder frame 20 in the form of a ring. The holder frame 20 is arranged with a plurality of holding segments for holding the sub-assembly Wa. Specifically, in this embodiment, the holder frame is arranged with eight segments 22A to 22H. The transfer apparatus 16 comprises an expanding/contracting mechanism to expand (radially move outward) and contract (radially move inward) these segments 22A to 22H with respect to the holder frame 20. As shown in FIG. 2, the holding segments 22A to 22H are arranged equally inside the ring-shaped holder frame 20 around the circumferential direction thereof. The segments 22A to 22H each has a supporting member 24 in the form of a circular arc. The segment 22A (or 22B,... 22H) is constructed in such a manner that a projection 28 (in this embodiment, two projections) serving as a contact member for holding the sub-assembly Wa is provided on an inner surface of the supporting member 24. The supporting members 24 are coupled to the expanding/contracting mechanism via a corresponding drive shaft (or a drive arm) 26. In transferring the sub-assembly Wa, the expanding/contracting mechanism is driven to move the holding segments 22A to 22H to hold the sub-assembly Wa which is inside in a state that the work Wa is placed on an inner side of the segments 22A to 22H. It is to be noted that each holding segment has a supporting member 24, a drive shaft 26, and projections 28, although, in FIG. 2, such detail is shown only for the segment 22A. Although not illustrated, the expanding/contracting mechanism comprises a ring member mounted to the holder frame 20, a cylinder for rotating the ring member about a rotary axis of the holder frame 20, and a link member for converting a rotary movement of the ring member to a radial reciprocal movement of the holding segments. The drive shafts 26 of the respective segments 22A to 22H are coupled to the link member. The holding segments are changed from a tread ring holding state to a tread ring releasing state, and vice versa in the following manner. Specifically, when the cylinder is driven to rotate the ring member about the rotary axis of the holder frame 20, the segments 22A to 22H are simultaneously moved in radial directions of the holder frame 20. The segments are moved in their inner radial directions to set the holding state, while moved in their outer radial directions to set the releasing state. In the holding state, the projections 28 of each segment come into pressing contact with the sub-assembly Wa to hold it from the outside. As described above, each supporting member 24 has two projections 28 arranged along the inner circumferential direction of holder frame (see FIG. 2). For example, the segment 22A has projections 28A-1, and 28A-2, the segment 22B has projections 28B-1 and 28B-2, ... in the circumferential direction of holder frame. Further, as shown in FIG. 3, in the holding state of tread ring, these projections 28 are arranged along the circumferential direction of the holder frame spaced at the same interval P. Each projection 28 has a flat surface on the lead end thereof. All the projections 28 have the same dimensions with respect to the circumferential direction of holder frame, (in FIG. 3, directions extending left and right sides) and in the widthwise direction of tyre (in FIG. 3, forward and rearward directions, orthogonal to the left and right directions). However, the height of projection 28, i.e., the dimension in the radial direction of the holder frame is set at any of four different values, (a) , (b), (c), and (d). The height of projection is set such that the projections adjacent to each other along the circumferential direction of the holder frame have heights different to each other. Specifically, two projections 28, 28 on one supporting member 24 have heights different from each other. Further, between the supporting members adjacent to each other in the circumferential direction of the holder frame, the projection on one supporting member and the projection on the other supporting member, disposed next to each other are different in height. For example, the projection 28A-2 of the segment 22A and the projection 28B-1 of the segment 22B are different in height, the projection 28B-2 of the segment 22B and the projection 28C-1 of the segment 22C are different in height, respectively, and so forth. In this embodiment, the dimensions of the projection 28 in the circumferential direction and in the widthwise direction of tyre are respectively set at 20 mm. As cescribed above, the height of projection 28 is selected from among four different types (a) , (b), (c), and (d) shown in TABLE-1. The projections 28 of each supporting member 24 of the segments 22A to 22H have the height arrangement as shown in TABLE-2. type a b c d height 0.5 mm 1.0 mm 1.5 mm 2.0 mm segment 22A 22B 22C 22D 22E 22F 22G 22H type d a b a d c b c d a b c b a d c More specifically, when the projections 28 of the segments 22A to 22H are arranged in the order mentioned above, recesses formed on the sub-assembly (tread ring) Wa by the pressing contact with the projections 28 of the segments 22A to 22H in the holding state of tread ring have varied radial depths from one another in the circumferential direction of the tread ring. Accordingly, RFV resulting from these recesses is varied in the circumferential direction of the tyre. Thereby, there can be attained the same effect (reducing RFV) as in tyres fabricated with use of the conventional transfer apparatus in which projections are arranged at a varied interval, i.e., RFV can be reduced. In addition, there can be avoided the phenomenon that the RFV is generated at a relatively shorter time period. Accordingly, although the projections 28, contact members for the sub-assembly Wa are provided in the circumferential direction of tyre at the same interval, tyres fabricated with use of the green tyre building system 10 incorporating the inventive transfer apparatus have effectively reduced RFV in the higher modes, as shown in the following experimental data. Experimental Data TABLE-3 shows results of RFV obtained by conducting the measurement test according to JASO. The measurements were carried out for tyre of the size, 165/70R13, mounted on a wheel rim of 4.5JJ X 13 inch. RFV in MODES 0A 1H 2H 3H 4H 5H 6H 7H 8H 9H 10H SP1 4.9 2.6 2.4 0.5 06. 0.4 0.2 0.1 0.1 0.1 0.1 SP2 4.6 3.5 0.8 0.7 0.5 0.5 0.2 0.0 0.1 0.1 0.0 SP3 3.0 1.0 1.3 1.5 0.4 0.2 0.5 0.2 0.2 0.1 0.2 SP4 2.7 1.3 1.4 0.7 1.1 0.4 0.3 0.1 0.2 0.1 0.1 SP5 5.7 3.9 2.5 1.1 0.8 0.4 0.4 0.3 0.3 0.1 0.1 SP6 4.0 1.7 0.5 1.2 1.5 0.5 0.3 0.2 0.1 0.1 0.0 SP7 5.8 4.2 1.0 1.3 0.9 0.6 0.4 0.2 0.1 0.1 0.0 SP8 3.1 1.0 1.8 1.5 0.9 0.5 0.4 0.0 0.1 0.1 0.0 SP9 2.3 0.3 1.0 0.4 1.0 0.4 0.2 0.3 0.1 0.0 0.0 SP10 3.8 2.1 1.0 0.7 0.7 0.7 0.2 0.1 0.1 0.2 0.0 X 3.99 2.16 1.37 0.96 0.84 0.46 0.31 0.15 0.14 0.1 0.05 σ 1.17 1.28 0.63 0.39 0.3 0.13 0.1 0.1 0.07 0.04 0.07 (Unit: Kg Where: SP1 to SP10 = tyre samples X = average value of RFV in each column; and σ = standard deviation of values (RFV) in respective columns. FIG. 4 is a graph showing the relationship between RFV (mean value) and higher modes regarding the measurement results in TABLE-3. The phantom line and dotted line in FIG. 4 represent the results of measurement regarding tyres (comparative tyres) fabricated by the conventional green tyre building system. Specifically, the phantom line (alternate long and two short dash line) represents the results of measurement for comparative tyres fabricated by the conventional tyre building system (first conventional system) incorporated with the transfer apparatus in which projections identical to each other in configuration (dimension) are provided along the circumferential direction of tyre at a varied interval, whereas the dotted line represents the results of measurement for comparative tyres fabricated by another type of conventional tyre building system (second conventional system) incorporated with the transfer apparatus in which projections identical to each other in configuration (dimension) are provided along the circumferential direction of tyre at the same interval. As shown in FIG. 4, in tyres fabricated by the green tyre building system 10 of this invention incorporated with the inventive transfer apparatus 16, RFV in the higher modes can be greatly reduced, compared to the comparative tyres fabricated by the second conventional system, although both in the conventional transfer apparatus and in the inventive transfer apparatus, the projections are arranged at the same interval. Further, RFV in the inventive tyres is substantially reduced as low as the comparative tyres fabricated by the first conventional system in which the projections are arranged in the circumferential direction of tyre at a varied interval. Accordingly, as is apparent from the results of experiment, when the height of projections 28 is differentiated from one another in the above mentioned order, RFV in the higher modes can be effectively reduced. As mentioned above, when the transfer apparatus 16 of the green tyre building system 10 is constructed in such a manner that the projections 28 of the segments 22A to 22H are set at different heights from one another, the RFV of a finished tyre in the higher modes is reduced greatly, although the projections 28 are provided at the same interval. With this construction, by detachably mounting the projections 28 to the supporting members 24 by means of bolts or nuts, segments of substantially the same structure can be used except for the projections 28. Accordingly, the parts constituting the segments 22A to 22H can be made common to one another except the projections 28, with the result that maintenance of tyre can be improved and cumbersome operation trying to design the segments different from one another in structure can be avoided. As a result, it enhances standardisation of the parts. In the foregoing embodiment, the transfer apparatus 16 is constructed in such a manner that the projections 28 are provided at the same interval along the circumferential direction of tyre. Alternatively, the transfer apparatus may be constructed in combination with the arrangement of first conventional system. That is, the transfer apparatus as an altered form is provided with the projections different in height along the circumferential direction of tyre at a varied interval. With this altered arrangement, RFV of tyre in the higher modes can be more reliably reduced because of the combined effect obtained by the feature that the projections are provided at the varied interval and the feature that the height of projection is desirably selected from among a plurality of different values. To sum up, the transfer apparatus according to the present invention is advantageous in that it can reliably reduce RFV in the higher modes even where the projections cannot be provided at varied intervals due to structural constraints and so forth. This is because merely differentiating the height of projection surely reduces RFV in the higher modes, as evidenced in the experiment data. It is to be noted that the number of segments, number of projections on one supporting member, specific configuration of projection, and specific dimension of projection such as height are not limited to the above, but may be optimally set to attain an effect of more reliably reducing RFV in the higher nodes, considering various factors such as construction of transfer apparatus, structure of tyre to be fabricated, and required performance on tyre. It is desirable to set the height of the projections in the range of 0.5 to 4.0 mm in accordance with the structure of tread. Preferably, it may be desirable to set the height of projection in the range of 0.5 to 2.0 mm. This is because of the following reasons. When the height of projection is smaller than 0.5 mm, it is difficult to effectively reduce RFV of tyre in the higher modes, and it is likely to deteriorate the ability of holding the sub-assembly Wa. In contrast, when the height of a projection exceeds 4.0 mm, it impairs the external appearance of the tyre and also it may likely to adversely affect the uniformity of tyre to a non-negligible extent. The dimensions of the projections in the circumferential direction and in the widthwise direction of tyre in the foregoing embodiment are respectively set at 20 mm. The effect of reducing RFV in the higher modes is attainable, as far as the dimensions lie within the range of 10 to 30 mm. If the dimension is smaller than 10 mm, however, the force applied to the tread ring in the holding state becomes too large, thereby impairing the external appearance of tyre. On the contrary, if the dimension far exceeds 30 mm, a portion of the projection 28 is abutted against a tread shoulder, thereby impairing the external appearance of tyre. In this case, it may also likely to cause a drawback that air remains on an inner side of the tread ring, i.e., in between the uppermost layer of carcass plies and the tread ring in building a green tyre. Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such change and modifications depart from the scope of the invention, they should be construed as being included therein.

Claims: A tread ring transfer apparatus for use in a green tyre building system (10) adapted for holding and transferring a tyre component which is formed in a cylindrical shape, comprising a holder frame (20) in the form of a ring; and a plurality of holding segments (22) provided along a circumferential direction of the holder frame and radially movable inward and outward to hold and release the tyre component respectively, each holding segment (20) including at least one contact member (28) which is adapted for pressing contact with the tyre component when the holding segments are moved radially inwards, characterised in that a contact member (28) of one of the plurality of segments (22) is different from another contact member of the other segment in height in the radial direction. A tread ring transfer apparatus according to claim 1, characterised in that the holding segments (22) are equally spaced in the circumferential direction of the holder frame (20) and the contact members (28) of the holding segments are equally spaced in the circumferential direction of the holder frame (20) when the holding segments (22) are radially moved inwards to hold the tyre component. A tread ring transfer apparatus according to claim 1 or 2, characterised in that the heights of the contact members (28) are set such that the contact members (28) adjacent to each other along the circumferential direction of the holder frame are different in height. A tread ring transfer apparatus according to any of claims 1-3, characterised in that the height of each contact member (28) in the radial direction is set in the range of 0.5 to 4.0 mm.

Inventors: SUZUKI KAZUYA, SUZUKI, KAZUYA
Applicants: SUMITOMO RUBBER IND, SUMITOMO RUBBER INDUSTRIES LIMITED
Application year: 1997
Main classification: B29D30
IPC codes: B29D30