US3044533A

US3044533A - Apparatus for the manufacture of pneumatic tyres

Info

Publication number: US3044533A
Application number: US731419A
Authority: US
Inventors: Lowe Jack Milner
Original assignee: Dunlop Rubber Co Ltd
Current assignee: Dunlop Rubber Co Ltd
Priority date: 1957-05-01
Filing date: 1958-04-28
Publication date: 1962-07-17
Anticipated expiration: 1979-07-17
Also published as: DE1115913B; FR1206023A

Description

J. M. LOWE July 17, 1962 APPARATUS FOR THE MANUFACTURE OF PNEUMATIC TYRES Filed April 28, 1958 3 Sheets-Sheet 1 h a "gil"l"llem July 17, 1962 J. M. LOWE 3,

APPARATUS FOR THE MANUFACTURE OF PNEUMATIC TYRES Filed April 28, 1958 3 Sheets-Sheet 2 fvg w J. M. LOWE July 17, 1962 APPARATUS FOR THE MANUFACTURE OF PNEUMATIC TYRES Filed April 28, 1958 3 Sheets-Sheet 3 3,044,533 APPARATUS FOR IfHE MANUFACTURE OF PNEUMATIC TYRES Jack Milner Lowe, Sutton Coldfield, England, assignor to Dunlop Rubber Company Limited, London, England, a British company Filed Apr. 28, 1958, Ser. No. 731,419 Claims priority, application Great Britain May 1, 1957 12 Claims. (Cl. 156-401) This invention relates to apparatus for the manufacture of pneumatic tyres.

In the specification of co-pending patent application Serial No. 696,156, filed November 13, 1957, now Patent No. 2,943,668 there is described tyre building apparatus comprising a building drum and cylindrical supporting members located co-axially one at each end of the drum to support the side portions of tyre building fabric extending beyond bead wires located adjacent to each side of the building drum. An inflatable annular air bag is mounted on each supporting member, and a sleeve is provided which is freely movable telescopically over the drum and each supporting member. Each of the sup porting members is provided with an abutment for causing, upon inflation of the associated bag against the abutment and sleeve, movement of the bag and sleeve axially with respect to the drum so as to effect turn-over of the fabric around the adjacent bead wire and onto the building surface of the drum.

It has now been discovered that ply turn-over apparatus of the kind referred to in the preceding paragraph may be successfully operated without the use of a freely movable telescopic sleeve providing that suitably designed annular air bags are utilised and it is an object of the invention to provide such apparatus.

According to the invention tyre building apparatus comrates atom prises a collapsible building drum, cylindrical supporting members located coaxially one at each end of the drum, an annular airbag carried on each member to support an end of tyre building fabric projecting beyond the end of the drum, each of said supporting members providing abutment means for a portion of the inner wall of the air bag when inflated, whereby the upper wall is urged axially inwards to roll the projecting end of the fabric round a bead wire located on the fabric adjacent the end of the drum.

As in the apparatus described in said co-pending application Ser. No. 696,156, now Patent 2,943,668 the thrust which, upon inflation of the bag, propels the air bag over the building drum is a function of the inflation pressure and the amount by which the efiective crosssectional area of the abutment exceeds the effective crosssectional area of the drum plus the superposed tyre building fabric.

In the apparatus according to the invention it is preferable to use air bags which have been specially constructed, by the use of suitable rubber compounds and/ or fabric reinforcements, to resist undue radial expansion, since the working pressure required to effect turn-over and to consolidate the turned-over plies might otherwise cause the bags to expand sufficiently to distort the ply edges.

It will be appreciated that it is necessary to provide an annular air bag, for turning over the fabric, which has a circumference, taken around an axial cross-section, of at least twice the length of the fabric to be turned over.

The abutment means may comprise a shoulder formed on each of the supporting members'or may comprise an inflatable tube or tubes to form a shoulder upon inflation thereof. In one form of the invention the tube or tubes is. or are surrounded bysegments which, upon expansion of the tube or tubes, assume a frusto-conical shape tapering towards the building drum.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 is an axial cross-sectional view of apparatus in accordance with the invention;

FIGURES 2-8 are diagrammatic cross sectional views of the apparatus of FIGURE 1 showing consecutive stages in its operation;

FIGURE 9 is an axial cross-sectional view of part of an air bag.

The apparatus comprises essentially a collapsible building drum 1 and a pair of cylindrical supporting members 2 and 3 mounted co-axially one on each side of the building drum and attached to a hollow supporting shaft 4 by means of screws (not illustrated). The shaft 4 is carried in a pair of spaced-apart bearings mounted in pedestals (the bearings and pedestals are not illustrated) located outboard of one of the supporting members.

The collapsible building drum 1 comprises a cylindrical shell 5 upon which is mounted an annular fabricreinforced inflatable tube 6, and surrounding the tube is located a lurality of rigid segments 7, each segment having a tongue 7a at each end which locates, in the collapsed state of the drum with an annular surface 8,'

and with a second annular surface 9 when the drum is in the expanded state. In the collapsed state the segments 7 are separated by a small clearance space but otherwise surround the entire circumference of the tube 6. Each of the segments 7 is provided midway between its ends with a radially outwardly extending projection 7b. A resilient rubber sleeve 10 of substantial thickness surrounds the segments 7, the outer periphery of the sleeve 10 forming the building surface of the drum. The inner periphery of the sleeve 10 has an annular slot 11 formed midway between the end faces thereof within which the projections 7b on the segments 7 are located to position the sleeve '10 axially.

Detachable rubber shoulder rings 12, having projecting ribs 12a on their inner surfaces for engagement with corresponding grooves on the sleeve 10, are fitted, one at each end of the sleeve 10.

The supporting members 2 and 3 are each of similar construction, and one only will therefore be described. The supporting member 2 comprises two rigid cylindrical shells 13 and 14 supported co-axially with the building drum 1. A plurality of rigid segments 15, which in the contracted state fit together in cylindrical form, surround the'shell 14. These segments 15 constitute abutment means. The radially outward movement of the segments 15 is opposed by thin rubber bands (not illustrated) which surround the segments and are located in shallow grooves in the segments. A pair of coaxial inflatable fabric-reinforced tubes 16 is locatedbetween the segments 15 and the shell 14 and the tubes are inflatable via a common inflation tube 17 to expand the cylinder formed by the segments.

The" segments 15 are provided at their ends nearer to the building drum with stop plates 18 for engagement with the inner surface of the shell 13 to limit the radially outward movement of the said ends of the segments. At the ends of the segments remote from the building drum the radially outward movement of each of the segments is limited by the engagement of the head of a bolt 19, attached to the segment, with a stop 20 rigidly connected to the cylindrical shell 14. The segments 15, when fully expanded, take up a frusto-conical form (see FIGURES 4 I air bag 21 (see FIGURE 9) has a nose portion 22, which lies adjacent to the building drum, the wall of which is of rubber of low tensile modulus, e.g. having 25% extension for a load of 70 lbs.;per square inch, whilst the remainder 23 of the wall'of the bag is of rubber of higher tensile modulus e.g. having 25 extension for a load of 140 lbs. per square inch. A ring 24 of expansible resilient rubber is attached to the bag as shown, for a purpose to be described, and an inflation tube 25 is attached to the bag in the conventional manner. The inside surfaces of the bag 21 are smeared with silicone grease and powdered with French chalk, and the outer surface of the bag is graphited before cure. Before curing the bag, a loop of polyvinyl-chloride-covered metal wire (not illustrated) is inserted between the inside surfaces of the bag with one of its ends projecting through the inflation tube and. the

other end overlying the hole through which the inflation tube passes. The loop extends towards the end 21:: of the bag 21 for approximately athird of the distance between the inflation tube and 'the said end. After the bag has been cured, the loop of wire, which during cure has' formed grooves in the inside walls of the bag for a purpose to be described, is pulled out through theinflation tube. The wall thickness of the bag 21 is A; of an inch, the outside diameter of the bag when unexpanded and whenv carried on a supporting member is 12 inches and the expanded diameter is approximately 15% inches.

In the assembled apparatus shown in FIGURE 1 it will be'noted that the diameters of the building drum 1 and adjacent portions of the supporting members in the collapsed state are slightly smaller than those of the outer surfaces of the remaining parts of the supporting members, and the bag shown in FIGURE 9 has been performed to conform to this shape. The object of this reduced diameter is to compensate for the increase in thickness resulting from the placing of an inner lining 26 and chafer strips 27 on the drum 1 before the plies of tyre-building fabric are added. The plies are thus laid on a substantially flat cylinder, which helps to maintain uniform ply joints. i

Theoperation of the apparatus just outlined in the manufacture of a tyre cover will now be described.

With the drum 1 and each of the'supporting members 2 and 3 in the collapsed state, an inner lining 26 and chafer strips 27 are applied to the drum as shown in FIGURE 1. A pairof plies 28 is then applied to the building drum in the usual manner, side portions 28a and 28b of the pair of plies 28 extending one over each of the air bags 21 carried by the supporting members 2 and 3 respectively.

Bead wire assemblies

29 and 30 are then passed over the plies from the free end of the apparatus and are located in position adjacent to the shoulders 12 of the building drum.

The building drum is then expanded, as shown in FIG- URE 2," by inflating the associated tube 6, the

bead wire assemblies

29 and 30 and the chafer strips 27 being held inflation of the associated tubes 16 through the common inflation tube 17, a shoulder forming portion 15a thus being raised clear ofthe portion 13 of the supporting member. Pressure of the air bag 21 against this shoulder and against the axially projected area of the frusto-conical surface formed by the segments 15 causes the air bag to move automatically axially over the building drum, carrying with it the side portion 28a of the pair of plies 28. As the .air bag moves down the slope of the frusto-conical surface formed by the segments '15; the resultant pressure causing the movement of the bag is progressively decreased, the frusto-conical form of the surface thus limiting the tendency of the bag to overrun.

The low tensile modulus rubber nose portion 22 of the bag 21 conforms closely to the profile of the bead assembly 29 as it rolls the plies onto it and is anchored beneath the bead assembly 29 by the rubber ring 24, thus ensuring good consolidation of the plies in the bead region. The overlying and surrounding portions of tyre-building fabric help to prevent excessive bulging of the portion 22 of the bag 21. The remaining portion 23 of the bag 21 of high tensile modulus rubber, and resist undue expansion of the bag under inflation pressure. 'An inflation pressure of 2%. lbs. per square inch has been found to give satisfactory thrust and consolidation of the tyre building fabric turned over.

When the bag 21 has rolled clear of the shoulder 15a the rolling action ceases (see FIGURE 5), in which position the edge 28a of the pair of plies 28 has been turned over and pressed down firmly to the central portion of the plies.

The bag 21 is then returned to its original position on the supporting member 2 by deflating the tubes 16, thus rcturning the segments 15 to the position shown in FIGURE 6, whereby the presure of the bag 21 against the shoulder formed by the bead and ply assembly on the expanded building drum 1 causes the bag to roll back from the building drum to the supporting member 2. Deflation of the bag 21 commences during the rolling back of the bag and is continued with the bag in the position shown in FIG- URE 7, the final state of the bag on the supporting memher 2 being shown in FIGURE 8. FIGURE 8 also shows the first stage in the turning over of the edge 28b of the ply, which takes place in a similar manner to that describedfor the edge 28a.

When the type building operation is completed, the tube 6 of: the drum 1 is deflated to cause the drum to assume a collapsed state and allow removal of the built tyre cover.

During the rolling back of the bag 21 from the building drum, there is a tendency for a ruck to be formed in the bag, particularly above the shoulder portion 15a where the bag is stretched during the ply turn over operation. The tendency for rucks to form is reduced by the graphite appliedto the inner surfaces of the bag as described earli er. When a ruck is formed, there can be difliculty in deflating the air bag, and for this reason grooves are provided on the inside surface of the bag, as described earlier, to allow air to escape past the ruck to the tube 25.

In the use of the apparatus just described, the sequence of the operations may be varied, for instance, the rolling bags may be inflated after instead of before the expansion of the segments on the supporting member.

In an alternative construction, the bag has the same proportions as in the embodiment just described and is of the rubber compound utilised for the rubber nose thereof, the portion of the bag, apart from the nose, being reinforced by means of a knitted fabric, of steel or textile cords, having a known vlimit of stretch such that upon inflation of the bag the expansion thereof is limited to about 15% inches diameter. Such a construction enables higher inflation pressures to be utilised.

In a further alternative air bag construction, the reinforcement consists of a yarn of cotton-covered rubber thread, sold under the registered Trade Mark Lastex, having appropriate stretch characteristics such that the required limited expansion is obtained.

Crimped :cords may also be used as a' bag reinforcement, the degree of crimping being such that upon expansion of the bag the expansion is limited by straightening of the cords.

In a further alternative embodiment of the invention in the case of each supporting member 2 and 3, the segments 15 are dispensed with and the tubes 16 are replaced by an expandable bag reinforced so as to be capable, upon inflation, of assuming a frusto-conical shape, tapering towards the building drum, which will produce movement of the rolling bag towards and away from the building drum upon inflation and deflation respectively of the expandable bag.

inflation of the air bags to an accurate predetermined pressure may be achieved by discharging a cylinder of air of known volume and at a known pressure into the air bag.

Having now described my invention-what I claim is:

1. Tyre building apparatus comprising a collapsible building drum, an assembly of supporting members arranged in a cylinder located coaxially with said drum, one at each end of the drurn, an annular air bag carried on said supporting members at each end of the drum to support the ends of tyre building fabric projecting beyond the ends of the drum, said bag when not inflated comprising a radially inner cylindrical wall on said supporting members and a radially outer wall on said inner wall, said radially outer wall comprising a nose portion adjacent to said drum of low tensile modulus compared with the remainder of the bag to expand over the end of said drum when said bag is inflated, each said assembly of supporting members being expansible at the axially outer end thereof to a greater diameter than the portion at the inner end thereof and to a diameter greater than the diameter of the building surface of the building drum, to urge the outer wall of the air bag, when the air bag is inflated, axially towards the building drum to roll the projecting end of the fabric around a bead wire located on the fabric adjacent the end of the 2. Tyre building apparatus according to claim 1 wherein the wall of each of the said air bags is composed of rubber of a low tensile modulus reinforced with fabric, the expansion of each of the air bags being limited to a predetermined value by means of the fabric.

3. Tyre building apparatus according to claim 2 wherein the fabric reinforcement is a knitted fabric.

4. Tyre building apparatus according to claim 1 wherein each of the said air bags is provided, on the internal surface thereof, with a groove communicating with means for deflating the bag and extending axially to provide means whereby, during deflation of the bag, air entrapped in a portion of the bag may be released through the groove to the said means for deflating the bag.

5. Tyre building apparatus according to claim 1 incorporating a collapsible building drum collapsible from a fully expanded cylindrical state to a cylindrical state of reduced diameter, and air bags in which the radially innermost walls of the nose portion of each bag is thickened around its entire circumference, eaoh bag being disposed so that the thickened nose portion extends over the end portion of the drum.

6. Tyre building apparatus according to claim 1 wherein the collapsible building drum comprises a cylindrical shell having coaxially mounted thereon an inflatable annular tube, a plurality of axially extending rigid segments surrounding the shell and tube, means for inflating the tube so that the overlying segments are disposed on a pitch circle of increased diameter, and a sleeve of resilient expansible material surrounding the segments.

7. Tyre building apparatus according to claim 6 wherein means are provided at each end of each of the segments for limiting the radial movement of the segments upon inflation of the said tube.

8. Tyre building apparatus according to claim 6 wherein a radially outwardly extending projection is formed on each segment engaging with an annular slot formed on the inner periphery of the surrounding sleeve so as to locate the sleeve relative to the segments.

9. Tyre building apparatus according to claim 6 wherein a shoulder ring of resilient expansible material is detachably attached to an end of the sleeve.

10. Tyre building apparatus according to claim 1 wherein said supporting members are axially extending rigid segments located side-by-s-ide on a common pitch cirdle, and comprising an annular inflatable tube located coaxially within the segments, means for inflating said tube so that the segments are disposed on a pitch circle of increased diameter, and means for restraining radially outward movement of the segments to a lesser diameter at the end adjacent said drum than at the end farther from said drum so that the assembled segments take a frustoconical shape toward and coaxial with said drum.

l1. Tyre building apparatus comprising a collapsible building drum, cylindrical supporting members coaxial with said drum, one at each end of the drum and extending from an inner end adjacent ran-end of said drum to an outer end, each said supporting member being expansible to a greater diameter at its outer than at its inner end, and an annular air bag of expansible material for each supporting member, having one end adjacent the end of said drum and comprising a radially inner cylindrical wall supported on said supporting member and a radially outer cylindrical wall supported on said inner cylindrical wall when said bag is not inflated, said outer wall comprising a nose portion of low tensile modulus compared with the remainder of said wall so that said nose portion will expand over the end of said drum when said bag is inflated, the outer cylindrical wall of each of said "air bags having a limit of circumferential expansion under fluid pressure sufiicient to expand said nose over said drum and to form an axially movable substantially cylindrical wall spaced from said inner wall.

12. The tyre building apparatus of claim 11 in which each of said supports comprises longitudinal elements in cylindrical formation about the axis of the support and stops to limit the radially outward movement of said elements at said inner end to a lesser distance than at the outer end to form a frusto-conical structure.